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A comparative study of the residential behavior of juvenile salmonids Newman, Murray A. 1960

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-A COMPARATIVE STUDY OF THE RESIDENTIAL BEHAVIOR OF JUVENILE SALMONIDS by MURRAY ARTHUR NEWMAN B. S., U n i v e r s i t y of Chicago, 1949 M. A., U n i v e r s i t y of C a l i f o r n i a , 1951 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of ZOOLOGY l e accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1960 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without" rny w r i t t e n permission. Department of ^ ° ^ y t ( m -The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date Wat Pnniersttg of ^r i i t sh (ftolumlroi Faculty of Graduate Studies PROGRAMME OF THE FINAL O R A L E X A M I N A T I O N F O R T H E D E G R E E O F D O C T O R OF PHILOSOPHY of M U R R A Y ARTHUR NEWMAN _ B.S., University of Chicago, 1949 M . A . , University of California, 1951 IN ROOM 3332, BIOLOGICAL SCIENCES BUILDING WEDNESDAY, OCTOBER 14th, 1959 at 3:45 P.M. COMMITTEE IN CHARGE F. H . Soward: Chairman W. S. H O A R C. B. F I N N E G A N M . D . F. U D V A R D Y P. A . L A R K I N P. F O R D D . C . G . M a c K A Y R. F. S C A G E L External Examiner: M . Keenleyside, Fisheries Research Board of Canada GRADUATE STUDIES Field of Study: Zoology Comparative Ethology W . S. Hoar Population Dynamics P. A. Larkin Introduction to Biological Oceanography W . M . Cameron Other Studies: Introduction to Dynamic Oceanography G . L. Pickard Introduction to Synoptic Oceanography W . M . Cameron Palaeontology W . J. Okulitch P U B L I C A T I O N S Newman, M . A. 1956. Social behavior and interspecific competition, in two trout species. Physiol. Zool., 29: 64-81. 1957. Reptiles and amphibians in the beautiful new Van-couver Aquarium. Aquar. Jour., 28: 311-313. 1957. New Vancouver Public Aquarium. Parks and Recrea-tions, 40: 21-24. 1958. The Aquarium as a teacher. B.C. Teacher, 37: 188-190. 1958. A friendly nod to a cephalopod—Octopus apollyon. Aquar. Jour., 29: 256-258. 1958. Vancouver Public Aquarium Guide. Van. Publ. Aquar. Assoc. 1959. Skates in the Public Aquarium. Canadian Audubon, 21: 18-21. A COMPARATIVE STUDY OF THE RESIDENTIAL BEHAVIOR OF JUVENILE SALMONIDS A B S T R A C T Some juvenile salmonids readily form schools while others dis-perse under the same conditions. These latter species do not totally disperse, however, and will aggregate in response to various factors. They select common environments in nature, follow each other in pursuit of food, condense into a group when frightened and some-times swim in small "gangs." The selection of the environment is partly related to innate "preference" for particular physical factors and partly induced by external considerations such as presence of food and exposure to predation. Intraspecific social interference is probably an important factor in the location of individuals in a stream. Interspecific social interference may tend to separate species occupying the same waters. One of the main differences in behavior between the juveniles of the early migrant species and the residential species is in continu-ousness of movement. A l l of the residential species are intermittent, alternating tonic immobility with darting swimming motions. The migrants are much more continuous swimmers. Residential species form social hierarchies based on aggressive contacts.; The: intensity of nipping and the endogenous movements involved vary among the different species. It is postulated that there is a phylogenetic progression from infrequent but damaging at-tacking behavior to more frequent but less damaging behavior and finally to more ritualized behavior in which nipping is reduced. Pacific salmon may have undergone a regressive evolution in juvenile residential behavior. Residential fish are believed to be localized within a common home range rather than a private territory. When displaced from their home area they repeatedly roam back and forth and may return if possible. Within the home range the individuals compete for food and shelter through a dominance order. Aggressive be-havior is probably significant in natural selection, in thwarting movements up and downstream and thus stabilizing populations, and in enabling maximum utilization of home range area through dispersion. ABSTRACT Juvenile f i s h belonging to three genera and ten species of salmonids, were compared in f i e l d and laboratory studies* The main objectives were to describe the aggressive social behavior i n a comparative way and to study those components of behavior associated with stream residence. In comparisons of aggregating tendencies of lake trout, rainbow trout, cutthroat trout, coho salmon and chum salmon i t was found that chum fry formed relatively tight schools while the others did not. Coho fry aggregated when feeding and dispersed afterwards. Both rainbow and cutthroat showed a preference for shadowed portions of their containers. Rainbow selected the deep end of a tank graded from shallow to deep, while chum fry swam back and forth. Rainbow showed no selection for a small waterfall. It was shown that food, predatory fish and dominant individuals affected the selection of a l o -cation. From these experiments i t was reasoned that r e s i -dent and migrant fish have different innate environmental preferences but that these can be modified by external factors. The rate of locomotion was shown to be highest in migrant chum fry, lowest i n resident fishes and intermediate in lake trout. The continuous swimming of chum fry was con-trasted with the discontinuous swimming of residents. Again lake trout were intermediate. Standard observations were made of intraspeoific groups in the laboratory. Resident fishes were aggressive and de-veloped social hierarchies based on fighting, displays and nipping. Most nipping was performed by dominant f i s h and a l l of the ac t i v i t i e s of the subordinates were influenced by the presence of the dominant individual i n their group. Some migrant fishes were aggressive, others were not. Ghum fry nipped and chased each other but, evidently because of their continuous swimming movements, did not develop sta-b i l i z e d dominance orders. Lake trout, sockeye fry and pink fry were not aggressive and did not develop social hierar-chies. Dominant coho fry attacked intruders more vigor-ously than they did members of their own group and the i n -truders often died. It was observed that intruders showed a characteristic "escape behavior" which may have identi-f i e d them and singled them out for attack. In f i e l d studies carried out during different seasons, i t was observed that individual coho fry exchanged posir-tions and moved about within a home range. They did not appear to rest r i c t themselves to private territories. During winter floods the home range was vacated and the fish occu-pied pools along the stream edge. In spring pre-migrant smolts were i n pools while newly emerged fry were i n shallow margins. Predation by smolts appeared to affect the lo-cation of the fry. Interspecific combinations were observed in the lab-oratory. Rainbow trout were most aggressive. The aggressive a c t i v i t i e s of spawning adults were similar to those of the juveniles but the actual repro-ductive movements were unique to the adults. Agonistic behavior appeared to be primitive i n lake trout with increasing specialization through dolly varden to brook trout. It was highly developed with specific variations in displays i n brook trout, cutthroat trout, rainbow trout and coho salmon. The other species within the genus Oncorhynchus exhibited a degeneration in r e s i -dential behavior. i i i TABLE OF CONTENTS Acknowledgem en ts Introduction 1 Sources and descriptions of specimens 6 Materials and methods 24 Adjustment of specimens to new tanks following handling 27 Aggregation i n a uniform environment 31 Distribution of individuals in relation to different environmental conditions 41 Response to a waterfall 42 Response to shadow vs. illumination 46 Response to alternatives in depth 51 Introduction of food 61 Comparison of undisturbed activity 62 Results of standard observations of behavior 66 Methods 66 Behavior of juvenile lake trout 71 Behavior of older lake trout 86 Dolly varden behavior 86 Eastern brook trout behavior 108 Rainbow trout behavior 128 Behavior of older rainbow trout 144 Cutthroat trout behavior 145 Coho salmon fry behavior 158 Coho smolt behavior 174 Coho grilse behavior 175 iv Chinook salmon fry behavior 175 Sockeye fry behavior 175 Sockeye emolt behavior 176 Sockeye grilse behavior 176 Chum salmon fry behavior 177 Pink salmon fry behavior 178 Comparisons 178 Prior residence and group t e r r i t o r i a l i t y 208 Prior residence 208 Group t e r r i t o r i a l i t y 214 Behavior pf translocated residential trout 217 Inhabitation of a home range 217 Relative abundance of juvenile coho and rainbows 221 Interspecific behavior 221 Lake trout and dolly varden 221 Lake trout and rainbow trout 224 Rainbow trout and brook trout 224 Rainbow trout and cutthroat trout 225 Rainbow trout and coho salmon 229 Coho salmon and brook trout 232 Conclusions on interspecific behavior 232 Aggressive behavior of spawning adults 232 Rainbow trout 234 Pacific salmon 237 Discussion 241 Aggregation 241 V Habitat selection 244 Activity' 249 Comfort movements 250 Response to danger 253 Ter r i t o r i a l i t y 255 Home range 262 Social organization 264 Interspecific behavior 267 Ontogeny of agonistic behavior 271 Phylogeny of residential behavior 275 Summary 279 Literature cited 287 v i LIST OF FIGURES Figure Page 1. Coho smolts which had been retained i n freshwater u n t i l Autumn. 18 2. A male coho which had died naturally-following spawning. 19 3. Sockeye smolts which had been retained i n freshwater u n t i l Autumn. 21 4. Chum fry i n freshwater i n summer 22 5. Adult male pink salmon. 23 6. Adult female pink salmon. 24 7. Tanks and viewing s l o t to conceal observer from f i s h . 26 8. The step tank i n which salmonids were ob-served i n r e l a t i o n to alternatives i n depth. 53 9. Generalised alarm posture of lake trout. 76 10. Resting posture of lake trout. 77 11. Lake trout gaping 78 12. Frontal display of attacking lake trout. 80 13. A lake trout examining earthworms which i t would not eat. 83 14. Front view of lake trout examining earth-worms. 83 15. Generalized alarm posture of do l l y varden. 95 16. Lake trout i n front and do l l y varden i n back. . Contrasting resting postures 96 v i i Figure Page 17. Dolly varden settling on resting lake trout 97 18. Frontal display of attacking dolly varden. 99 19. Dolly varden biting at substrate beneath another f i s h . 100 20. Biting movement of attacking dolly varden. 101 21. Attacking dolly varden nipping at retreating fi s h . 102 22. Fighting dolly varden ci r c l i n g each other 103 23. Fighting dolly varden. 103 24. Dolly varden coming close to one another . while feeding. 105 25. Dolly varden examining substrate where food was present. 106 26. Dominant brook trout swimming above subordi-nate of same species. 109 27. Brook trout swimming up and down the glass walls of their tank ("escape swimming"). I l l 28. Threat displays of brook trout. Lateral display in foreground. Frontal display in back. 119 29. Brook trout in foreground assumes high i n -tensity lateral display. 120 30. Forward progression of similarly directed, displaying brook trout 121 31.. Brook trout at l e f t defending i t s e l f by la t e r a l l y wagging i t s body. 122 v i i i Figure Page •32. Brook trout at l e f t making extreme un-dulations of i t s body in defense against attack. 123 33. Fighting brook trout slowly c i r c l i n g each other. 124 34. Mutually displaying brook trout. 125 35. Fighting brook trout i n display. 126 36. Heightened coloration of fighting rainbow trout. 128 37. Unusual retention of fighting color in dominant rainbow trout. 129 38. Rainbow trout frontal display at back, lateral display in front. 137 39. Rainbow trout dominant in lateral display at right. 138 40. Rainbow at l e f t defending i t s e l f by wagging i t s t a i l at i t retreats. . 139 41. Rainbow nipping usually did not contact the opponent. 140 42. Sometimes one rainbow actually contacted while nipping. 140 43. Dominant rainbows chased their subordinates relentlessly. 141 44. Rainbow trout with earthworm in mouth 142 45. A subordinate cutthroat at l e f t and dominant rainbow at right. 145 ix Figure Page 46. Generalized alarm posture of cutthroat trout. 151 47 Cutthroat trout completing gaping movement. 152 48. Cutthroat trout in foreground exhibits a frontal-type display i n lateral position. Its opponent shows alarm posture. 153 49. Cutthroat trout at right displaying. 154 50. Dorsal f i n down in cutthroat trout display. 154 51. Subordinate coho salmon. 158 52. Low intensity lateral display of coho salmon. 159 53. High intensity lateral display of coho on right as brook trout approaches. 168 54. Coho feeding on bottom. 171 55. Alarmed coho immobile over feeding area. 171 56. Immobile coho over feeding area. 172 57. Two male pink salmon moving upstream side to side in lateral display. 238 58. Male pink salmon nipping at another. 238 59. Gaping male pink salmon. 239 60. Paired male and female pink salmon over nest in the Vancouver Public Aquarium. 239 61. Female pink salmon digging the redd. 240 62. Female chum salmon digging redd i n stream while male waits nearby. 240 X LIST O F TABLES Table Page I Delayed mortality of trout following trans-port from hatchery to laboratory. 29 II Aggregating compared in four species in a 150 cm tank divided by lines into five divisions. 35 III Aggregating compared in four species in a 213 cm trough divided by lines into six divisions. 37 IV Aggregating compared in four species in a 427 cm trough divided by lines into six divisions. 40 V Number of rainbow trout in each division of a 150 cm tank with waterfall. 43 VI Positions of four small and one larger rainbow trout in relation to waterfall. No feeding. 45 VII Positions of four small and one larger rainbow parr in relation to waterfall. Individuals fed through waterfall. 47 VIII Distribution of ten rainbow fry in a washtub half of which was exposed to daylight, half in the shadow of a board. 49 IX Distribution of five rainbow parr in a 150 cm tank. Half of the tank was shaded, half illuminated. 50 xi Distribution of five cutthroat trout parr in a 150 cm tank. Half of the tank was shaded, half illuminated. Positions of five chum salmon fry in a tank divided into four depths. Positions of five chum salmon fry in a tank divided into four depths following the i n -troduction of a predatory fish (20 cm lake trout). Distribution of four rainbow trout parr in a step tank after adjustment to the tank. Distribution of the same four rainbow trout parr following the introduction of an i n -dividual 20 cm in length. Distribution of the same four rainbow trout parr following the introduction of a 20 cm lake trout. The number of unoccupied sections of a four-section tank Containing coho fry. Comparative activity based on the number of lines crossed by six fish i n a 427 cm trough divided by five equidistant lines. The estimated average distance traversed by each fish per minute in a 427 cm trough. SynopsiB of the behavior of the four lake trout in Group 1. x i i Table 1 Page XX Synopsis of the behavior of the four lake trout in Group 2. 74 XXI The location of immobile fish on the sub-strate or in midwater. 75 XXII Synopsis of the behavior of the four dolly varden in Group 1. 87 XXXIII Synopsis of the behavior of the four dolly varden in Group 2 88 XXIV Dolly varden "peck orders" based on eight observations of Group 1. 90 XXV Dolly varden "peck orders" based on eight observations of Group 2. 91 XXVI Aggressiveness among four dolly varden prior to starvation, during starvation and following 42 days of starvation. 92 XXVII The location of immobile dolly varden on the substrate or in midwater. 94 XXVIII Time required for i n i t i a t i o n of feeding and • nipping ; by .-dolly varden.! following the intro-duction of food. 107 XXIX Synopsis of the behavior of the four brook trout in Group 1. 112 XXX Synopsis, of the behavior of the four brook trout in Group 2. 113 XXXI Brook trout "peck orders" based on eight observations of Group 1. 114 x i i i Table XXXII XXXIII XXXIV XXXV XXXVI XXXVII XXXVIII XXXIX XL XLI XLII XLI 11 Brook trout "peck orders" based on eight observations of Group 2. The location of immobile brook trout on the substrate or in midwater. Time required for i n i t i a t i o n of feeding and nipping by brook trout following i n -troduction of food. Synopsis of the behavior of the four rain-bow trout in Group 1. Synopsis of the behavior of the four rain-bow trout in Group 2. . Rainbow trout "peck orders" based on eight observations of Group 1. Rainbow trout "peek orders" based on eight observations of Group 2. Time required for i n i t i a t i o n of feeding and nipping by rainbow trout following introduction of food. Synopsis of the behavior of the four cut-throat trout in Group 1. Synopsis of the behavior of the four cut-throat trout in.Group 2. Cutthroat trout "peck orders" based on eight observations,of Group 1. Cutthroat'trout "peck orders" based on eight observations of Group 2. Page 115 116 127 131 132 133 134 143 147 148 149 150 xiv Table Page XLIV Time required for i n i t i a t i o n of feeding and nipping by cutthroat trout following i n -troduction of food. 157 XLV Synopsis of the behavior of the four coho fry in.Group 1. 160 XLVI Synopsis of the behavior of the four coho fry in Group 2. 161 XLVII Coho salmon "peck orders" based on eight observations of Group 1. 162 XLVIII Coho salmon "peek orders" based on eight observations of Group 2. 163 XLIX The location of immobile coho salmon with relation to the bottom. 165 L Time required for i n i t i a t i o n of feeding and nipping by coho salmon following introduction of food. 173 LI The proportion of time devoted by each species to particular a c t i v i t i e s . 180 LII Comparison of nipping in salmonids. 182 LIII Number of nips, threats, gapes, snaps and chafes recorded in a l l standard obser-vations. 188 LIV The frequency of gaping and snapping in lake trout. 190 LV Number of gapes in relation to social i. position in hierarchy 192 XV Table Page LVI Number of nipping permutations observed before and after feeding in a l l standard observations. 194 LYII Effect of sudden flood-light illumination on nipping among ten juvenile brook trout. 196 LVIII Number of nips recorded for dominants as compared with number of nips recorded for subordinates in a l l standard observations. 197 LIX Number of nips per fi s h per hour computed from previous table. . 198 LX Number of times dominant fish nipped fish of lower ranks in a l l standard observations. 200 LXI Comparison of agonistic actions. 204 LXII The number of times a newly introduced coho i s nipped by the dominant as compared with the other subordinates. 210 LXIII The number of times a newly introduced coho i s nipped by the dominant as compared with other subordinates. 213 LXIV Distribution of nipping between a resident group of rainbows and a group of four rain-bows introduced one month later. 215 LXV Comparative abundance of juvenile coho salmon and rainbow trout in quiet waters of Weaver Creek. 222 xvi Table LXVT Relative abundance of juvenile coho and rainbows in r i f f l e s i n four sweeps of a seine. LXVII Nipping between rainbow and brook trout in a ten gallon tank. LXVIII Nipping relations among four rainbow trout (Group 1) and four cutthroat trout (Group 1) in a 150 cm tank. LXIX Nipping relations among four rainbow trout (Group 2) and four cutthroat trout(Group 3) in a 150 cm tank. LXX Nipping relations among five juvenile rainbow trout and five juvenile coho salmon. LXXI Nipping relations among five juvenile coho salmon and five juvenile brook trout. LXXII Principal behavioral differences affecting the formation of residence. x v i i ACKNOWLEDGEMENTS I am indebted to Dr. W. S. Hoar for advice and intellectual stimulation during this study. The Fish and Game Branch of the Provincial Department of Rec-reation and Conservation under i t s Director, Mr. Frank Butler, and former Chief Fisheries Biologist, Dr. Peter Larkin, provided financial assistance throughout two summers. The Fish and Game Branch also provided many hatchery trout for study. In his former capacity as Research Biologist of the Fish and Game Branch, Dr. G. C Lindsey made i t possible for me to use his f i e l d f a c i l -i t i e s at Loon Lake. Dr. Paul Needham similarly allowed the use of the University of California Sagehen Creek Project near Truckee, California. Many people assisted i n the f i e l d and hatchery studies. Among these were George Dibblee, Harold Harvey, Donald McAllister, S. B. Smith and J. Terpenning. Assistance in the preparation of this manuscript has been given by Drs. W. S. Hoar, Peter Larkin and Miklos Udvardy. The help of a l l of these persons i s gratefully acknowledged. -1-INTRODUOTION The comparative method in the study of animal be-havior has been described by Lorenz (1950) who states that i t i s based on the particulate nature of genetically determined innate behavior patterns* It has been suc-cessfully employed by zoologists to study phylogenetic aspects of behavior among species of different animal groups, particularly arthropods, birds and fishes. Ex-amples of these studies are those on ducks by Helnroth (1910) and Lorenz (1941), gulls by Tinbergen (1953), oi c h l i d fishes (Baerends and Baerends-Van Roon, 1950), centrarchid fishes (Breder, 1936), xiphophorin fishes (Clark,Aronson and Gordon, 1954) and percid fishes (Winn, 1958). Some of the most detailed of these phylogenetic studies have been concerned with spiders and insects (Crane, 1949, 1953). In investigating the behavior of termites, Emerson (1938) and Schmidt (1955) have shown that nest-building i s probably entirely Innate and that a phylogeny can be worked out on the basis of the nests of different species. In a recent paper, Emerson (1956) reveals that some species of termites can only be dis-tinguished from others on the basis of their behavior. He refers to these as "ethospecies." The comparative approach i s predicated on the presence of innate behavior patterns. The innateness of a certain proportion of an animal's behavior has long been - 2 -recognized by zoologists and the evolution of behavior has been a subject of interest since Darwin's time. During the early Darwinian period G. J. Romanes, J* Fabre, K. Groos and C. 0. Whitman were outstanding students of behavior. Ecologists in the decades just before and after 1900, according to Allee (1946), introduced a naturalistic emphasis and asked the following questions: 1) Do animals have definite reactions that enable them to find habitat niches that match their ecological tolerances? 2) Are animal responses adaptive? 3) Is e given behavior pattern innate or conditioned (learned)? These questions are s t i l l being asked and are pertinent to the problems in this paper. Psychologists, i n pursuit of their studies of learning and modifiability of actions, have sometimes opposed the ooncept of instinctive behavior (Lehrman, 1953) and frequently do not consider i t at a l l as a factor i n -fluencing the movements of their experimental animals. In recent years, however, as Lorenz (1950, 1955), Tinbergen (1942, 1951, 1953), Baerende (1955, 1957) and their col-legues have emerged as leaders i n the study of animal behavior, the importance of instinct has become more widely recognized. Thorpe (1948, 1951, 1956), through his efforts to reconcile the conoepts of instinctive and learned behavior, has contributed to this wide acceptance. Hoar '8 studies of salmon (1958b) have furthered acceptance 3-of the concept of innate behavior in North America. It i e often d i f f i c u l t and not always possible to dif-ferentiate between learned and unlearned elements i n the behavior of an animal. For this reason Hinde and Tin-berg en (1958) have advised that the investigator assume a broad approach i n his studies by considering causation and function of behavior as well as analysis of partic-ulate elements. It ie with this broad approach in mind that this study of the comparative residential behavior of juvenile salmonids has been undertaken. The many salmonids i n British Columbia are partic-ularly suitable for comparative study. Their l i f e his-tories are complex and varied and are distinguished by rapid changes i n form and behavior which can be related to their remarkable migrations and to reproduction. Distinct differences, presumably of a genetic nature, exist in the pattern and timing of their behavioral episodes. Some species l i v e their entire lives i n fresh-water, others may or may not migrate to the sea, while s t i l l others are obligatory early migrants which die i f retained in freshwater (Hoar, 1958b). Each episode in the l i f e history of a species may have particular behavior patterns associated with i t whioh adapt the animal to i t s environment or to the problem of moving from one environment to another. Thus a species may exhibit different behavior patterns during dispersion following emergence from i t s natal gravel, during juvenile residence i n a stream, during downstream migration, during i t s oceanic l i f e , during i t s upstream migration and during i t s spawning period. The behavior of juvenile Pacific salmon has been ex-tensively investigated by Hoar (1951, 1953, 1956, 1958a, 1958b) and associates (Hoar, MacKinnon and Redlioh, 1952; Keenleyside and Hoar, 1954; MacKinnon and Hoar, 1953). These studies have been mainly directed toward the eluci-dation of internal and external factors associated with downstream migration in an attempt to discover i t s under-lying causes. The point of view of the present study concerns the localization of young salmonids in particular areas and the social behavior which results among the individuals in a shared environment. Both residential and non-residential specimens were observed in an attempt to discover differ-ences which might be significant i n causing their varia-tions in l i f e history. Hoar (1953) differentiates two main types of juv-enile salmonids; the schooling ones which undergo a down-stream migration soon after hatching and the t e r r i t o r i a l ones that remain for a period in a stream. Early smolt transformation, increased nocturnal activity and scho-oling are associated with those species that move directly to the sea. The schooling species are chum salmon (0ncorhynohu8 keta), pink salmon (0. gorbuscha) -5-and sockeye salmon (0. nerka). Delayed smolt transfor-mation (or none at a l l ) , daylight activity and orientation to a particular place characterize the t e r r i t o r i a l species. These are coho salmon (0. kisutch), Atlantic salmon (Salmo  salar), rainbow trout (S. gairdnerl) and brown trout (•£• trutta). Brook trout ( Salvelinus fontinalis) belong with the t e r r i t o r i a l species (Newman, 1956) as do also arctic char (Salvelinus alpinus. Fabricius, 1953). Even t e r r i t o r i a l species tend to form loose aggre-gations in nature. Observations i n a stream (Newman, 1956) indicate that to a certain extent trout l i v e i n groups that are restricted to a home range rather than simply to territories. The problem thus arises whether the t e r r i t o r i a l species exhibiting aggressive behavior are selecting a common environment or whether they are drawn together by^aggregating tendencies similar to those i n schooling species but of lower motivation. The particulate actions or "endogenous movements" (Lorenz, 1950) which are exhibited in social relations have not been oompiled and compared for many species of trout and salmon. The behavior of young rainbow trout i s described by Stringer and Hoar (1955)), that of young Pacific salmon by Hoar (1958b), that of Arctio char by Fabricius (1953) and Fabricius and Gustafson (1954), that of rainbow and brook trout by Newman (1956), that of Atlantic salmon by Keenleyside (1957) and that of -6-Atlantic Balmon and brown trout by Kalleberg (1958). l o s t of these works do not describe the particulate actions i n great detail. Dominance relations have been studied among rainbow trout (Stringer and Hoar, 1955) and i n brook and rainbow trout (Newman, 1956) but again comparative information i s lacking for the other species. The present work i s concerned with differences and similarities i n aggregation, habitat selection, rates of undisturbed activity, particulate endogenous movements, aggressiveness, interspecific behavior and other aspects of behavior which might reveal themselves i n the course of observation. Its broad scope and the d i f f i c u l t y of obtaining species at the right times prevented each experiment from including a l l salmonids. In many cases i t was not possible to pursue the problems intensively enough to resolve them. It i s f e l t , however, that this broad, exploratory approach has been valuable not only for the problems i t solved but for those i t suggested. SOURCES AND DESCRIPTIONS OF FISHES USED IN STUDY The spec!68 most intensively studied were lake trout (Salvelinus namaycush), dolly varden (jg. malma), eastern brook trout (S. fontinalis), coastal cutthroat trout (Salmo olarkl c l a r k i ) , rainbow trout (s. gairdnerl) and coho salmon (Oncorhvnchue kisutch). The other four species -7- - " ':: of Pacific salmon were a l l observed in various parts of the study. Some specimens were collected from streams while others were obtained from fish hatcheries. The r e l i a b i l i t y of using hatchery-raised specimens as material for study might be questioned on the basis that such a different environment might affect behavior. It would have been desirable to have used only wild f i s h , but these were not always available. Even when they were available i t was not always possible to obtain a sufficient number in a uniformly small size. Differences between hatchery and wild fish were not specifically assessed, but i t was clear that the major d i f -ferences between species were not attributable to this d i f -ference in origin. For example, a l l of the lake trout were raised i n a hatchery, yet these were quite different from hatchery-raised brook or rainbow trout. It i s possible, however, that development in a hatchery may affect some as-pects of behavior and this should be investigated at some time in the future. Lake trout, Salvelinus namaycush (Walbaum) These were obtained in December, 1954, from the Sumraerland Hatchery where they were hatched in the winter of 1953. Sample sizes in Sept., 1955, were as follows: Weight Total Length 48.4 g 195 mm 34.9 170 64.3 202 30.5 168 They were observed i n December, 1954 and February, June, July, August, September and December, 1955. A number of them were placed on exhibit in the Vancouver Public Aquarium where they were observed casually through 1959. During the year that they were systematically observed they did not undergo much change in appearance. They had relatively large heads, long snouts, big mouths and large eyes (Fig. 10). Their slender, gray bodies were covered with tan spots which extended on to the dorsal and caudal fin s . A l l the other fins were transparent and colorless. Dolly varden, Salvelinus malma (Walbaum) A number of small dolly varden were seined in the Su— mallo River along the Hope-Princeton Highway i n September, 1955. Only the email ones were brought back to the Uni-versity. Of these there appeared to be two size classes representing two different ages. Some of the larger ones were gravid females. No fry were obtained presumably because the last spawning period occured one year before in the Au-tumn. Sample sizes in October, 1955, were as follows: Weight Total Length 20.8 128 mm 35.1 160 20.1 130 18.2 125 Juvenile dolly varden had smaller heads, shorter snouts, smaller mouths, smaller eyes and slightly fuller bodies than had the young lake trout. The underyearlings (Fig. 19) were light tan in color. Along each side was a row of 7-11 large oval parr marks surmounted by a less distinct row of smaller parr marks. The median ridge possessed another row. Small l i g h t , evenly-spaced spots were beginning to sppear along the sides of the underyearlings. These spots did not con-trast much with the general background color of the fish and . were not conspicuous. The dorsal, caudal and pectoral fins were transparent and without pattern. The ventral margin of the caudal and leading edge of the pectorals were faintly orange. The pelvic and anal fins were most colorful but, like the other f i n s , were transparent and without melanic pattern. Their leading edges were bright, opaque white on the distal half and bright orange proximally and behind the white border. The orange color faded into the pale, transparent remaining portions of the fins. The older and larger dolly varden (Fig. 16) were col-ored differently than the underyearlings. The parr marks were more obscure and their bodies were darker. The small light colored spots which were just appearing on the smaller fi s h were brightly contrasted against the dorsal and lateral body surfaces. They extended over the top of the head and became obscure on the sides of the head. These spots were smaller than the corresponding ones on the lake trout. The dolly varden of British Columbia i s l i t t l e different from the arctic char of Europe (Dymond, 1932) and was for--10-merly considered as a subspecies but now is recognized a6 a separate species (Carl, Clemens and Lindsey, 1959). Eastern brook trout, Salvelinus fontinalis(Mitchill) This species has i t s natural distribution to the east of the Rocky Mountains but has been introduced i n some waters of British Columbia. Eggs were obtained from the B. C. Game Commission^ Summerland Hatchery in late 1954. These eggs hatched in the winter of 1954-1955. The young fi s h were observed in the winter of 1955-1956. Sample sizes of these fish i n December, 1955, were as follows: Weight Total Length 3.6 g 78 mm 4.5 83 2.4 69 3.0 73 Their markings (Fig. 29) were more ornate and colorful than those of dolly varden and lake trout. They were ob-served for only several months during which no great change in appearance was noted. Body shape was similar to dolly varden although the forward part of the head appeared some-what shorter. The 7-11 parr marks were broader and more i r -regular in shape than those of either dolly varden or lake trout and the light areas between them narrower than on the other species. The dorsal markings were broken up into smal-ler units so that secondary rows of parr marks were not evi-dent. The background color was tan-pink darkening dorsally to brown. There were very few light spots. Some of these -11-were red with blue borders as in adult brook trout. The anal and pelvic fins were long and colorful. Their leading edges were white with a heavy black line behind. The remainder of these fins was reddish. The lower lobe of the caudal had a color pattern similar to, but somewhat fainter than, that of the anal f i n . The pectoral fins and upper caudal lobes were colorless and transparent. The dorsal f i n was transparent with a white edge. It had dense black marks arranged in patterns which varied in different individuals. Rainbow trout, Salmo gairdneri Richardson A l l rainbow trout used in this study were of the var-iety known as the "Kamloops" trout originally defined by David Starr Jordan as a subspecies of the steelhead trout when that fish was considered a species separate from the rainbow trout. The current point of view (Carl, Clemens and Lindsey, 1959) i s that the steelhead, rainbow and Kamloops trout belong to a variable complex composed of several eco-types, and the differences i n size between the individuals of one population and those of another are caused by environ-mental rather than genetic factors. Genetic differences be-tween populations have been indicated by differences in mer-i s t i c characters (Neave, 1944). These may represent normal raciation resulting from isolation rather than caused of the size and migratory differences among the three forms of trout. Specimens were obtained from the B. C. Game Commission's Lloyd Creek Hatchery at Cultus Lake in the autumn of 1953 -12-and observed as two year olds in 1955. Fish of the year were obtained from the hatchery in October and December, 1954, and observed through the autumn, winter and following spring. Newly hatched fry were obtained in July, 1955, and observed at the Loon Lake Hatchery. Fish hatched i n 1955 were observed through 1955 and early 1956. Fry which had recently absorbed their yolk and risen from the bottom gravel were 25-30 mm in length in July. In May, 1955, fish hatched in 1954 were as follows: Weight Total Length 4.1 g 78 mm 9.7 101 5.0 85 4.5 78 Underyearling rainbows were so similar to underyearling cutthroats that they were often d i f f i c u l t to distinguish. The best way to immediately separate them was by the more conspicuous white border on the rainbow dorsal f i n (Fig. 36). Other differences included less speckling in the rainbow, parr marks which were narrower and longer in a vertical d i -mension, differently arranged secondary parr marks and a continuous black border around the adipose f i n . The hatchery f i s h were not brightly colored and no red was apparent on their fins or ventral surface. Fish caught in Weaver Creek (the outlet of Weaver Lake which flows into the Harrison River) had red pelvic and anal fins. -13-During their eecond year, rainbows tended to lose their parr marks. They did not develop the intense spotting characteristic of coastal cutthroat of the same age, nor did they develop a silvery smolt. For these reasons, although the parr marks lessened in intensity, they did not wane as much as i n cutthroat trout or Atlantic salmon. Young Kamloops trout in some interior lakes develop a very silvery smolt which may obscure their parr marks at an earlier age. Those i n Loon Lake are a good example. As the rainbows grew, their fins became proportion-ately smaller and lost their white borders, thus becoming less distinctive. Field observations of translocated rainbows were made at the Sagehen Creek experimental stream of the University of California near Truckee, California, in the summer of 1954. The spawning of adult rainbow trout was observed at the outlet of Loon Lake i n May, 1955. These fi s h were about 25 to 35 cm in length. Post-reproductive adults of the same size were ob-served in a hatchery trough in early August, 1955, to compare their aggregation and activity with that of ju-veniles. Casual observations of larger rainbows were made in the Vancouver Public Aquarium. Coastal cutthroat trout, Salmo clarki clarki Richardson Coastal cutthroat trout, which hatched i n the spring • -14-of 1954 In the B. 0. Game Commission's Lloyd Creek Hatchery at CultuB Lake, were obtained i n October and December, 1954 and observed through the winter and into the spring of 1955. The sizes of four individuals i n May, 1955, were as follows: Weight Total Length 6.0 g 90 mm 5.5 92 3.9 83 3.8 77 Cutthroat trout fry hatched in the spring of 1955 were obtained from the hatchery and observed in early August of that year. These fish were 35-40 mm in length. Juvenile coastal cutthroat trout were collected in a seine in the Serpentine River i n the autumn of 1955 and observed that winter. These fish were more brightly colored than those hatched and reared i n captivity, having more red on their pelvic and anal fins and on their throats. The throat marks of hatchery f i s h were often pale and yellowish in color. Hatchery-reared underyearlings were slender l i t t l e trout with a body color grading from a brownish tan above to white below. Their main parr marks were oval, some-what smaller than those of dolly varden, more regular i n shape than those of brook trout and more numerous than those of rainbows. The spaces between the parr marks -15-were broader than those i n brook trout. The secondary parr marks were small and regular but not as close to-gether as in brook trout. Black spots (rather than light colored ones) speckled the sides and dorsal surface. These spots were also distributed on the dorsal, adipose and caudal f i n s . Several spots were usually present on the adipose fins but there were none on anal, pelvic or pectoral fins. The dorsal f i n was tipped by a small amount of white or yellow. Cutthroat trout begin to lose their parr marks after they are one year old but the loss i s not a rapid one brought about by a silvery smolt. In specimens nearing two years of age the parr marks are obscured by dense speckling. Coho salmon, Oncorhynchus kisutch (Walbaum) Young coho salmon of various ages were observed both in the laboratory and in the f i e l d . Most of the lab-oratory f i s h were collected from streams but some were hatched in the laboratory from eggs stripped from wild f i s h . Smolts hatched in the winter of 1954-1955 were ob-served i n February and June of 1955 to determine degree of aggregation. Fry hatched in the laboratory in 1954-1955 were studied i n an outdoor trough at the Loon Lake Trout Hatchery i n July, 1955. Fry obtained in the Salmon River in September, 1955, were observed in October, November and December of that year and January of 1956. Sample sizes of fry in October were as follows: Weight Total Length 2.3 g 67 mm 1.5 61 2.6 68 3.4 77 Juvenile coho were observed casually during the summers of 1955 and 1956 in streams about Vancouver. Systematic observations were made of fish in Weaver Creek during the autumn and winter of 1957 and spring of 1958. Casual observations of one, two and three year old fish and of spawning adults were made i n the Vancouver Public Aquarium. Juvenile ooho varied i n color according to age, loca l i t y of capture and other factors. During their f i r s t summer they were brightest. Those in the wild were more colorful than those hatched and reared i n cap-t i v i t y . Even wild smelts caught i n the spring at Weaver Creek had more color than laboratory f i s h . Coho fry removed from Weaver Creek i n September and observed in air were dark brown along the dorsal surface, lighter brown along the sides and very light colored below with a slight yellowish-orange t i n t . Each side had 8-10 dark, narrow parr marks which extended well below the lat e r a l line. Between these primary marks were smaller ones located high on the sides. The fins were orange-red, pelvic fins being brightest. The lead-ing rays of the dorsal and anal fins were long and white along their forward edge. The white on the dorsal f i n was restricted to the t i p . There were no black spots on the fins as on fins of rainbow and cutthroat trout. A black line separated the white edge of the fine from the red part. The appearance of l i v i n g wild fry which had been maintained in the laboratory for several months was de-scribed in December. These fish lacked the orange mark-ings and yellowish-orange tint observed previously but varied considerably in lightness or darkness of body according to social position i n their group. Their dor-sal surfaces were freckled with small, round black spots. In the following spring the coho yearlings i n the laboratory oontinued to fade in color. The spotting of the dorsal surface increased and the intensity of the parr marks decreased. The white, black and red markings on the dorsal and anal fins disappeared and the leading rays of these fins ceased being longer than the other rays. Coho smolts observed in May at Weaver Creek re-tained some of the pink coloration of the fry but were considerably faded. While the fins retained some of the -18-earlier ooloration, the relative elongation of the leading rays was no longer apparent. Smolts retained in the laboratory until the following autumn are pictured in Fig. 1. These fish were highly speckled on their dorsal surfaces and quite silvery along Fig. 1 - Coho smolts which had been retained in freshwater until Autumn. their sides. The tips of their caudal and dorsal fins had darkened somewhat. Coho yearlings maintained i n seawater at the Aquarium had very dark tips to their finB. Although most of them were quite silvery, their parr marks remained very dark. -19-One coho retained in seawater in the Aquarium until i t was three years old grew to a length of 30-35 cm. Its dorsal and caudal tips were quite black, i t s body silvery but i t s parr marks s t i l l perceptible. This fish was considerably stunted. Wild coho of the same age are very silvery and have no parr marks. Adult wild coho were obtained in July, 1956, at the fi s h trap in the Capilano River by permission of the Department of Fisheries of Canada. They survived i n the Aquarium until November of that year but did not spawn. Fig. 2 shows a spawning male coho which had died along the bank of Weaver Creek. 4 Fig. 2 - A male coho which had died naturally following spawning. -20-Ghinook salmon, 0. tshawytsoha (Walbaum) This species was not systematically observed but fry hatched in the laboratory were watched in the summer of 1955 in glass tanks. These fish closely resembled coho fry in deepness of body and distribution of parr marks. They were not as colorful and lacked the pro-longated dorsal and anal f i n rays* Spawning adult springs were observed in the Har-rison River. Sockeye salmon, 0. nerka Groups of sockeye fry were observed in July, 1957. These fry had hatched in the previous winter. Their brownish colored bodies had well developed parr marks. They were more slender than coho or spring fry. Sockeye smolts (Fig. 3) were observed in September and October of 1955. These fish had been captured at the outlet of Oultus Lake during their springtime migration to the sea and held throughout the summer in freshwater. They were slender, silvery f i s h , 10-13 cm. i n length, with narrow parr marks which were beginning to disappear. Their fins were transparent and colorless. Stunted sockeye salmon held in seawater i n the Vancouver Public Aquarium were observed but not system-at i c a l l y studied throughout 1957 and 1958. These two to three year old fis h were 16-20 cm long. They were Fig. 3 - Sockeye smolts which had been retained in freshwater until Autumn. somewhat deeper bodied than the smolts but otherwise simi-lar i n appearance. Spawning sockeye salmon were observed at Weaver Creek, Harrison River and in captivity i n the Aquarium. Chum salmon, 0. keta (Walbaum) Chum fry were hatched i n the University laboratory during the winter of 1954-55 and studied at the Loon Lake Hatchery in July, 1955. At that time their activity and aggregating tendency was compared with that of other species. Others were hatched in the winter of 1956 and 1957 -22-and observed in small groups in glass tanks. Chum fry (Fig. 4) are slender, silvery l i t t l e f i s h with short parr marks just reaching or barely crossing Fig. 4 - Chum fry in freshwater i n summer the lateral line. Their dorsal surfaces may be green or brown and their transparent fins have dusky tips. They are more silvery than any of the previous fry and when they f i r s t emerge from the gravel their smolt i s f u l l y developed. They resemble diminutive sockeye smolts but have relatively shorter heads and more dorsally located parr marks. -23-Spawning chum salmon were obssrved in the outlet of Cultus Lake in the autumn of 1956. Pink salmon, 0. gorbuscha (Walbaum) Pink salmon fry were hatched i n the Aquarium in the winter of 1956-57 and observed in the spring of 1957. These fish lack parr marks and are intensely silvery i n color. They are somewhat smaller than chum fry of the same age but similar i n shape. Adult pink salmon were observed in the outlet of Cultus Lake, in Jones Creek and i n the Aquarium. These are illustrated i n Figs. 5 and 6. Fig. 5 - Adult male pink salmon. -24-Fig. 6 - Adult female pink salmon. MATERIALS AND METHODS The approach to this study has been mainly obser-vational rather than experimental and the intention has been to describe natural, unstimulated behavior of each species as closely as possible. Most of the work was done in the fisheries laboratory of the University of British Columbia but some took place i n B. C. Fish and Game Branch trout hatcheries and some in the f i e l d . The fins of a l l specimens observed i n small groups in glass tanks were differentially clipped to provide -35-positive identification. The parts removed were the tipper caudal lobe, lower caudal lobe, parts of both caudal lobes and a piece of the anal f i n . The dorsal f i n was never clipped because of i t s greater s i g n i f i -cance as a sign stimulus. The presence of an observer was found to easily change, alter or interrupt the normal acti v i t i e s of con-fined salmonid fi s h . They were alert, sensitive to movement and vibration, rapid to respond and hard to approach, they responded to slight stimuli by becoming motionless and remaining this way for long periods of time. Frequently the observer watched them for 15 minutes or more after stationing himself i n front of their tank before they resumed what appeared to be un-disturbed behavior. It was impossible to make satis-factory observations in a room frequently entered by other people and a l l movement and noise were carefully avoided. The indoor observations were made in darkened rooms where the observer watched f i s h i n illuminated tanks through s l i t s i n screens or through special viewers (Fig. 7). Uniform illumination was maintained by incandescent lights above the tanks which were covered with frosted glass. Light intensity varied from 30 to 50 foot candles. Water circulation was accomplished by permitting a tri c k l e of water to enter at one end of each tank and to -26-F i g . 7 - Tanks and viewing s l o t to conceal observer from f i s h . be siphoned out at the other. Water temperature which varied between 8 and 12°C was determined primarily by the temperature of the incoming flow. A l l water used was dechlorinated. I t was found necessary to allow time for experi-mental f i s h to recover from being transported before being studied. Hew specimens rested at least a week i n troughs i n the University hatchery before they were transferred to experimental tanks. Once i n these tanks they were allowed to settle for at least 34 hours before being viewed for quantitative information. The period necessary for adjustment varied i n different species and also among individuals of the same species. Specific descriptions of technique are described in the various sections of this paper. ADJUSTMENT TO A NEW TiNK FOLLOWING HANDLING The adjustment of a fish to a new tank had both behavioral and physiological aspects. It had f i r s t to recover physiologically from the effects of handling. Graham (1949) showed that trout (Salvelinus fontinalis) consume as much Og following handling as they do after exercise and that this heightened metabolism continues for hours. Another effect was the change i n buoyancy when a fi s h was transferred to water of a different temp-erature. This caused i t either to sink to the bottom or to float to the surface. As a rule, the more severe the handling of fi s h the greater the time required for ad-justment of a physiological nature. In cases of rough handling, mortalities frequently occurred even though the fish were not actually bruised. On one occasion these mortalities were carefully recorded when rainbow and cutthroat trout were obtained at Smith Falls Hatchery, Cultus Lake, and transported to the University of British Columbia, a distance of about 70 -28 miles. Equal weights of f i s h were placed i n separate fry cans and the weights were within those considered safe for transporting purposes by the hatchery super-visor. Individuals began dying on the third day (Table I) following transport and continued dying for seven days thus indicating a lethal, physiological response to handling. Since some individuals did not die unti l ten days after transport i t can be assumed that some of those which survived took ten or more days to recover and achieve physiological adjustment within their new en-vironment. An interesting point was that mortality was higher among cutthroat trout than among rainbows i n d i -cating a species difference i n rate of adjustment. These observations suggest that the physiological effect of handling persists for a long time and, i n those fish which survive, must be a significant factor i n the pre-vention of early adjustment and normal behavior i n the new tank. Sometimes individuals never adjusted behaviorally to their new observation tank even though they had been in a University hatchery trough for a long period of time. These unadjusted fish often died after transfer to a new tank. Lack of adjustment was indicated by failure to eat, over-reaction to alarm stimuli, failure to relate socially to other f i s h , absence of aggressive behavior and frequent escape movements. In general, chars (species of the genus -29-Table I Delayed mortality of trout following transport from hatchery to laboratory. No. of fish Survived Died in group Number Percent Number Percent Rainbow Anaes-Trout thetized 100 65 65 35 35 thetized 88 68 77 20 23 Cutthroat Anaee-Trout thetized 99 39 38 6 0 61 Unanaes-thetized 164 73 45 91 55 -30-Salvelinus) adjusted most readily while outthroat trout ( Salmo clarki) adjusted most slowly. Small f i s h adjusted more rapidly than larger ones. Lack of physiological adjustment was sometimes in d i -cated by other signs such as improper buoyancy, rapid res-piratory movements, frequent snapping of jaws and blanched color. Occasionally fish that had recently been handled would show aggressive behavior despite showing signs of stress. One outthroat was observed to nip and threaten another shortly before i t died. This was unusual, however, because those f i s h which showed signs of physiological stress were ordinarily without aggressive behavior. The usual sequence i n behavior of newly introduced salmonids was f i r s t a blanching and a cessation of movement accompanied by settling to the bottom with the fins erect. This persisted for minutes or hours and f i n a l l y was followed by "escape" swimming i n which a l l f i s h swam persistently back and forth and up and down in the corners. Frequently they swam up and down the glass at one location for hours at a time. Finally they responded aggressively and fought as has previously been described (Newman, 1956}. Even after the f i r s t appearance of aggressive behavior, normal residential behavior did not necessarily develop. Sometimes the smaller fis h became aggressive before more powerful ones did and a temporary hierarchy appeared in which a small f i s h nipped a larger one which i n turn per--31-sistently showed escape behavior. This temporary hierarchy would continue for several days before the large fish be-came aggressively motivated and attacked the small one. Frequently individual fi s h showed the absence of action patterns characteristic to their species for long periods of time following introduction into a tank. This inhibition was particularly common in cutthroat trout. After f i s h adjusted physiologically and behaviorally to their new environment they had to adjust socially before relatively stable residential behavior was seen. The ag-gressively motivated f i s h attacked each other and estab-lished a pattern of activity with relation to each other which became persistent within the particular spatial con-ditions. At this juncture they were truly residential. Such a state developed within a day or two or sometimes re-quired a week or longer. Probably, the more complex the environment i s , the longer i s the time required for estab-lishing s t a b i l i t y . Within the simple confines of a small rectangular tank stable and stereotyped social orders may develop more quickly than in nature. AGGREGATION IN A UNIFORM ENVIRONMENT Three experiments were performed to attempt to measure the innate tendency of the various species to ag-gregate in a uniform environment. The purpose was to de-termine whether individuals of a species automatically -32-selected the company of other individuals and to what ex-tent this varied from species to species. Several problems made this d i f f i c u l t to determine. One problem was the timing of the observations in relation to handling of the f i s h . I t was hoped that observations could be made of the fish after they recovered from the disturbance of handling but prior to the development of any fixed habits in rela-tion to the new tank or to one another. It was necessary that they not be fed in the experi-mental tank so as to prevent their assembling at a feeding location at the appearance of the observer. To prevent starvation from becoming a factor the observations had to be carried out rapidly. The main problem was to f i x conditions in such a.way that distribution of the fish would be a function of avoid-ance or attraction of individuals and not a common response to the physical environment. Laboratory experiments. Two experiments were undertaken i n the laboratory, one in February and the other in late May and early June. The f i r s t involved the use of a shallow, narrow glass tank having an inside length of 150 cm. This tank was divided by lines into five sections. Thus the position of a fi s h could be recorded as being in a numbered section defined by these lines. Shadows were eliminated by placing incandescent bulbs -33-so that they illuminated the whole surface. Over the top of the tank was placed frosted glass to diffuse the ligh t . Intensity was about 50 foot candles at the center and 30 foot candles at the ends. The flow of water into the tank was reduced to a tri c k l e and the temperature remained at 12°C. Species used were lake trout, rainbow trout, cutthroat trout and coho salmon. The rainbow and cutthroat trout were hatched the previous spring and were in the "parr" stage. The lake trout were slightly over a year old and were more advanced i n development than the previous species. The coho salmon likewise were slightly over a year old. They were smolts with pale color, though possibly pre-migratory. Five fish were observed at a time from a po-sition behind a screen at the side of the tank. They were placed i n the tank on the day before observations began. There were ten periods of observation for each species. During each period the positions of a l l the individuals in the group were recorded on ten consecutive minutes. The criterion of aggregation was the number of sec-tions not occupied. Since the more aggregated the in d i -viduals were, the less area they covered, the number of un-occupied sections gave a direct measure of aggregation in each case. Expressed in percentage of sections occupied, the greater the percentage, the more dispersed were the i n -dividuals and the less they were aggregated. Since there -34-were the same number of fish as there were sections, 100 percent occupation of the sections would indicate one fish per section. If a l l fish were in one section over a ten minute period this would be indicated by a minimum of 20 percent occupation. Table II gives the results of this f i r s t experiment. Lake trout showed the highest percent of section oocupation (63$) and therefore the greatest dispersion. The other three showed a slightly lower percentage of section oc-cupation, almost identical in each case (56%). Behavior of the fish in the four groups was quite different. The lake trout showed no nipping, schooling or aggregating. Typical behavior was a slow swimming back and forth independent of the other individuals. One rainbow trout was very aggressive and chased the other members of i t s group much of the time. This aggressive behavior often caused the fish whioh were attacked to aggregate at one end of the tank. The cutthroat trout remained motionless and only occasionally nipped one another. Coho salmon were not observed to nip each other. They were inactive and oc-casionally aggregated. A second experiment was performed in the laboratory i n late May and early June. Six fish were used per group and observed in a metal trough 213 cm long divided by lines into six equal sections. Observations were made from be-hind a screen looking down on to the surface of the trough -35-Table II Aggregating compared in four species in a 150 cm tank divided by lines into 5 divisions. Five fish per observation. The numbers represent the number of empty divisions in ten consecutive, one-minute tabulations. The higher the number, the greater the degree of aggregation. Lake Trout Rainbow Cutthroat Coho Smolt Feb. Parr Feb. Parr Feb. Feb. 33 23 34 31 13 34 19 35 31 36 19 31 17 37 30 37 20 33 24 20 17 18 17 21 24 20 27 19 16 23 23 21 16 19 23 22 18 18 24 35 Total 184 221 330 322 Average 18.4 22.1 22.0 22.2 Total Sections Available 500 500 500 500 ^Unoccupied 37 44 44 44 ^Occupied 63 56 56 56 -36-from one end. As before, low temperatures (ll-12°0) were maintained by trickling water through the system. Glass was placed over the trough to prevent the fish from jumping out. Light was provided by a flourescent ceiling fixture centered to minimize shadows. Intensity varied because of outside light coming i n through windows but direct sunlight was screened from the tank. The specimens were taken from the same stocks as used i n February. The coho by this time were more ad-vanced i n their smolt but the other species were much the same as before. Total dispersion would be indicated by a l l of the sections being occupied but since there were six fish and six sections, the minimum number of sections occupied would be recorded as 16% rather than 20% as with five sections. Table III gives the result of this experiment. Lake, rainbow and cutthroat trout were relatively dispersed (they oocupied 61-64% of available sections) while coho salmon smolts aggregated much more and restricted themselves to only 37% of the sections. As i n the f i r s t experiment the actual a c t i v i t i e s of the f i s h i n each group were different from each other. Lake trout swam Blowly and independently back and forth, oc-caisionally resting on the bottom. Several of the rainbow trout nipped and chased each other while the other three aggregated quietly. Cutthroat trout occasionally threatened -37-Table III Aggregating compared i n four species in a 213 cm trough divided by lines into 6 divisions. Six fish per observation. The numbers represent the number of empty divisions in ten consecutive one-minute records. The higher the number, the greater the aggregating tendency. Lake Trout Rainbow Cutthroat Goho Smolt June Parr May Parr May June 24 20 19 34 24 24 20 35 24 21 18 38 28 30 28 39 24 21 24 37 20 24 17 31 21 24 18 36 21 26 24 37 21 25 23 36 25 21 25 39 Total 232 236 216 362 Average 23.2 23.6 21.6 36.2 Total Sections Available 600 600 600 600 ^occupied 39 39 36 63 ocupied 61 61 64 37 -38-but were not observed to nip and generally were not very active. One coho salmon swam independently about while the other five aggregated much of the time in a corner. Occasional nipping was seen. Hatchery experiment -The smallness of the glass tank and metal trough closely confined the fish and i t was thought that, i n a larger tank where individuals could disperse farther, natural tendencies to aggregate or disperse would be more clearly discernable. For that reason additional observa-tions were made in July using a large, outside hatchery trough at the Loon Lake Trout Hatchery. This trough had the following inside measurements: 42? cm long x 91 cm deep x 97 cm wide. Six divisions were made by drawing five equidistant transverse lines on the bottom. The water depth was maintained at 33 cm by a standpipe. At greater depth i t was d i f f i c u l t to see a l l the fi s h . Observations were made through the hatchery building window to the trough which was outside. Thus the observer was partly concealed. The temperature varied from 11 to 17°G and the flow of water was turned off to avoid bias i n distribution. A l l of the juvenile fishes used were underyearlings hatched during the previous winter and spring with the exception of the lake trout which were hatched one year earlier. A l l of the juveniles were transported from -39-the University to the hatchery, a distance of 250 miles, lo mortalities, either immediate or delayed, occurred and the fish were presumed i n good condition when observations began three days later. In addition to these juveniles, newly spawned rainbow trout, 20-25 cm i n length, were also studied. Six fish were used for each series of observations. They were placed in the tank the day before observations began. A series consisted of eleven periods of observation during each of which the positions of the six individuals were recorded every minute for ten minutes. The chum salmon fry aggregated much more than any other group of fish (Table IV), while the adult rainbows were most dispersed. Lake trout,juveniles, rainbow fry and coho fry were intermediate i n degree of aggregation while the cutthroat trout showed a lower tendency to aggregate. Conclusions about aggregation 1. Chum fry aggregated much more than any other species observed. 2. In the 150 cm tank and 213 cm trough the differences in aggregation in lake trout, rainbow trout and cut-throat trout were not significant.* 3. Coho smolts i n June observed i n the 213 cm trough * 25% level of significance according to Dixon and Mood sign test (Dixon, W. J. and Mood, A. M. 1946*. The s t a t i s t i c a l sign test. Jour. Amer. Statist. Assoc. 41:557-566). -40-Table IV Aggregating compared i n four Bpecies in a 427 om trough divided by lines into 6 divisions. Six fish per observation. The numbers represent the number of empty divisions in ten, consecutive one minute records. The higher the number the greater the aggregating tendency. J m y Lake Rainbow Cutthroat Coho Chum Rainbow Trout Fry Fry Fry Fry Adults 28 23 18 31 47 15 33 30 23 37 45 21 33 33 26 42 46 12 31 27 28 34 42 20 33 34 22 34 37 22 41 23 29 30 50 4 30 36 23 27 45 12 41 38 16 30 49 10 25 25 33 29 48 28 25 26 23 23 50 17 27 27 16 24 43 37 Total 347 322 257 341 502 198 Average 31.5 29.2 23.3 31.0 45.6 18 Total Sections Available 660 660 660 660 660 660 ^Unoccupied 56 49 39 52 76 30 ^Occupied 44 51 61 48 24 70 aggregated significantly more than lake trout, rainbow trout and cutthroat' trout .-*' 4. The observed difference between coho in February and coho i n June may have been caused by a change in be-havior or may have been due to the difference i n tank sizes. Goho fry in July did not aggregate as much as coho smolts in June. 5. Lake trout appeared to disperse more in the small tanks than in the 427 cm trough but the actual distances between individuals was probably less within the con-finement of the small tanks. The evidence from the 427 cm trough suggests that lake trout had a greater tendency to aggregate than did cutthroat fry and adult rainbow but that they did not aggregate significantly more than rainbow and coho fry. 5. The evidence from the 427 cm trough suggests that a l -though lake trout, rainbow fry, cutthroat fry and coho fry did not tightly aggregate as did chum salmon fry, they aggregated more than would be expected i f they were randomly dispersed. DISTRIBUTION OF INDIVIDUALS IN RELATION TO DIFFERENT ENVIRONMENTAL CONDITIONS From the previous experiments i t was demonstrated that lake trout, rainbow trout, cutthroat trout and coho salmon fry did not aggregate very much in a relatively uniform * ifo level of significance. -42-environment. I n a previous paper (Newman, 1956) s e v e r a l t r o u t were shown to occupy a pool together. Since t r o u t show l i t t l e i n n a t e a t t r a c t i o n to each other, the c l o s e presence of these i n d i v i d u a l s must r e s u l t from a common se-l e c t i o n of a p a r t i c u l a r environment. Three environmental v a r i a t i o n s were used e x p e r i m e n t a l l y , the object being to de-termine whether these p a r t i c u l a r f e a t u r e s were s e l e c t e d , avoided or ignored. They were a w a t e r f a l l , a shadow and a p o o l . Response to a w a t e r f a l l Use of f i v e s i m i l a r I n d i v i d u a l s . F i v e rainbow t r o u t p arr of about the same s i z e were i n t r o d u c e d February 25 i n t o a 150 em g l a s s tank d i v i d e d by l i n e s i n t o f i v e s e c t i o n s . I n t o one end poured water from a conveying trough at a r a t e of four l i t e r s per minute. A constant l e v e l of water was maintained i n the tank by a standpipe a t the opposite end. Temperature v a r i e d from 7 to 8°C. I l l u m i n a t i o n of approx-i m a t e l y 40 foot candles was provided by incandescent bulbs s h i n i n g through a tank cover of f r o s t e d g l a s s . On the f o l l o w i n g day, the p o s i t i o n s of the f i v e t r o u t were recorded every h a l f hour, on ten consecutive minutes ten times (Table V). There was no s e l e c t i o n of the water-f a l l observed. However, the l a r g e s t and most aggressive t r o u t h e l d p o s i t i o n c l o s e s t to the w a t e r f a l l and chased i n -tru d e r s away. Another aggressive f i s h remained at the op-p o s i t e end o f the tank and chased the mOre subordinate f i s h toward the center. This tended to concentrate them i n an -43-Table V Number of rainbow trout in each division of a 150 cm tank. Each a i n e e r represents ten observations.( Five f i s h . No feeding. Waterfall I II III IV V Ten observations 8 3 7 33 10 it n 4 6 8 33 10 n n 0 9 6 35 10 it II 4 5 8 33 10 u tt 8 5 4 33 10 H n 10 4 5 21 10 n n 13 0 6 20 11 it H 11 0 9 31 9 II it 9 1 10 20 10 n II 9 1 9 33 9 Total 76 34 73 219 99 -44-intermediate location in division IV. It was conceivable that the individuals would have selected a position near the waterfall in the absence of a powerful dominant. This was d i f f i c u l t to test, however, because the removal of one dominant f i s h usually resulted in another taking i t s place. Therefore, i t was decided to observe a group consisting of four small rainbow trout and one noticably larger individual. Use of one large and four small individuals. The same tank was used under the same conditions as before. The ob-ject this time was to determine i f the larger, and pre-sumably dominant, fish would select the waterfall. The five trout were introduced into the tank and on the following day were observed every half hour. Table VI shows that the dominant fish did not select a position near the waterfall. One small fish remained beneath the waterfall and occasionally nipped and chased others but i t did not consistently defend the position. The large fish remained immobile most of the time. The waterfall, by i t s e l f , did not attract the trout. Use of four small and one large individuals fed via the  waterfall. It was decided to place small worms in the trough conveying water to the waterfall to see how this would affect the distribution of the five trout used in the previous ex-periment. The food was introduced into the trough from behind a concealing screen beyond the vision of the f i s h . Obser-vations were made on two days following the beginning of regular feeding. -45-Table VI Positions of four small and one larger rainbow trout in relation to waterfall. No feeding. "L w indicates position of large f i s h . Each r l i n e i r represents ten observations. Waterfall I II III IV V 10L - 20 15 0 4 1 6L - 17 11 3 4L - 5; 4 13 12 4 9L - 2 L - 9 13 L - 10 2 9L - 7 8 7 9 11 10L - 3 10 9 11 0 10L 20 1 4 2 10L - 11 22 3 12 1 10L - 3 21 10 10 10 10L 10 6 11 6 10L 4 13 16L - 99 IL - 105 39 82L mm 39 IL - 118 Table VII shews that after food had been introduced via the waterfall, the largest parr was in the two sections closest to the waterfall 97 out of 100 observations. While previously i t had not been aggressive, after the appearance of food at the waterfall the largest f i s h began ohasing and attacking the smaller ones when they approached the end of the tank having the waterfall. Table VII gives the timing of the observation with regard to feeding and shows the presence of other fish near the waterfall fifteen minutes after feeding. In the hours thereafter the large f i s h , which became dominant, was successful i n chasing most of them away, thus t e r r i t o r i a l i z i n g the region of the waterfall. It i s interesting to note that the dominant remained near the waterfall many hours after feeding despite the absence of food. This experiment Indicates that, although juvenile trout do not innately select a waterfall for a position, they w i l l do so readily i f the waterfall i s associated with some v i t a l factor i n their lives such as food. Once they select the waterfall they tend to remain there even in the absence of food. Response to shadow vs. illumination Rainbow fry i n a washtub. An experiment was performed at the Loon Lake trout hatchery with newly hatched trout fry to determine how they would distribute themselves in a -47-Table VII Posttione of four small and one larger rainbow parr in relation to waterfall; Individuals fed through waterfall. Each line represents ten observations. Time Sinee Feeding Waterfall I II III IV V 15 min. 8L - 16 2L - 14 8 1 1 3 hours 7L - 5 3L - 9 11 5 10 7 hours 8L - 2 1L - 5 1L - 13 11 9 16 hours 7L - 2 3L - 3 15 11 9 15 min. 4L - 15 4L - 10 8 5 2L - 2 3 hours 2L 8L - 1 28 6 5 23 hours 3L - 1 7L - 7 18 7 7 15 min. 8L 9 2L - 16 11 3 1 3 hour8 2L - 1 8L - 3 19 7 11 15 min. 8L mm 15 2L 12 5 2 6 Total 57 L — u 66 40L 79 1L -136 58 2L - 61 -48-washtub which was half in open daylight, half beneath the shadow of a board. Ten fry were taken directly from the hatchery trough and placed i n a tub f i l l e d with 20 cm of water also taken from the trough. Their positions were noted every half minute for five minutes. Six sets of fry were observed in the same fashion. Table VIII shows that the majority of individuals in each group selected the side of the tub in the shade. Rainbow parr in a glass tank, half of which was illum- inated, half in the shade. Half of the narrow, 150 cm tank used previously was exposed to incandescent light of 40 foot candles; the other half was shaded by a piece of tarpaper. Three groups, each with five rainbow parr, were used. In each group one trout was perceptibly larger than the other four. Observations were made the day following introduction of f i s h into the tank. Positions of the trout were noted every one half minute for five minutes. Table IX presents the results of these observations Individuals in a l l three groups tended to remain in the shaded portion of the tank. lone of the larger fish defended the shaded portion but none of the groups remained in the tank long enough to adjust to i t . The fish were not fed while in the observation tank. Cutthroat parr in a glass tank, half of which was i l l - uminated, half in the shade. The same tank and experimental arrangement used i n the previous experiment were used for -49. Table VIII Distribution of ten rainbow fry in a washtub half of which was exposed to daylight, half i n the shadow of a board. Illuminated Portion Shadowed Portion Group I II III IV V VI I II III IV V VI 5 1 3 3 1 0 5 9 7 7 9 10 4 3 2 2 1 1 6 7 8 8 9 J9 3 5 4 o 2 1 7 5 6 10 8 9 3 2 3 0 0 3 7 8 6 10 10 7 7 3 3 1 0 1 3 7 7 9 10 9 5 1 1 2 3 1 5 9 9 8 7 9 5 2 2 4 3 1 5 8 8 6 7 9 3 5 5 0 1 0 7 5 5 10 9 10 1 4 1 1 1 2 9 6 9 9 9 8 3 2 2 2 2 2 7 8 8 8 8 8 39 28 26 15 14 12 61 72 74 85 86 88 -50-Table IX Distribution of five rainbow parr in a 150 cm tank. Half of the tank was shaded, half illuminated. Each line represents ten observations. "L" indicates position of larger f i s h . No feeding. Light Dark Fish not active Group I 6L 4L - 40 no aggressiveness 8L - 1 2L - 39 12 10L - 28 Large f i s h not aggressive. Group II 2 10L - 38 Others inactive 10 10L - 30 10L - 4 36 8 10L - 32 8 10L - 32 Fish not adjusted to tank. Large f i s l 10 10L - 30 not aggressive. Small fish in light Group III 10 10L - 30 nips others 10 10L - 30 11 10L - 29 the observation of three groups of cutthroat trout parr. Each group again consisted of four fish of the same size plus one slightly larger. The f i r s t group showed no ten-dency to select either portion of the tank but swam back and forth in an unsettled fashion (Table X). The second group of cutthroat behaved like the rainbow parr in that they tended to remain in the dark half of the tank and showed no aggressiveness. The third group was unique. The largest individual selected the dark area and chased the others into the illuminated area. Using the sta t i s t i c s alone this evidence would be misinterpreted as a prefer-ence for the illuminated half of the tank. The response of trout to light or shadow was not a simple phototactie one. In the f i r s t experiment rainbow fry showed a preference for shadow as a fright manifestation following their placement in a new environment. In the second experiment rainbow parr showed some tendency to re-main in shadow in preference to a more illuminated section. In the third experiment (Table X), where cutthroat trout were used, most of the fi s h were found in the brighter half, following the development of aggressive activity in the large f i s h . The latter fish chased the others away and selected the shadows for i t s e l f . Responses to alternatives i n depth A concrete tank was used having inside dimensions of 173cm long x 74cm wide x 59cm deep. A false wooden bottom Table X Distribution of five cutthroat trout parr i n a 150 cm tank. Half of the tank was shaded, half illum-inated. Each line represents ten observations. Light Dark <7L - 17 3L - 23 Large fish not aggressive. Fish Group I 9 IOL - 31 swim back & forth 7L - 21 3L - 19 14 IOL - 26 12 IOL - 28 II 10 IOL - 30 aggressive. Fish  Group 10 IOL - 30 10 IOL - 30 30 IOL Large fish oocupied dark 36 IOL - 4 portion and chased other away. Group III 40 IOL 36 IOL - 4 39 IOL - 1 -53-c o n s i s t i n g of f o u r steps was placed i n the tank which c r e -ated four areas each w i t h a d i f f e r e n t depth. A continuous flow of water was maintained and drawn o f f by a standpipe. The behavior of the f i s h was observed through a m i r r o r angled over the tank as i l l u s t r a t e d i n F i g . 8. Behavior of f i v e chum salmon f r y . F i v e chum salmon f r y were i n t r o d u c e d i n t o the tank. On the subsequent day t h e i r p o s i t i o n s were observed at £ minute i n t e r v a l s ten times. These observations were repeated on ten occasions through the day. None of the f i v e chum salmon f r y remained long i n any p o s i t i o n (Table XI). They were almost c o n t i n u a l l y a c t i v e , F i g . 8 - The step tank i n which salmonids were observed i n r e l a t i o n to a l t e r n a t i v e s i n depth. Table XI Positions of five chum salmon fry in a tank divided, into four depths. Each r l i h e - represents ten observations. Shallowest Deepest I II III IV 5 20 9 16 8 10 13 19 10 10 12 18 9 16 19 6 12 9 17 12 7 21 9 13 11 5 21 13 16 2 12 20 8 18 15 9 15 11 7 18 Totals 111 122 134 144 -55-swimming in a school in a straight line from one end of the tank to the other. In the evening following the observations, a 20 cm lake trout was placed into the tank with the salmon fry. On the next day another series of observations was made in which the positions of the fry were tabulated. The results of these observations are shown on Table HIT',. The lake trout chased the salmon fry but remained most pf the time in the deepest section. The salmon fry avoided the deepest section after having been chased by the trout. During several observations the lake trout chased the smal-ler fish into shallower water and remained there briefly allowing the salmon to escape into deep water. This ac-counts for the two rows in which relatively large numbers were recorded at the deep end. The salmon fry quickly learned to avoid the section con-taining the predator f i s h and restricted their swimming to shallower portions of the tank. Near the end of the obser-vations one salmon disappeared - evidently eaten by the trout. Behavior of four rainbow trout parr. Four rainbow trout parr were placed in the step tank and fed daily for five days to determine how they would distribute themselves after establishing dominance. Ten observations were then made on each of the five subsequent days just prior to a daily feeding. The results are indicated on fable XIII. The trout tended to remain i n the deepest section of the tank. One fish dominated the others but was not sue--56= Table XII Positions of five chum salmon fry i n a tank divided into four depths following the introduction of a predatory fish (20 cm lake trout). Each linerrep-resents ten observations. Shallowest Deepest I II III IV 22 19 6 3 32 15 2 1 27 13 4 6 11 9 13 17 19 27 4 17 32 7 9 2 41 0 9 0 15 9 10 16 *31 8 1 0 *21 15 4 0 251 122 62 45 * One salmon fry missing and presumably eaten by lake trout. -57-Table XIII Distribution of four rainbow trout parr in a step tank after adjustment to the tank. Each line rep-resents ten \ minute observations. Shallowest Deepest I II III IV 0 5 5 30 0 3 23 15 0 0 6 34 0 0 11 39 0 0 7 33 Totals 0 7 53 141 -58-cessful in driving them into the shallow sections. The seven sorties into shallow water were made as exploratory efforts during l u l l s i n aggressive activity and did not result from fleeing from an aggressive dominant. A 20 cm. rainbow trout was added to the tank to de-termine i t s effect on distribution of the smaller individ-uals. The large fish swam to the bottom in the deepest section and rested there. The smaller residents ceased nipping and chasing one another and approached. A movement of the large f i s h caused the others to scatter rapidly. The large f i s h chased one of the residents and i t swam into section II. Table XIV indicates the positions of the five f i s h . A comparison of this table with the previous one shows that the presence of the large fis h caused the small ones to disperse significantly into shallow water. The large rainbow was not active and did not respond much to the smaller ones. During the observation when i t entered shallow water i t was "escape" swimming (see p.70). The large rainbow was replaced with a 20 cm lake trout which swam to the deepest section and rested there on the bottom. Table XV l i s t s the results of five observation periods on the two subsequent days/ The lake trout con-stituted a greater predatory threat than did the rainbow trout and f i n a l l y captured one of the small f i s h . Disper-sion of the small fish into shallow water was greater than in the presence of the other f i s h . Conclusions about experiments with step tank. The -59-Table XIV Distribution of four rainbow trout parr following the introduction of an individual 20 cm i n length. Each line represents ten jr minute observations. Shallowest Deepest I II III IV 10 0 L - 28 9L - 2 10 12 L - 17 9L - 1 1 18 14 IOL - 7 L - 10 4L 2L 2L - 30 10 10 10 IOL - 10 Totals L - 41 4L - 40 4L - 69 40L - 50 —60— Table XV Distribution of the same four rainbow trout parr following the introduction of a 20 cm lake trout. Each line represents ten \ minute observations. Shallowest Deepest I II III IV 10 30 0 10 Lake 10 14 16 10 « 10 28 2 10 » •10 10 10 10 « •10 10 10 10 " 50 92 38 50 Lake * One rainbow eaten by Lake Trout -61- • -. chum salmon fry and rainbow trout parr differed i n that the f i r s t did not select any part of the tank but swam actively back and forth without regard to depth. The rainbow parr tended to select the deepest portion or pool. The two species were similar in that they quickly learned to avoid the deep section when i t contained a po-tential predator. In the case of the rainbow, the greater threat imposed by the presence of the lake trout caused a greater displacement of the small fish into shallow water than When a similar sized rainbow trout was present. When the dominant fish was not much larger than the subordinates i t was not able to displace them into shallow water. Again, the movements of juvenile salmonids could not be described s t r i c t l y in terms of a simple taxis but had to be considered in the light of biological factors in the environment. Though there appeared to be innate di f f e r -ences between the response of chum fry and rainbow trout to water depth, these responses were quickly altered by the introduction of predatory f i s h . Introduction of food Four coho fry were placed by themselves in the step tank where they were fed daily for one week before obser-ving. It was noticed that the introduction of food caused changes in dispersion and aggregation, so tabulations of unoccupied sections of the tank were made before feeding -62-and immediately after introduction of food. The food was scattered in the tank to prevent biasing the results to-ward aggregation by having a l l the specimens rushing to a single focal point. In a l l cases (Table XVI) the fish were more dispersed prior to feeding than after. Introduction of food caused great excitement among them and they f o l -lowed each other. This following caused them to swim in a group. After a few minutes of feeding, however, nipping would begin with the result that they once more dispersed. Thus feeding brought about successive aggregation and dis-persion. This pattern of behavior may be an important one in nature, for dispersed f i s h would be more li k e l y to apprehend the presence of food than aggregated ones. If the i n d i -viduals were close enough to see each other then they could follow one another when food was located., Upon the ex-haustion of the food supply, the resumption of aggressive-ness would cause them to once more disperse. COMPARISON OF UNDISTURBED ACTIVITY One of the most obvious differences between fish of one species and those of another i s their average rate of locomotion while undisturbed. Some species are character-ized by continuous swimming, others by discontinuous swim-ming, some by rapid movement, others by slow movement. Rates of movement were investigated in the 427 cm hatchery trough described on page 38 by counting the number of lines Table XVI The number of unoccupied sections of a four-section tank containing four coho fry. Ten ^ minute obser-vations before feeding and ten just after feeding. Unoccupied section Unoccupied section Before feeding After feeding 4 12 17 13 18 19 20 20 -64-crossed per minute by six individuals of each species. One hundred observations were made of each group. The fish used were lake trout, rainbow fry, cutthroat fry, coho fry, chum fry and spent, adult rainbow trout. Table XVII l i s t s the lines crossed in ten minute per-iods and the total lines crossed for each group. Chum fry exhibited the greatest degree of activity and were sig-nificantly different ( l percent level of significance) from a l l other species examined. Lake trout were next most ac-tive but were not significently more so than rainbow or coho fry. There was a significant difference in activity at the 1 percent level between lake trout and cutthroat fry and spent rainbow adults. RainbOw fry, coho fry and cut-throat fry were not significantly different from one another, although rainbow and cutthroat fry approached the 5 percent lev e l . At the inactive end of the scale the rainbow adults were different from coho fry at the 5 percent and from a l l the others at the 1 percent level. While the distance between two lines was only 71 cm, the crossing from one line to the next averaged a greater distance for two reasons: lateral deviation in roaming and movement around the ends of the trough. The width of the trough was 97 cm and the distance around each end was 239 cm. If one assumes a fi s h averaged 90 cm in eight out of ten transits and 240 cm in the other two, then the distance travelled per li n e crossed averaged 120 cm. On this basis i t i s possible to estimate the average distance traversed -65-1 Table XVII Comparative activity based on the number of lines crossed by 6 fish i n a 437 cm trough divided by 5 equidistant lines. Each number represents ten minutes of observation repeated hourly. Lake Trout Rainbow Fry Cutthroat Fry Coho Fry Chum Fry Rainbow Adult8 250 80 60 84 358 4 146 78 85 44 377 22 137 87 72 64 302 29 78 118 65 83 369 12 144 93 71 20 336 6 212 81 59 4 467 33 168 107 49 18 507 9 102 115 40 66 403 49 102 100 48 62 390 13 169 101 25 190 421 21 Totals 1508 960 574 635 3930 198 -66-, per minute by each species (Table XVIII). Comparing the juveniles, we fi n d the behavior of the chum salmon fry to be distinct. The continuous, relatively rapid swimming of these fish i s probably associated with their migration to the sea. The swimming activity of lake trout was intermediate between chum salmon and the other species. Rainbow, cutthroat and coho fry had intermittant swimming movements in which the total distances traversed were less because of the periods of inactivity separating the periods of movement. RESULTS OF STANDARD OBSERVATIONS OF BEHAVIOR Methods Intraspecific groups of four fish were studied i n half, sections of the long, narrow glass tanks previously de-scribed. These tanks had inside lengths of 150 cm. They were divided by aluminum screens which separated groups in equal halves. A small flow of water passed through the tanks and maintained uniform low temperatures. Lake trout, dolly varden, brook trout, rainbow trout, cutthroat trout and coho salmon fry were intensively studied. Two groups of each species were observed. A l l individuals were marked by clipping their fins as has been previously described. Three types of observations were made on each group of f i s h . Qualitative observations. The main object here was to discover what the fish did and to describe aggressive be-havior, t e r r i t o r i a l i t y , prey behavior, resting, comfort -67-Table XVIII The estimated average distance traversed by each fish per minute i n a 427 cm trough. Each average based on 100 observations. In cm. Lake Rainbow Cutthroat Coho Chum Rainbow Trout Fry Fry Fry Fry Adults 302 cm 192 115 127 786 40 -68-movements, feeding and schooling: as they occurred. Qual-ita t i v e observations were made of many other specimens as well as those in the standard groups. These additional specimens included lake trout, rainbow trout, coho salmon, sockeye salmon, chum salmon and pink salmon at the Vancouver Public Aquarium as well as Chinook salmon fry held briefly at the University of British Columbia. The specimens exhibited various displays which differed somewhat from species to species. Frontal display: an attacking orientation of one fish as i t faced i t s opponent. Lateral display: a defensive positioning of the Bide of the body toward an aggressive opponent. Lateral tail-wagging: the side to side movement of the body and t a i l of a fish i n lateral display. Retreating tail-wagging: a r i g i d side to side movement of the body and t a i l as the fish retreated from i t s attacker. Substrate-biting threat: a threat movement carried out by a fish swimming rapidly toward another and then biting at an object on the bottom directly below the other. Crouching: an attitude of in f e r i o r i t y (Baerends and Baerends-van Roon, 1950) adopted by one fish when attacked by another. Quantification of aggressive actions. Each group was observed for eight 15 minute periods of which four preceded -69-feeding and four followed a 15 minute feeding period. The number of nips, threats, gapes, snaps and chafes were recorded for each fish and related to position i n the social hierarchy. Each group was observed during i t s feeding period to ascertain when each fish began feeding and how soon afterwards i t began nipping the others. A "nip" was an aggressive motion of one fish toward another accompanied by a biting movement. Actual con-tact did not always occur as the attacked fish usually retreated rapidly. A "threat" was an aggressive movement of a display nature or an aggressive intention movement which was only partially expressed and was not accompanied by a nip. A "gape" was a yawn-like stretching of the jaws. "Snaps" were quick, undirected snapping movements of the jaws. "Chafes" were movements of the side of the body over the bottom of the tank, performed as though the fish were scratching i t s e l f in response to i r r i t a t i o n . Activity analysis. It was noted that some fish rested more than others, some swam about more than others and in general the pattern of activity varied -70-from species to species. In order to quantify these differences each group was observed for five minutes just prior to feeding on four occasions. Each obser-vation period involved ten consecutive records at \ minute intervals of the particular activity being per-formed by each fi s h . The observable categories were immobility, nipping and chasing, retreating, food samp-li n g , escape swimming, aimlessly swimming and threat-ening. "Immobile" fish were inactive individuals which might be resting, alarmed or inhibited. The underlying cause was often d i f f i c u l t to determine. "Hipping and chasing" fish were actively aggres-sive individuals attacking others which might or might not have been retreating. "Retreating" fish were actively fleeing from more aggressive pursuers. "Food sampling" fish swam around examining part-icles in the water or on the bottom, biting at them and moving them around in their mouths, usually then ejecting them and swimming to another location. "Escape swimming" fish repeatedly swam up and down in the corners of their tank as though attempting to escape. While doing so they were relatively unre--71-sponsive to other influences such as dominant or sub-ordinate individuals or the presence of particles of potential food value. "Aimlessly swimming" constituted a category of moving fish which were not chasing, retreating, food sampling or escape swimming. The fish were thus moving without apparent object. In most cases this action was definably different from the others. "Threatening" included both actual display and the expression of interrupted intention movements. From these observations and others sufficient i n -formation was obtained to give general descriptions of the behavior of each species. Behavior of juvenile lake trout Hipping. Only eight nips and one threat were recorded for both groups, thus indicating a very low level of aggressiveness in the species. In Group I nipping was performed by the three smallest fish and was not associated with the development of a dom-inance relationship. In Group 2 the largest fis h nipped twice and was avoided by the three other individuals in i t s tank. No definite dominance -72-relationship evolved, however. Nipping was not followed by-chasing and i t appeared to be a feeding manifestation, per-haps a displaced feeding action pattern, rather than a purely social one. A summary of the observations in given in Table XIX for group I and in Table XX for Group 2. Activity. There was considerable variation in activity among the different individuals. LLOI was immobile 10% of the time and LAN2 remained immobile in 82% of the observations and swam in 13% of them. One correlation existed between proclivity to feed and activity. LUPI, LLOI and LUP2 ate most readily and included the two most active specimens. In general lake trout were distinguished by Blow, aimless swimming. There was much simultaneity of action whereby a l l would be active or a l l would be immobile at the same time. Immobile fi s h sometimes positioned themselves in mid-water and sometimes on the bottom (Table XXI). Individuals usually selected one or the other but not both. This was possibly associated with the degree of inflation of their swim bladderB and consequent differences in density. T e r r i t o r i a l i t y . There was no defense of any partic-ular area nor was there any observable tendency to remain i n or return to one place. Their slow, continuous movements tended to carry them away from particular locations. Prey behavior. Immobility in lake trout was usually a resting phase but occasionally represented inhibition in response to outside stimulation. Mild disturbance caused -73-Table XIX Synopsis of the behavior of the four lake trout in Group 1. Part A, activity analysis based on 40 records per fish. Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish LADI LANI LUPI LL0I Totals Weight 48.4g 34.9 44.5 35.6 # io # i # °h # lo # i Immobile 22 55 13 32 21 52 4 10 60 37.i Kipping & Chasing Retreating 1 3 1 <1 Food Sampling Escape Swimming Aimless Swimming 18 45 26 65 19 48 36 90 99 62.5 Threatening Part B Fish LADI LANI LUPI LLOI Totals Gapes 11 6 12 4 33 Nips 2 1 3 6 Threats 1 1 - 7 4 J -Table XX Synopsis of the. behavior of the four lake trout in Group 2.. Part A, activity analysis based on 40 records per fish. Part B, number of gapes, nips and threats i n eight 15 minute observations. Part A Fish LADS LAN2 LUP2 LL02 Totals Weight 47.5g 30.5 i 64.3 41.8 # *. # $ # $ # fo # fo Immobile 26 65 33 82 8 20 10 25 77 48.1 Nipping & Chasing Retreating Food Sampling 1 3 10 25 11 6.9 Escape Swimming 1 3 1 .7 Aimless Swimming 12 29 7 18 22 55 30 75 71 44.3 Threatening Part B Fish LAD2 LAN 2 LUP2 LL02 Tot als Gapes 12 8 7 4 31 Nips 2 Threats 0 -75-Table XXI The location of immobile fish on the substrate or in midwater derived from activity analysis. Group I Fish LADI LANI LUPI LLOI Totals Midwater 1 12 19 4 36 Bottom 21 1 2 0 24 Group 2 Fish LAD2 LANS ! LUP2 LL02 Totals Midwater 3 6 0 10 19 Bottom 23 27 8 0 58 -76-a fish to stop moving and to adopt a "generalized alarm posture" whereby the body stiffened and the fins were erected (Fig. 9). This prey response probably represented a state of readiness for flight and may be general for a l l fishes. Fig. 9 - Generalized alarm posture of lake trout. If frightened but not chased, lake trout darkened slightly, but i f vigorously chased or captured and placed in another tank they lightened in color and assumed a generalized alarm posture. They were relatively insensitive to the approach of -77-l a r g e objects and f o r t h i s reason were e a s i l y n e t t e d by drawing a dip net slowly over them. I f the net was moved too r a p i d l y , the f i s h suddenly darted away. Resting posture. While r e s t i n g i n contact w i t h the bottom they supported themselves w i t h t h e i r f i n s ( F i g . 10) which were u s u a l l y maintained i n a p a r t l y contracted s t a t e , but d i d not expand t h e i r p e c t o r a l s and prop t h e i r head up as d i d d o l l y varden. They were q u i t e t o l e r a n t of the c l o s e presence of other f i s h and o f t e n r e s t e d s i d e by s i d e touching each other. F i g . 10 - R e s t i n g posture of lake t r o u t . Rhythm and comfort movements. A rhythm of a c t i v i t y was noted i n which a f i s h r e s t e d f o r a b r i e f p e r i o d , then swam around the tank s e v e r a l times and f r e q u e n t l y returned -76-to the same spot where i t again rested. Impending activity was often presaged by i t s opening i t s mouth very widely followed by a lateral stretching of i t s g i l l s and opercles and a downward stretching of the hyals (Fig. 11). This Fig. 11 - Lake trout gaping. gaping movement resembled a yawn and was usually followed by quick snapping of the jaws. Another precursor to move-ment was a rapid jerking or twitching of the body followed by a quick dart forward during which the dorsal and caudal fins flickered as i f in response to an i r r i t a n t . Sometimes a fish was catapulted into activity by a sudden upward flexing of the head and a snapping of the jaws. Gaping was associated with inactivity. The two fis h i n each group which had the highest percentage of immo--79-b i l i t y , gaped most frequently (Tables XIX and XX) Moving fish frequently snapped their jaws. This i n -volved rapid opening and closing of the mouth which jerked the head upward and resembled a hiccup in terrestrial ani-mals. Occasionally chafing (Pabricius, 1953) was seen. This consisted of darting at the bottom, turning on the side and scratching the side on the bottom in a rapid, continuous, forward movement. Sometimes a fish darted to the Burface, opened i t s mouth, took in some air and swam downward again usually moving i t s mouth and emitting bubbles. This appeared to be a way of f i l l i n g the air bladder and may have been related to selecting a midwater resting position by decreasing density. Gaping, snapping, flickering of the fins, chafing and darting to the Buffape are referred to as "comfort actions" by Baerends and Baerends-Van Roon (1950) who consider them as actions which alleviate i r r i t a t i o n . Attack, threat and defense. Attacking behavior consis-ted of a number of components which, even though charac-t e r i s t i c of the species, were not expressed in a l l aggres-sive situations by a particular individual. Lake trout were capable of expressing some aggressive components but did 8 0 very seldom. High intensity attack was accompanied by a frontal - 8 Q -di8play (Fig. 12). The fi s h opened i t s mouth slightly, depressed i t s dorsal f i n and extended i t s hyal bones and their associated membranes on the ventral surface thus i n -creasing the apparent size of the head. It arched i t s back and bent i t s head slightly upwards. The caudal fin Fig. 12 - Frontal display of attacking lake trout. expanded, the pectorals remained along side the body but carried out normal locomotory movements, while the anal and pelvies maintained a normal semi-expanded state. These characteristics appeared simultaneously as the attacking f i s h approached i t s adversary. They constituted the posture -81-ana attitude of the attacking fish while i t was in motion rather than a threat which substituted for attack. At the moment of contact and immediately afterward elements of defense, such as raising the dorsal f i n , some-times appeared. No definite lateral display, la t e r a l t a i l wagging or retreating t a i l wagging was ever observed. The elevation of the dorsal f i n i n social situations seemed to be partial or complete assumption of a generalized alarm posture. Threat behavior was poorly developed and rarely seen. The only type observed was an occasional intention movement in which an aggressive approach was interrupted either by the aggressive f i s h i t s e l f or by the avoidance of the other f i s h . Approaching was rapid when the aggressor was in frontal display. Otherwise the approach was slow and deliberate and frequently followed by examining behavior. Nipping consisted mainly of biting and involved actual contact. One lake trout was never observed chasing another and nipping at the retreating f i s h . A l l of the recorded nips represented fish which slowly approached a resting f i s h and b i t i t , usually on the t a i l . This bite resembled a food sampling movement rather than a social nip. Since the mouth of this species was large and the teeth strong, i t was capable of biting quite forcefully. Fish which had been' bitten tended to avoid the fi s h -8-2J-whioh had bitten them but no retreating was ever seen. Avoiding was a rather typical pattern of behavior among lake trout partly in consequence of their slow, continuous swimming which contrasted with the intermittant darting and stopping movements of the other species. This carried one f i s h close to another which may have been approaching from the opposite direction. As they came near each other the smaller one of the two would usually alter i t s course to avoid contact with the larger one. Lake trout were never observed to crouch and contract their fins at the approach of another. Feeding. Lake trout were predatory in their feeding habits and mainly ate only moving objects, particularly small fish. They exhibited two types of behavior with regard to food. The f i r s t was directed toward a moving object and seizing i t while i t was in f l i g h t . The second was a slow and deliberate movement toward a stationary object nearby followed by an examination of the object and perhaps a mouthing of i t . During the examination (Figs. 13 and 14) the eyes of the f i s h moved and the f i s h sometimes swam around the object and viewed i t from different vantages. Biting at stationary objects of potential food value resembled the aggressive biting of a stationary opponent. Once the object was seized i t was shaken back and forth by la t e r a l movements of the head. This probably k i l l e d i t s prey, thus preventing any injury that might result from Fig. 14 - Front view of lake trout examining earthworms. -84-defensive efforts of the prey, and i t contributed to the breaking up of the food into smaller pieces. In addition to prey shaking, the lake trout usually adjusted the position of i t s prey i n i t s mouth by spitting i t out and biting hold of i t again from the other end. The prey was usually, but not always, swallowed head f i r s t . One fis h repeatedly examined, snapped up and violently re-arranged an earthworm i n i t s mouth; spit i t out and picked i t up from the other end. Unlike dolly varden i t would not eat an earthworm possibly because i t lacked the "head" stimulus present i n salmon fry i t was accustomed to eating. No lake trout was observed to eat worms although they ate other things such as canned salmon which lacked the shape of small f i s h . Even canned salmon was usually spit out several times and grabbed again in the course of feeding. Since they fed on individual salmon fry which dis-persed through the tank they did not develop social feeding patterns as did subsequent species. They did not m i l l around a feeding area biting at the substrate and bumping into one another. Frequently an individual would become excited by the presence of small food fish and dart after one, seize i t and k i l l and then reject i t without eating i t . A lake trout that had successfully swallowed a small fish was often more eager for food than one that had not yet fed. This led to over-eating whereby the t a i l of the last small fish would extend out the mouth of the lake trout making res--85-piratory opening and closing of the mouth d i f f i c u l t . When small coho and chum salmon were placed in the tank for food, the chums were usually eaten f i r s t . Evi-dently the continuous swimming motion of the chums was a stronger prey stimulus than the immobility of the cryp-t i c a l l y colored coho salmon. When one fish captured a small salmon i t moved rapidly away from other fish and devoured i t s prey at a distance. This avoiding movement was extremely attractive to the others and they generally followed, attempting to snap the fry from the mouth of i t s captor. A modification of this avoidance feeding pattern was seen in fish kept in the 427 cm trough. When a fi s h rose to the surface for food, i t snapped at the food, dove to-ward the bottom, then turned at a right angle and swam rapidly to one side. This turning evidently functioned as an avoidance pattern possibly in relation to predators as well as competitors. In the Vancouver Public Aquarium lake trout were fed chunks of meat and fi s h . They learned to take these readily but most feeding was performed on pieces dropping through the water. They preferred these to pieces on the bottom of the tank. Schooling. Schooling was not observed among lake trout but their tendency to follow another fish which had captured a salmon fry was suggestive of schooling. Behavior of older lake trout Six specimens of the lake trout studied i n 1954 and 1955 s t i l l survived in the Vancouver Public Aquarium in the summer of 1959 at which time they were 46-56 cm in length. From 1956 u n t i l 1959 they had been maintained i n a 220 gallon glass-fronted, concrete tank into which cold fresh-water constantly flowed. During these three years the fish l i v e d compatibly without expressing any of the aggressiveness so characteristic of rainbow trout and coho salmon under similar confinement. They fed well and grew at similar rates. There was not a great difference i n the size of the individuals i n 1959 and no evidence of domination by one f i s h . Dolly varden behavior dipping. In contrast to lake trout, dolly varden were extremely aggressive. Over 1000 nips were recorded during the standard observations of the two groups (Tables XXII and XXIII). In both groups most of the nipping was done by a single fish which emerged dominant following aggressive fighting marked by great vigor but l i t t l e display. After the i n i t i a l fight the dominant regularly nipped and chased the others. Fighting occurred quite often between dominant and subordinates particularly after feeding, but each of the two dominant fish maintained i t s position throughout a l l observations. Most nipping occurred following feeding -87-Table XXII Synopsis of the behavior of the four dolly varden in Group 1. Part A, activity analysis based on 40 records per f i s h . Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish DADI DANI DUPI DLOI Totals Social #2 Position #1 #4 #3 # Immobile 30 32 36 33 131 81.8 Nipping & Chasing 2 6 8 5.0 Retreating 5 6 3.7 Food Sampling 3 2 5 3.1 Escape Swimming 2 1 3 1.9 Aimless Swimming 2 5 7 4.3 Threatening 0 0 Part B Fish DADI DANI DUPI DLOI Totals Gapes 10 10 5 1 26 Nips 38 406 0 2 446 Threats 23 38 2 6 69 -88-Table XXIII Synopsis of the behavior of the four dolly varden in Group 2. Part A, activity analysis based on 40 rec-ords per f i s h . Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish DAD2 BAH 2 DUP2 DL02 Totals Social Position #4 #1 #2 #3 # * Immobile 33 29 36 29 127 79.4 Hipping & Chasing 8 2 2 12 7.5 Retreating 4 4 8 5.0 Food Sampling 1 2 3 1.9 Escape Swimming 2 2 1.3 Aimless Swimming 1 3 3 7 4.3 Threatening 1 1 .6 Part B Fish DAD2 DAH 2 DUP2 DL02 Totals Gapes 6 12 7 7 32 Hips 9 605 58 16 688 Threats 6 10 23 13 52 -89-(Table LIII). The social relations are indicated as "peck orders" (Tables XXIV & XXV). Effect of starvation on aggressiveness. Starvation has been shown to increase aggressiveness among some animals (Errington, 1946) and the question arose as to what extent i t would increase that of juvenile salmonids. The second group of four juvenile dolly varden was maintained over a period of 42 days without food. Table XXVI records the number of nips, threats, gapes and snaps observed before and after feeding for four periods prior to the beginning of starvation, then shows them after seven days, 41 days and f i n a l l y 42 days of starvation. During the period of starvation aggressiveness de-creased and at the end of 41 days the f i s h showed very l i t t l e a c tivity of any kind. On the last day of observation they were presented with food. Contrary to expectation, feeding movements were slow and relatively noh-corapetitive. The dominant attacked one of i t s subordinates eight minutes following the introduction of food. Two fish carried out a brief reciprocal encounter. After a short period of aggressiveness a l l four became quiet and rested on the bottom. The f i s h showed no indication of distress following this long period without food and did not look particularly thin. The main difference in their behavior was a reduced activity which probably conserved energy and prolonged survival. -90-Table XXIV Dolly varden "peck orders" based on eight observations of Group 1. Numbers represent fiBh of different social positions. Arrows point from attacker to fish attacked. Before Feeding After Feeding 1 *2 \&_ ^ 3 1 >2 1^-—^3 ^ 4 Table XXV Dolly varden "peck ordere" based on eight observations of Group 2. Numbers represent fis h of different social positions. Arrows point from attacker to fish attacked. Before Feeding After Feeding . 2 1<- >3 ^ ^ 4 1 < _ ^ 3 5 -92-Table XXVI Aggressiveness among four dolly varden prior to starvation, during starvation and following 42 days of starvation. Records indicate before and after feeding. NIPS THREATS GAPES f i SNAPS' Before After Before After Before After Before After 20 165 2 8 2 1 3 0 72 134 4 0 7 1 7 0 4 186 0 10 9 4 47 6 7 89 6 3 6 2 31 1 7 Days 11 0 4 7 mm Starvation 41 Days 1 1 3 4 _ Starvation 1 — 1 — 1 — 16 — 4 — 2 — 3 _ 34 _ 3 — 0 — 1 — 17 — After Feed-ing on the 42nd day of Starvation 21 — 4 — 0 — 68 -83-Aotivity. Dolly varden were more sedentary as well a8 more aggressive than lake trout. A l l of the dolly varden in both groups were immobile a large proportion of time. A l l of the immobility of Group 2 fish and over half of that in Group 1 fish occurred i n contact with the bottom (Table XXVII). The fish which occasionally remained immobile i n midwater were the two lowest members in the dominance order in Group 1. These fish were driven from the bottom of the tank by the dominant fish and were usually prevented from resting on the bottom. The slow, aimless swimming of the lake trout was seldom performed by thiB species. Most of their activity was con-cerned with aggressive behavior and feeding. T e r r i t o r i a l i t y . Dominant dolly varden often chased others away from the feeding area, then returned there and maintained a station. Sub-areas of the tank were not com-monly defended against intrusion of other members of the group, but elements of defense were seen and there was some tendency to rest in particular locations. Prey behavior. Unusual disturbance caused a cessation of movement and usually a sinking to the bottom where the fi s h remained immobile i n a generalized alarm posture ( f i g . 15). This posture was similar to that B e e n in lake trout i n that the body was r i g i d and the fins expanded. It was unoriented in relation to an approaching fish and probably had no display significance. Table XXVII The location of immobile dolly varden on the sub-strate or i n midwater. Group 1 Fish DADI (#2) DANI (#1) DUPI (#4) DLOI (#3) Totals Midwater 0 0 26 26 52 Bottom 30 32 10 7 79 Group 2 Fish DAD2 (#4) DAN2 (#1) DUP2 (#2) DL02 (#3) Totals Midwater 0 0 0 0 0 Bottom 33 29 36 29 127 - 9 5 -Fig. 15 - Generalized alarm posture of dolly varden. Dolly varden were quite insensitive to the approach of large objects and, as with lake trout, could be netted easily. In this respect the species differed from members of both. Salmo and Oncorhynchus. Sometimes one could net a dolly varden and slowly move i t around i t s tank without the fis h becoming disturbed or even moving appreciably, but as i t was drawn from the water i t began struggling. In the same way an immobile fish would suddenly become active and dart away when a particular threshold of stimulation was achieved. This threshold was relatively high for both lake trout and dolly varden. Whitehouse (1945), in a dis-cussion of the sporting qualities of salmonids, comments that the dolly varden does not struggle on the hook, and -96-hence i s not a good game f i s h , but struggles in the boat after i t i s caught. Opposed to this i s the sporting rainbow trout which struggles in the water and then dies quickly in the boat. These differences may be related to differences in level of stimulation required to release a flight res-ponse. Resting posture. While resting on the bottom, dolly varden supported themselves on their fins which varied in their state of expansion (Fig. 16). When not stimulated Fig. 16 - Lake trout in front and dolly varden in back. Contrasting resting postures. by outside disturbance or other f i s h they relaxed their fins thus lowering the body and keeping i t horizontal. Mild stimulation, as caused by an approaching f i s h , often -97-made a resting fi s h expand i t s pectorals, bend i t s body and l i f t up i t s head in an alert posture. Frequently one fish would l i e across another fish which also rested on the bottom and prop i t s head or t a i l up into an awkward angle. During such periods of rest members of a group tolerated each other without signs of aggression although there was l i t t l e indication of positive attraction. Sometimes, however, a swimming dolly varden slowed down, erected a l l of i t s fins in midwater and gradually sank toward another fish f i n a l l y alighting on top of i t (Fig 17), an action suggesting a selection of the presence of other fish or perhaps an ele-vation as a resting place. Generally, individuals of this species were less tolerant of each other than were lake trout. Fig. 17 - Dolly varden settling on resting lake trout. Rhythm and comfort movements. At various intervals resting fish became aroused either spontaneously or as a result of outside stimulation, and, like the arctic char (Fabricius, 1953), swam about performing various ac t i v i t i e s such as feeding, chasing or attempting to escape. After awhile they again returned to the bottom and rested. This behavior was quite rhythmic i n pattern. As in lake trout activity was usually anticipated in resting dolly varden by gaping movements, snapping of jaws or flickering of fins. Gaping was associated with inactivity and more gapes were recorded before feeding than afterwards. Another cor-relation occurred between dominance and gaping; the frequency being higher in the two highest individuals in each hierarchy. Chafing seldom occurred. Attack, threat and defense. Frontal display (Fig. 18) was common among fish which had recently been placed to-gether or which were excited by the presence of food. It was the same as that which ocoured i n lake trout but was much more frequently expressed. As in lake trout i t was not maintained as a posture of a stationary f i s h and was never used solely as a threat as in an intention movement. It i s the posture of great aggressive intensity in an at-tacking f i s h . No well-developed, erected-fin, lateral display was exhibited by dolly varden. Lateral tail-wagging and re-treating tail-wagging were likewise not observed. -99-Fig. 18 - Frontal display of attacking dolly varden. Threat behavior was not well developed and intention movements were not frequently observed. When one fish moved toward another i t tried to bite i t and did not quickly cease i t s attempt. One activity which had threat function was substrate biting, an activity which resembled displacement digging i n the male three-spine stickleback (Tinbergen and van Iersel, 1947). A fish feeding on the bottom would hold i t s body oblique with i t s head down and i t s eyes examining objects beneath i t . Then i t would bite at the bottom taking a mouth-full of detritus and swim forward moving i t s mouth rapidly, f i n a l l y stopping and spitting out the detritus. It would usually do this a number of times with increasing -100-i n t e n s i t y and undulatory movements of the body. Suddenly i t would dart at another f i s h and b i t e at the su b s t r a t e immediately beneath i t ( F i g . 19). This would d i s t u r b the other f i s h , f r e q u e n t l y make i t r e t r e a t a b i t and often p r e c i p i t a t e a t t a c k i n g behavior. F i g . 19 - D o l l y varden b i t i n g at su b s t r a t e beneath another f i s h . The a t t a c k i n g f i s h u s u a l l y approached i t s opponent r a p i d l y and d i r e c t l y but i f the l a t t e r d i d not r e t r e a t at the beginning of the approach, the movement of the a t t a c k e r would slacken. The a t t a c k e r opened i t s mouth w i d e l y and b i t the other ( F i g . 20)on any part of i t s body. Since the f i s h which was a t t a c k e d u s u a l l y r e t r e a t e d , the atta c k u s u a l l y -101-Fig. 20 - Biting movement of attacking dolly varden. came from the rear and the t a i l was bitten. Sometimes the biting fi s h actually held on to the other fish, particu-l a r l y to a f i n , and shook i t . Usually the attacker chased i t s opponent and nipped at i t several times (Fig. 21). Movements of chase were not sharply differentiated from approach but depended upon the retreat of the other f i s h . Lowering the hyals, arching the body and depressing the dorsal f i n were not usual attitudes of the chasing f i s h . Hipping consisted of biting movements made by a chasing fish which failed to touch i t s opponent. Fighting occurred between two or more fish which were in a state of high aggressive intensity and involved frontal display - 1 0 2 -Fig. 21 - Attaoking dolly varden nipping at retreating f i s h . and biting. When the fish faced in the same direction they simultaneously lowered their dorsal fins and hyal mechanisms, arched their backs and swam forward eye to eye each attemp-ting to turn upon the other. One then succeeded in turning and biting the other. Sometimes this was followed by re-ciprocal biting and sometimes by a repeat of the eye to eye performance. If one turned so that the two fish were oriented in opposite directions they circled rapidly chasing each other and frequently biting each other around the t a i l (Figs. 22 and 23). During the circlin g they elevated their dorsal fins as they always did in turning and the appear-ance of the frontal display was considerably altered. -103-Fig. 23 - Fighting dolly varden. -10&-Fighting movements were rapid and continuous, and directed toward positioning the fish for biting i t s opponent. Figh-ting was not interrupted by display and frontal display was expressed in the attacking movement and not as a substitute for actual attack. The duration of fighting was usually several minutes or less but i t sometimes extended to ten or fifteen minutes in exceptional cases. Dolly varden fought f a i r l y frequently particularly following feeding and particularly i n new groups or in groups not dominated by a persistently aggressive individual. If the dominant fish in the group was a persistent and savage chaser i t suppressed aggressive activity in the others and no fighting took place. Alless aggressive fish usually retreated by swimming rapidly away. Frequently retreat was preceded by an ag-gressive exchange. Subordinate fish did not crouch or depress their dorsal fins at the approach of a dominant. Individual rec-ognition appeared to be poorly developed. Feeding. When foods such as small white worms (Enchy- traeus sp.) were introduced into a tank dolly varden rushed to them and fed very actively while milling around bumping into each other (Fig. 24). Feeding movements were primarily directed to the bottom but particles were taken in the water and at the surface as well. Manoevering was required in obtaining food and the fins were usually erected and active. -105-Fig. 24 - Dolly varden coming close to one another while feeding. The fish circled, held their heads close to the bottom examining i t carefully (Fig. 25) and darted at the worms. Frequently they bit the substrate, l i f t e d up their heads, spit out the detritus and darted at the worms dropping from i t to the bottom. The c i r c l i n g and darting about stirred up a cloud of dir t which contained small worms and this seemed to stimulate them to greater activity. Biting at food resembled the type of aggressive biting which was directed at a stationary opponent. When a relatively large object like an earthworm or minnow was taken into the mouth i t was vigorously shaken back and forth by lateral movements of the head and rear--106 -Fig. 25 - Dolly varden examining substrate where food was present. ranged in the mouth by vigorous biting movements. Once a dolly varden had captured a large worm i t darted away from other fish and avoided them. As in lake trout this action attracted the others and caused them to follow. Dominant fish usually began feeding immediately when food was offered them (Table XXVIII) while subordinate fish often delayed a minute or two. One subordinate in Group 1 failed to feed at a l l on three occasions. The dominant fed several minutes then began nipping the others and chasing them from the feeding area. This resulted in the dominant fish getting most of the food. Table XXVIII Time r e q u i r e d f o r i n i t i a t i o n of feeding and n i p p i n g by d o l l y varden f o l l o w i n g i n t r o d u c t i o n of food. Four observations of each group. Each number represents the number of subordinates beginning t o feed. "Dn designates dominant f i s h , "n" beginning of n i p p i n g . Minutes A f t e r Group 1 Group 2 Food Introduced Obs. 1 Obs. 2 Obs. 3 Obs. 4 Obs. 1 Obs. 2 Obs. 3 Obs. 4 15 14  13  12  11  10 • • 9 ; s ; ; •  .7 6 n n 5 n  4- 1 n 3 2 l , n n i l n n 1 D 2 1 D 3 1 D,l 0 D D,l D,l 3 D D,2 2 N. B. A l l f i s h f e d . -108-Schooling. Dolly varden did not form schools but under certain conditions small groups formed and moved about in loose association more as a "gang" than a school. Such a gang was observed moving around i n a deep pool, fifteen feet in diameter in the Sumallo River during a bright, sunlit afternoon in September. The fish moved i n a group around the edge of the pool, feeding and hunting and f i n a l l y returning to a deep area where they rested. Then one or several fish started out once again and the others followed. This "following" was reminiscent of the "following" observed among dolly varden in the laboratory. As a feeding dolly varden darted at a food particle i t s movements attracted other fish which followed i t . Eastern brook trout behavior Soon after they were placed together brook trout fought with each other until one fish in each group became dominant. Thereafter occasional fighting occurred f o l -lowing feeding between the dominant and the fish second in rank i n both groups but each dominant fish held i t s po-sit i o n . In both groups the number two fish was slightly larger than the dominant snd in both groups the number two fi s h frequently contested dominance. During the i n i t i a l fishting the color of the com-batants intensified in a way which accentuated their -10&-markings. F o l l o w i n g the i n i t i a l f i g h t the v i c t o r gradually-l i g h t e n e d i n c o l o r w h i l e the defeated f i s h darkened. Sub-ordin a t e s were g e n e r a l l y darker than dominant f i s h and remained so most of the time ( F i g . 26). I f they became aggressive they o f t e n l i g h t e n e d i n c o l o r . Some v a r i a t i o n i n c o l o r p a t t e r n of subordinates was observed. Sometimes the sides were very dark w h i l e the d o r s a l surface l i g h t e n e d to a pale c o l o r . F i g . 26 - Dominant brook t r o u t swimming above subordinate of same species. Nipping. Dominance r e l a t i o n s were f a i r l y s t a b l e except between the dominant f i s h and the next most ag-g r e s s i v e ones. These r e l a t i o n s were c h a r a c t e r i z e d by l e s s f i g h t i n g and l e s s threatening than among d o l l y varden but -mo-more variable and expressive display. After the i n i t i a l encounters, nipping and chasing tended to replace fighting. The dominant f i s h nipped and chased i t s retreating subor-dinates, particularly after feeding. Tables XXIX and XXX show that a to t a l of 194 nips were recorded for group 1 and 240 nips for group 2. A l l but a small number of nips were performed by the dominant f i s h . The direction of nipping for each observation i s schematized in Tables XXXI and XXXII as peck orders. The number of nipping permutations in which the dominant fish was attacked by subordinates was greater after feeding. Activity. Brook trout remained immobile much of the time regardless of rank (Tables XXIX and XXX). Dominant fis h nipped and chased more while subordinates frequently retreated. Subordinates often performed escape swimming (Fig. 27) but i n general dominants had more freedom of action. The dominant fish i n each group tended to position iCself in relation to the feeding area both when on the bottom and in midwater. Subordinates avoided the dominant most of the time and rested i n corners or at the side. Im-mobile fish remained on the bottom somewhat more than they did i n midwater (Table XXXIII). T e r r i t o r i a l i t y . Dominant brook trout chased subordi-nates away from the feeding area and tended to remain there. Subordinates did not defend local areas very often from one another but did BO occasionally. - I l l -Fig. 27 - Brook trout swimming up and down the glass walls of their tank ("escape swimming"). Prey behavior. Brook trout reacted to potential danger as did the other residential species f i r s t by be-coming immobile and assuming a generalized alarm posture and fi n a l l y by f l i g h t . The alarm posture was sometimes assumed when one individual was approached by another in a social group but was most commonly adopted by fish which were strange to each other and which had not yet resolved their positions with regard to one another. Among fish which had lived in the same tank over an extended period, the alarm posture was seldom seen except as induced by a stimulus outside their tank. -las-Table XXIX Synopsis of the behavior of the four brook trout i n Group 1. Part A, activity analysis based on 40 records per f i s h . Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish BADI BANI BUPI BLOI Totals Social Position #1 #2 #4 #3 Immobile 31 14 11 30 86 53.75 Nipping & Chasing 1 1 .62 Retreating 1 1 .62 Food Sampling 1 1 1 3 1.88 Escape Swimming 6 26 20 8 60 37.50 Aimless Swimming 1 7 1 9 5.63 Threatening Part B Fish BADI BANI BUPI BLOI Totals Gapes 6 5 3 2 16 Nips 184 8 0 2 194 Threats 10 4 0 0 14 - H S -Table XXX Synopsis of the behavior of the four brook trout in Group 2. Part A, activity analysiB based on 40 records per fish. Part B, number of gapes, nips and Threats in eight 15 minute observations. Part A Fish BAB2 BAH2 BUP2 BL02 Totals Social Position #4 #3 #1 #2 # * Immobile 35 22 26 20 103 64.37 lipping & Chasing 1 11 12 7.50 Retreating 5 6 11 6.88 Food Sampling 2 2 .4 12.50 Escape Swimming 3 9 12 24 15.00 Aimless Swimming 2 1 3 6 3.75 Threatening Part B Fish' ' BAD2 BAH 2 BUP2 BL02 Totals Gapes 2 5 6 5 18 Hips 10 229 1 240 Threats 3 4 4 11 -114-Table XXXI Brook trout "peck orders" based on eight observations of Group 1. Numbers represent f i s h of d i f f e r e n t s o c i a l positions. Arrows point from attacker to f i s h attacked. Before Feeding After Feeding No nips 2 l ^ - > 3 ^ 4 No nips 1 4 — ^ 2 No nips -115-Table XXXII Brook trout "peck orders" based on eight observations of Group 2. Numbers represent fish of different social positions. Arrows point from attacker to fish attacked. Before Feeding After Feeding JL f& 1 * ^ ; 7 O ^ ^ 4 1 2 ^ 4 2 1 ^ ^ 3 ^ # 1<— A 3 :>4 _2 1 < — ^ 3 ^ " ^ 4 >^2 1 ^ — - > 3 ^ " ^ 4 -116-Table XXXIII The location of immobile brook trout on the substrate or in midwater. Group 1 Fish BADI (#1) BANI (#2) BUPI (#4) BLOI (#3) Totals Midwater Bottom 11 0 11 10 32 20 14 0 30 54' Group 2 Fish BAD2 (#4) BAN2 (#3) BUP2 (#1) BL02 (#2) Totals Midwater Bottom 11 16 6 13 46 24 6 20 7 57 -117-Resting posture. Resting brook trout supported them-selves on their fins and altered their posture and body flexure by changing the degree of expansion of their pec-torals i n the same way as did dolly varden. Sometimes subordinates rested upon each other but brook trout were less tolerant of the immediate presence of other f i s h than were dolly varden or lake trout. Rhythm and comfort movements. Brook trout were mark-edly phasic i n act i v i t i e s and at some times appeared to be more disposed to certain types of behavior than at others. This was particularly evident in dominant fish which were free to express their moods without external compulsion. Three different types of behavior could be distinguished which seemed to reflect an underlying state or mood. These were immobility, nipping and chasing and escape swimming Fish were observed to rest prolonged periods during which they did not attack each other or particularly respond to one another. Aggressive relations and escape swimming motions also appeared in prolonged periods. Each of these states involved characteristic actions. Resting f i s h were frequently observed to stretch their jaws in gaping motions. Aggressiveness and feeding were similarly linked. Aggressive fish interrupted nipping and chasing to bite at objects on the bottom or in suspension, then resumed their nipping and chasing; Feeding activity often preceded aggression as though the movements of feeding - l i a -aided the t r a n s i t i o n from one state to another. Sometimes, however, the f i s h would not feed or would not feed enough to bring about aggressive a c t i v i t y . Comfort movements were expressed as i n d o l l y varden. Gaping occurred somewhat more frequently i n the two highest ranking f i s h i n each group. I t may have been somewhat sup-pressed i n the subordinates whose i n a c t i v i t y d i d not always constitute rest but represented i n h i b i t i o n of a c t i v i t y by the dominant f i s h . Attack, threat and defense. Brook trout had highly developed threat behavior involving f r o n t a l display, l a t e r a l display, substrate b i t i n g and intention movements. Frontal display was usually directed toward strange f i s h and ag-gressive subordinates. L a t e r a l display was more defensive and was usually adopted by a f i s h when attacked by another. Frontal display ( F i g . 28) usually appeared i n f i s h which were at a distance equal to t h e i r body lengths or l e s s . As one brook trout commenced an attack i t lowered i t s hyals and dorsal f i n , arched i t s badk and turned s t i f f l y toward i t s opponent with i t s mouth s l i g h t l y open. The movement was generally very slow and the propulsion afforded by the undulation of the t a i l was retarded by the pectoral f i n s which were spread wide and held at right angles to the body. This action was very s i m i l a r to the equivalent one of d o l l y varden but d i f f e r e d c h i e f l y i n i t s slowness which made i t more conspicuous and of greater display value. -119-Fig. 28 - Threat displays of brook trout. Lateral display in foreground. Frontal display in back. Since the attacking fis h moved slowly i t provided more time for i t s opponent to retreat or counter with a lateral display. This enabled relatively complex behavioral inter-plays to develop between two individuals. Reciprocal dis-plays often occurred without actual biting. Lateral display (Fig. 29) oriented so that the de-fending fish exposed i t s side to i t s opponent while main-taining a position slightly in advance of i t . The display consisted of f u l l expansion of the fins with maximum erec--120-F i g . 29 - Brook tr o u t i n foreground assumes high i n t e n s i t y l a t e r a l d i s p l a y . t i o n of the d o r s a l . The body remained h o r i z o n t a l but assumed a head up, t a i l up, b e l l y down curvature. As i n f r o n t a l d i s p l a y , the v e n t r a l membranes of the head were expanded and the p e c t o r a l s were h e l d f u l l y expanded at r i g h t angles to the body. The body undulated r i g i d l y but forward movement was retar d e d by the out - t h r u s t pec-t o r a l f i n s . L a t e r a l d i s p l a y , which was defensive i n nature, was an expression of aggressive motivation j u s t as was f r o n t a l -121-dieplay. In the absence of aggressiveness, brook trout retreated rather than showed lateral display. It usually occurred in response to a frontal display from another fish but sometimes was adopted toward a strange fish pre-ceding frontal display. In an active aggressive encounter one fis h showed a frontal display and the other a lateral display, then they would reverse. Frequently both would display laterally and would move slowly forward eye to eye as shown in Fig. 30. As the attaoking fish approached, the defending one increased the amplitude of i t s body undulations and struck Fig. 30 - Forward progression of similarly directed, displaying brook trout. Non-participating subordinate on bottom of tank. -122-the attacker with i t s body and t a i l in a lateral t a i l -wagging motion (Figs. 31 and 32). When the attacker approached from the rear the de-fending fish wagged i t s f u l l y expanded caudal f i n back and forth and thus struck i t s opponent. Both lateral and retreating t a i l wagging were performed by fish i n lateral display. Intention movements developed threat significance through the association of individuals and were frequently performed by dominant fish toward subordinates. A movement of a dominant toward a subordinate became sufficient to cause i t to move away without necessitating chasing. In-tention movements largely replaced frontal displays after the establishment of dominance relations. Fig. 31 - Brook trout at l e f t defending i t s e l f by laterally wagging i t s body. -123-Fig. 32 - Brook trout at l e f t making extreme undulations of i t s body in defense against attack. The approach of an attacking fish in frontal display was usually slow but an attacking dominant fish approached i t s subordinates more rapidly. Biting, chasing and nipping were essentially the same movements as seen in dolly varden. Brook trout subordinates were quicker to avoid or retreat from dominant fish than were dolly varden. This may have indicated more acute recognition. Aggressive relations were less damaging among brook trout than among dolly varden. -124-The f i g h t i n g of brook trout was s i m i l a r to that of d o l l y varden i n that when the two combatants were f a c i n g i n the same d i r e c t i o n they made p a r a l l e l forward movements w i t h the eye of one c l o s e t o the eye of the other but, when they faced i n opposite d i r e c t i o n s , they chased each other i n a t i g h t c i r c l e ( F i g . 33). However, d i s p l a y was much more important and f i g h t i n g f i s h ( F i g s 34 and 35) were almost continuously i n e i t h e r f r o n t a l o r l a t e r a l d i s p l a y . F i g h t i n g movements were much slower than i n d o l l y varden and both l a t e r a l and f r o n t a l d i s p l a y s were h e l d as postures F i g . 33 - F i g h t i n g brook t r o u t s l o w l y c i r c l i n g each other. -125-which interrupted biting. This lengthened the duration of fight8 and one persisted for 25 minutes. As a rule, how-ever, a fight was a short duel of displays accompanied by several bites and lasting only a few minutes. Brook trout fought most often after feeding and when among strange f i s h . Fighting was extremely rare among unfed fish which had been together long enough to establish a dominance order. In both groups of four fis h which were intensively studied, the dominant fish had not firmly established their positions with regard to the individuals second in rank. Because of this, occasional fighting was observed. This was believed to be an unusual situation. Fig. 34 - Mutually displaying brook trout. -126-F i g . 35 - F i g h t i n g brook t r o u t i n d i s p l a y . Most subordinates crouched at the approach of the dominant f i s h and depressed t h e i r f i n s . Feeding. The movements of feeding were e s s e n t i a l l y the same as i n d o l l y varden. In the two groups s t u d i e d , a l l f i s h were observed to f e e d at each feeding p e r i o d r e g a r d l e s s of rank (Table XXXIV). I n most cases the dom-in a n t f i s h s t a r t e d feeding f i r s t and continued feeding l o n g e s t . The presence of food and the a c t i v i t y of feeding u s u a l l y e l i c i t e d n i p p i n g which began from two to 15 minutes a f t e r the i n t r o d u c t i o n of food. Table XXXIV Time r e q u i r e d f o r i n i t i a t i o n of feeding and nipping by brook t r o u t f o l l o w i n g i n t r o d u c t i o n of food. Four observations of each group. Each number represents the number of s u b o r d i -nates beginning to feed. "Dn designates dominant f i s h , " n M beginning of n i p p i n g . Minutes A f t e r Group 1 Group 2  Food Introduced Obs. 1 Obs. 2 Obs. 3 Obs. 4 Obs. 1 Obs. 2 Obs. 3 Obs.'4 15 ; n,D,2  14  13 1 12  11  10 ~ 9 , 8 n 7  6  5  4 3 n n 2 n n 1 1 n 1 2 3 2 3 0 D,l D,3 1 D,3 D D^ 2 ID D N.B. A l l f i s h f e d . -13ft-Schooling. Brook trout did not school but behaved in a way similar to dolly varden. They were observed to form gangs i n Sagehen Creek, California. Rainbow trout behavior Dominance was determined by vigorous i n i t i a l fighting soon after rainbow trout were placed together. During the fighting, color patterns became intensified (Fig. 36) as they had in brook trout. Sometimes the victor maintained i t s heightened color after achieving dominance as i l l u s -trated by the dominant fish in Fig 37. This fish was some-what darker below than above and maintained i t s spots and parr marks in bold r e l i e f . The color of a dominant rainbow usually faded after the establishment of i t s position. Fig. 36 - Heightened coloration of fighting rainbow trout. -129-F i g . 37 - Unusual r e t e n t i o n of f i g h t i n g c o l o r i n dominant rainbow t r o u t . Subordinates darkened f o l l o w i n g defeat and t h e i r be-h a v i o r was c h a r a c t e r i z e d by depression of t h e i r f i n s and avoidance of dominant i n d i v i d u a l s . They tended to crouch e i t h e r on the bottom or i n the corners of t h e i r tank. As they were chased by the dominant they became i n c r e a s i n g l y dark and subdued. On one occasion four two-year-old rainbows were placed together. One of them was very dark and sank immediately to the bottom where i t remained throughout the observations. I t never swam around or p a r t i c i p a t e d i n b e h a v i o r a l i n t e r -p l a y except t o be attacked by other f i s h . I t c o n t i n u a l l y maintained a depressed-fin posture on the bottom and -130 suggested in every way a fish which had adopted the habitual role of a subordinate and was unable to compete for domi-nance under new circumstances. Nipping. Dominance relations were quite stable and the same fish remained dominant throughout each observation. Nipping was more vigorous, more damaging and more frequent than among brook trout. In the f i r s t group, 392 nips were re-corded (Table XXXV) and i n the second group 263 nips were ob-served (Table XXXVI). As in previous species most of the nip-ping was done by the dominant individual in each group. The direction of nipping for each observation i s schematized in Tables XXXVII and XXXVIII as peck orders. Activity. Dominant rainbow trout were more active than brook trout but movement of subordinate fis h was i n -hibited by dominants and they were relatively inactive. Dom-inant activity was more diversified than that of subordinates. Dominant rainbows differed from dominants of Salvelinus species in that they almost never rested on the bottom. Whenever subordinates rested i n contact with the bottom this behavior appeared to be induced by other individuals rather than spontaneously motivated as in Salvelinus. T e r r i t o r i a l i t y . Dominant rainbows usually "patrolled" the feeding area and attacked any subordinates which entered i t . There were many examples of defense of areas connected with feeding but relatively l i t t l e defense of other sub-divisions of a tank -131-Table XXXV Synopsis of the behavior of the four rainbow.trout i n Group 1. Part A, a c t i v i t y analysis based on 40 records per f i s h . Part B, number of gapes, nips and threats i n eight 15 minute observations. Part A Fish KADI KANI KUPI KLOI Totals S o c i a l P o s i t i o n #1 #4 #3 #2 # * Immobile 4 6 32 29 71 44.38 Nipping & Chasing 1? 2 1 20 12.50 Retreating 16 3 5 24 15.00 Food Sampling 12 6 18 11.25 Escape Swimming 4 10 2 16 10.00 Aimless Swimming Threatening 3 2 3 3 11 6.87 Part B Fish KADI KANI KUPI KLOI Totals Gapes 19 2 0 1 22 Nips 288 17 49 38 392 Threats 30 6, 25 28 89 / -133-Table XXXVI Synopsis of the behavior of the four rainbow trout in Group 2. Part A, activity analysis based on 40 records per fis h . Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish KAD2 KAH2 KuP2 KL02 ' i Totals Social Position #3 #1 #3 #4 # f Immobile 37 1 34 35 97 60.63 Hipping & Chasing 11 1 13 7.50 Retreating 3 5 14 33 13.75 Food Sampling 5 3.13 Escape Swimming 15 1 16 10.00 Aimless Swimming 8 8 5.00 Threatening Part B Fish KAD2 KAHS KUP3 KL02 Totals Gapes 7 8 5 9 39 Hips 3 353 8 1 263 Threats 10 10 7 5 32 -133-Table XXXVII Rainbow trout "peck orders" based on eight obser-vations of Group 1. Numbers represent f i s h of different social positions. Arrows point from attacker to fish attacked. Before Feeding After Feeding ^ ^3 ' 1 • 1 — >3 », -134-Table XXXVIII Rainbow trout "peck orders" based on eight obser-vations of Group 2. Numbers represent fis h of dif-ferent social positions. Arrows point from attacker to f i s h attacked. Before Feeding After Feeding 1 >2 No nips 2 ^ — > 3 1 ^ 5 3 >-4 2 1 ^ —-> 3 ^ 4 ^ ^ 2 3 ^ 2 1 < ^ 3 „ 2 1 ^3 -135-Prey behavior. It was more d i f f i c u l t for a human observer to approach rainbow trout without disturbing them than i t was to approach any of the species of Salvelinus. They responded to potential danger by ceasing to move and by establishing a generalized alarm posture which was shat-tered by a further increase i n the alarming stimulus. When a dipnet was brought near one i t did not hold position but darted rapidly and frantically away. Thus there appeared to be a difference in the c r i t i c a l flight distance between the two genera. Another difference was i n the greater i n -tensity of flight exhibited by rainbow trout. Individuals frequently died of their exertions in attempting to escape but such deaths were never observed among lake trout, dolly varden or eastern brook trout. Rhythm and comfort movements. Rainbow trout were phasic like other species and their behavior was quite different on different occasions. The three types of be-havior which seemed to express underlying moods were tonic immobility, non-aggressive escape swimming and social-feeding behavior. The exact relationship between feeding and aggressiveness was not entirely clear but they again appeared to be linked. In addition to these behavior phases, there were rhythms of activity within a phase. These rhythms were most evident in dominant fish since they were not restricted by other individuals. A -136-ten minute record of the behavior of the dominant fish in Group 2 revealed cycles in which i t attacked for five seoonde and rested for 15. Comfort movements were similar to those in other species. Attack, threat and defense. Rainbow trout displays were intermediate in complexity between dolly varden and brook trout and different i n several ways from those of Salvelinus species. Threatening was f a i r l y well developed but not as detached from physical attack as i n brook trout. Frontal and lateral displays took place among highly motivated fish and substrate biting occurred f o l l -owing feeding. Dominant f i s h made many intention move-ments during periods of low motivation. The frontal display of rainbow trout (Fig. 38) was quite different from that of Salvelinus species and seemed to be an extension of lateral display. An attacking rain-bow oarried i t s dorsal f i n erect and a l l i t s other fins extended. As i t moved toward another f i s h i t opened i t s mouth a l i t t l e and only slightly lowered the ventral parts of i t s head. It held i t s peotorals out to the side, undulated i t s body, and usually moved toward i t s opponent with i t s head down and i t s t a i l up. It did not arch i t s back as did cgalvelinus species. Lateral display was poorly differentiated from frontal display in that they both involved fin-up postures in -137-F i g . 38 - Rainbow t r o u t f r o n t a l d i s p l a y at back, l a t e r a l d i s p l a y i n f r o n t . which the body was f l e x e d r a t h e r than arched. The ex-p r e s s i o n of the l a t e r a l d i s p l a y depended upon high ag-g r e s s i v e m o t i v a t i o n and, as i n brook t r o u t , i t f r e q u e n t l y preceded f r o n t a l d i s p l a y and a t t a c k . I t occurred a l s o as a defensive d i s p l a y i n response to the attack of another f i s h , but only when the attacked f i s h i t s e l f was aggress-i v e l y motivated. The l a t e r a l l y d i s p l a y i n g rainbow of t e n d i s p l a y e d at a greater distance from i t s object than d i d brook t r o u t , f r e q u e n t l y s e v e r a l times the l e n g t h of the f i s h . I t assumed a r i g i d posture i n which the caudal end u s u a l l y sank lower than the head ( F i g s . 38 and 3 9 ) . I t s oblique body f o l l o w e d the movements of i t s opponent -13 8-Fig. 39 - Rainbow trout dominant i n lateral display at right. and maintained i t s side toward i t while at the same time i t moved i t s t a i l back and forth. The hyals were only slightly lowered, i f at a l l , during the display. Lateral tail-wagging was similar to that in brook trout. Retreating tail-wagging defended an aggressively motivated fish from an attacker from the rear. During this display the body was usually slightly oblique with the head down and the widely expanded t a i l up as i t beat back and forth at the head of the attacker (Fig. 40) The attacker'8 approach was sometimes slow and some-times rapid. If slow, i t maintained i t s frontal display -139-Fig. 40 - Rainbow at l e f t defending i t s e l f by wagging i t s t a i l as i t retreats. up to the side of the other fish. When the approach was rapid, most of the elements of frontal display such as the erection of the dorsal, the out-thrust pectorals and the body undulation were not present. Nipping usually did not involve actual contact (Fig. 41) but sometimes did (Fig. 42). Dominants pursued their subordinates relentlessly and nipped as many as ten times in a single chase (Fig. 43). Fighting occurred in the same circumstances as among dolly varden or brook trout. It was essentially the same as the fighting of those species although somewhat faster. When parallel, reciprocally displaying fish moved forward Fig. 41 - Rainbow nipping usually did not contact the opponent. Fig. 42 - Sometimes one rainbow actually contacted while nipping. -141-Fig. 43 - Dominant rainbows chased their subordinates relentlessly. eye to eye and when facing in opposite directions they circled. The greater use of display in rainbow trout as compared to dolly varden made their movements more inter-mittant since they moved more slowly or came to a stop while displaying and moved rapidly while attacking. Avoiding, retreating and crouching were performed as by brook trout. Feeding. Midwater orientation of rainbow trout caused them to respond more actively to food particles in sus-pension or at the surface than did members of the genus -142-S a l v e l i n u s . Large rainbows appeared to be l e s s predatory than lake t r o u t of the same s i z e and nipped small t r o u t w i t h i n a s o c i a l framework ra t h e r than f e d upon them as prey. Rainbow t r o u t f e d on earthworms ( F i g . 44) when these were a v a i l a b l e and shook them and rearranged them i n t h e i r mouths the same way as l a k e t r o u t rearranged s m a l l f i s h t h a t they had s e i z e d . Feeding was i n f l u e n c e d by rank. The dominant f i s h almost always began feeding f i r s t (Table XXXIX) and con-t i n u e d eating longest. At l e a s t one subordinate f a i l e d t o feed during each observation. The dominant f i s h began n i p p i n g one to 15 minutes a f t e r the i n t r o d u c t i o n of food and chased the subordinates away from the feeding area. Thus, not only d i d some subordinates get nothing to eat, F i g . 44 - Rainbow t r o u t w i t h earthworm i n mouth. Table XXXIX Time required for in i t i a t i o n of feeding and nipping by rainbow trout following intro-duction of food. Four observations of each group. Each number represents the number of subordinates beginning to feed. ,fD" designates dominant fish, "n n beginning of nipping. Minutes After Group 1 Group 2 Food Introduced Obs. 1 Obs. 2 Obs. 3 Obs. 4 Obs. 1 Obs. 2 Obs. 3 Obs. 4 15 n 14 13 12 11 10 1 l,n 9 8 - n 7 l,n 1 6 5 D 1 4 3 " l,n 2 n 1 1 n •1 0 D D • D,l D D,l D,l D N . B. In a l l cases dominant prevented some orall from feeding. -144-but those which ate did not consume as great a quantity as did the r dominant:' c; f i s h . Schooling. Schooling was not observed among rainbow trout. Behavior of older rainbow trout Rainbow trout of the "Kamloops trout" type were ob-tained from the Provincial Fish and Game Branch's Smith Falls Hatchery at Oultus Lake and maintained at the Vancouver Public Aquarium i n freshwater. These were several years old upon arri v a l at the Aquarium. During the year while under observation they remained very ag-gressive. In a 220 gallon tank one fish dominated the others and chased them continuously. Some of the sub-ordinates died. Two-year old rainbow trout ("steelheads") were ob-tained from the same source and converted to seawater. At the time of writing these had been under observation for two years and some were developing spawning coloration. They remained aggressive throughout the entire period. In a 220 gallon tank one individual tended to dominate the others and to chase them vigorously. Under these conditions some individuals grew faster than others. Later, a l l were placed in a 12,000 gallon tank where ag-gressive encounters s t i l l took place but where severe domination by one fish was not evident. Growth may have -145-been more uniform in this tank. It was observed that a l l fed well and grew perceptibly where previously subordinate fish often did not feed. Cutthroat trout behavior Dominance relations developed as i n other species through i n i t i a l aggressive encounters involving display and fighting. Color patterns were intensified during these encounters but following their resolution the dom-inant fish faded while subordinates usually developed a dark band along each side (Fig. 45). Dominance relations did not appear to be as secure as they were in other species because the dominant individuals were not as Fig. 45 - A subordinate cutthroat at l e f t and dominant rainbow at right. -146-aggressive as those of other species. This may have been related to poorer adjustment to aquarium conditions or to lower level of aggressive motivation. Nipping. Cutthroats nipped less and were less ag-gressive than rainbow trout (Tables XL and XLI). A large part of the total number of nips recorded for Group 1 were performed by the fish second in rank. In Group 2 nipping by subordinates was comparatively insignificant. The nipping interrelationships are indicated in Tables XLII and XLIII. Activity. Dominant cutthroats were somewhat more active than subordinates though less active than dominant rainbow trout. Cutthroats resembled rainbows i n that they did not rest on the bottom but held position i n midwater. Te r r i t o r i a l i t y . Cutthroats showed .territorial char-acteristics similar to those shown by dolly varden, brook trout and rainbow trout. Prey behavior. Cutthroat trout behaved as i f they were constantly frightened and remained motionless in a generalized alarm posture (Fig. 46) much of the time. If startled, they would dart away and become increasingly agitated. If chased back and forth by the observer they would often die as they frantically attempted to escape. In these respects they were similar to, but more extreme, than rainbow trout. -147-Table XL Synopsis of the behavior of the four cutthroat trout i n Group 1. Part A, activity analysis based on 40 records per f i s h . Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish CADI CANI ' CUPI 1 CLOI Totals Social Position #1 #4 #3 #2 # $ Immobile 13 25 17 26 80 53.33 Nipping & Chasing 7 1 8 5.33 Retreating 2 2 4 2.66 Food Sampling 10 2 3 3 18 12.00 Escape Swim-ming 3 4 11 2 20 13.34 Aimless Swimming Threatening 4 1 7 8 20 13.34 Part B Fish CADI CANI CUPI CLOI Totals Gapes 12 3 0 2 17 Nips 115 1 25 68 209 Threats 41 19 43 46 149 -146-Table XLI Synopsis of the behavior of the four cutthroat trout in Group 2. Part A , activity analysis based on 40 records per fish . Part B , number of gapes, nips and threats in eight 15 minute observations. Part A Fish CAD2 CAN 2 CUP2 CL02 Totals Social Position #1 #3 #3 #4 Immobile 2© 23 34 26 103 64.37 Nipping & Chasing 3 3 1.88 Retreating 1 2 1 4 2.50 Food Sampling Escape Swimming 9 5 10 24 15.00 Aimless Swimming 6 11 3 3 23 14.37 Threatening 2 1 3 1.88 Part B Fish CAD2 CAN 2 CUP2 CL02 Totals Gapes 5 4 9 8 26 Nips 140 10 2 2 154 Threats 27 7 12 15 61 -149-Table XLII Cutthroat trout "peck orders" based on eight observations of Group 1. Numbers represent fish of different social positions. Arrows point from attacker to fish attacked. Before Feeding After Feeding 2 vl/ >3 2> > 3 1< 2 , 4(died) 2 'is * 3 4(died) 2 1 ^ ^3 ,2 •>3 -1'5'Q-Table X L I I I Cutthroat t r o u t "peck orders" based on eight ob-ser v a t i o n s of Group 2. Numbers represent f i s h of d i f f e r e n t s o c i a l p o s i t i o n s . Arrows point from a t t a c k e r to f i s h a t t a c k e d Before Feeding A f t e r Feeding 2 1 < 3 4 s^ 2 1 ^ ^ _ ^ 3 2 v. 2 1 3 ^ 4 No nips 4/ -151-F i g . 46 - Generalized alarm posture of cutthroat t r o u t . Rhythm and comfort movements. Cutthroats showed var i o u s behavior phases but they were l e s s a c t i v e than rainbows and t h e i r moods were harder to d i s t i n g u i s h . T h e i r i m m o b i l i t y was u s u a l l y a motionlessness which pre-ceded f l i g h t r a t h e r than one of r e s t and a l l of t h e i r behavior i n an aquarium was c h a r a c t e r i z e d by i n h i b i t i o n i n which a c t i o n patterns were seldom f u l l y expressed. P o s s i b l y i t was t h i s i n h i b i t i o n which prevented the cut-t h r o a t from being as i n t e n s e l y aggressive as rainbow t r o u t Snapping of the jaws and f l i c k e r i n g of the f i n s were common and seemed to be r e l a t e d t o the poor adjustment of t h i s species to c a p t i v i t y . Gaping commonly occurred. -152-F i g . 47 shows a cu t t h r o a t completing a gaping movement. Attack, t h r e a t and defense. D i s p l a y movements were r e l a t e d to the e x h i b i t i o n of the red throat s t r i p e s and were q u i t e d i f f e r e n t from those of the c l o s e l y r e l a t e d rainbow t r o u t . They resembled the d i s p l a y s of S a l v e l i n u s s p e c i e s . Before and during a t t a c k a c u t t h r o a t would sometimes assume a f r o n t a l d i s p l a y ( F i g . 48) i d e n t i c a l to that of brook t r o u t . I t arched i t s back, lowered i t s d o r s a l f i n , spread out i t s p e c t o r a l s , lowered the v e n t r a l membranes of i t s head and turned upon i t s opponent w h i l e c o a r s e l y undulating the body. The g l o s s o h y a l was depressed lower than i t was i n any of the other salmonids and thus s t r e t -ched and exposed the v e n t r a l membranes of the head to an F i g . 47 - Cutthroat t r o u t completing gaping movement. -153-F i g . 48 - Cutthroat t r o u t i n foreground e x h i b i t s a f r o n t a l -type d i s p l a y i n l a t e r a l p o s i t i o n . I t s oppo-nent shows alarm posture. extreme degree. In t h i s way the red s t r i p e s normally concealed by the f o l d s l y i n g between the dentaries and ceratohyals were maximally e x h i b i t e d . While d i s p l a y i n g , a c u t t h r o a t u s u a l l y moved very s l o w l y i f at a l l and would h o l d a l a t e r a l p o s i t i o n to one s i d e w h i l e i n a posture of f r o n t a l d i s p l a y ( F i g s . 49 and 50). This use of a f r o n t a l posture i n a l a t e r a l p o s i t i o n was e x h i b i t e d by the three species of S a l v e l i n u s during a build-up of aggressiveness j u s t p r i o r to t u r n i n g and a t t a c k i n g t h e i r opponents. I t thus preceded and s i g -n a l i z e d immediate a t t a c k . In the c u t t h r o a t , however, the -154-Fig. 50 - Dorsal f i n down in cutthroat trout display. -155-frontal display was held for longer periods i n lateral position and occurred frequently without subsequent attack. It thus represented an extension of frontal display func-tion and a displacement of lateral display; a phenomenon analogous but opposite to that in the rainbow trout in which the la t e r a l display displaced the frontal. The lateral display was different from those of brook and rainbow trout which were characterized by erected fins and a slightly bowed body oriented in relation to an attacking f i s h . Instead, the arched frontal display was expressed i n a lateral position. Lateral t a i l wagging and retreating t a i l wagging were not observed. Following the establishment of a dominance order intention movements constituted the most common form of threat. These were usually effective in causing ano-ther fish to withdraw. Approaching, biting, chasing and nipping were similar to these actions in rainbow trout. Nipping did not appear to be as physically injurious as in rainbow but cutthroats were more disturbed by being nipped than were rainbows. Fighting occurred very rarely among cutthroats. It resembled fighting among dolly varden i n that only frontal display was seen and in that the fighting f i s h frequently circled. Cutthroats retreated as a result of very slight -156-stimulation and retreat frequently transformed into wild, headlong f l i g h t . A dominant fish would attack a subor-dinate causing i t to dart away and, as the dominant pursued, the subordinate moved more and more erratically, darting into comers, striking the glass sides of the tank and losing the normal manoeverability possessed by retreating salmonids of other species. Sometimes the fright of the subordinate was strangely communicated to the fish chasing i t and instead of chasing, i t suddenly took on a frightened appearance and darted along with i t s opponent. Subordinates often lowered their dorsal fins and crouched down at the approach of a more aggressive fish as in rainbow and brook trout. Feeding. Feeding movements resembled those of rainbow trout except that they were not as vigorous. Here again the cutthroats appeared to be inhibited in captivity. Table XLIV shows that most fish fed at feeding time though the i n i t i a t i o n of feeding by subordinates was often de-layed a few minutes. On one occasion: the dominant fish of Group 2 fa i l e d to feed. Nipping usually interrupted feeding. Cutthroats 12-15 cm long or longer readily fed on salmon fry. Just as in the case of lake trout, ^there were two predatory approaches: a rapid dart at a f i s h followed by a rapid dart when the small fish began to flee. T a b l e X L I V Time r e q u i r e d f o r i n i t i a t i o n o f f e e d i n g and n i p p i n g by c u t t h r o a t t r o u t f o l l o w i n g i n t r o -d u c t i o n o f f o o d . F o u r o b s e r v a t i o n s o f e a c h g r o u p . E a c h number r e p r e s e n t s t h e number o f s u b o r d i n a t e s b e g i n n i n g t o f e e d . " D n d e s i g n a t e s d o m i n a n t f i s h , " n n b e g i n n i n g o f n i p p i n g . M i n u t e s A f t e r Group 1 Group 2 F o o d I n t r o d u c e d O b s . 1 O b s . 2 O b s . 3 O b s . 4 O b s . 1 O b s . 2 O b s . 3 O b s . 4 15 14 13 12 n 11 10 9 8 n 7 1 n 6 n 1 5 n 1 4 2 1 n 3 n 1 2 1 1 1 0 D , l D , l D , l D , l D , l D , 3 D , 2 3 N . B . F a i l u r e t o f e e d i n o n l y two c a s e s . -15 8-Schooling. Cutthroats d i d not school but they were more t o l e r a n t of the c l o s e presence of other i n d i v i d u a l s than were rainbow t r o u t and f r e q u e n t l y s e v e r a l would h o l d p o s i t i o n c l o s e to one another f o r a per i o d . Coho salmon f r y behavior Coho f r y fought v i g o r o u s l y w i t h one another s h o r t l y a f t e r being pl a c e d together. The v i c t o r i n a tank became dominant and the l o s e r s became subordinate. Less c o l o r change was a s s o c i a t e d w i t h f i g h t i n g and s o c i a l p o s i t i o n than among t r o u t but subordinates were u s u a l l y darker than dominants. F i g s . 51 and 52 con t r a s t the c o l o r and appearance of a dominant and a subordinate coho. F i g . 51 - Subordinate coho salmon. -159-F i g . 52 - Low i n t e n s i t y l a t e r a l d i s p l a y of coho salmon. Nipping. Dominance r e l a t i o n s were very s t a b l e w i t h the dominant f i s h doing most of the n i p p i n g i n each group. Table XLV shows that the dominant made 372 n i p s out of a t o t a l of 425 f o r Group 1. T a b l e XLVI shows that the dominant f i s h i n Group 2 made 256 n i p s out of a t o t a l of 303. Nipping replaced f i g h t i n g a f t e r the i n i t i a l en-counters and was f r e q u e n t l y severe. Nipping permutations are i n d i c a t e d as peck orders i n Tables XLVII and XLVIII. A c t i v i t y . Coho f r y remained immobile a h i g h pro-p o r t i o n of the time. Dominants were more a c t i v e than subordinates (Tables XLV and XLVI) and much of the i n a c -t i v i t y of the l a t t e r represented i n h i b i t i o n . Dominants possessed more freedom of movement and more o f t e n searched -ISO-Table XLV Synopsis of the behavior of the four coho f r y i n Group 1. Part A, a c t i v i t y analysis based on 40 records per f i s h . Part B, number of gapes, nips and threats i n eight 15 minute observations. Part A Fis h COADI COANI COUPI C0L0I Totals Social P o s i t i o n #2 #3 #4 #1 # 1» Immobile 34 40 40 6 120 75.00 Nipping & Chasing 2 2 1.25 Retreating 1 1 .63 Food Sampling 15 15 9.37 Escape Swimming Aimless Swimming 5 14 19 11.87 Threatening 3 3 1.88 Part B Fis h COADI COANI COUPI C0L0I Totals Gap es 3 5 5 9 22 Nips 34 19 0 372 425 Threats 19 11 0 16 46 -161-Table XLVI Synopsis of the behavior of the four coho fry i n Group 2. Part A, activity analysis based on 40 records per fi s h . Part B, number of gapes, nips and threats in eight 15 minute observations. Part A Fish GOADS CO AN 2 C0UP2 COL 02 Totals Social Position #3 #1 #3 #4 # 1o Immobile 33 18 25 32 107 66.88 Nipping & Chasing 2 6 4 12 7.50 Retreating 4 4 5 13 8.13 Food Sampling 4 2 2 8 5.00 Escape Swimming 1 1 .63 Aimless Swimming 2 11 5 18 11.33 Threatening 1 1 .63 Part B Fish C0AD3 C0AN2 C0UP2 C0L02 Totals Gapes 8 6 9 1 24 Nips 33 256 15 0 303 Threats 13 21 7 0 41 -162-Table XLVII Coho salmon "peek orders" based on eight obser-vations of Group 1. Numbers represent fis h of different social positions. Arrows point from attacker to fish attacked. Before Feeding After Feeding v—"ti _2 «*2 \<——>3 ^ ^ 4 -163-Table XLVIII Coho salmon "peck orders" based on eight obser-vations of Group 2. Numbers represent fish of different social positions. Arrows point from attacker to fish attacked Before Feeding After Feeding 4 >4 —->3 ^*4 1 ... ) 3 No nips ^ ) -164-f o r food than d i d subordinates. Dominants never rested on the bottom of t h e i r tank (Table XLIX) and subordinates d i d so only when severely dominated. Movement consisted of very r a p i d darts and sudden stops. They often darted, stopped, turned and darted back to t h e i r o r i g i n a l l o c a t i o n . This frequent turning and r a p i d darting was d i s t i n c t i v e to the species. T e r r i t o r i a l i t y . Dominant coho f r y occupied and pa-t r o l l e d the feeding area within t h e i r tank and nipped sub-ordinates whenever they approached. The darting movements, followed by a return to the o r i g i n a l locations was an important manifestation of t e r r i t o r i a l behavior. Prey behavior. Coho f r y were extremely s e n s i t i v e to outside stimulation. In t h i s regard they were intermediate between rainbow and cutthroat trout. They could not be approached by the observer as e a s i l y as char could. They frequently maintained an alarm posture i n res-ponse to outside stimulus but the existence of alarm man-i f e s t a t i o n s d i d not appear to prevent a c t i v i t y as i n cut-throat trout. Coho f r y would show alarm, dart at a food p a r t i c l e , then stop and resume the alarm posture. Their movement consisted of darting swimming and stopping motions i n which the alarm posture was frequently adopted. Rhythm and comfort movements. The main indications of differences of mood were i n the greater readiness of the f i s h to feed or nip at some times rather than others. -165-Table XLIX The location of immobile coho salmon with relation to the bottom. Group 1 Fish 1 C0ADI(#2/) COANI(#3) C0UPI("#4) C0L0l(#l) rotals Midwater Bottom 34 30 4 0 6 10 110 10 Group 2 Fish C0AD2(#3) C0AN2(#1) C0UP2(#2) C0L02(#4) Totals Midwater Bottom 24 18 16 12 8 9 20 70 37 -166-Sometimes they remained motionless without feeding a l -though, u n l i k e c u t t h r o a t t r o u t , they u s u a l l y responded r e a d i l y t o food or other f i s h even though i n a g e n e r a l i z e d alarm posture. Rhythms of a c t i v i t y were d i f f i c u l t to detect because of the general s t a t e of t o n i c i m m o b i l i t y . Escape behavior was r a r e l y observed and thereby c o u l d not c o n s t i t u t e a separate behavior phase. Frequency of gaping,^ c o u l d not be c o r r e l a t e d w i t h the most i n a c t i v e f i s h p o s s i b l y because t h e i r i n a c t i v i t y was o f t e n induced by i n h i b i t i o n and was not n e c e s s a r i l y a r e s t i n g s t a t e . A t t a c k , t h r e a t and defense. Coho f r y were very ag-g r e s s i v e and they devoted a l a r g e p a r t of t h e i r energies to a t t a c k i n g and r e t r e a t i n g . Threat d i s p l a y s were w e l l developed and most f r e q u e n t l y used i n encounters between f i s h strange to each other. F r o n t a l d i s p l a y resembled that i n char and cutthroat t r o u t i n that the d o r s a l f i n was lowered and the h y a l p a r t s of the head were lowered (but l e s s extremely than i n the other s p e c i e s ) . I t d i f f e r e d from the a c t i o n of the other species i n that the body was not hunched, e v i -d e n t l y because the deeper body of the coho was not as f l e x i b l e and would not bend i n t o the p e c u l i a r l y arched shape c h a r a c t e r i s t i c of the f r o n t a l d i s p l a y s o f the other s p e c i e s . The body was u s u a l l y o b l i q u e w i t h the head down and the t a i l up. The p e c t o r a l f i n s were h e l d s t r a i g h t -16?-out from the Bides as i n brook, rainbow and cutthroat trout. Frontal display was of short duration and was never maintained i n a l a t e r a l p o s i t i o n as i t was i n cut-throat trout. A f i s h usually lowered i t s dorsal f i n as i t turned to attack i t s opponent and t h i s became the posture of attack. The display was adopted both when the attacker was near another f i s h and when i t was 10-15 em away. The great r a p i d i t y of motion of coho may have been a factor i n the display being expressed at a greater d i s -tance than i n the other species. Lateral display ( F i g . 53) was quite similar to that of rainbow trout. The dorsal was f u l l y erected and a l l other f i n s were r i g i d l y expanded. The side of the d i s -playing f i s h was oriented toward i t s opponent and the body took on an oblique posture. The more vigorous the display, the more extreme became the angle of the f i s h u n t i l i t was almost v e r t i c a l with the head up and the t a i l down ( F i g . 53). The pectorals were held f u l l y expanded straight out from the body and t h i s retarded forward movement induced by gross wagging of the t a i l . The hyal region was s l i g h t l y extended. As i n other species t h i s display appeared only i n aggressively motivated i n d i v i d u a l s when attacked or threatened by others and as a precursor to f r o n t a l display and attack. Lateral t a i l wagging and retreating t a i l wagging were frequent defensive actions. The stouter body of the coho -168-F i g . 53 - High i n t e n s i t y l a t e r a l d i s p l a y of coho on r i g h t as brook t r o u t approaches. d i d not permit as extreme sinuous movements as seen i n brook t r o u t . Coho f r y f r e q u e n t l y made i n t e n t i o n movements. One f i s h d i s p l a y e d at another then rushed at i t and stopped j u s t before i t came i n contact w i t h the other. This d i f -f e r e d from o r d i n a r y n i p p i n g i n th a t the a t t a c k i n g f i s h stopped before reaching i t s opponent i n s t e a d of missing as a r e s u l t of the evasive movements of the r e t r e a t i n g f i s h . These i n t e n t i o n movements occurred i n various de-grees. A f i s h might only lower i t s d o r s a l f i n , i t might t u r n toward the other w i t h or without elements of f r o n t a l d i s p l a y or i t might rush d i r e c t l y at the other. Although -169-frontal display was not separate from approaching, inter-ruption of attack gave i t more threat significance than had the frontal display of the dolly varden. Substrate biting beneath another fish was a common threat action among coho fry. The approach of an attacking coho was often very swift. It would hurl i t s e l f at i t s opponent i f the latter were at a distance. It the two fish were close together the attacker would sometimes merely turn and bite without rapid approach. Coho did not chase each other in extended runs as did other species. The typical pattern was a darting movement toward the other fish followed by a nip and a return to i t s original position. No sustained fighting such as that for dolly varden, and brook, rainbow and cutthroat trout was ever observed. Aggressive encounters were short, sharp and fast-moving, followed by a separation and perhaps another encounter after a few moments. During an encounter coho sharply changed their displays and postures. A threatening fish held i t s head up and beat i t s t a i l back and forth while i t s body was very r i g i d and i t s dorsal and anal f i n were expanded. Suddenly i t lowered i t s dorsal, leveled i t s body and turned toward i t s opponent. It would rock back >, and forth between the head-up lateral display and the head-down frontal display, dart suddenly at the other -170-f i s h , stop, turn up into l a t e r a l display, dart away wagging i t s t a i l i n a retreating tail-wag and then stop absolutely s t i l l and remain that way for a few moments. Aggressive encounters were more abrupt, intermittant and rapid than i n other species. Intention movements i n the form of rapi d , interrupted rushes were common. Avoidance was not a common behavior pattern since coho di d not very often swim aimlessly about as did lake trout. Coho generally retreated under control and, because aggressive i n d i v i d u a l s did not chase f a r , they did not need to retreat a great distance. They d i d not e a s i l y lose control and damage themselves as did cutthroat trout. Subordinates contracted th e i r f i n s at the approach of a dominant ( F i g . 51) i n midwater or crouched down when near the bottom. Feeding. Coho f r y were unbelievably rapid feeders. They took most of the i r food i n midwater before i t reached the bottom but fed on objects on the bottom as well as above i t ( F i g . 54). During feeding their behavior changed quickly. At one moment they fed while c i r c l i n g r a p i d l y . At the next they became completely immobile and ignored any remaining food ( F i g . 55 and 56). Suddenly they became ac t i v e and p a t r o l l e d i n a group back and forth across the bottom and ejecting mouthfuls of d e t r i t u s . P a t r o l l i n g gradually subsided and the dominant chased the subordinates from the feeding area where i t remained b i t i n g at the sub--171-F i g . 54 - Coho feeding on bottom. F i g . 55 - Alarmed coho immobile over feeding area. -1>72-F i g . 56 - Immobile coho over feeding area. s t r a t e and d a r t i n g out at the others. Most f i s h f e d immediately as food was p l a c e d i n the tank (Table L ) . Those which d i d not were subordinates. On two occasions a subordinate d i d not feed at a l l . The dominant f i s h began n i p p i n g 3-10 minutes a f t e r food was introduced. This r e s u l t e d i n the expulsion of the subor-dinates from the feeding area. Schooling. Coho f r y d i d not school but under some con d i t i o n s they aggregated more than Salmo and S a l v e l i n u s d i d . They were intermediate i n t h i s regard between the preceding non-schooling species and the school i n g species of Onoorhynchus. The formation of gangs ocourred among coho and they had a greater tendency t o move i n feeding Table L Time r e q u i r e d f o r i n i t i a t i o n of feeding and n i p p i n g by coho salmon f o l l o w i n g i n t r o d u c t i o n of food. Four observations of each group. Each number represents the number of su b o r d i -nates beginning t o feed. "D" designates dominant f i s h , "n" beginning of n i p p i n g . Minutes A f t e r Group 1 Group 2 Food I n t r o d u c t i o n Obs. 1 Obs72 Obs. 3 Obs. 4 Obs. 1 Obs. 2 Obs. 3 Obs. 4 15 ; i  14  13  12_ 11 10 n 9  8  7  6 n n 5 n n 4 3 n n 1 n 2 1 1 • 0 D,2 D,2 D,2 D,2 D,3 D,3 D,3 D,3 N. B. F a i l u r e to feed i n two cases. -174-groups than the others. They were more s e n s i t i v e to p o t e n t i a l danger than char or rainbow t r o u t . Under c o n d i t i o n s of s l i g h t disturbance they drew together and f o l l o w e d each other more than d i d the other s p e c i e s . Cutthroat t r o u t , which were more sen-s i t i v e than coho, u s u a l l y l o s t c o n t r o l more q u i c k l y and s c a t t e r e d r a t h e r than drew together and followed. Subordinates seemed t o t o l e r a t e each other and, i n groups of t e n , 5-8 f i s h f r e q u e n t l y c l u s t e r e d together as a r e s u l t of the aggressive a c t i v i t y of a dominant f i s h . Coho smolt behavior Coho salmon smolts were i n h i b i t e d i n a c t i o n and more e a s i l y f r i g h t e n e d than f r y when c o n f i n e d i n a small tank. They of t e n remained motionless i n a group f o r long per-i o d s at a time q u i t e near the bottom of the tank although not a c t u a l l y touching i t as d i d S a l v e l i n u s s p e c i e s . They showed considerable aggressive behavior but expressed i t i n a more e r r a t i c sequence than seen i n f r y . Although they nipped f r e q u e n t l y they d i d not chase very much and the development of dominance was obscured by the tendency f o r a l l i n d i v i d u a l s to become immobilized i n a group. They showed very l i t t l e d i s p l a y and confined the use of t h r e a t t o i n t e n t i o n movements. -175-Coho g r i l s e behavior Coho salmon smolts were converted from freshwater to seawater i n the Vancouver P u b l i c Aquarium i n 1956 and 1957. They remained aggressive throughout the e n t i r e p e r i o d of obse r v a t i o n . In a 220 g a l l o n e x h i b i t tank one f i s h emerged dominant and t h e i r m o r t a l i t y was hig h . At the end of two years a l l subordinates had died w h i l e the dominant r e -mained i n good c o n d i t i o n . Chinook salmon f r y behavior Chinook f r y observed i n summer were midwater i n o r i e n -t a t i o n and i n t e r m i t t a n t i n swimming motion. They were aggressive and formed dominance r e l a t i o n s f o l l o w i n g en-counters i n which d i s p l a y was l e s s w e l l developed than i n coho f r y and more suggestive of coho smolt behavior. No c o l o r changes were observed but t h i s species was not as thoroughly s t u d i e d as previous ones and t h i s may have been missed. Sockeye f r y behavior Sockeye f r y , observed soon a f t e r emerging from the g r a v e l i n the s p r i n g , d i d not n i p , chase or form dominance r e l a t i o n s . They were as a c t i v e as coho f r y but not as r a p i d i n movement. They swam up and down i n the corners of the tank much of the time (escape swimming) as d i d -176-brook t r o u t and dominant rainbow t r o u t . Sockeye smolt behavior Sockeye salmon smolts were observed i n freshwater at the end of summer at a time when they would o r d i n a r i l y be i n the ocean. They tended to aggregate and remain immo-b i l e . There was very l i t t l e aggressiveness, although a few nips were recorded, and no development of a dominance r e l a t i o n s h i p . Some "escape swimming" and considerable simultaneous a c t i o n was observed whereby a l l would be ac-t i v e , then a l l immobile. There was a strong tendency t o f o l l o w one another but the low l e v e l of a c t i v i t y prevented the formation o f moving schools as observed among chum f r y . When a rainbow t r o u t was p l a c e d i n the tank, i t s aggressive approaches caused sockeyes t o elev a t e t h e i r d o r s a l f i n s i n g e n e r a l i z e d alarm. They d i d not u s u a l l y r e t r e a t but when they d i d they swam i n r a p i d , u n c o n t r o l l e d movements. Sockeye g r i l s e behavior Sockeye salmon g r i l s e obtained from the B i o l o g i c a l S t a t i o n at Uanaimo were maintained f o r two years i n sea-water i n the Vancouver P u b l i c Aquarium. During t h i s p e r i o d only o c c a s i o n a l n i p p i n g was observed and no i n d i v i d u a l emerged dominant. The behavior of these f i s h c o n t r a s t e d markedly w i t h that of coho salmon and steelhead t r o u t -17 7-under the same circumstances. Sockeye salmon showed con-s i d e r a b l e u n i f o r m i t y i n s i z e at the end of two years a l -though they were much sma l l e r than they would have been under n a t u r a l c o n d i t i o n s . Chum salmon f r y behavior Chum f r y were observed i n the s p r i n g soon a f t e r they emerged from the g r a v e l . They showed a s u r p r i s i n g amount of aggressiveness. One f i s h became dominant and chased the other three. When e x c i t e d the dominant f i s h showed a l a t -e r a l d i s p l a y resembling t h a t of the brook t r o u t . The slender body was h e l d r i g i d l y and s l i g h t l y curved w i t h the b e l l y down and the head and t a i l h e l d higher. The c o l o r -l e s s d o r s a l f i n was erected. There was l i t t l e o r i e n t a t i o n o f t h i s posture w i t h regard to the other f i s h . There was much a c t i v i t y i n the tank. Instead of being i n h i b i t e d , the subordinate f i s h when chased swam r a p i d l y back and f o r t h pursued by the dominant. The subordinate d i d not crouch nor depress i t s f i n s . A f t e r f eeding a l l f i s h moved about i n a gang swimming, feeding and n i p p i n g . There was a con s i d e r a b l e amount of n i p p i n g back and f o r t h among the i n d i v i d u a l s . There were no observable c o l o r d i f f e r e n c e s among the i n d i v i d u a l s i n r e l a t i o n t o dominance p o s i t i o n . While one f i s h dominated the others i t did. not e x e r c i s e as much i n f l u e n c e on the a c t i v i t i e s of the subordinates as i n r e s i d e n t i a l species. -178-A group of 100 or more chum f r y was converted to sea-water i n the Vancouver P u b l i c Aquarium i n the s p r i n g of 1957 and observed through the summer. They grew r a p i d l y d u r i n g t h i s p e r i o d but unaccountably d i e d i n the autumn of that year. They f r e q u e n t l y nipped each other but no s i n g l e i n d i v i d u a l became dominant. Their s t r o n g , mutual a t t r a c t i o n appeared t o negate the e f f e c t s of n i p p i n g and no f i s h were s e v e r e l y chased or subordinated. Pink salmon f r y Pink salmon were observed soon a f t e r they emerged from the g r a v e l a t a time during which they would normally have been mi g r a t i n g downstream. They were never observed to n i p each other or to show any aggressive m a n i f e s t a t i o n s . They f r e q u e n t l y f o l l o w e d but never chased each other. Comparisons :./.^ ot^ 3Stlbc5n-;;Oi-3tj?meo<loyoted to p a r t i c u l a r a c t i v i t i e s . The t i m i n g and expression of d i f f e r e n t a c t i v i t i e s of r e s -i d e n t i a l species can only be understood when the e f f e c t s of aggressiveness are taken i n t o c o n s i d e r a t i o n . A l l the a c t i v i t i e s of subordinates were i n f l u e n c e d by the presence of the dominant f i s h . The l a t t e r , on the other hand, had grea t e r freedom of a c t i o n and moved about without r e s t r i c -t i o n . Movements of a dominant f i s h were a f f e c t e d i n v a r i o u s ways by subordinates. Dominants were s t i m u l a t e d -179-t o chase subordinates when they were very a c t i v e . When a f i s h darted a f t e r food the dominant was quick to f o l l o w . Because of the d i f f e r e n c e i n behavior between dominants and subordinates, t h e i r a c t i v i t i e s are recorded separately on Table L I . The data f o r l a k e t r o u t were combined since they d i d not develop dominance r e l a t i o n s . Immobility of l a k e t r o u t , d o l l y varden and brook t r o u t mainly represented r e s t i n g . They were comparatively i n -s e n s i t i v e to disturbance and d i d not o f t e n " f r e e z e " i n response to the observer or t o each other. Immobility of rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon often rep-resented alarm. Subordinates of these three species were more o f t e n immobile than dominants and t h i s l a c k of a c t i v -i t y r e s u l t e d from the i n h i b i t o r y e f f e c t of aggressive dom-ina n t f i s h . As a species the d o l l y varden was l e a s t a c t i v e although subordinate coho salmon f r y , under severe domi-n a t i o n were j u s t as i n a c t i v e as d o l l y varden. I n h i b i t o r y e f f e c t s of domination were not as marked i n d o l l y varden and brook t r o u t as they were i n rainbow t r o u t , c u tthroat t r o u t and coho salmon. In brook t r o u t the dominant f i s h were l e s s a c t i v e than the subordinates. The a c t i v i t y of the subordinates was t o l e r a t e d i n t h i s species whereby i t was not i n the others. Rainbow t r o u t dominants were l e a s t o f t e n immobile as i n d i v i d u a l s . Chum salmon f r y were not num e r i c a l l y recorded i n t h i s study but t h e i r apparent lack of periods of i m m o b i l i t y i n t e r s p e r s e d i n periods of a c t i v i t y c o n t r a s t e d markedly w i t h a l l of the above. Table L I The p r o p o r t i o n of time devoted by each species to p a r t i c u l a r a c t i v i t i e s . Based on two groups of each s p e c i e s . A c t i v i t i e s of dominants and subordinates l i s t e d separately.. "Dom" s i g n i f i e s dominant f i s h , "Sub" subordinate. Lake Trout A l l F i s h D o l l y Varden Eastern Brook Trout Rainbow Trout Cutthroat Trout Coho Salmon Fry Dom Sub Dom Sub Dom Sub Dom Sub Dom Sub Immobile Nipping and Chasing R e t r e a t i n g Food Sampling Escape Swimming Aimless Swimming 42.81% 76.25 82.08 71.25 55.00 6.25 67.91 40.00 62.91 30.00 84.58 0 17.50 2.50 15.00 .41 35.00 1.66 12.50 .41 10.00 2.50 0 3.75 .31 0 5.83 0 5.00 0 19.16 0 3.33 0 5.83 2.50 2.50 1.25 2.50 21.25 2.50 12.50 3.33 23.75 1.66 0 2 .0a 7 .50 32.50 23.75 5.41 15 .00 13.33 0 .41 53.11 3.75 4.58 5.00 4.58 10.00 0 7.50 7.08 31.25 5.00 Threatening 0 0 .41 0 0 3.75 3.25 10.00 7.08 5.00 0 The amount of n i p p i n g v a r i e d widely i n the d i f f e r e n t s p e c i e s . Lake t r o u t never nipped or chased each other i n these observations. In the other f i v e species dominant f i s h performed' most of the n i p p i n g . Rainbow trout dominants n i p -ped most o f t e n . These observations d i f f e r e d somewhat from the numerical t a b u l a t i o n (Table L I I ) which i n c l u d e d not only those nips recorded before feeding but a l s o those recorded a f t e r the i n t r o d u c t i o n of food. Here l a k e t r o u t nipped e i g h t times and d o l l y varden, which were c o n s i s t e n t l y more a c t i v e a f t e r f e e d i n g , nipped 1133 times as compared to 727 f o r rainbow t r o u t . Of the two groups of chum f r y s t u d i e d the number of n i p s recorded f o r one compared w i t h the most ag-g r e s s i v e group of d o l l y varden and the average of the two groups was the second l a r g e s t number f o r any species s t u d i e d . Wo n i p p i n g was ever observed among pink f r y . This agrees w i t h the f i n d i n g s of Hoar (1958b) although K. Groot (personal communication) r e p o r t s having o c c a s i o n a l l y seen n i p p i n g among i n d i v i d u a l s of t h i s s p e c i e s . Sockeye f r y were never ob-served to n i p each other. Hoar (1954) reports having seen n i p p i n g or chasing behavior i n sockeye f r y only f i v e times i n two summers of research. Sockeye smolts nipped 14 times i n f o u r hours and they have been observed to o c c a s i o n a l l y n i p under c e r t a i n circumstances by Hoar (1954, 1958b) and H. W. Newman (1959). Spring salmon f r y nipped f r e q u e n t l y and appeared comparable w i t h other aggressive s p e c i e s . Unfor t u n a t e l y an exact count was not made of t h e i r n i p p i n g . -182-Table L I I Comparison of n i p p i n g i n salmonids. Each number represents one-half hour of observation of f o u r f i s h . Two groups of each species were s t u d i e d . Species Group 1 Group 2 T o t a l s Lake t r o u t 2 0 4 0 0 0 1 1 8 D o l l y varden 62 140 128 117 184 211 193 100 1133 Brook t r o u t 76 34 65 35 37 128 40 35 450 Rainbow t r o u t 79 66 143 103 1 63 120 79 654 Cutthroat t r o u t 62 41 33 78 8 83 61 1 365 Coho f r y 170 60 124 71 104 43 142 13 727 Sockeye f r y 0 0 0 0 0 0 0 0 0 Sockeye smolt 9 0 2 0 0 1 2 0 14 Chum f r y 164 237 150 127 29 25 76 53 861 Pink f r y 0 0 0 0 0 0 0 0 0 -1B3-Salmonid species can thus be separated into two d i s t i n c t groups: those which nip only r a r e l y and those which nip f r e -quently and regularly. The f i r s t group includes lake trout, pink salmon and sockeye salmon. The second group includes d o l l y varden, brook trout, rainbow trout, cutthroat trout, coho salmon, spring salmon and chum salmon. The presence of chum salmon i n t h i s group was t o t a l l y unexpected and incon-s i s t e n t with the schooling nature of the species. Retreating was a response to an aggressive dominant and was therefore only seen regularly i n the subordinates of those species where dominance was a feature i n behavior. Dolly varden were p a r t i c u l a r l y i n s e n s i t i v e to the approach of a dominant and usually d i d not retreat u n t i l attacked. The other r e s i d e n t i a l species retreated i f a dominant made an intention movement. Retreating was a controlled swimming action i n d o l l y varden, brook trout, rainbow trout and coho f r y . They swam just f a s t enough to prevent the dominant from contacting them and usually avoided obstacles by turning. Cutthroat subordinates and sockeye smolts when chased by a rainbow trout l o B t control during r e t r e a t i n g and moved ra p i d l y about s t r i k i n g the walls of the tank and damaging themselves. Food searching and sampling was done most often by dominant rainbow trout, cutthroat trout and coho salmon. Subordinates of these species were usually chased when they moved and t h i s i n t e r f e r e d with feeding movements. Feeding -18*-movements of dominant and subordinate d o l l y varden were s i m i l a r i n frequency w h i l e subordinate brook t r o u t showed more of t h i s behavior than d i d the dominants. Escape swimming was observed i n most species when f i r s t placed i n a new tank. In the standard observations i t was performed by some f i s h during periods when they were not alarmed and when they were apparently not disposed to feeding or aggressiveness. I t was r a r e l y observed i n l a k e t r o u t , d o l l y varden or coho salmon and was most common i n brook t r o u t . Rainbow t r o u t dominants showed a high f r e -quency of escape swimming but t h i s type of movement was i n h i b i t e d i n subordinates. Escape behavior has been i n -t e r p r e t e d by Hoar (1958b) as a p p e t i t i v e behavior ("searching behavior by which the animal f i n d s the corresponding r e -l e a s i n g or s a t i s f y i n g s i t u a t i o n " - Baerends, 1957, p. 248). I t s appearance among r e s i d e n t i a l species may i n d i c a t e a "homing" a c t i v i t y when d i s p l a c e d from t h e i r customary sur-roundings. Escape swimming of brook t r o u t and rainbow dominants, may be a r e f l e c t i o n of the inadequacy of a small tank to f u l f i l l t h e i r needs f o r residence. Conversely the r a r i t y of escape swimming i n coho f r y suggests that they i are b e t t e r able to adjust to r e s t r i c t e d q u a r t e r s . The slow, aimless swimming of l a k e t r o u t was unique to them but reminiscent of the continuous movement of chum and pink salmon. Of the other species only coho salmon f r y dominants performed aimless movements f r e q u e n t l y . -185-these c o n s i s t e d of short e x c u r s i o n s , f o l l o w e d by t u r n i n g and r e t u r n i n g to a previous l o c a t i o n . They were d i s c o n t i n -uous, i n t e r r u p t e d movements of a d i f f e r e n t character than those of l a k e t r o u t . Threatening i n c l u d e d both d i s p l a y and i n t e n t i o n move-ments. I n the a n a l y s i s of a c t i v i t y (Table L l ) no t h r e a t -ening was recorded f o r l a k e trout or brook t r o u t and almost none f o r d o l l y varden, w h i l e cutthroat t r o u t showed greatest use of t h r e a t . Table L I I I r e v e a l s t h a t threatening was more common f o l l o w i n g feeding than before. Most t h r e a t s were i n t e r r u p t e d i n t e n t i o n movements. Although brook t r o u t d i d not threaten very o f t e n they were conspicuous f o r the elaborateness of t h e i r d i s p l a y s . Cycles of a c t i v i t y and s t a t e s of mood. Short c y c l e s of a c t i v i t y were observed i n lak e t r o u t , d o l l y varden and rainbow t r o u t . In l a k e t r o u t these c y c l e s c o n s i s t e d of a l t e r n a t e r e s t i n g on the bottom f o r \ t o 3 minutes and swim-ming about the tank f o r s e v e r a l minutes. D o l l y varden r e s t e d longer and i n c l u d e d n i p p i n g and chasing i n t h e i r a c t i v e p e r i o d s . The c y c l e s of rainbow t r o u t dominants were s h o r t e r and more i n t e n s i v e and i n v o l v e d more r a p i d movements than i n e i t h e r of the other two species. F i v e second ac-t i v i t y periods a l t e r n a t e d w i t h 15 seoond r e s t s . Short c y c l e s were obscured i n brook t r o u t by what may have been longer c y c l e s of a c t i v i t y . Brook t r o u t were p a r t i c u l a r l y phasic and a t some times they were predisposed toward d i f f e r e n t types of a c t i v i t i e s than at others. Uo -186-p a r t i c u l a r p a t t e r n f o r r e p e t i t i o n o f ki n d s of a c t i v i t i e s was discovered although e x t e r n a l events such as the a d d i t i o n of food to the tank and movement of the observer a f f e c t e d behavior of the f i s h . These phases were evident, i n varying degrees, i n a l l species s t u d i e d and are i n t e r p r e t e d t o i n -d i c a t e d i f f e r i n g i n t e r n a l s t a t e s or moods (von H o i s t , 1950). I n h i b i t i o n of subordinates and the constant high l e v e l of alarm i n c u t t h r o a t t r o u t , coho salmon and sockeye smolts made the expression of short c y c l e s and moods l e s s evident than i n others. R e s t i n g . A l l species of S a l v e l i n u s tended to r e s t on the bottom w h i l e Salmo and Oncorhynchus r e s t e d i n midwater. Lake t r o u t r e s t e d f l a t l y on the bottom without f i n support but d o l l y varden and brook t r o u t supported t h e i r heads by e r e c t i n g t h e i r p e c t o r a l f i n s . This elevated the head and enabled a gr e a t e r range of v i s i o n w h i l e a t the same time m a i n t a i n i n g c l o s e contact w i t h the s u b s t r a t e . Salmo and Oncorhynchus d i d not r e s t on the bottom but subordinate i n -d i v i d u a l s of these genera o c c a s i o n a l l y remained immobile there as a r e s u l t of the i n h i b i t i n g e f f e c t of a severe dom-i n a n t f i s h . Comfort behavior. Although i t d i f f e r e d i n frequency i n d i f f e r e n t f i s h e s , comfort behavior was s i m i l a r i n a l l s p e c i e s . A l l gaped, snapped t h e i r jaws, f l i c k e r e d t h e i r f i n s and gulped a i r at the surface at various times. Chafing s i d e s on the bottom was extremely r a r e and only l a k e t r o u t were observed t o do t h i s during periods of numerical tab-u l a t i o n . Other species were seen t o chafe on d i f f e r e n t -18:7-occasions and i t i s b e l i e v e d that a l l species perform t h i s a c t i o n a t one time or another. Records of n i p s , t h r e a t s , gapes, snaps and chafes are i n d i c a t e d on Table L I I I . The p o s s i b i l i t y of c h a f i n g being a d i s p l a c e d redd-d i g g i n g a c t i o n was considered, but upon w i t n e s s i n g the redd-d i g g i n g of mature salmon i t was discovered that the movements of body and t a i l under these circumstances were q u i t e d i f -f e r e n t . Chafing appears to be a rubbing of the s i d e of the f i s h i n response to s k i n i r r i t a t i o n as has been concluded by Baerends and.Baerends-van Roon (1950). An experiment was performed to determine i f the f r e -quency of snapping and gaping were a f u n c t i o n of low oxygen c o n c e n t r a t i o n . Two 15 g a l l o n tanks were f i l l e d w i t h water and two l a k e t r o u t were introduced i n t o each one. The water was not c i r c u l a t e d . I n t o one tank was bubbled a i r through an a i r stone. The other tank r e c e i v e d no a i r . A f t e r 24 hours the f i s h i n the two tanks were observed f o r 15 minutes and the number of snaps and gapes were counted. Then the a e r a t o r was t r a n s f e r r e d t o the other tank. This was r e -peated on three days. The r e s u l t s are i n d i c a t e d on Table LIV. • The aerated f i s h were more a c t i v e than those which were not aerated. The l a t t e r r e s p i r e d very f o r c e f u l l y , opening t h e i r mouths twice as f a r as the others (20° as c o n t r a s t e d with 5-10°). The frequency of opercular move-ments i n the non-aerated f i s h was 100-110 per minute. That of the aerated f i s h was 70 per minute. -188-Table L I I I Number of n i p s , t h r e a t s , gapes, snaps and chafes recorded i n a l l standard observations. "Bef." s i g -n i f i e s before f e e d i n g , " A f t . " , a f t e r feeding. Lake Trout Nips Threats Gapes Snaps Chafes Bef. . A f t . Bef. A f t . Bef. A f t . Bef. A f t . Bef. A f t . 2 0 1 0 7 5 47 37 2 0 Group I 0 0 0 0 4 8 41 39 0 0 1 3 0 0 4 2 38 42 2 0 0 0 0 0 2 1 30 32 0 0 0 0 0 0 4 4 80 41 0 1 Group I I 0 0 0 0 3 3 71 52 0 0 1 0 0 0 4 4 34 30 0 0 1 0 0 0 5 4 19 40 0 0 T o t a l 5 3 1 0 33 31 360 313 4 1 D o l l y varden 5 57 1 7 4 1 4 1 0 0 Group I 20 117 0 9 5 0 6 1 0 0 1 127 0 7 7 1 26 1 0 0 17 100 0 4 7 1 21 0 0 0 20 164 2 8 2 1 3 0 0 0 Group I I 72 134 4 0 7 1 7 0 0 0 4 186 0 10 9 4 47 6 0 0 7 89 6 3 6 2 31 1 0 0 T o t a l 146 974 13 48 47 11 145 10 0 0 Brook Trout 13 63 3 3 6 2 14 4 0 0 Group I 0 34 0 0 1 0 2 0 0 0 0 65 0 8 0 0 1 0 0 0 0 35 0 0 4 3 4 3 0 0 TT 1 36 0 7 5 0 3 0 0 0 Group I I 4 i 87 0 4 3 1 1 0 0 0 12 28 0 0 4 1 5 0 0 0 5 30 0 0 4 1 4 0 0 0 T o t a l 72 378 3 22 27 8 34 7 0 0 -189-Table LIII (continued) Rainbow t r o u t Nips Threats Gapes Snaps Chafes Bef. A f t . Bef. A f t . Bef. A f t . Bef. A f t . Bef. A f t 66 13 4 2 3 1 _ 0 0 Group I 39 27 2 10 6 0 _ mm 0 0 39 104 7 46 6 0 _ 0 0 94 9 7 10 5 1 - - 0 0 1 0 0 0 3 0 0 0 Group II 10 53 0 8 6 0 mm 0 0 109 11 1 9 6 4 0 0 38 41 8 5 5 5 - - 0 0 T o t a l 396 258 29 90 40 11 mm 0 0 Cutthroat Trout 11 51 5 31 5 1 mm ^m 0 6 Group I 5 36 23 21 5 1 mm -m 0 0 14 20 24 19 2 1 0 0 41 37 8 16 2 0 - - 0 0 1 7 6 11 7 2 0 0 Group II 4 77 2 4 4 1 mm 0 0 14 47 6 21 4 1 mm 0 0 0 1 2 9 6 1 - - 0 0 T o t a l 90 277 76 132 35 8 _ mm 0 0 Coho Fry 12 158 1 8 12 2 28 2 0 0 Group I 17 43 1 0 4 0 5 4 0 0 32 92 0 0 1 0 34 10 0 0 10 61 0 10 4 1 45 3 0 0 8 96 3 1 4 0 32 0 0 0 Group II 16 28 1 2 5 0 47 5 0 0 40 102 1 0 8 1 12 8 0 0 0 13 0 5 6 0 55 70 0 0 T o t a l 135 593 7 26 44 4 258 102 0 0 -180-Table LIV The frequency of gaping and snapping i n l a k e t r o u t . Two f i s h per tank, 15 minute observations. Snaps Aerated tank Non-aerated tank 34 63 24 59 12 36 Gapes Aerated tank Non-aerated tank 1 6 5 5 2 0 -191-No r e l a t i o n s h i p was found between the frequency of gaping and-aeration. Snapping frequency was higher i n non-aerated f i s h and may have been an i n d i c a t o r of s t r e s s . Since the mouths of the f i s h were opening and c l o s i n g more r a p i d l y i n r e s p i r a t i o n the snapping movements may have been merely a response t o the pain caused by p r i c k i n g the membranes around t h e i r mouths w i t h t h e i r t e e t h . These snapping move-ments are conspicuous i n a number of s p e c i e s . Gaping was most f r e q u e n t l y observed i n r e s t i n g f i s h j u s t p r i o r to swimming or i n swimming f i s h j u s t p r i o r to r e s t i n g . Table L I I I shows t h a t more gapes were recorded before feeding than a f t e r i n a l l groups of d o l l y varden, brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon f r y . Few gapes were observed during the p e r i o d of height-ened a c t i v i t y which u s u a l l y f o l l o w e d feeding. Lake t r o u t u s u a l l y gaped i n a s s o c i a t i o n w i t h changing s t a t e s of a c t i v i t y a l s o but the number of gapes recorded f o l l o w i n g feeding was not s i g n i f i c a n t l y l e s s than before. This may have been r e l a t e d to the f a i l u r e of some members of t h i s species to take the food provided them. :..; ,. . Gaping was a l s o c o r r e l a t e d w i t h dominance d e s p i t e dom-in a n t f i s h i n many cases being more a c t i v e than subordinate ones. Table LV r e v e a l s that dominant f i s h yawned more f r e -q u ently than subordinates. This i s a t t r i b u t e d t o the i n -h i b i t i n g e f f e c t of the dominant f i s h on the a c t i v i t i e s of others i n the group. Their i n a c t i v i t y d i d not represent -192-Table LV Number of gapes i n r e l a t i o n to s o c i a l p o s i t i o n i n h i e r a r c h y . Dominants gaped most o f t e n . Group 1 Group 2 S o c i a l Rank Dom. #2 #3 #4 Dom. #2 #3 #4 D o l l y varden 10 10 1 5 12 7 7 6 Brook t r o u t 6 5 2 3 6 5 5 2 Rainbow t r o u t 19 1 0 2 8 7 5 9 Cutthroat t r o u t 12 2 0 4 5 4 9 8 Coho salmon 9 3 5 5 6 9 8 1 -193-r e s t i n g and was not, t h e r e f o r e , accompanied by gaping. A n a l y s i s of n i p p i n g . Nipping d i d not take place con-t i n u o u s l y but occurred p e r i o d i c a l l y . There were rhythms of a c t i v i t y w i t h i n which r e s t i n g feeding and n i p p i n g be-ha v i o r a l t e r n a t e d . The i n t r o d u c t i o n of food r e s u l t s i n the p r e c i p i t a t i o n of aggressive behavior f o l l o w i n g f eeding (Newman, 1956). More n i p s were recorded f o l l o w i n g than p r i o r to feeding i n d o l l y varden, brook t r o u t , c u t t h r o a t t r o u t and coho salmon (Table L I I I ) but rainbow t r o u t were i n c o n s i s t e n t w i t h the ot h e r s . I t was not c l e a r why t h i s was so as i t had not been the case i n the previous study of rainbow t r o u t (Newman, 1956). When food was introduced i n t o the tanks c o n t a i n i n g the two groups of rainbow t r o u t , the dominants chased the subordinate f i s h from the feeding areas and then p a t r o l l e d the areas without making aggressive e f f o r t s at any d i s t a n c e . The subordinates remained away and were not at t a c k e d so lon g as the dominant i n each group was preoccupied w i t h feeding. When d o l l y varden, brook t r o u t , c u t t h r o a t t r o u t and coho salmon were fe d they ate t h e i r food, g r a d u a l l y became aggressive and f i n a l l y nipped and ehased each other. The dominant f i s h i n each group u s u a l l y became very aggressive and terminated aggressive interchanges among subordinates by v i g o r o u s l y n i p p i n g a l l the a c t i v e ones. The number of n i p p i n g permutations was greater f o l l o w -i n g feeding (Table LVI) f o r d o l l y varden, brook t r o u t , -19 4-Table LVT Number of n i p p i n g permutations observed before and a f t e r feeding i n a l l standard observations. D o l l y Varden T o t a l Before Feeding 1 4 1 2 5 5 3 3 24 A f t e r Feeding 5 5 4 4 7 6 10 4 45 Brook Trout Before Feeding 2 0 0 0 1 3 4 3 13 A f t e r Feeding 3 3 2 5 5 5 5 3 31 Rainbow Before Feeding 7 3 4 5 1 2 4 3 29 Trout A f t e r Feeding 2 4 9 3 0 5 2 5 30 Cutthroat Before Feeding 3 4 4 6 1 3 3 0 24 Trout A f t e r Feeding 8 6 4 5 3 3 6 1 36 Coho Salmon Fry Before Feeding 6 3 2 2 4 3 4 0 24 A f t e r Feeding 6 2 4 5 5 5 4 6 37 -195-rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon f r y . Feeding not only brought about more intense n i p p i n g between p a r t i c -u l a r i n d i v i d u a l s but a l s o i n c r e a s e d the number of i n d i v i d -u a l s p a r t i c i p a t i n g i n aggressive exchanges. This has been diagramed i n "peck orders" f o r each s p e c i e s . I t was observed that b r i g h t l i g h t f r e q u e n t l y depressed aggressive a c t i v i t y among t r o u t and t h a t when subjected to i t they o f t e n maintained a g e n e r a l i z e d alarm posture. A group of ten brook t r o u t were observed over a number of days and the number of n i p s i n ten minute periods was recorded each day p r i o r t o feeding. On one day f l o o d l i g h t s were ; p l a c e d over the tank and under t h i s i n t e n s e i l l u m i n a t i o n more n i p s were recorded than usual (Table L V U ) . By t h i s time the f i s h had become c o n d i t i o n e d t o a s s o c i a t e the pre-sence of the observer w i t h food. The b r i g h t l i g h t e v i d e n t l y s i g n a l i z e d the presence of food and p r e c i p i t a t e d aggressive a c t i v i t y i n a circumstance that normally would depress t h i s type o f behavior. Most n i p p i n g was performed by dominant f i s h . Table L V I I I compares the number of n i p s performed by dominant and subordinate i n d i v i d u a l s . Since only one f i s h dominated i n each group of f o u r , there were three times as many subor-d i n a t e i n d i v i d u a l s as there were dominants. Table LIX com-pares the number of n i p s per dominant per hour w i t h the number of nips per subordinate t o dominant n i p p i n g and shows that n i p p i n g v a r i e d from 1:6.2 i n c u t t h r o a t s to 1:57.5 i n brook t r o u t . -196-Table LVII E f f e c t of sudden, f l o o d - l i g h t i l l u m i n a t i o n on n i p p i n g among ten j u v e n i l e brook t r o u t i n ten g a l l o n tank. Nipping and feeding movements recorded d a i l y i n ten minute periods p r i o r to feeding. Nips Feeding Movements 0 1 5 11 0 0 3 11 1 13 30 5 14 5 24 15 3 20 23 5 30 4 F l o o d - l i g h t *53 87 24 8 26 9 37 6 41 17 58 17 -197-Table LvTII Number of n i p s recorded f o r dominants as compared w i t h number of n i p s recorded f o r subordinates i n a l l s tan-dard observations. "D" s i g n i f i e s dominant, "S", subor-dinat e. T o t a l D o l l y Varden Brook Trout D 55 135 122 95 167 192 158 88' 1012 S 7 5 6 22 17 19 35 12 123 D 76 34 42 33 35 123 36 35 414 S O 0 8 2 2 5 4 0 21 D 65 57 78 90 1 57 119 75 542 Rainbow Trout S 14 9 65 13 0 6 1 4 112 D 16 27 9 58 7 79 51 0 247 Cutthroat Trout S 46 15 25 20 1 2 10 1 120 D 137 59 120 56 83 27 137 8 627 Coho Salmon S 33 1 4 15 21 16 5 5 100 -198-Table LIX Number of n i p s per f i s h per hour computed from previous t a b l e . Dominants Subordinates D o l l y Varden 253.0 10.3 Brook Trout 103.5 1.8 Rainbow Trout 135.5 9.3 Cutthroat Trout 61.8 10.0 Coho Salmon Fry 156.8 8.4 -199-Dominance r e l a t i o n s i n i n t r a s p e c i f i c groups of d o l l y varden, brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon appeared bo be q u i t e s t a b l e . Once a p a r t i c u l a r i n -d i v i d u a l had achieved dominance the others d i d not u s u a l l y a t t a c k i t . Thus the r e l a t i o n s h i p was c h a r a c t e r i z e d by "peck r i g h t " ( A l l e e , 1952) i n which a dominant nipped a subor-d i n a t e but not the reverse. On occasion, and u s u a l l y f o l -l o wing f e e d i n g , subordinates attacked t h e i r dominants. Nipping of the dominant was observed most often among cut-t h r o a t t r o u t and l e a s t often among coho salmon f r y . Although one i n d i v i d u a l i n each group stood out as a dominant which d i d most of the n i p p i n g , the other three c o u l d u s u a l l y be d i f f e r e n t i a t e d i n terms of r e l a t i v e pos-i t i o n s i n a s o c i a l h i e r a r c h y . U s u a l l y , the higher i t s p o s i t i o n i n the h i e r a r c h y , the greater the number of times a f i s h nipped the others and the fewer the f i s h which nipped i t . Table LX r e v e a l s the number of times the dominant f i s h i n each group nipped the number two, number three and num-ber fou r f i s h . Dominants i n the d i f f e r e n t groups d i d not c o n s i s t e n t l y a t t a c k any one p o s i t i o n of subordinate. They d i d not c o n s i s t e n t l y a t t a c k the number two f i s h which would represent the most th r e a t e n i n g p o s i t i o n . Nor d i d they con-s i s t e n t l y a t t a c k the number four f i s h which would be the weakest and most e a s i l y attacked. I t was common, however, f o r an i n d i v i d u a l to be s i n g l e d out and attacked more f r e -quently by the dominant f i s h than were the others. In four -200-Table LX Number of times dominant f i s h nipped f i s h of lower ranks i n a l l standard observations. Group 1 Group I I S o c i a l P o s i t i o n #2 #3 #4 #3 #3 #4 D o l l y Varden 236 122 48 102 280 220 Brook Trout 103 30 51 114 77 38 Rainbow Trout 93 106 89 156 77 19 Cutthroat Trout 42 60 13 43 43 53 Coho Salmon 97 142 132 92 130 34 -201-groups t h i s f i s h was second i n l i n e i n the h i e r a r c h y , i n f i v e groups i t was t h i r d and i n one group i t was f o u r t h . Such a f i s h g e n e r a l l y made i t s e l f conspicuous to the domi-nant f i s h during periods when the dominant was a g g r e s s i v e l y motivated. I t d i d t h i s by being more a c t i v e , by feeding near the dominant, by a t t a c k i n g other i n d i v i d u a l s , by es-cape swimming or by r e t r e a t i n g i n an u n c o n t r o l l e d manner which e x c i t e d a t t e n t i o n . T e r r i t o r i a l i t y . A l l of the r e s i d e n t i a l species f u l -f i l l e d Noble's requirement (1939) of t e r r i t o r i a l i t y i n that they defended areas at one time or another. Lake t r o u t were n e i t h e r aggressive nor o r i e n t e d i n r e l a t i o n to o b j e c t s on the bottom. Chum were too a c t i v e t o show t e r r i t o r i a l behavior and never r e l a t e d to bottom objects d e s p i t e e x h i b i t i n g ag-g r e s s i v e behavior. Pink f r y were unaggressive and c o n t i n -uously moving w h i l e sockeye f r y were unaggressive but l e s s a c t i v e . Thus none of the n o n - r e s i d e n t i a l f i s h were t e r -r i t o r i a l . Response to danger. J u v e n i l e char, t r o u t and coho salmon responded to out s i d e disturbance by ceasing t o move, adopting a g e n e r a l i z e d alarm posture and d a r t i n g away as the alarming stimulus reached a p a r t i c u l a r t h r e s h o l d . Lake t r o u t and d o l l y varden were comparatively i n s e n s i t i v e to d i s t u r -bance, brook t r o u t somewhat more s e n s i t i v e w h i l e rainbow t r o u t , coho salmon and c u t t h r o a t t r o u t were exceedingly sen-s i t i v e . -202-This immobile response to alarm stimulus c o n t r a s t s w i t h the one described by Hoar (1958b) f o r downstream migrants ( i . e . a r a p i d change i n the d i r e c t i o n of swimming). Remain-i n g i n the "home" when alarmed may be an important char-a c t e r i s t i c of r e s i d e n t i a l f i s h e s . Feeding. The movements of feeding d i d not appear q u a l i t a t i v e l y d i f f e r e n t i n the v a r i o u s species but d i f f e r e d i n r a p i d i t y and i n the objects toward which they were d i -r e c t e d . A l l species r e a d i l y ate worms except the l a k e t r o u t which p r e f e r r e d l i v e f i s h but which would a l s o take canned salmon and p i e c e s of meat and f r e s h f i s h . Coho salmon f r y were f a s t e r i n t h e i r feeding movements than any of the species of t r o u t and char. Feeding was i n t e n s e l y s o c i a l i n character f o r a l l s p e c i e s . Movement toward food by one i n d i v i d u a l e l i c i t e d f o l l o w i n g on the part of the others. The f i s h which obtained food moved away from the others w h i l e they f o l l o w e d and t r i e d t o take the food object away. Keenleyside (1955) s t a t e s t h a t feeding f i s h are a stronger stimulus than food alone i n b r i n g i n g other f i s h to food. This i n t e r a c t i o n probably caused a greater consumption of food than would have taken p l a c e i f the f i s h were i s o l a t e d s i n c e they p a r t i c i p a t e d even when gorged w i t h food and when they were presumably no longer "hungry". Comparison of a g o n i s t i c d i s p l a y s . The a d j e c t i v e "ago-n i s t i c " was proposed by Scott and Fredericson (1951) to -203-i n c l u d e both a t t a c k i n g and r e t r e a t i n g elements of aggressive behavior. Equivalent a g o n i s t i c d i s p l a y s o f t e n d i f f e r e d from species to species but d i d not n e c e s s a r i l y do so. D i f f e r -ences were obscured by frequent f a i l u r e to f u l l y express a d i s p l a y through v a r i a t i o n s i n i n t e n s i t y . F u l l e s t expression of l a t e r a l d i s p l a y , f r o n t a l d i s p l a y , l a t e r a l t a i l wagging, r e t r e a t i n g t a i l wagging and f i g h t i n g occurred w i t h i n a few days of p l a c i n g f i s h together i n a new tank. A f t e r d e f i n i t e r e l a t i o n s were e s t a b l i s h e d among the i n d i v i d u a l s , n i p p i n g , c hasing, r e t r e a t i n g , a v o i d i n g and crouching became t y p i c a l a c t i o n s and t h r e a t d i s p l a y s and f i g h t i n g were seldom seen. When they appeared, they were g e n e r a l l y only p a r t i a l l y ex-pressed i n the form of i n t e n t i o n movements. Table LXI gives a synopsis pf a g o n i s t i c behavior i n which equivalent patterns are compared. In some cases par-t i c u l a r behavior patterns are r e f e r r e d t o as "not observed" and i n others as "not s t u d i e d " . Where patterns were s t u d i e d but not observed the presumption i s that they are r a r e l y or never expressed by the j u v e n i l e s of that species. F r o n t a l d i s p l a y i s an a t t a c k i n g o r i e n t a t i o n of the f r o n t of a f i s h toward an opponent as described by Baerends and Baerends-van Roon (1950) i n c i c h l i d s . . Elements of the d i s p l a y were seen i n l a k e t r o u t , d o l l y varden, brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho f r y but were not observed i n other salmon sp e c i e s . Arching of the back, 1 TABLE. LXI COMPAR ISON OF AOONIST IC ACT IONS L A K E T R O U T (5a/r«/r*t*> *uvmaycfrt»AJ O O L L V V A i R O E N BROOK T R O U T (S. randi^Us) R A I N B O W T R O U T C U T T H R O A T T R O U T C O H O <:ALI*VON PM ) o c * m < i t L r v m m CO. *.*.rk±) CHUM SftLI-WN FRY (O. (ut*,) CHINOOK SALMON FRY CO. tsAoMyttcAa.) PINK, SALMON FRY F r o n t a l pivplau Portal f i n lowered, bod4 m a r -ked l u, artked and head bent* sliqktlu upwards From " neck". Koatk etiqkttu opened. H u a l apparatus expanded downwards. Pisplau Mldom expressed. Frequantlu, expressed. S a m e a s lake, t r o u t but more frequently expressed. F r o n t a l display d i f f e r e n t From, preceding species. Dorsal fin- erected , kual apparaXus s l iqkt l i| expanded downward, sodv) not curved but oblique wiltt keaddown a n d taU ujp. Fre-quently expressed. *>arAC as u * lake t r o u t but more Frcqwtntlu, expressed-Dorsal Fin lowered. bodi| not Curved. Hvfal OLppar -atTu4 o n l u <l iqktlv^ axpanded down-w a r d . Bodu obl ique witk. kead down and t a l l u p . FrequentU| expressed. Hot observed Not observed Not s t u d i e d N o t observed L o t ora l Ditplau No t r u e la tera l display. 1 f viqorouslu, a t t a c k e d a l a k e trou.t som«£i»uas a s s u m e d a qeuarali-xed alarm posture.. N o t observed Wall developad lateral d i spku j . f u l l expansion of f ins • fcodij maintained Cik. kor<-s.owtal position but assumed concave euirvature witk. vsoad up, bellu d o w n , t a i l u p . 8004 quivered • Mqal apparatus expanded downward. Mou.1l* closed. Pitptaq oriented at Mqkt auqle to opponent. Well developed l a t e r a l displau but diFFe*-ew* From tkat o f brook t r o u t i n tkat bodif oblique uMk k e a d u p a s i d t a i l down, not muck bodu. curvature cvud kual apparalus stic^ktlif expanded douiruuard. faouXu closed. Well developed lateral display but different f r o m preceding i n tkat dorsal f in , is louier-ed. Otker f ins expanded, dodu, kor'iuontal,5liqkt-ttf curved, riq'td, qu'tverinq. Wi^al apparatus expanded d o w n w a r d ax-posinq red ctnpes On ceratohu^lls tAoutk. closed. 5im'ila.r to lateral display of rainboui t r o u t but ma*) become Vertical Mutt kead up a n d t a i l d o w n . No body; curvature, b e -ccvu.se of riqidlTi) o f s toutav bodu- ' Not observed. Lateral display as i n brook trout but not well orienfed toward opponent, rivals d i d n o t w. -tend d o w n w a r d as Far as i n brook trout Not s t u d i e d N o t observed L a t e r a l Tout Wuqo/i-no, Not observed N o t obtarvod Caudal F i n Fullu expanded a n d Waqqcd back otni. Fortk at opponent. Wkole body vM^dulattd wi tkout For-ward progression. AH Fins expanded Sam.e as in. brook t rout but bodif rnore riq'id a n d levt s inuous . $ame as in . rausbow trout 5ame as m- ra'«nb»w t r o u t Not observed. Same as in- brook •trout". N o t s tudied. N o t observed Retreat -no T a i l Waqq tnq N a t observed Not observed C a u d a l Fin. fultu axpanded a n d Waqqad back ound Fortk at k e a d L oF ckasinq opponent, bodu usually tliekt-\v\ oblique. » w i m Wead down • fame av i n brook - t rout Sam-e as In. brook t r o u t $ama as i n brook -trout but* bodq more r i q ' i d a n d moi>e-mants nyuck more r a p i d . Not observed s W t a i i n brook t r o u t Not s tudied Not observed F i q k t i n q Not observed Two or more f i s k tarn . O M d attempt to bi t* eack otker. Pluck c i rc l ing and b'ttina- Frontal display espresso in attackenq movement but not as a Substitute for a t t a c k . Display muck more evident t k a u (n dolls varden. Less pkus'tcal c o u -loot. Lateral and Frontal displays • Pluck ta i l waaqine • Oisplaus were Slow and prolonged in, durat ion . Display a n d pkijsical contact tkou^k (ess display tkaikansonq brook t rout . rOou| be prolonqed. 5'im'ilar to brook t r o u t except For differences i n d isplace . f \ a ^ be pro longed. Vim i l a r lb brook t rout except For d'lFFerences i n d i s p l a y s , more tiaj\& p o s t u r e a n d muck OjreoXer spaad o f moue-m e n t . N o t observed Not observed Fvqktmq was o b -served tb take piece but not s t u d i e d -Not observed CroucnAna, Not observed Sometimes lowered Use d o r s a l f i n aV a f f r o a c k of dominant f isk. Crouck wel l deveioped. Subordinate lowered its dorsal Fin. and contractu otkur fins a t approacn of dominant. If nsneUu darkened in, color o r remained d a r k . It cowered-Crouck well deveioped, same as in. brook t r o u t . Crouck vueli developed , suwve at in . brook t r o u t . Crouck uM.ll developed,so.inc. as (in- brook t r o i A * . i 1 Not observed. Not Observed Not s t u d i e d N o t observed Nippinq a n d Ckae' in^ TjpicoJ mppine O n d cJcOSinq d i d not occur. Sometimes owl frsn nvovul slowlu alongside ounotker a n d bit it. 6"i1i"r-q preceded bu euam'injnq. No cVuxsinq • fc'iti,s were directed a t stationarq* opponents. Nipping and ckatine PrequetCt. Would approotk slowlu, or rapid It- and then, btte opponent or. part o f bod*- . Ckased r*tr»e*inq opponent a n d nipped several times dw/inq ekese. Nipped eitker moving or stationary Opponents. Hipp'm^ a n d cnasinq Frequent. Same a * amonq dellif varden. Nippinq aud c k a t i M ^ frequant" as amonq doll<< varden • Nipping a v d ckas'inj\ as a.vnono\ doll u v a r d e n . Nippinq a n d eJnaSin^ v e r u r a p i d . Usuelltf nipped o n l u once durirvq a ckase. Ckase Snort and r a p i d . Kipped botk c^ati'onaru a n d movinq opponents. Not observed. Nipping audckas'in^ Frequent and r a p i d . Ktanu, n ips pe*-G U A M -Ni'ppino a n d eVnsine Was observed tb take plate but n o t •rludied N o t observed -Retreat inq and Avoiding Avoided larger f i s k bat d i d not r e t r e a t Swam rapidly *u<au f rom more aq^ressive f i s k usually only after a * aq^ressive exekauqe. 5warn rapidly a ^ a u frowi more aa^rcssive f i f k toiCnout tSut necaesiXi^ of ae/^resove 4»cJkaM^e . Same as Us, brook trout- ^ a m e as i n , brook trowct. 9ame as i n brook trout- N o t observed. Rerreodunc^ rapid a n d prolonged. Retreattinq observed but not studied-Not observed. Substrate-bit inq Tnreci.t S o m e t i m e s Vit* s u b s t r a t e just in front of auotktr Fi%k uAtkout Front oA d i s p l a u . Same as i n l a k e t r o u t . Sanee as i n l a k e t r o u t . 5a.me as in . l a k e t r o u t . Samue as m lake t r o u t • Same as i n . l a k e t r o u t . Not observed. N o t observed . Not Stiedied . Not observed . -205-depression of the d o r s a l f i n and p u f f i n g out of the throat were expressed i n motion by a t t a c k i n g l a k e t r o u t and d o l l y varden w h i l e , i n brook t r o u t they were e x h i b i t e d by a slow moving or momentarily stopped a t t a c k e r and thus conveyed more of a t h r e a t than an a c t i o n . The d i s p l a y was w e l l de-veloped but s l i g h t l y d i f f e r e n t i n rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon f r y . I t was not observed i n the f r y of the other salmon s p e c i e s . Rainbow t r o u t expanded i n -s t e a d of depressed the d o r s a l f i n , d i d not puff out the t h r o a t and t i l t e d the body w i t h the head down. Cutthroat t r o u t arched the back, depressed the d o r s a l f i n and puffed out the t h r o a t thus e x h i b i t i n g t h e i r prominent red marks. Coho f r y t i l t e d the body head downwards, depressed the d o r s a l and d i d not puff out the t h r o a t . L a t e r a l d i s p l a y i s a defensive o r i e n t a t i o n of the s i d e o f the body toward an aggressive opponent o c c u r r i n g only i n a g g r e s s i v e l y motivated i n d i v i d u a l s . I t was described by Baerends and Baerends-van Roon (1950) i n c i e h l i d f i s h e s and has been seen i n a number of other species. I t w a B not observed i n l a k e t r o u t or d o l l y varden but reached i t s f u l l e s t development i n brook t r o u t where the expansion of the f i n s r e v e a l e d t h e i r b r i g h t c o l o r patterns and c o n t r a s t i n g markings. The brook t r o u t p u f f e d out i t s throat by expanding i t s h y a l s t r u c t u r e s downward thus i n c r e a s i n g the expres-siveness of i t s d i s p l a y . L a t e r a l d i s p l a y s were a l s o ob-served i n rainbow t r o u t , c u t t h r o a t t r o u t , coho f r y and chum -206-f r y . They were not observed i n other salmon f r y . As i n the case of the f r o n t a l d i s p l a y there was a c e r t a i n amount of v a r i a t i o n among the species i n the appearance of the d i s p l a y . Rainbow t r o u t h e l d t h e i r bodies o b l i q u e l y w i t h the head up and d i d not puff out the t h r o a t . Cutthroat t r o u t c a r r i e d the f r o n t a l d i s p l a y i n t o a l a t e r a l p o s i t i o n by de-p r e s s i n g the d o r s a l f i n and p u f f i n g out the t h r o a t . Coho f r y h e l d t h e i r bodies o b l i q u e l y and sometimes almost ver-t i c a l l y w i t h the head up without expanding the t h r o a t . The most s u r p r i s i n g d i s p l a y was that of chum f r y which was very s i m i l a r t o that of brook t r o u t though not as w e l l o r i e n t e d toward other f i s h . This aggressive m a n i f e s t a t i o n , l i k e i t s frequent n i p p i n g , was d i f f i c u l t to r e c o n c i l e w i t h i t s school-i n g behavior. L a t e r a l t a i l - w a g g i n g and r e t r e a t i n g t ail-wagging have been a l l u d e d to as " t a i l - b e a t i n g 1 1 by Baerends and Baerends-van Roon (1950) and are an extension of l a t e r a l d i s p l a y i n which the f i s h makes a continued and more i n t e n s i v e e f f o r t to defend i t s e l f against an a t t a c k e r by beating i t s t a i l sideways. These ac t i o n s were observed i n a l l of the species which c a r r i e d out l a t e r a l d i s p l a y s and only d i f f e r e d by v i r t u e of d i f f e r e n c e s i n body shape. Those species which were long and t h i n were capable of more extreme undulations than those which were more s t o u t . F i g h t i n g o n l y occurred i n those species having a high l e v e l of aggressiveness as i t depended upon two i n d i v i d u a l s -307-being i n t e n s e l y motivated at the same time. I t was ob-^ served i n d o l l y varden, brook t r o u t , rainbow t r o u t , c u t -t h r o a t t r o u t , coho f r y and Chinook f r y but not i n l a k e t r o u t , sockeye f r y , chum f r y or pink f r y . D o l l y varden were very d i r e c t f i g h t e r s using l i t t l e d i s p l a y and much d i r e c t b i t i n g . Brook t r o u t were most s t y l i z e d i n t h e i r f i g h t i n g w h i l e rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon f r y were intermediate i n t h i s regard. Chum salmon f r y moved about so much that there was never any sus t a i n e d f i g h t i n g d e s p i t e a high frequency of n i p p i n g and chasing. Crouching i s r e f e r r e d t o as " a t t i t u d e of I n f e r i o r i t y " by Baerends and BaerendB-van Boon (1950). I t was not ob-served i n l a k e t r o u t , p o o r l y developed i n d o l l y varden, w e l l developed i n brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho f r y , and not observed i n the other salmon s p e c i e s . Keenleyside (1957) described the appearance of a j u v e n i l e A t l a n t i c salmon a f t e r i t had been repeatedly a t t a c k e d by a more aggressive f i s h . I t s c o l o r a t i o n resem-b l e d that of a crouching rainbow subordinate: "that part o f the body below the l a t e r a l l i n e turned dark brown or black w h i l e the upper part remained l i g h t brown. The l a t e r a l ; l i n e was blear.Iy .the upper border of the darkened area. Sometimes a few dark brown i r r e g u l a r streaks or blotches showed up as bands across the back of the f i s h . The eyes l o s t t h e i r yellow colour and turned dark grey or black." -208-Nipping and chasing d i d not occur among l a k e t r o u t hut was frequent and i n t e n s e among d o l l y varden, brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t , coho f r y and chum f r y . Coho f r y d i d not chase subordinates very f a r but returned q u i c k l y t o an o r i g i n a l l o c a t i o n without r e p e t i t i v e n i p p i n g . Chinook f r y a l s o nipped and chased each other. Lake t r o u t tended to t u r n and a v o i d l a r g e r i n d i v i d u a l s as they approached but d i d not a c t u a l l y r e t r e a t from them. The b i t i n g of the substrate beneath another f i s h was used as a t h r e a t by a l l but sockeye, chum and pink f r y . I t was not s t u d i e d i n Chinook f r y . I t commonly occurred d u r i n g feeding and o f t e n preceded an aggressive interchange. PRIOR RESIDENCE AND GROUP TERRITORIALITY P r i o r residence Several authors, ( A l l e e , 1952; Braddock, 1945, 1949; Noble, 1939b) observed that dominant animals a t t a c k new i n d i v i d u a l s more r e a d i l y than they do i n d i v i d u a l s which have been i n t h e i r presence over a p e r i o d of time. This phenomenon was examined i n young coho salmon. Four coho f r y were p l a c e d i n a s m a l l tank and d e v e l -oped a s t a b l e dominance r e l a t i o n s h i p over a p e r i o d of s e v e r a l weeks. The dominant f i s h (C0L0I) was very aggres-s i v e . On October 11 a subordinate f i s h was removed and was r e p l a c e d by another. -209-On October 14, the new f i s h was observed to be very dark and subordinated. The dominant f i s h f r e q u e n t l y a t -tacked i t before food was in t r o d u c e d i n t o the tank but a f t e r f e e d i n g the dominant a t t a c k e d the r e s i d e n t subordinates (Table L X I I ) . The new f i s h d i d not feed and when attacked i t remained immobile i n a corner near the surface. I t died on October 15. On October 16 a second new coho was introduced. This f i s h was l a r g e r than the others i n the group, the lengths and weights of which were as f o l l o w s : T o t a l Length Weight COADI 67 mm 2.3 g COAWI 61 1.5 C0L0I (Dom.) 68 2.6 New F i s h #2 77 3.4 On October 21, the second new f i s h , d e s p i te i t s l a r g e r s i z e , was observed to be very dark and subordinated. A t a b u l a t i o n of n i p s f o r f i f t e e n minutes before feeding and f i f t e e n minutes a f t e r feeding revealed that the dominant nipped i t more oft e n than the other two subordinates (Table L X I I ) . F o l l o w i n g f e e d i n g , i t was attacked by the dominant and chased v i g o r o u s l y . I t was very dark and a g i t a t e d . On October 23 i t was removed and repl a c e d by another f i s h . The dominant coho a t t a c k e d the t h i r d new i n d i v i d u a l immediately and r a p i d l y chased i t back and f o r t h . The new f i s h darkened i n c o l o r , r e t r e a t e d f r a n t i c a l l y and -210-Table LXII The number of times a newly int r o d u c e d coho i s n i p -ped by the dominant as compared w i t h the other sub-o r d i n a t e s . F i f t e e n minutes before and f i f t e e n min-utes a f t e r feeding. Four d i f f e r e n t new f i s h were used. Before Feeding A f t e r Feeding Fate of Mew F i s h D0M>New DOM^SUBl D0MASUB2 F i s h DOM^&ew F i s h D0M»SUB1 D0M>SUB2 29 3 0 19 18 51 Died 0 5 5 37 3 6 Removed 45 3 0 1 30 18 Died 0 0 0 7 27 5 Died f i n a l l y r e s t e d on the bottom r a p i d l y opening and c l o s i n g i t s g i l l covers as though gasping f o r breath. S h o r t l y t h e r e a f t e r the two r e s i d e n t subordinates a t t a c k e d the new i n d i v i d u a l . On October 25, a t a b u l a t i o n of n i p s was made (Table L X I l ) . The t h i r d new f i s h was chased almost continuously i n a f i f t e e n minute observation before feeding. Although i t was very dark, i t d i d not behave as an adjusted s u b o r d i -nate. I t r a i s e d i n s t e a d of lowered i t s d o r s a l f i n at the approach of the dominant. In other words i t showed a gen-e r a l i z e d alarm posture i n s t e a d of a crouch. When food was p l a c e d i n the tank the new f i s h remained i n a c t i v e i n a cor-ner and d i d not eat. A f t e r the food was consumed, the dominant chased i t s a c t i v e subordinates r a t h e r than the new f i s h . L a t e r i n the day the dominant resumed chasing the t h i r d new f i s h and the l a t t e r d i e d i n the afternoon. A f o u r t h new coho was placed i n the tank i n the evening- of October 25. The dominant began chasing i t i n ten minutes. The dominant approached, examined the new f i s h as i t r e s t e d on the bottom, then nipped i t without expression of any t h r e a t . The new f i s h q u i c k l y r e t r e a t e d , gasping and moving i t s p e c t o r a l s r a p i d l y . The dominant then chased i t continuously f o r the remainder of the observation p e r i o d . On October 26 the f o u r t h new f i s h d i d not eat any food placed i n - t h e tank. I t was very dark. Whenever the dominant a t t a c k e d , i t r e t r e a t e d w i l d l y . -212-On October 27 the f o u r t h new f i s h d ied. I t s weight of 4.1 g was ever 50 percent greater than that of the dominant f i s h . S i m i l a r observations were made on a second group of f o u r j u v e n i l e coho i n which a dominance order e v o l -ved, one subordinate was removed and was replaced by a new coho of about the same s i z e . The new f i s h was immediately chased and nipped by the dominant. On October 25 the new f i s h was very dark. When food was placed i n the tank, i t d i d not feed very much. Soon i t was att a c k e d by the dominant. I t was att a c k e d more o f t e n a f t e r feeding than before (Table L X I I I ) . These experiments demonstrated that dominant r e s i d e n t s u s u a l l y attack strange i n d i v i d u a l s more se-v e r e l y than they do f a m i l i a r subordinates, and that the consequence of t h i s severe treatment can be death i f the new f i s h cannot escape. The new f i s h d i d not behave as d i d the r e s i d e n t subordinates, a f a c t which may have caused the dominant to tend t o attack them more of t e n . I t was not apparent whether the dominant was responding to them as i n d i v i d u a l s or was r e a c t i n g -213-Table L X I I I The number of times a newly i n t r o d u c e d coho i s n i p -ped by the dominant as compared w i t h other subor-d i n a t e s . F i f t e e n minutes before and f i f t e e n min-utes a f t e r feeding. Before Feeding A f t e r Feeding DOM-New D0M-SUB1 D0M-SUB2 DOM-New D0M-SUB1 D0M-SUB2 F i s h F i s h Oct. 23 2 8 8 29 11 7 Oct. 25 0 2 5 14 13 6 -214-to t h e i r d i f f e r e n t appearance and behavior. Group t e r r i t o r i a l i t y The h o s t i l e behavior of o r i g i n a l residents of a tank toward a newly introduced specimen prompted an experiment inv o l v i n g a resident group i n r e l a t i o n to a newly introduced group of f i s h of the same species. A narrow tank 180 cm i n length was divided i n two by an- aluminum screen. Four juvenile rainbow trout were placed i n one section of the tank and fed daily for one month, during which time they established a domi-nance order and adjusted to th e i r new environment. Four hew specimens were then introduced into the empty compartment and the p a r t i t i o n was removed. Four hours l a t e r the new trout were escape swim-ming and being occasionally nipped. The pr i o r r e s i -dents were s t i l l i n t h e i r o r i g i n a l h a l f of the tank. On that day and the four subsequent ones nipping was recorded for f i f t e e n minutes pr i o r to feeding and for f i f t e e n minutes following a f i f t e e n minute feeding period (Table LXIV). Table LXIV D i s t r i b u t i o n of n i p p i n g between a r e s i d e n t group of rainbows and a group of f o u r rainbows introduced one month l a t e r , "NF" designates new f i s h , "Dom" dominant, "Sub" subordinate. Before and a f t e r feeding. Dec 12 fr. Dec 13 *— Dec 17 Dec '18 Dec 19 T o t a l s 1 B e f . ' A f t . Bef."' Aft.' Bef. ' Aft . ' Bef. ' A f t . Bef.' A f t . Dom Sub 1 Dom + Sub 2 Dom •* Sub 3 Dom * 4 NF 8 0 0 27 2 0 1 48 4 7 1 21 14 9 2 84 7 10 1 3 7 4 12 52 6 0 0 0 2 3 3 54 7 5 2 6 8 17 3 43 65 55 25 338 Sub 1 Sub 1 Sub 1 Sub 1 Dom Sub * Sub * 4 NS • 1 2 0 3 2 ' 18 0 0 0 2 1 4 2 14 1 0 0 6 0 7 1 0 0 0 0 1 0 0 1 1 0 0 1 13 0 4 2 3 0 0 1 2 3 15 10 60 Sub 2 Sub 2 Sub 2 Sub 2 •» Dom •» Sub -» Sub * 4 NF 0 1 0 3 2 ' 0 0 0 G 0 0 0 1 0 0 1 0 4 0 0 0 1 0 0 2 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 0 1 5 13 Sub 3 Sub 3 Sub 3 Sub 3 •» Dom -» Sub •» Sub * 4 NF 0 1 0 2 0 ' 2 0 0 0 0 0 1 2 0 0 0 0 0 0 1 2 1 0 0 0 0 0 2 0 6 0 0 0 0 0 0 0 1 0 0 0 4 0 4 4 14 NF * Dom NF * Sub 1 NF * Sub 2 NF * Sub 3 NF * 3 NF 0 0 0 0 17 0 4 6 x 0 9 -1 0 0 1 2 0 0 0 0 7 0 0 1 4 5 0 0 0 2 3 0 1 1 1 4 0 4 0 2 12 0 0 8 3 19 0 0 0 7 4 1 9 16 20 - 82 -216-A l l members of the f i r s t group tended to remain i n t h e i r o r i g i n a l h a l f of the tank and t o attack the more r e c e n t l y i n t r o d u c e d i n d i v i d u a l s when they entered t h i s space. This a c t i o n was p a r t i c u l a r l y s i g n i f i c a n t i n t h a t food was placed i n the o r i g i n a l h a l f of the tank and thus the new f i s h were prevented from f e e d i n g . As the dominant became aggressive the new f i s h r e t r e a -t e d i n t o the new h a l f of the tank but the o r i g i n a l r e s i d e n t s r e t r e a t e d w i t h i n the o r i g i n a l space.'' ^ • A l l of the o r i g i n a l r e s i d e n t s a t t a c k e d the new f i s h and the dominant r e s i d e n t a t t a c k e d them more o f t e n than i t d i d i t s own subordinates (145 vs 338 n i p s ) . The new f i s h a t t a c k e d one another more o f t e n than they d i d the o r i g i n a l r e s i d e n t s . Resident subordinates lowered t h e i r f i n s i n a crouch a t the approach of the dominant but the non-r e s i d e n t s d i d not. Thus the o r i g i n a l group tended to behave as a u n i t which opposed i n t r u s i o n of new members i n t o the t e r r i t o r y of the group. Residents attacked new a r r i v a l s more v i g o r o u s l y than they d i d each other. -217-BEHAVIOR OF TRANSLOCATED RESIDENTIAL TROUT The escape swimming behavior of j u v e n i l e salmonids when they are f i r s t p laced i n a new tank has been described s e v e r a l times i n t h i s paper. I n the summer of 1954 stream observations were made of d i s p l a c e d rainbow t r o u t at the U n i v e r s i t y of C a l i f o r n i a Sagehen Creek P r o j e c t near Truckee, C a l i f o r n i a . Specimens were seined and then t r a n s p o r t e d one-half m i l e upstream to a screened-off p o r t i o n of the stream. There they were observed through the windows of a submerged ob-s e r v a t i o n tank i l l u s t r a t e d by Needham (1953). I t was 152 cm long and thus s u f f i c i e n t l y l a r g e to permit the observer to l i e down w i t h i n i t w h i l e l o o k i n g through panes of g l a s s at the f i s h i n the stream. I t was very d i f f i c u l t to confine these f i s h because of continuous r a p i d swimming up and down the screens and u l t i m a t e escape under or around them. Despite the absence of r e s i d e n t i a l f i s h i n t h i s l o c a t i o n the newly i n t r o d u c e d specimens c o u l d not be induced to remain and take up r e s -idence. E v i d e n t l y t h e i r m o t i v a t i o n to r e t u r n to t h e i r own home l o c a t i o n was very strong. INHABITATION OF A HOME RANGE Stream observations were made of j u v e n i l e coho salmon at Weaver Creek, a t r i b u t a r y of Ha r r i s o n R i v e r . The stream -218-was v i s i t e d on September 8, 15, 25 and December 15, 1957. I t was again v i s i t e d on May 9, 1958. On September 9, 1957, the stream was observed to be very low and f a i r l y warm (62° F.). I n the quiet p o r t i o n s of the stream young coho salmon were d i s t r i b u t e d f a i r l y evenly and each occupied about one square fo o t of stream bottom. A Bmall s e c t i o n of stream c o n t a i n i n g ten j u v e n i l e coho was observed f o r f i f t e e n minutes d u r i n g which time 48 n i p s and 19 t h r e a t s were tab u l a t e d . On September 15, 1957, a s e c t i o n of stream which sloped to a pool 1-g- f e e t i n depth was seined. 227 j u v e n i l e coho salmon were captured and r e l e a s e d a f t e r c l i p p i n g each of t h e i r upper caudal f i n l o b e s . Capture of these f i s h r e q u i r e d nine sweeps of the net over the area. A f t e r each sweep f i s h were marked and r e l e a s e d . On the l a s t sweep nine unmarked and 46 marked f i s h were caught. On September 25, 1957, the same s e c t i o n of stream was once more seined to determine whether the p r e v i o u s l y marked f i s h remained there. During the i n t e r v e n i n g time the weather had remained c l e a r and warm except f o r one day when there was a heavy r a i n f a l l . The l e v e l of the stream was s t i l l low and i t s temperature was 58° F. In 15 sweeps of the net 47 marked and 88 unmarked eohos were captured. A pool which had continuous q u i e t water between i t and the t e s t area 30 f e e t downstream was seined. Three marked and 58 unmarked f i s h were c o l l e c t e d . -219-The c l o s e s t downstream s t r e t c h of quiet water was seined. This was about 100 feet downstream of the t e s t area and sep-a r a t e d from i t by r i f f l e s . No marked f i s h were found among the 64 unmarked ones. A second s t r e t c h of q u i e t water about 150 fee t down-stream of the t e s t area was seined. I t y i e l d e d no marked f i s h out of 61 unmarked specimens. From t h i s experiment i t was concluded that the home range of the f i s h i n v o l v e d the t e s t area and the quie t water a d j o i n i n g i t upstream. Only about o n e - t h i r d of the t o t a l r e s i d e n t s were marked on September 15. When the area was seined a second time the marked and unmarked specimens had rearranged themselves w i t h i n the area of t h e i r f a m i l i a r i t y . Fewer f i s h were obtained but there was no evidence of s t r a y -i n g . M o r t a l i t y may have been a f a c t o r . I n d i v i d u a l s were observed i n another pool to deter-mine how great were the distances which they moved. The b a s i c question was: does a coho r e s t r i c t i t s e l f to i t s one square foot of area and defend i t as a t e r r i t o r y or does i t move about and exchange places w i t h the f i s h around i t ? One f i s h was observed f o r ten minutes. During t h i s time i t moved eight f e e t downstream then two and one h a l f f e e t across the stream. Movement of both f i s h was uneven. They swam, stopped, f e d and made i n t e n t i o n movements at other s . There appeared t o be no r e s t r i c t i o n to a s i n g l e spot but a general u t i l i z a t i o n of a common home range. -220-When the stream was v i s i t e d on December 15, 1957, i t was very h i g h and very f a s t . The water temperature was 42° F. The channel had changed con s i d e r a b l y and at the t e s t l o c a t i o n was a t u r b i d t o r r e n t 2^ f e e t deep. No f i s h c o u l d be obtained by s e i n i n g and none were seen at that p l a c e . On i n s p e c t i n g the stream a deep, protected pool was found beneath a tumble of l o g s about 60 f e e t upstream. This pool was at the edge of the creek out of i t s main c u r r e n t . Many small coho were seen i n the pool but none could be caught to examine whether they were c l i p p e d or not. In an area four f e e t long by 18 inches wide observable between two l o g s about 35 f i s h c o u l d be seen. They were a l l o r i e n -t e d upstream and were separated by a distance of two to s i x i n c h e s . On May 9 of the f o l l o w i n g s p r i n g Weaver Creek was once more v i s i t e d . The leaves were u n f o l d i n g on the vege-t a t i o n , the water temperature was 52° and the a i r temper-ature 70°. The water l e v e l had receded from i t s w i n t e r high point and at the t e s t l o c a t i o n the current was strong but once more i n h a b i t a b l e f o r small salmon. This l o c a t i o n was Beined and, w h i l e three coho smolts were captured, none had been c l i p p e d . S n a i l coho salmon f r y were numerous i n q u i e t eddies near the edge of the stream. Many were i n slow-moving, semi-detached s e c t i o n s at the sides of the creek but none were i n deeper pools. The pools were occupied by groups -221-o f smolts which had not yet migrated to the sea. About 100 smolts were seen i n a pool two to three f e e t deep under a l o g . I t was n o t i c e d that the smolts made excursions i n t o shallower water where they appeared to be preying o n i f r y of t h e i r own s p e c i e s . The f r y maintained a distance from them and r e t r e a t e d i n t o the shallowest p o r t i o n s along the mar-g i n s of the stream. R e l a t i v e abundance of j u v e n i l e coho and rainbows Small steelhead t r o u t (anadromous rainbows) i n h a b i t e d Weaver Creek as w e l l as j u v e n i l e coho salmon. The salmon were much more abundant than the t r o u t i n areas of q u i e t water (Table LXV). C o l l e c t i o n s made i n r i f f l e s r e v e aled t h a t , w h i l e there were fewer f i s h , there were p r o p o r t i o n -a t e l y more rainbows (Table LXVI). INTERSPECIFIC BEHAVIOR I n t e r s p e c i f i c behavior was s t u d i e d by p l a c i n g two species together i n small tanks. Lake t r o u t and d o l l y varden Two d o l l y varden and two s l i g h t l y l a r g e r l a k e t r o u t were placed together i n h a l f a s e c t i o n of a 180 cm tank. • They were observed over a p e r i o d of a week during which the two l a k e t r o u t a t t a c k e d the d o l l y varden s e v e r a l times and i n h i b i t e d the aggressiveness observed p r e v i o u s l y i n those -222-Table LXV Comparative abundance of j u v e n i l e coho salmon and rainbow t r o u t i n qui e t waters of Weaver Creek. Coho Salmon Rainbow Trout Sept. 15 227 26 Sept. 25 Location #1 135 2 Lo c a t i o n #2 64 2 Loca t i o n #3 61 6 Loca t i o n #4 61 6 -223-Table LXVI R e l a t i v e abundance of j u v e n i l e coho and rainbows i n r i f f l e s i n four sweeps of a sein e . Number of Number o f Coho Rainbow 0 3 1 5 0 6 0 5 -224-two specimens. No n i p p i n g and chasing took place even between the d o l l y varden. The two l a k e t r o u t c a r r i e d out t h e i r t y p i c a l slow swimming motions back and f o r t h w h i l e the other two f i s h were cons i d e r a b l y subdued. The l a k e t r o u t were not very aggressive but a b i t e from one of t h e i r t e e t h - f i l l e d mouths seemed adequate to reduce the aggres-siveness of d o l l y varden. Lake t r o u t and rainbow t r o u t The two d o l l y varden were removed and repl a c e d by two rainbow t r o u t of about the same s i z e as the l a k e t r o u t . One rainbow t r o u t was p a r t i c u l a r l y aggressive. I t nipped the l a k e t r o u t and over a p e r i o d of f i v e days caused these two f i s h to remain qui e t i n one corner w h i l e i t p a t r o l l e d the center s e c t i o n of the tank. There never was any r e a l f i g h t i n g . U s u a l l y the l a k e t r o u t met the approach of the rainbow t r o u t w i t h a g e n e r a l i z e d alarm posture, occasions a l l y w i t h r a p i d f l i g h t and r a r e l y w i t h f r o n t a l d i s p l a y . Lake t r o u t often avoided the aggressive rainbow. As among d o l l y varden, however, the l a k e t r o u t showed more aggres-s i v e behavior w h i l e w i t h the rainbow t r o u t than they d i d i n i n t r a s p e c i f i c groups. Rainbow t r o u t and brook t r o u t F i v e j u v e n i l e rainbow t r o u t and f i v e j u v e n i l e brook t r o u t of about the same s i z e were s t u d i e d i n a ten g a l l o n -225-tank for one week. Records of nipping are indicated i n Table.LXVII. The largest rainbow was a very aggressive dominant which subordinated a l l f i s h of both species and chased them from the feeding area. The others tended to aggregate at one side. One rainbow was somewhat aggres-sive and established i t s e l f as a weak subdominant. The rainbows were more active than the brook trout. The l a t t e r were frequently attacked by rainbows and somewhat subdued by them. Rainbow trout and outthroat trout The observations of the f i r s t group of rainbow trout and the f i r s t group of cutthroat trout were made while each species was separated by a b a r r i e r i n a narrow tank 180 cm i n length. Following the i n t r a s p e c i f i c observa-tions the b a r r i e r was removed. The two dominants immediately swam into the opposite ends of the tank. Soon they threatened each other and a f t e r ten minutes most of the f i s h were aggressively a c t i v e . The aggressive actions of the rainbows were stronger and more vigorous than those of the cutthroats. The l a t t e r species displayed and chased but d i d not f r e -quently contact opponents while nipping. After one hour the rainbows had defeated a l l the cutthroats. The dominant rainbow v i o l e n t l y attacked other f i s h of both species but even the most subordinate r a i n -bow chased the previously dominant cutthroat. -226-Table LXVII Nipping between rainbow and brook t r o u t i n a ten g a l l o n tank. F i v e f i s h of each species i n v o l v e d . Before Feeding A f t e r Feeding Rainbow Brook Rainbow 4/ Rainbow Br|)ok Rainbow Br^ok Brook Rainbow Br^ok Rainbow Br(|ok B r ^ o k Rainbow Rainbow Brook 3 6 1 0 52 52 2 0 10 7 1 0 29 35 1 1 9 26 1 0 10 34 11 0 4 16 0 0 10 42 10 0 -22.7-On the f o l l o w i n g day the c u t t h r o a t s had darkened from a l i g h t c o l o r t o almost b l a c k . The dominant rainbow was extremely v i c i o u s and f i n a l l y chased a l l other f i s h from the o r i g i n a l rainbow end of the tank where food was i n t r o -duced. The dominant rainbow nipped the c u t t h r o a t s much more than i t d i d i t s own 'subordinates (Table LXVIII). When food was i n t r o d u c e d the dominant rainbow f e d immediately but the p r e v i o u s l y dominant c u t t h r o a t d i d not begin feeding f o r f o u r minutes and then was chased away. Thus the r a i n -bows dominated the c u t t h r o a t s and prevented them from feedin g . Group 2 rainbows and Group 2 c u t t h r o a t s were a l s o observed i n i n t r a s p e c i f i c groups a t opposite ends of a d i -v i d e d tank. When these observations were terminated the b a r r i e r was removed. Within 15 minutes the two dominant f i s h threatened and attacked each other. The cutthroat dominant disengaged and r e s t e d . Meanwhile the rainbow dominant attacked the other c u t t h r o a t s . One hour and a h a l f a f t e r the b a r r i e r had been removed the rainbow dominant had defeated a l l opponents and was v i g o r o u s l y chasing them. On the f o l l o w i n g day n i p p i n g was t a b u l a t e d f o r 15 minutes before feeding and 15 minutes a f t e r a 15 minute f e e d i n g p e r i o d (Table LXIX). As i n the previous obser-v a t i o n the rainbow t r o u t were much more aggressive than -228-Table LXVIII Nipping r e l a t i o n s among four rainbow t r o u t (Group l ) and four c u t t h r o a t t r o u t (Group 1) i n a 150 cm tank. 15 minutes before feeding. 15 minutes a f t e r feeding. Before Feeding A f t e r Feeding Rainbow Rainbow Cut- Cut-I I throat thr.Oat * I \ * Cut- v Ml • . Cut-t h r o a t Rainbow Rainbow t h r o a t 100 18 Rainbow Rainbow Cut- Cut-^ 1 t h r o a t throat Cut- * \|/ out-:1 thro at Rainbow Rainbow throat 66 37 -2 28-t h e c u t t h r o a t and prevented them from feeding. The r a i n -bows attacked the c u t t h r o a t s more o f t e n than they d i d t h e i r own species. Two j u v e n i l e rainbow t r o u t and two j u v e n i l e coho salmon were place d together i n a small tank and s t u d i e d f o r ten days. A complete i n t e r s p e c i f i c h i e r a r c h y developed as f o l l o w s : One rainbow was dominant and nipped a l l o t h e r s , one coho nipped one rainbow and one coho, the second rainbow n i p -ped the second coho w h i l e the l a t t e r f i s h d i d not n i p any other f i s h . While the coho were dominated by a rainbow, the salmon were f a s t e r i n o b t a i n i n g food. O c c a s i o n a l l y the subordinate coho f a i l e d to feed. In another experiment f i v e j u v e n i l e rainbows were p l a c e d w i t h f i v e j u v e n i l e coho i n a s m a l l tank. One r a i n -bow dominated a l l others but a coho became a subdominant over members of i t s own spec i e s . Table LXX shows the n i p -p i n g r e l a t i o n e . Rainbows performed more n i p p i n g than d i d coho but nipped t h e i r own species about the same number of times as the other. Rainbow t r o u t and coho salmon Rainboi Coho -230-Table LXIX Nipping r e l a t i o n s among four rainbow t r o u t (Group 2) and four c u t t h r o a t t r o u t (Group 2) i n a 180 cm tank. 15 minutes before feeding and 15 minutes a f t e r f e e d i n g . Before Feeding A f t e r Feeding Rainbow Rainbow Cut- Cut-|. I throat throat A i 4 t h r o a t Rainbow Rainbow throat 96 Rainbow Rainbow Cut- Cut-th r o a t throat Oilt- V Cut-th r o a t Rainbow Rainbow throat Mt-42 14 21 20 -231-Table LXX Nipping r e l a t i o n s among f i v e j u v e n i l e rainbow t r o u t and f i v e j u v e n i l e coho salmon. 15 minutes before feeding and 15 minutes a f t e r f e e d i n g . Before Feeding A f t e r Feeding Rainbow Colio Rainbow Rainbow Coho Rainbow Coho Cono Rainbow Coho Raj^ibow Rainbow Coho Rainbow Coho Cabo 12 4 3 17 34 16 5 23 6 2 16 14 14 15 14 24 33 23 3 5 28 26 12 13 25 41 8 13 45 42 3 12 -232-Coho salmon and brook t r o u t Five j u v e n i l e coho and f i v e j u v e n i l e brook t r o u t were p l a c e d together i n a small tank and observed f o r one week. The l a r g e s t coho dominated during the f i r s t two observa-t i o n s . Then the l a r g e s t brook t r o u t became aggressive and r e p l a c e d the coho as dominant f i s h . There was no sub-dominant. Table LXXI shows the n i p p i n g r e l a t i o n s . Conclusions on i n t e r s p e c i f i c behavior l ) D i f f e r e n t species recognized aggressive manifes-t a t i o n s i n other species. 2) Lake t r o u t , despite being r e l a t i v e l y unagressive, showed more aggressiveness when w i t h aggressive s p e c i e s . 3) Rainbow t r o u t were the most aggressive of a l l species observed and defeated l a k e t r o u t , brook t r o u t , c u t t h r o a t t r o u t and coho salmon. 4) I n t e r -s p e c i f i c dominance r e s u l t e d i n the r e p r e s s i o n of feeding of one species by the other and i n t e r f e r e n c e i n a l l the a c t i v i t i e s of the subordinate species. 5) Coho salmon were s w i f t e r than rainbows i n o b t a i n i n g food and t h i s may have compensated f o r the subordinance of coho salmon to rainbow t r o u t . AGGRESSIVE BEHAVIOR OF SPAWNING ADULTS The spawning of rainbow t r o u t , coho salmon, sockeye salmon, ohum salmon and pink salmon was observed i n nature -233-Table LXXI Hipping r e l a t i o n s among f i v e j u v e n i l e coho salmon and f i v e j u v e n i l e brook t r o u t . 15 minutes before feeding and 15 minutes a f t e r f e e d i n g . Before Feeding ( A f t e r Feeding ( / Coho Brook Coho Coho Bro.ok Coho Brook Brook Brook Coho COho Br^ok Coho Br|x>k Brook 0 4 0 1 7 13 6 8 1 3 0 1 8 44 4 7 1 1 41 5 3 3 80 23 0 6 26 4 0 0 46 16 -234-A d d i t i o n a l observations were-made of the spawning of coho, sockeye and chum salmon i n the Vancouver P u b l i c Aquarium. Rainbow t r o u t The spawning of rainbow t r o u t was s t u d i e d from a b l i n d at the o u t l e t of Loon Lake, near C l i n t o n , B r i t i s h Columbia, i n May, 1955. Trout c a r r y out p e l a g i c l i v e s i n Loon Lake where they are numerous and r a t h e r s m a l l . The average a d u l t s i z e i s about 12 inches. Upon maturing s e x u a l l y they migrate e i t h e r upstream i n t o the i n l e t at one end of the l a k e or downstream i n t o the o u t l e t a t the other. When the t r o u t f i r s t migrated i n t o the o u t l e t they formed i n a c t i v e aggregations along the banks of the stream c o n s i s t i n g of 50 or more f i s h . They remained mo t i o n l e s s , c l o s e together (as c l o s e as 2-3 i n c h e s ) , o r i e n t e d i n t o the c u r r e n t and completely non-aggressive. Over the g r a v e l there were spawning groups of 10 to 20 f i s h which d i s -p l ayed and nipped and chased i n a way s i m i l a r to j u v e n i l e s . From time t o time one of the aggregating f i s h l e f t i t s group and entered the spawning area where i t became a c t i v e l y a g gressive. Both males and females showed aggressive behavior. There appeared t o be p r e l i m i n a r y aggressive d i s p l a y between f i s h new t o each other. Two f i s h would move i n t o p a r a l l e l p o s i t i o n s and undulate t h e i r bodies. At that time t h e i r f i n s were broadly expanded i n t o a l a t e r a l d i s p l a y . The -235-moving t a i l of one f i s h would s t r i k e and displace the other f i s h i n defensive " t a i l wagging" acts. After the period of display, or associated with i t , the f i s h fought, and one chased the other away. Most of the f i g h t i n g took place near the surface and the f i g h t i n g f i s h splashed as they attacked each other. The number of splashes was highest i n l a t e afternoon. This may have been correlated with that being the time of highest tem-perature or with that being the time of greatest migra-tory movement. Fighting appeared to be an a c t i v i t y taking place between f i s h new to each other and thus might well . be associated with movements of migratory i n d i v i d u a l s . Nipping behavior within the spawning group was very s i m i l a r to the nipping and chasing among an organized group of juveniles. There was r e l a t i v e l y l i t t l e display and much "automatic", rather stereotyped, nipping. The "r i p e " females spent much of the time on the bottom and nipped any f i s h ahead of them. Each female had a large male attendant which oriented alongside of the female with i t s snout at the l e v e l of the female's dorsal f i n . The male nipped and chased a l l intruders, p a r t i c u l a r l y those approaching:from the rear. Females competed for redd positions and large ones generally held positions and dislodged smaller ones. Neither the males nor the females remained with a -236-p a r t i c u l a r mate very long. Spawning was a group a c t i v i t y r a t h e r than a p a i r e d one. One l a r g e male was observed to move back and f o r t h between two females and each time i t l e f t one i t was r e p l a c e d by smaller males, n i p p i n g and chasing as they approached. This suggested the presence of a dominance order among the spawners and resembled r o t a t i n g t e r r i t o r i a l i t y among j u v e n i l e t r o u t i n streams (Newman, 1956). Orgasm c o u l d not be d i f f e r e n t i a t e d i n the behavior of the t r o u t . Two a c t i o n patterns were s t r i c t l y r e l a t e d t o r eproduction and not expressed by j u v e n i l e s . These were the redd d i g g i n g of the female and the q u i v e r i n g of the male. These a c t i o n s were r h y t h m i c a l l y a l t e r n a t e d w i t h n i p p i n g and chasing. The female nipped and chased an i n -t r u d e r , s e t t l e d on the redd and remained motionless there f o r about 30 seconds. There always seemed to be t h i s motionless p e r i o d which was then f o l l o w e d by the f i s h t u r n i n g on i t s s i d e , r a p i d l y undulating i t s body w h i l e i t moved forward. As soon as the female o r i e n t e d i t s e l f the male moved along side and underwent a spasm of movement, a " q u i v e r i n g . " A f t e r spawning, aggressive behavior disappeared and the spent f i s h moved over to the bank and aggregated as d i d the prespawning f i s h . The p e r i o d of time between spawning and the l o s s of aggressiveness was not determined. The sharp changes i n behavior from non-aggressiveness - 2 3 7 -t o aggressiveness and back were suggestive of the l o s s of aggressiveness that occurred when j u v e n i l e s were moved to a new l o c a t i o n and the r e s t i t u t i o n of t h i s behavior oc-c u r r i n g as the f i s h became f a m i l i a r w i t h t h e i r new environ-ment. P a c i f i c Salmon The general c h a r a c t e r i s t i c s of salmon spawning were s i m i l a r to that of rainbow t r o u t . Groups of salmon en-t e r e d the spawning streams where they were i n a c t i v e f o r a p e r i o d . This was followed by aggressive encounters i n which females e s t a b l i s h e d t e r r i t o r i e s and males fought among each other f o r p o s i t i o n s alongside the females. A l l four species of salmon observed were v i g o r o u s l y aggressive. As was the case f o r rainbow t r o u t , spawning of salmon was a h i g h l y s o c i a l phenomenon i n v o l v i n g many i n d i v i d -u a l s and not j u s t i s o l a t e d p a i r s . Male pink salmon performed l a t e r a l d i s p l a y s and moved eye t o eye i n forward progression i n a stream ( F i g . 57). They were very aggressive and i n the Aquarium of t e n nipped and chased each other. In the confinement of the Aquarium tank nips sometimes i n v o l v e d a c t u a l b i t i n g ( F i g . 58). Adul t pink salmon f r e q u e n t l y gaped ( F i g . 59) j u s t as had j u v e n i l e salmonids. But the reproductive behavior, which i n v o l v e d p a i r i n g ( F i g . 6 0), redd d i g g i n g ( F i g . 6 1), quiv-e r i n g of the male, orgasm and other a c t s , was unique to -238-a d u l t salmon and never observed among j u v e n i l e s . While not s y s t e m a t i c a l l y s t u d i e d , the movements of c o u r t i n g chum salmon appeared s i m i l a r to those of pink salmon. I t was observed, however, that the markings of the female chum ( F i g . 62) during redd digging were con-spicuou s l y d i f f e r e n t from those of the female pink. F i g . 57 - Two male pink salmon moving upstream side to si d e i n l a t e r a l d i s p l a y . F i g . 58 - Male pink salmon n i p p i n g at another - 2 3 9 -F i g . 60 - P a i r e d male and female pink salmon over nest i n the Vancouver P u b l i c Aquarium. -240-F i g . 62 - Female chum salmon digging redd i n stream w h i l e male wait s nearby. -241-DISCUSSION The evidence suggests that j u v e n i l e d o l l y varden, brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon share many s p e c i a l i z e d b e h a v i o r a l c h a r a c t e r i s t i c s which enable them to e s t a b l i s h l o c a l i z e d areas of residence. On the other hand, the j u v e n i l e s of species of P a c i f i c salmon c h a r a c t e r i z e d by e a r l y down-stream migrations are q u i t e d i f f e r e n t i n behavior. Aggregation I n d i v i d u a l s of the r e s i d e n t i a l species have l i t t l e n a t u r a l a t t r a c t i o n t o each other as contrasted w i t h chum salmon f r y which r e a d i l y come together and form schools. Although not aggressive themselves, j u v e n i l e l a k e t r o u t show l i t t l e i f any more aggregating tendency than do the aggres-s i v e species and do not form schools. F l u c t u a t i o n i n the den s i t y of schools i s w e l l known i n species which r e g u l a r l y swim i n t i g h t ^ a g g r e g a t i o n s . Con-v e r s e l y , f l u c t u a t i o n s i n the tendency to remain i s o l a t e d occur among non-schooling f i s h . Among stream r e s i d e n t s mutual a t t r a c t i o n i s o f t e n i n c r e a s e d by an alarm stimulus i n the absence of adequate environmental cover. S t a r t l i n g u s u a l l y r e s u l t s i n a more c l o s e l y k n i t school (Hoar, -242-MacKinnon & R e d l i c h , 1952). Coho salmon f r y were observed t o condense i n t o a moving aggregation i n a shallow, sandy-bottom stream as a person waded i n i t . When the person came out of the stream the f i s h g r a d u a l l y returned t o t h e i r o r i g i n a l spaced c o n d i t i o n . The formation of small swimming gangs as observed among d o l l y varden and brook t r o u t occurred spontaneously and was not induced by an o u t s i d e alarm s t i m u l u s . Katz (1953) maintains that the same s i t u a t i o n can produce d i f -f e r e n t responses according to the s t a t e of the animal and i t can be assumed that the n i p p i n g and chasing seen at one time and the formation of gangs seen at other times rep-resented d i f f e r e n t s t a t e s or moods. Movement of these f i s h appeared t o be a p p e t i t i v e and was probably induced by hun-ger w h i l e the l o s s of contact w i t h t h e i r normal s t a t i o n s c r e a t e d an alarm s i t u a t i o n which c o u l d be met by the cover provided by other i n d i v i d u a l s . Lake t r o u t were unique i n that they o r i e n t e d to n e i t h e r the p h y s i c a l environment nor to other i n d i v i d u a l s . Their slow, continuous swimming was suggestive of the swim-ming a c t i v i t y of chum f r y but there was no s c h o o l i n g . Lake t r o u t were l e s s s e n s i t i v e to alarm s t i m u l i than other species and t h i s absence of alarm may be s i g n i f i c a n t i n t h e i r f a i l u r e t o seek the cover of other f i s h w h i l e i n -243-open spaces. Schooling appears to represent a cover response of f i s h out of contact w i t h known fea t u r e s of the p h y s i c a l environment. When groups of f i s h are introduced i n t o an aquarium they form dense schools which g r a d u a l l y d i s -perse over a p e r i o d of time (Breder and Halpern, 1946; Keenleyside, 1955; Noble and C u r t i s , 1939). This decrease i n s c h o o l i n g tendency may be caused by growing f a m i l i a r i t y w i t h the p h y s i c a l surroundings and l o s s of alarm. Chum salmon f r y swam together when f i r s t placed i n a ten g a l l o n tank but l a t e r swam independently of one another. The non-s c h o o l i n g salmonids were l e s s a c t i v e than chum f r y and u s u a l l y d i d not swim i n a group when f i r s t placed i n a tank. However, they formed non-moving aggregations which g r a d u a l l y d i s p e r s e d w i t h time. Hoar (1958b) has shown that coho f r y form t y p i c a l schools i n s e v e r a l d i f f e r e n t s i t u a t i o n s . "The s i m p l e s t way t o demonstrate t h i s r e a c t i o n i s t o place some coho f r y With a , ischool of pink or chum f r y . The coho f r y im-mediately show 'follow-the l e a d e r ' behavior c h a r a c t e r i s t i c o f many sc h o o l i n g f i s h (Keenleyside, 1955). Coho smolts w i l l show the same r e a c t i o n to a school of sockeye smolts. In both cases, however, i f there i s adequate space the coho -244-p r e s e n t l y s e t t l e down to more s o l i t a r y a c t i v i t i e s . " He d e s c r i b e d s c h o o l i n g behavior i n coho f r y trapped during a downstream m i g r a t i o n . When placed i n a 360 cm trough they formed moving schools which broke up a f t e r about 30 minutes. These examples r e v e a l the behavior of j u v e n i l e f i s h e i t h e r d i s p l a c e d from t h e i r home areas or l a c k i n g any r e l a t i o n to a home area. Coho f r y were observed to f o l l o w one another during f e e d i n g and form small feeding groups which l a t e r d i s -persed as the f i s h became aggressive. The r e l a t i o n s h i p between feeding and heightened aggressiveness i s a very fundamental one i n salmonids and i t s value may l i e i n the e f f i c i e n t u t i l i z a t i o n of a v a i l a b l e foods. Dispersed f i s h would be more l i k e l y y t o see i n s e c t s dropping i n t o a stream r at d i v e r s e p l a c e s . Once an i n s e c t was seen the f i s h would dart a f t e r i t and be f o l l o w e d by o t h e r s . I f there were s e v e r a l i n s e c t s , or a hatch of f l i e s , the f o l l o w i n g i n -d i v i d u a l s would o b t a i n food a l s o . Soon the e l i c i t a t i o n of aggressiveness would b r i n g about the o r i g i n a l d i s p e r s i o n capable of apprehending the maximum amount of food. H a b i t a t s e l e c t i o n That a d i s p e r s i o n occurs f o l l o w i n g feeding does not -246-mean that the f i s h are completely spread out by i t . Their behavior i s analogous t o t h a t of "distance type" animals (Hediger, 1950) that w i l l not t o l e r a t e another i n d i v i d u a l w i t h i n a given d i s t a n c e . There are many such animals which r e s t together but are separated by a minimum d i s t a n c e . These animals c o n t r a s t w i t h "contact types" which touch each other w h i l e r e s t i n g . Despite the low aggregating tendency of r e s i d e n t i a l salmonids they are u s u a l l y found l i v i n g i n groups i n nature. To what extent i n t e r n a l mo-t i v a t i n g f a c t o r s are r e s p o n s i b l e f o r t h i s grouping was not r e v e a l e d by t h i s study but experiments i n s e l e c t i n g par-t i c u l a r environments suggested that t r o u t do seek out s i m i l a r c o n d i t i o n s and may be brought together i n t h i s way. I n two d i f f e r e n t experiments both rainbow f r y and rainbow parr were recorded i n shaded p o r t i o n s of a tank more o f t e n than i n i l l u m i n a t e d ones. When the experiment was repeated using c u t t h r o a t t r o u t one of these f i s h chased the others from the dark end of the tank thus pro-ducing r e s u l t s which i n d i c a t e d more f i s h i n the i l l u m i -nated end. I t was concluded from these observations that under some c o n d i t i o n s t r o u t showed an innate preference f o r shade as opposed to i l l u m i n a t i o n but that t h i s p r e f -erence could be a l t e r e d by the presence of a g g r e s s i v e , -847-t e r r i t o r i a l i n d i v i d u a l s . A s i m i l a r preference was shown by rainbo?/ t r o u t f o r the deep end of a tank which was d i v i d e d i n t o p o r t i o n s of va r i o u s depths. Chum salmon t e s t e d i n the same tank showed no such preference but swam back and f o r t h without regard to depth. Preference was q u i c k l y changed by the i n t r o d u c t i o n of a l a r g e r f i s h . When a l a r g e rainbow was pl a c e d w i t h the sm a l l ones many of them moved i n t o shallower water l e a v i n g the deep end t o the l a r g e r f i s h . The pre-sence of a predatory l a k e t r o u t had even greater e f f e c t . When i t was placed i n the tank w i t h the chums they seldom swam over the deepest p a r t of the tank. When i t was pl a c e d w i t h the small rainbow t r o u t they vacated the deep end e n t i r e l y . Fishermen have n o t i c e d the presence of t r o u t below w a t e r f a l l s but when a sm a l l w a t e r f a l l was placed at the end of a tank c o n t a i n i n g small t r o u t the f i s h d i d not remain i n i t s v i c i n i t y . The s i g n i f i c a n c e of the w a t e r f a l l changed, however, when food was in t r o d u c e d through i t i n t o the tank. The l a r g e s t f i s h t e r r i t o r i a l i z e d i t and tended to chase other f i s h away. Even long a f t e r any food had passed over the w a t e r f a l l the l a r g e s t rainbow remained nearby. The presence of food was the f a c t o r s e l e c t e d and t h i s was r e a d i l y a s s o c i a t e d w i t h the l o c a t i o n of the -248-w a t e r f a l l . These experiments i n d i c a t e that the grouping of salmonids i n a stream represents a balance between innate preference f o r s i m i l a r environmental c o n d i t i o n s and ex-t e r n a l modifying f a c t o r s . Hoar (1958b) has described the expression of behavior i n j u v e n i l e salmonids i n terms of f i v e d i r e c t i v e f a c t o r s : l i g h t , temperature, c u r r e n t , s a l -i n i t y and p h y s i c a l o b j e c t s i n the environment. To t h i s l i s t should be added b i o l o g i c a l i n t e r f e r e n c e ( M i y a d i , 1960) as another d i r e c t i v e f a c t o r of great importance. The presence of pre d a t o r s , aggressive i n d i v i d u a l s of the same or of d i f f e r e n t species and any other i n d i v i d u a l s which would act to r e p e l or a t t r a c t , a f f e c t the d i s t r i b u t i o n of r e s i d e n t i a l f i s h . One of the most i n t e r e s t i n g examples i s the p o s s i b l e r e l a t i o n s h i p between coho f r y and coho smolt i n Weaver Creek where i t was observed that whenever the f r y wandered i n t o pools they were chased and sometimes devoured by the smolts. This could w e l l be a mechanism f o r the l o c a l i z a t i o n of coho f r y i n the shallow margins of the stream. F i x a t i o n of an i n d i v i d u a l f i s h i n a p a r t i c u l a r h a b i t a t was probably brought about through h a b i t . I t was f r e q u e n t l y noted that i n d i v i d u a l s r e s t e d i n the same place even though c o n d i t i o n s i n tha t place changed. Hediger -249-(1950, 1955) presents many examples of h a b i t u a l movements and r e s t i n g spots among mammals and emphasizes t h a t they always move along paths. He quotes E. T. Seton as saying i n 1909 that "no w i l d animal roams at random over the country." Hediger envisages the personal l i v i n g space of each animal as a system of b i o l o g i c a l l y s i g n i f i c a n t p o i n t s i n v o l v i n g a home, temporary p o s i t i o n s of s h e l t e r and f e e d i n g p l a c e s . I t i s recognized that f i s h a l s o es-t a b l i s h h a b i t u a l s p a t i a l r e l a t i o n s . Hoar (1958a) demon-s t r a t e d that downstream-migrating chum, sockeye and pink salmon q u i c k l y e s t a b l i s h a constant course i n a c i r c u l a r channel and that schools tend t o t r a v e l i n p a r t i c u l a r areas of a maze. The m o t i v a t i o n f o r s e l e c t i n g a d e f i n i t e l o c a t i o n l i e s i n the i n n a t e behavior of the r e s i d e n t i a l f i s h . I n 1951 Hoar emphasized that one of the most important f e a t u r e s of the behavior of coho f r y i s the d e f i n i t e r e l a t i o n which they show to p a r t i c u l a r objects i n t h e i r v i c i n i t y . I t i s t h i s behavior which i s l a c k i n g i n l a k e t r o u t , chum f r y , pink f r y and sockeye f r y that prevents the development of residence. A c t i v i t y The p a t t e r n of a c t i v i t y was q u i t e d i f f e r e n t between r e s i d e n t i a l species and migrant s p e c i e s . The compulsion -2*50-of both chum and pink f r y to swim continuously must be one of the main reasons f o r t h e i r not developing residence. This must a l s o be a f a c t o r i n the l i f e of l a k e t r o u t , s i n c e they swim f o r extended periods at a continuous r a t e . The d a r t i n g movements of the r e s i d e n t i a l species were f o l -lowed by a consummatory a c t i o n such as n i p p i n g or feeding and then ended w i t h a r e t u r n to a r e s t i n g l o c a t i o n . Studies of the c r u i s i n g speed of j u v e n i l e coho salmon ( B r e t t , Hollands and A l d e r d i c e , 1958) have demonstrated t h a t they can maintain a maximum r a t e of 30 cm per second f o r one hour. Such an a b i l i t y i s important to a r e s i d e n -t i a l f i s h l i v i n g i n a stream since i t o r i e n t s against a c u r r e n t but coho f r y probably s e l e c t much slower currents t o i n h a b i t . K a l l e b e r g (1958) has shown that when a current flows at a r a t e of 30 cm per second A t l a n t i c salmon f r y h o l d p o s i t i o n on the bottom where they f i n d p r o t e c t i o n from the f l o w . At l e s s e r flows they move i n t o open water. I t should be emphasized that a s u s t a i n e d r a p i d r a t e of swimming i s not t y p i c a l of r e s i d e n t i a l salmonids. Comfort movements The comfort movements were very s i m i l a r i n the d i f -f e r e n t species and i t i s probable that they are p r i m a r i l y n o n - s o c i a l and serve s i m i l a r f u n c t i o n s i n a l l s p e c i e s . I t i s reasonable to assume that the gaping movements of j u v e n i l e salmonids are yawns. Yawning i s b e l i e v e d to -2-51-be common to a l l vertebrateB (Cocks, 1910) and has been observed i n man, dogs, c a t s , owls, crows, g u l l s , k i t t i -wakes, l i z a r d s , c r o c o d i l e s , newts and many species Of f i s h e s ( E l m h i r s t , 1910). Mammalian p h y s i o l o g i s t s consider yawning to be a r e s p i r a t o r y movement (C a r l s o n and Johnson, 1946) but i t s wide-spread occurrence among water-breathing v e r t e b r a t e s as w e l l as a i r - b r e a t h i n g ones suggests i t i s a s s o c i a t e d w i t h a more general system. K o r t l a n d t (1940) i n a d i s c u s s i o n of cormorant behavior, maintains yawning i s a s t r e t c h i n g movement which serves to stim u l a t e meta-b o l i c a c t i v i t i e s . The most p l a u s i b l e hypothesis ( E l m h i r s t , 1910) i s that s t r e t c h i n g and t e n s i o n i n v o l v e d i n yawning f l u s h e s the b r a i n w i t h blood during periods of s l u g g i s h -ness and heightens the responsiveness of the organism. Darwin (1872) d e s c r i b e d yawning i n humans and p o i n t e d out that the muscles of the body are s t r o n g l y c o n t r a c t e d and those around the eyes so much that t e a r s are f r e q u e n t l y secreted. The muscles of a f i s h are l i k e w i s e s t r e t c h e d d u r i n g yawning and the pharyngeal and t h o r a c i c c o n t r a c t i o n s must c e r t a i n l y a f f e c t the immediate c i r c u l a t i o n of blood. Yawning has achieved secondary f u n c t i o n s o f t e n of a s i g n a l nature. I t i n d i c a t e s awakening and impending a c t i o n when appearing i n a r e s t i n g animal. Conversely i t i n d i -cates a slowing-down or impending c e s s a t i o n of a c t i v i t y i n a moving animal. This can be of great importance to subordinates i n a s o c i a l h i e r a r c h y because i t can s i g n i f y -2<5'3-periods within which they can feed and move about without being attacked by the dominant. Such s i g n a l i z i n g probably takes place i n salmonid hierarchies but was not d e f i n i t e l y established as fact i n these studies. Occasionally subordinate f i s h , which were frequently and v i c i o u s l y attacked by t h e i r dominant, yawned repeatedly during l u l l s of attack and retreat while they cowered i n a corner of the i r tank. During such periods a subordinate showed great stress i n that i t s color was dark, i t s g i l l covers were moving r a p i d l y , i t s pectoral f i n s f l u t t e r e d quickly back and forth and i t s body was suspended limply at an angle. It was d e f i n i t e l y not re s t i n g , nor were i t s yawns a manifestation of rest i n g . They were analagous to so-c a l l e d "nervous yawns" exhibited by humans under tension or suppressed excitement. They may have been symptomatic of the same ph y s i o l o g i c a l conditions as those present during changes of state between sleep and wakefulness or they may have been displacement a c t i v i t i e s . Like any action which occurs regularly under d e f i n i t e and predictable con-d i t i o n s , these yawns may have had sign a l function. Yawn-like gaping has been observed i n many contexts. Hediger (1955) refers to "temper" yawning seen among hip-popotami and monkeys and interpreted as danger signals. In an in v e s t i g a t i o n of the reproductive behavior of Cottus  gobio. Morris (1954) observed a male undergoing a phase of displacement yawning when f i r s t presented with a female. -2-53-He d i d not consider t h i s behavior t o have a s i g n a l f u n c t i o n . Darwin (1872) described r e c i p r o c a l threat behavior of bab-,00ns which had been placed together f o r the f i r s t time. They sat opposite each other a l t e r n a t e l y opening t h e i r mouths and ended by r e a l l y yawning. Several authors (Needham and T a f t , 1934; Jones and B a l l , 1954; F a b r i c i u s and Gustafson, 1954) have described a yawn-like gaping i n spawning salmonids at the moment of orgasm. The problem i n a l l of these cases i s whether the opening of the mouth can be c l a s s i f i e d as the same a c t i o n under such d i v e r s e moods. Reproductive gaping may r e s u l t from the s t r a i n i n g of body muscles i n the act of extruding the sex products - or i t may be a genuine d i s p l a c e d a c t i o n p a t t e r n . Response to danger The response to danger of r e s i d e n t i a l species may be s p e c i a l i z e d i n t h a t they i n i t i a l l y assume a " g e n e r a l i z e d alarm p o s t u r e " i n which the body i s r i g i d , immobile and ready f o r a c t i o n . This posture, i n which a l l the f i n s were expanded, was observed i n l a k e t r o u t as w e l l as r e s i d e n t i a l species but i t s absence was not d e f i n i t e l y determined i n downstream migrants. Hoar's (1958b) d e s c r i p t i o n of sharp d i r e c t i o n a l changes i n the swimming movements of downstream migrants suggests that they may have a d i f f e r e n t response. F a b r i c i u s (1955) has shown that w h i l e a r c t i c char are slow to respond to p o t e n t i a l danger approaching from the -254-si&e and through the water, they respond more r a p i d l y to movement of l a r g e objects above the surface of the water. This was l i k e w i s e observed f o r a l l species of salmonids s t u d i e d i n t h i s i n v e s t i g a t i o n . F a b r i c i u s p o s t u l a t e s that the more northern l i v i n g chars evolved where there were few underwater enemies but a normal complement of f i s h -e a t i n g b i r d s i n the a i r . Trout evolved i n more southern l a t i t u d e s and became adapted to enemies both under and above the water. The perpetuation of such d i f f e r e n c e s i n r e -sponse could be a f a c t o r i n contemporary d i s t r i b u t i o n of the species by enabling good s u r v i v a l of t r o u t and coho salmon f r y i n waters c o n t a i n i n g p i s c i v o r o u s f i s h e s but poor s u r v i v a l of char i n these waters. An example of con-s i d e r a b l e i n t e r e s t i s the l a k e t r o u t i n the Great Lakes where the i n t r o d u c t i o n of the lamprey has s e r i o u s l y deple-t e d the p o p u l a t i o n . The c h a r a c t e r i s t i c r e s t i n g on the bot-tom and the slowness to respond to the approach of another f i s h makes the l a k e t r o u t extremely v u l n e r a b l e to a t t a c k . However, the a b i l i t y to i n s t a n t l y m o b i l i z e escape may have dangerous p h y s i o l o g i c a l consequences r e f l e c t e d i n higher m o r t a l i t y under c o n d i t i o n s of great disturbance such as extended t r a n s p o r t a t i o n by f i s h e r i e s b i o l o g i s t s . The high m o r t a l i t y of cu t t h r o a t t r o u t f o l l o w i n g transpor-t a t i o n r e p o r t e d on page 27 i s a ease i n p o i n t . M o r t a l i t i e s among cut t h r o a t t r o u t were more common i n these s t u d i e s than f o r any other s p e c i e s . In g e n e r a l , handling mor-t a l i t i e s (as opposed to l o s s by disease) were higher i n Salmo and Oncorhynchus k i s u t c h than i n S a l v e l i n u s and were -265-more or l e s s p r o p o r t i o n a l t o the i n t e n s i t y of f l i g h t r e -sponse i n the speci e s . This high m o r t a l i t y may be due to a c i d i f i c a t i o n of the blood ( B l a c k , 1957a, b, c> 1958a, b) caused by i n t e n s e e x e r t i o n . Pink salmon f r y e v i d e n t l y l o s e t h e i r response to movement of predators from the a i r d u r i n g downstream mi-g r a t i o n . Hoar (1958b) observed that pink f r y d i d not hide under stones when s t a r t l e d from above but chum, coho and sockeye f r y d i d under the same circumstance. He a l s o demonstrated the v u l n e r a b i l i t y of t h i s species as compared to the others to avian p r e d a t i o n . 60 to 90 percent of the pink f r y were eaten by crows wh i l e p r e d a t i o n of the f r y of the other species was comparatively i n s i g n i f i c a n t . T e r r i t o r i a l i t y The concept of t e r r i t o r i a l i t y as intro d u c e d by orn-i t h o l o g i s t s has never been an e n t i r e l y s a t i s f a c t o r y one when a p p l i e d to r e s i d e n t i a l behavior of j u v e n i l e f i s h e s . The main reason f o r t h i s i s the great d i f f e r e n c e i n l i f e h i s t o r y between c o l d blooded and warm blooded vertebrates imposed by the e v o l u t i o n of p a r e n t a l care. J u v e n i l e c o l d blooded v e r t e b r a t e s may r e c e i v e p a r e n t a l p r o t e c t i o n over a short p e r i o d but j u v e n i l e b i r d s and mammals are p r o t e c t e d and f e d u n t i l they achieve adulthood. This n e c e s s i t a t e s the presence i n young f i s h e s of a l l the behavior p a t t e r n s r e q u i r e d f o r s u r v i v a l i n t h e i r p a r t i c u l a r environment but -266-o b v i a t e s them i n young b i r d s and mammals. To s u r v i v e , the young f i s h must p r o t e c t i t s e l f from i t s p h y s i c a l en-vironment, escape from i t s enemies and capture i t s food from time of hatching throughout i t s e n t i r e l i f e . Thus i t has extended, pre-reproductive independence and i t s own s o c i a l l i f e . O r n i t h o l o g i s t s have been p r i m a r i l y concerned w i t h the d i s t r i b u t i o n and aggressiveness of n e s t i n g b i r d s . A l l e e et a l (1949) o u t l i n e t e r r i t o r i a l o r g a n i z a t i o n s of b i r d s as f o l l o w s : 1. Mating and n e s t i n g combined w i t h space i n which to c o l l e c t food during the breeding season 2. Mating and n e s t i n g w i t h food c o l l e c t e d e l s e -where 3. Mating s t a t i o n only 4. Nesting region only a. S o l i t a r y i n d i v i d u a l s b. C o l o n i a l b i r d s 5. Nonbreeding t e r r i t o r i e s a. Roosting t e r r i t o r i e s b. Feeding t e r r i t o r i e s The t e r r i t o r i a l behavior of spawning salmon was de-s c r i b e d by Briggs (1953) as analogous t o category No 2 but possessing the dual f u n c t i o n of both a mating and n e s t i n g area. The t e r r i t o r i a l i t y of j u v e n i l e r e s i d e n t i a l s a l -monids might be placed i n category No 5b but f a c t o r s -25?,-a d d i t i o n a l to feeding such as s h e l t e r are important con-s i d e r a t i o n s . In an e f f o r t to s i m p l i f y the concept of t e r r i t o r y , Noble (1939) d e f i n e d i t as "any defended area". The problem of a p p l y i n g t h i s d e f i n i t i o n to young t r o u t and salmon l i e s i n the determination of the area defended. Since a n e s t i n g s i t e i s not i n v o l v e d there i s no s i n g l e f o c a l p o i n t of primary importance which demands an i n t e n -s i v e defense. Hoar (1951) s a i d about coho f r y i n a long tank that "by 24 hours one or more i n d i v i d u a l s are h o l d i n g t e r r i t o r y and d r i v i n g others from the area The f o c a l p o i n t f o r defence of t e r r i t o r y v a r i e s . For one f i s h i t may be beside the overflow pipe or beneath the edge of the overflow p l a t e ; f o r another a shadow produced by the sup-p o r t s between the windows may l o c a l i z e the area of a c t i v i t y . Almost any o b j e c t may d e f i n e a t e r r i t o r y . " I t i s most i n t e r e s t i n g to watch s m a l l coho defending t h e i r t e r r i t o r i e s . W i t h i n 60 seconds, an a c t i v e i n d i -v i d u a l that has been v i o l e n t l y s t a r t l e d from i t s area w i l l r e t u r n to i t s former l o c a t i o n and d r i v e away a l l f i s h from t h i s area." One i n d i v i d u a l "was defending a small area of compartment 6 at 9 a.m. (24 hours a f t e r i n t r o d u c t i o n to the aquarium). This coho r e s t e d at one s i d e of the overflow pipe and faced the end of the aquarium. Any f i s h coming i n t o the area was promptly chased away. At 8 p.m. t h i s same i n d i v i d u a l was f a c i n g i n the opposite d i -r e c t i o n and h o l d i n g a l l of compartments 5 and 6. By 9 a.m. -258-th e f o l l o w i n g day, two other dominant s p i r i t s had appeared. One h e l d compartment 2 and the other compartment 5 w h i l e the b u l l y of yesterday had returned to h i s o r i g i n a l l o -c a t i o n on the other s i d e of the overflow pipe, f a c i n g , as b e f o r e , the end of the aquarium. Most of the other f i s h were h e l d between the s t r o n g l y p a t r o l l e d compartments 2 and 5." The c h i e f example o f t e r r i t o r i a l i t y observed i n t h i s study was the tendency of the dominant f i B h i n a group to remain near the l o c a t i o n of feeding and t o d r i v e the sub-o r d i n a t e s away. The f a i l u r e of most of the specimens to form more d i s t i n c t t e r r i t o r i e s may have been caused by the s m a l l s i z e of the observation tanks. In reference to spawning t e r r i t o r i e s of a l p i n e char, F a b r i c i u s and Gustaf-son (1954) have s a i d that r e a l t e r r i t o r i e s can only be e s t a b l i s h e d i n a tank whose bottom area i s at l e a s t twice the minimum s i z e of a normal t e r r i t o r y . I f they are s m a l l e r than t h i s , a peck order develops. F i e l d obser-v a t i o n s of coho f r y r e v e a l e d that they occupied about one square f o o t each i n densely populated zones. The tanks used f o r d e t a i l e d study of coho f r y i n the l a b o r a t o r y had a f l o o r area of about 170 square inches and thus would be smaller than twice t h e normal t e r r i t o r y s i z e . Several other examples of t e r r i t o r i a l i t y were n o t i c e d . One was the rainbow t r o u t which t e r r i t o r i a l i z e d the area around a s m a l l w a t e r f a l l a f t e r food had passed i n t o the -259-tank through i t . Another was the cut t h r o a t t r o u t that chased a l l the other c u t t h r o a t from the shaded h a l f of a tank. Both of these observations have been p r e v i o u s l y described. There i s no question that j u v e n i l e salmonids f r e -quently chase others away from p a r t i c u l a r l o c a t i o n s . The problem i s whether there i s s u f f i c i e n t l o c a l i z a t i o n of ac-t i v i t y and defense of any one place to consider t h i s sim-i l a r i n nature to defense of a nest. I t should be emphasized that the t e r r i t o r i e s of young f i s h e s are subject to domination by other members of the same speeies, that they are f l e x i b l e i n s i z e and t h a t they are often v a r i a b l e i n l o c a t i o n . I n order t o r e c o n c i l e submission of a t e r r i t o r i a l green s u n f i s h (Lepomis c y a n e l l u s ) t o other more aggressive members of the same s p e c i e s , Greenberg (1947) coined the expression " p a r t i a l t e r r i t o r y . " He described the i n c l u s i o n of t e r r i t o r i a l members w i t h i n a s o c i a l h i e r a r c h y . A sim-i l a r s o c i a l h i e r a r c h y was described (Newman, 1956) f o r t r o u t i n Sagehen Creek, C a l i f o r n i a , where the i n d i v i d u a l s tended to remain i n the same l o c a t i o n . These t r o u t de-fended t h e i r r e s t i n g places from i n t r u s i o n by subordinate members w i t h i n a s o c i a l h i e r a r c h y . But when more dominant i n d i v i d u a l s swam away, t h e i r places were taken by subordi-nates which then defended the new l o c a t i o n s . I n other words they defended any one of s e v e r a l l o c a t i o n s w i t h equal -260-f a c i l i t y . This phenomenon was named " r o t a t i n g t e r r i t o r -i a l i t y . " I n the present study coho f r y were observed to move distances up to ten and one h a l f f e e t i n Weaver Creek de-s p i t e the f a c t that there appeared to be approximately one f i s h per square foot of area i n regions o f q u i e t water.-I t was not determined whether i n d i v i d u a l s returned t o par-t i c u l a r f o c a l p o i n t s or not. Perhaps there were many over-l a p p i n g t e r r i t o r i e s but there were no boundary disputes s i m i l a r to those which occur between the t e r r i t o r i e s of spawning f i s h or n e s t i n g b i r d s . I t looked more l i k e an assemblage of f i s h l i v i n g w i t h i n an area f a m i l i a r to a l l . I t i s the o p i n i o n of the w r i t e r that j u v e n i l e s a l -monids are u s u a l l y not d i s t r i b u t e d i n t e r r i t o r i a l mosaics ( K a l l e b e r g , 1958) but t h i s must be d e f i n i t e l y e s t a b l i s h e d by i n t e n s i v e f i e l d i n v e s t i g a t i o n . Coho f r y may be more t e r r i t o r i a l than t r o u t s i n c e they l i v e i n freshwater only a year and a l l are approximately the same s i z e . The presence of s e v e r a l year c l a s s e s , may be more conducive to the development of dominance orders i n t r o u t . Even so, p r e l i m i n a r y observations do not i n d i c a t e separate t e r -r i t o r i e s f o r each j u v e n i l e coho i n a stream. I t i s u s e f u l to d i s t i n g u i s h between the behavior i n -v o l v e d i n t e r r i t o r i a l i t y and the o r g a n i z a t i o n of i n d i v i d -u a l s which r e s u l t s from the behavior. We have been ques-t i o n i n g whether r e s i d e n t i a l salmonids d i s t r i b u t e them-s e l v e s i n a t e r r i t o r i a l p a t t e r n but have not doubted that -261-they e x h i b i t " t e r r i t o r i a l behavior." Tinbergen (1957) says that t e r r i t o r y i s the r e s u l t of two d i s t i n c t tendencies: attachment to a s i t e and h o s t i l i t y toward other members of the same sp e c i e s . Both of these tendencies are s t r o n g l y developed i n those species of salmonids which l i v e i n streams but one or both are miss i n g i n the others. Lake t r o u t , sockeye salmon and pink salmon show n e i t h e r s i t e attachment nor aggressiveness. Chum salmon are aggressive but l a c k attachment to a s i n g l e l o c a t i o n . I t would be i n t e r e s t i n g to determine whether there are any f i s h which show s i t e attachment without aggressiveness. Very l i k e l y some s p e c i a l i z e d , s t r e a m - l i v i n g f i s h l i k e Cottus would be of t h i s type. The sequence i n e s t a b l i s h i n g residence i n a stream by a newly emerged f r y no doubt s t a r t s w i t h s i t e attachment, w i t h o r i e n t a t i o n to objects on the bottom. Around the small f i s h may be many other f r y that &re l i k e w i s e h o l d i n g p o s i -t i o n . Factors a s s o c i a t e d w i t h the s e l e c t i o n of a p a r t i c u l a r p l a c e may be l a r g e l y a c c i d e n t a l . As the small f i s h be-comes f a m i l i a r w i t h the c o n f i g u r a t i o n s of i t s l o c a t i o n i t makes ex p l o r a t o r y excursions and has aggressive contacts w i t h i t s neighbors. Does i t r e t u r n to i t s o r i g i n a l spot as a r e s u l t of these contacts? P o s s i b l y . But as i t grows i t becomes f a m i l i a r w i t h an i n c r e a s i n g l y wide area which i n c l u d e s more and more i n d i v i d u a l s which are a l s o making excursions. F i n a l l y a l l may become f a m i l i a r w i t h the -262-l a r g e r zone bounded by more d i s t i n c t p h y s i c a l o b s t a c l e s . W i t h i n thiB zone t h e i r d i s t r i b u t i o n i s guided by l i g h t , depth, c u r r e n t , food and the l o c a t i o n of l a r g e r f i s h . At t h i s p o i n t they are sharing a common t e r r i t o r y w i t h i n which they are competing f o r l i m i t e d resources. The a b i l i t y of j u v e n i l e Balmonids t o d i s c r i m i n a t e between p r i o r r e s i d e n t s and new f i s h and t h e i r tendency to at t a c k the l a t t e r suggests the presence of a "group t e r -r i t o r i a l i t y . " The s i g n i f i c a n c e of the defense may l i e i n the e x c l u s i o n of non-residents. This would be a mechanism f o r s t a b i l i z i n g populations i n the stream. Home range The area of residence of j u v e n i l e t r o u t and salmon can probably be best i n t e r p r e t e d i n terms of a home range. This has been d e f i n e d by Burt (1943) as "the area, u s u a l l y around a home s i t e , over which the animal normally t r a v e l s . " The concept i s well-known among mammalogists but has only r e c e n t l y been considered by i c h t h y o l o g i s t s (Gerking, 1953, 1957; Newman, 1956). As Gerking (1957) says, i t i m p l i e s t h a t f i s h are not f r e e to roam over t h e i r e n t i r e body of water but that they normally t r a v e l over a r e s t r i c t e d area. This c o i n c i d e s w i t h Hediger's (1950) b e l i e f that w i l d animals l a c k u n l i m i t e d s p a t i a l freedom and that they move along h a b i t u a l routes throughout d e f i n i t e areas. The b e h a v i o r a l b a s i s of home range l i e s i n the ten--263-dency f o r s i t e attachment seen i n a l l r e s i d e n t i a l s a l -monids. I t does not depend upon defense. The s i z e and shape of the home range would be g r e a t l y i n f l u e n c e d by the nature of the body of water i n which the f i s h were l i v i n g s I n f a c t there might be some question as to whether home range would e x i s t at a l l i n a l a k e where p h y s i c a l boundaries might be l a c k i n g around small zones. "Homing" of v a r i o u s f i s h e s has been s t u d i e d i n l a k e s , however, and i t has been demonstrated ( H a s l e r , H o r r a l l , et a l , 1958; Hasler and Wisby, 1958; Shoemaker, 1952) that there i s a tendency f o r d i s p l a c e d f i s h to r e t u r n to t h e i r o r i g i n a l l o c a t i o n s . I t i s not being argued that a l l f i s h l i v i n g i n lak e s would e x h i b i t t h i s type of r e s t r i c t e d movements but rat h e r that those f i s h e x h i b i t i n g r e s i d e n t i a l behavior would probably l i m i t themselves to home ranges. Those f i s h which have undergone s i l v e r y smolts such as older rainbows i n the i n t e r i o r l a k e s of B r i t i s h Columbia may be e n t i r e l y p e l a g i c and show no s i t e attachment. The area of a home range f o r j u v e n i l e t r o u t and salmon probably v a r i e s w i t h the environmental c o n d i t i o n s w i t h i n the stream and w i t h the s i z e of the i n d i v i d u a l s i n v o l v e d . M i l l e r (1957) estimated that the s i z e of cut t h r o a t t r o u t home ranges i n Gorge creek, A l b e r t a , was about 20 yards, ten above and ten below the usual r e s t i n g place. N a t u r a l b a r r i e r s such as s w i f t water, u n s u i t a b l e shallow water, w a t e r f a l l s , e t c . probably form the boundaries w h i l e the -364-areas are centered around a pool or over-hanging hank that provides cover i n the event i t i s needed. One of the most i n t e r e s t i n g recent s t u d i e s on homing behavior concerned a marine s c u l p i n ( C l i n o c o t t u s a n a l i s ) . W i l l i a m s (1957) revealed that t h i s i n t e r t i d a l species f o l -lows the movement of the t i d e up and down by swimming along d e f i n i t e r o u t e s , at the lower ends of which are home po o l s . He emphasizes that t h e i r c y c l i c t i d a l movements must be very p r e c i s e to a v o i d the danger of s t r a n d i n g . The bond between a r e s i d e n t i a l f i s h and i t s home range i s very strong. Removal of a f i s h from i t s customary surroundings causes i t to swim back and f o r t h continuously f o r many hours i n an aquarium. This a p p e t i t i v e behavior (Hoar, 1958b) was observed i n t r a n s l o c a t e d r e s i d e n t i a l f i s h i n Sagehen Greek and. i s no doubt b a s i c to the homing reported by M i l l e r (1954) i n t r a n s l o c a t e d c u t t h r o a t t r o u t i n A l b e r t a . S o c i a l o r g a n i z a t i o n We have denied that aggressive behavior i s an impor-tan t cause f o r the formation of t e r r i t o r y and home range yet a l l r e s i d e n t i a l j u v e n i l e salmonids are very aggressive. What, then, i s the s i g n i f i c a n c e of t h i s behavior? I n the o p i n i o n of the w r i t e r i t s s i g n i f i c a n c e l i e s i n the f o r -mation of s o c i a l o r g a n i z a t i o n . w i t h i n the environment. -266-I n t r a s p e c i f i c aggressive behavior and a s s o c i a t e d s o c i a l o r g a n i z a t i o n i s w e l l known i n many species of i n -s e c t s , f i s h e s , b i r d s and mammals ( A l l e e , 1952). This study of dominance r e l a t i o n s was begun by Schjelderup-Ebbe (1922) and i n t e n s i v e l y i n v e s t i g a t e d by A l l e e and h i s c o l -leagues ( A l l e e , 1952). They discovered that i n t r a s p e c i f i c aggressiveness leads to the formation of s o c i a l rank orders based on f i g h t i n g and d i s p l a y and that once the r e l a t i o n -ships are e s t a b l i s h e d they tend to be perpetuated. We have observed that i n the l a b o r a t o r y s t a b l e dom-inance orders developed i n i n t r a s p e c i f i c groups of d o l l y varden, brook t r o u t ^ c u t t h r o a t t r o u t , rainbow t r o u t and coho salmon. The question remains whether such dominance de-velops i n nature. C e r t a i n l y the s i z e , shape and p h y s i c a l nature of the body of water i s important i n determining the number of f i s h present and the distance over which they move. For t h i s reason the s o c i e t i e s may be " f l u i d " as Hoar (1958b) suggests but observations i n C a l i f o r n i a (Newman, 1956) r e v e a l that dominance r e l a t i o n s among t r o u t do e x i s t i n nature Breder (1959) has r e c e n t l y expressed doubt as to whether s o c i a l h i e r a r c h y o f t e n i s important among f i s h e s because aggressiveness i s so r e a d i l y depressed by e x t e r n a l f a c t o r s such as s u f f o c a t i o n , poisons and changes of temp-er a t u r e . Animals i n f l i g h t do not eat even i f hungry ( K a t z , 1953) yet i t would be i d l e t o say they do not eat -366-i n nature. Thie "law of dominant i n t e r e s t " a f f e c t s a l l animal a c t i v i t i e s . In t h i s study i t was observed that the i n i t i a l alarm response was a c e s s a t i o n of a l l a c t i v i t y , i n c l u d i n g aggressiveness, and the adoption of an immobile s t a t e of readiness f o r f l i g h t . When the alarm stimulus was removed the f i s h resumed t h e i r n i p p i n g and chasing. I t i s not known to what extent, i f any, there might be a dominance order among the numerous coho f r y i n quiet p o r t i o n s of a stream. I t i s not necessary f o r a dominant f i s h to respond t o i t s subordinates as p a r t i c u l a r i n d i -v i d u a l s or f o r i t to remember which other f i s h are subor-d i n a t e or dominant because they make t h e i r p o s i t i o n s known by t h e i r behavior. Hence i t i s p o s s i b l e that c e r t a i n i n -d i v i d u a l s dominate l a r g e numbers of others i n places such as Weaver Creek where 227 coho f r y were taken from a small area. In observing groups of young coho or young rainbows at the Vancouver P u b l i c Aquarium, i t has been n o t i c e d that s i n g l e i n d i v i d u a l s o f t e n emerge dominant over l a r g e num-bers of others. I t remains to be e s t a b l i s h e d , however, to what extent a s o c i a l r e l a t i o n s h i p e x i s t s among coho f r y i n a stream. L a r k i n (1956) has i n d i c a t e d the need f o r c l a r i f i -c a t i o n of mechanisms i n the concept of f i s h competition. The dominance order provides a l o g i c a l mechanism f o r i n t r a s p e c i f i c competition and n a t u r a l s e l e c t i o n w i t h i n a r i g o r o u s environment c o n t a i n i n g d e f i c i e n t food sources. -267;-Aggressiveness i s p a r t i c u l a r l y i ntense i n r e l a t i o n to fe e d i n g and l o c a t i o n s where food i s a v a i l a b l e . Aggres-siveness i s a l s o r e l a t e d to p o s i t i o n s of s h e l t e r . Dom-in a n t i n d i v i d u a l s occupy the p o s i t i o n s p r o v i d i n g most food and best s h e l t e r and f o r c e subordinates i n t o l e s s d e s i r -a b l e p o s i t i o n s . I n t e r s p e c i f i c behavior Despite s p e c i f i c d i f f e r e n c e s i n the d e t a i l s of t h e i r behavior, i n d i v i d u a l s of one species c o u l d recognize the aggressive m a n i f e s t a t i o n s of i n d i v i d u a l s of another spe-c i e s . This was p a r t i c u l a r l y apparent among members of r e s i d e n t i a l s p e c i e s . For example rainbow t r o u t r e a c t e d to the expanded throat type of f r o n t a l d i s p l a y of cut t h r o a t t r o u t even though they d i d not possess such a d i s p l a y themselves. Members of i n t e r s p e c i f i c groups d i s p l a y e d according to t h e i r i n n a t e nature and developed s o c i a l h i e r -a r c h i e s as w e l l i n t e g r a t e d as though there were only a s i n g l e species present. This suggested that the f i s h c o u l d r e a d i l y l e a r n to respond to sign;-stimuli which were i n n a t e i n other s p e c i e s . When rainbow t r o u t were placed w i t h sockeye salmon smolts of about the same s i z e they a t t a c k e d them. The smolts r a i s e d t h e i r transparent d o r s a l f i n s i n a gener-a l i z e d alarm posture and f i n a l l y f l e d i n a w i l d r e t r e a t . A s o c i a l h i e r a r c h y d i d not develop between these two -368-species e v i d e n t l y because of the weak development of ago-n i s t i c behavior i n the smolts and t h e i r tendency to pas-s i v e l y aggregate i n a corner of the tank. S i m i l a r l y a s o c i a l h i e r a r c h y d i d not develop when rainbow t r o u t f r y were p l a c e d together w i t h chum salmon f r y . These salmon f r y showed considerable n i p p i n g be-ha v i o r but were so a c t i v e that they d i d not stay i n one p l a c e long enough to achieve a d e f i n i t e r e l a t i o n w i t h the t r o u t . Nipping among chum f r y always appears t o be secon-dary to something e l s e r a t h e r than primary i n importance as i t i s among r e s i d e n t i a l f i s h . Rainbow t r o u t were found to be the most aggressive species when matched against i n d i v i d u a l s of the same s i z e belonging to other species. They defeated l a k e t r o u t , brook t r o u t , c u tthroat t r o u t and coho salmon. They were not observed w i t h d o l l y varden but, s i n c e l a k e t r o u t de-f e a t e d t h i s species and rainbow t r o u t defeated l a k e t r o u t , i t was assumed th a t rainbow t r o u t would a l s o be able to subdue them. The data were at va r i a n c e w i t h published data (Newman, 1956) showing brook t r o u t dominant over rainbows i n nine out of twelve groups. The rainbow used i n the present study were exceedingly aggressive. Observations of them i n i n t r a s p e c i f i c groups as compared to observations of i n t r a s p e c i f i c groups of brook t r o u t provided other e v i -dence of greater i n t e n s i t y of aggressiveness expressed by rainbows. The C a l i f o r n i a s t r a i n may have been l e s s aggres-s i v e but f u r t h e r i n v e s t i g a t i o n i s warranted. -269-The r e l a t i o n s h i p s among the sympatric species were p a r t i c u l a r l y i n t e r e s t i n g . Rainbow t r o u t were much more aggressive than c u t t h r o a t t r o u t and r e a d i l y defeated them. They prevented them from feeding and i n t e r f e r e d w i t h a l l t h e i r movements. This c o u l d be an important mechanism a f f e c t i n g the d i s t r i b u t i o n of cutthroat t r o u t both along the coast and i n the i n t e r i o r . P opulations of c u t t h r o a t t r o u t have been known to disappear f o l l o w i n g i n t r o d u c t i o n of rainbow t r o u t ( M i l l e r , 1950). An i n v e s t i g a t i o n i n Sweden ( L i n d r o t h , 1956) found th a t where populations of j u v e n i l e brown t r o u t and j u v -e n i l e A t l a n t i c salmon were together the more aggressive t r o u t were d i s t r i b u t e d c l o s e to shore and the salmon were f a r t h e r o f f s h o r e . Where salmon alone were present i n a body of water they were d i s t r i b u t e d c l o s e to shore i n l o -c a l i t i e s comparable to those occupied by the t r o u t . This example of s o c i a l i n t e r f e r e n c e (Miyadi) i s suggestive of the d i s t r i b u t i o n a l changes among chum f r y and rainbow t r o u t reported e a r l i e r i n t h i s paper. There i s no question that populations of d i f f e r e n t s p e c ies of salmonids g r e a t l y a f f e c t each other. I n B r i t i s h Columbia c o a s t a l rainbow t r o u t (steelheads) are r e l a t i v e l y scarce i n r i v e r s u t i l i z e d by coho salmon. I t was estimated that there were over ten times as many coho f r y as there were rainbow f r y i n Weaver Creek. But i n the i n t e r i o r at l a k e s such as Loon l a k e near C l i n t o n where rainbows - 2 7 Q -(Kamloops t r o u t ) c o n s t i t u t e i n t r a s p e c i f i c p o p u l a t i o n s , young f i s h are much more abundant i n spawning t r i b u t a r i e s . The s i t u a t i o n i s s i m i l a r w i t h regard to d o l l y varden. I n southern B r i t i s h Columbia d o l l y varden are not o f t e n found i n great abundance i n c o a s t a l streams, nor are they p a r t i c u l a r l y abundant i n many mountain streams. In one stream, however, the Sumallo, a t r i b u t a r y of the Skagit r i v e r , they predominate over a very small rainbow t r o u t p o p u l a t i o n . In t h i s case the more bor e a l d o l l y varden may have an advantage over rainbow t r o u t i n colder water but be l e s s s u c c e s s f u l i n warmer water. I n t e r s p e c i f i c s o c i a l domination may w e l l be a s i g n i f -i c a n t f a c t o r i n the d i s t r i b u t i o n of a species where i t i s sympatric w i t h another having the same environmental r e -quirements. I t i s not n e c e s s a r i l y the deciding f a c t o r , though. Coho salmon f r y were defeated by rainbow t r o u t i n the l a b o r a t o r y yet appear to be more s u c c e s s f u l i n streams which the two species share along the southern coast of B r i t i s h Columbia. I t was observed that they were s w i f t i n feeding and i t was p o s t u l a t e d t h a t they might be more s u c c e s s f u l i n competition f o r food. When the two species were s t u d i e d i n Weaver Creek, coho were r e a d i l y observable i n unprotected quiet water w h i l e rainbows could u s u a l l y not be seen u n t i l they were captured i n a hand seine. The w i l l i n g n e s s to occupy open water without cover would pro--2<71-v i d e more space f o r coho and f a c i l i t a t e t h e i r c a p t u r i n g any a v a i l a b l e food before i t could be reached by rainbows. Ontogeny of a g o n i s t i c behavior Salmonids show pr o g r e s s i v e changes i n a g o n i s t i c be-h a v i o r which c o r r e l a t e w i t h changes of l i f e h i s t o r y through residence i n a stream, downstream m i g r a t i o n , p e l a g i c l i f e i n the sea, upstream m i g r a t i o n and spawning. There i s reason to b e l i e v e that aggressive behavior i s most i n t e n s e during periods of residence i n a stream and during the time of spawning, w h i l e i t i s l e a s t i n t e n s e during m i g r a t i o n and p e l a g i c occupation of a l a r g e body of water. Following the emergence of salmonid f r y from the g r a v e l there i s a d i s p e r s i o n which c o n s t i t u t e s a migration i n p i n k , chum and sockeye salmon. This d i s p e r s i o n may r e s u l t i n a downstream m i g r a t i o n of coho f r y i n some small c o a s t a l streams (Hoar, 1958b) but u s u a l l y merely d i s -t r i b u t e s the r e s i d e n t i a l species throughout the stream. Aggressive behavior probably appears i n most species as soon as the f i s h swim. Hoar r e p o r t s (1951) seeing i t i n coho f r y down to the smallest s i z e s a v a i l a b l e . I t was observed among rainbow t r o u t f r y at Loon Lake Hatchery soon a f t e r the absorption of t h e i r yolk sacs. This be-h a v i o r i s not seen immediately i n pink or sockeye f r y . The f a i l u r e to see i t i n the l a t t e r species may have been -308-r e l a t e d to the l i g h t i n t e n s i t y used during the study. Sockeye f r y are n o c t u r n a l (Hoar, 1958b), h i d i n g i n the g r a v e l during the day and emerging i n the evening as l i g h t i n t e n s i t y f a l l s below 10 f o o t candles. I f sockeye f r y were observed i n a small tank at low l i g h t i n t e n s i t y some aggressiveness might be seen. When the young f i s h become e s t a b l i s h e d i n t h e i r home ranges aggressiveness i n c r e a s e s . D i s p l a c e d f i s h were f r e -quently observed to show l i t t l e or no aggressive behavior w h i l e f i s h w i t h i n t h e i r own areas were always more aggres-s i v e than new f i s h placed w i t h them. This was not only t r u e f o r r e s i d e n t i a l species but a l s o t r u e f o r chum f r y which f r e q u e n t l y nipped each other when confined i n a s m a l l tank but seldom do so i n nature where t h e i r c o n t i n -uous swimming c a r r i e s them away from f a m i l i a r grounds. A g o n i s t i c d i s p l a y s reach a peak i n development during the p e r i o d of j u v e n i l e stream residence. At t h i s time the f i s h are h i g h l y c o l o r e d and t h e i r f i n s d i s t i n c t i v e l y marked. These markings i n conjunction w i t h the f l e x i b l e a c t i o n s of the manoeverable l i t t l e f i s h enable r e l a t i v e l y complicated s o c i a l i n t e r p l a y s to develop throughout the summer months. Autumn r a i n s cause the streams to f l o o d and wash out the f a m i l i a r environments of summer. Many f i s h are prob-a b l y d i s p l a c e d throughout the winter and many p e r i s h (Needham, 1953) but those t h a t remain seek s h e l t e r wherever -27-3-they can along the margins of the stream. S u r v i v a l de-pends upon the a b i l i t y t o r e s i s t displacement and to w i t h -stand r i g o r o u s p h y s i c a l c o n d i t i o n s such as low temperature, powerful c u r r e n t s and damaging driftwood. S o c i a l i n t e r -r e l a t i o n s h i p s based on a g o n i s t i c behavior such as e x i s t e d d u r i n g the low-water months of summer are probably r e -p l a c e d by greater t o l e r a t i o n and aggregation. P h y s i o l o g i c a l changes a s s o c i a t e d w i t h transformation to a s i l v e r y smolt are b e l i e v e d r e s p o n s i b l e f o r decreased aggressiveness of j u v e n i l e coho during the w i n t e r (Hoar, 1951) and of j u v e n i l e rainbow i n March and A p r i l ( S t r i n g e r and Hoar, 1955). This decrease i n aggressiveness i s a s s o c i a t e d w i t h downstream m i g r a t i o n of coho and rainbows and p o s s i b l y other r e s i d e n t i a l species. Coho migrate as y e a r l i n g s w h i l e other species are more v a r i a b l e and may or may not migrate. Rainbows u s u a l l y migrate downstream when two or three years o l d ( C a r l , Clemens and Lindsey, 1959). Those species which show aggressiveness as j u v e n i l e s may never cease n i p p i n g e n t i r e l y and probably are capable o f i n t e n s i v e n i p p i n g at any time i f i n the proper e n v i -ronment. J u v e n i l e coho salmon and rainbow t r o u t were ob-served t o r e t a i n t h e i r aggressiveness over two years i n seawater at the Vancouver P u b l i c Aquarium. When they were co n f i n e d i n 220 g a l l o n tanks n i p p i n g was in t e n s e . Even i n the l a r g e 12,000 g a l l o n tank steelheads nipped and chased each other. -274-T h e 8 e o l d e r coho salmon and rainbow t r o u t d i d not employ d i s p l a y s as d i d the small f i s h . I t may be that under the c o n d i t i o n s i n the open ocean that the n i p p i n g would be i n h i b i t e d as appears to be the case w i t h chum f r y i n open water. The absence of s h e l t e r produces alarm which r e s u l t s i n the disappearance of aggressive m a n i f e s t a t i o n s . Lake t r o u t and sockeye salmon maintained i n the Van-couver P u b l i c Aquarium under the same c o n d i t i o n s as the rainbows and coho salmon never nipped and chased each other. This r e v e a l s a fundamental d i f f e r e n c e between these f i s h e s and a l l the others w i t h the p o s s i b l e exception of pink salmon. J u v e n i l e pink salmon have been report e d by K. Groot (pe r s o n a l communication) to n i p each other but i t has not been a s c e r t a i n e d whether they ever develop, p r i o r to maturation, the p e r s i s t e n t aggressive behavior of coho or rainbows. Adult migrants are not aggressive when they f i r s t enter the spawning grounds. I t i s not known whether t h i s represents an i n h i b i t i o n under c o n d i t i o n s of alarm or Whether i t might r e s u l t from the p h y s i o l o g i c a l changes a s s o c i a t e d w i t h maturation. The i n i t i a t i o n of a g o n i s t i c behavior among spawning a d u l t s i s q u i t e sudden. The behavior i s complicated, i n -tense and somewhat s i m i l a r to j u v e n i l e behavior. I t has been s t u d i e d i n l a k e t r o u t (Royce, 1951) a l p i n e char ( F a b r i c i u s , 1953; F a b r i c i u s and Gustafson, 1954), eastern -275-brook t r o u t (Greeley, 1932; Hazzard, 1932), rainbow t r o u t ( B r i g g s , 1953; Needham and T a f t , 1934), cutthroat t r o u t (Cramer, 1940), brown t r o u t (Jones and B a l l , 1954), A t l a n -t i c salmon ( B e l d i n g , 1934; Jones and B a l l , 1954; Jones and K i n g , 1949, 1950) and P a c i f i c salmon ( B r i g g s , 1953; Burner, 1951; Chapman, 1943; S c h u l t z , 1938). A l l of the species which have been i n v e s t i g a t e d , w i t h the exception of the l a k e t r o u t (Royce, 1951) show h i g h l y developed a g o n i s t i c behavior at the time of spawning. This a g o n i s t i c behavior i s very s i m i l a r , and p o s s i b l y i d e n t i c a l , to that of j u v e n i l e s but has not been completely analyzed. The reproductive behavior i n c l u d i n g p a i r i n g , redd d i g g i n g , q u i v e r i n g and other movements are l i m i t e d to the a d u l t s and not present i n j u v e n i l e s . Phylogeny of r e s i d e n t i a l behavior The phylogenetic d i s t r i b u t i o n of these a g o n i s t i c be-h a v i o r p a t t e r n s r e v e a l s i n c r e a s i n g complexity i n the genus S a l v e l i n u s from l a k e t r o u t through d o l l y varden to brook t r o u t w i t h s p e c i f i c v a r i a t i o n s i n the patterns i n rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon and a gradual sub-sidence of them i n the genus Oncorhynchus. They are best c o r r e l a t e d w i t h those species having a j u v e n i l e p e r i o d of stream residence and p a r t i a l l y present or absent i n those species whose f r y migrate q u i c k l y to sea. The behavior of l a k e t r o u t appears p r i m i t i v e i n i t s -276-absence of l a t e r a l d i s p l a y , i t s d i r e c t and damaging f r o n t a l a s s a u l t on other f i s h , i t s low development of d i s p l a y , i t s f a i l u r e t o n i p and chase f i s h of i t s size and i t s s o l i t a r y , unrelatedness to other i n d i v i d u a l s . D o l l y varden c o n t r a s t w i t h l a k e t r o u t i n being extremely aggressive but do not have w e l l developed d i s p l a y s . The d i r e c t n e s s of t h e i r a t t a c k i n g behavior, t h e i r p o o r l y developed crouch at the approach of a dominant f i s h and the n e c e s s i t y of being a t -tacked to produce r e t r e a t i n g suggest a p r i m i t i v e s o c i a l behavior. Brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon f r y have d e f i n i t i v e t h r e a t d i s p l a y s which express i n t e n t i o n s of performing aggressive a c t s without neces-s i t a t i n g the a c t . As Tinbergen (1951) has so w e l l e l u c -i d a t e d , i n t r a s p e c i f i c f i g h t i n g may damage or k i l l i n d i -v i d u a l s and thus be a f a c t o r adversely a f f e c t i n g the sur-v i v a l of the species. The development of t h r e a t s , b l u f f s and d i s p l a y s are a d i s t i n c t advantage i n that they may s u b s t i t u t e f o r a c t u a l f i g h t i n g and prevent i n j u r y . The appearance of th r e a t d i s p l a y s thus suggests a more advanced l e v e l of s o c i a l e v o l u t i o n . Such an e v o l u t i o n a r y sequence beginning w i t h the l a k e t r o u t would be i n l i n e w i t h the p o i n t of view of Tchernavin (1939) who considered the e v o l u t i o n of salmonids to pro-gress from freshwater species to anadromous ones. The lak e t r o u t never, s o f a r as i s known, descends to the sea (Wynn-Edwards, 1952). I t has two other p r i m i t i v e c h a r a c t e r i s t i c s -377-which strengthen Vladyakov's (1954) contention that i t should be r e t a i n e d i n a separate genus ( C r i s t i v o m e r ) and which c o n t r i b u t e to our b e l i e f that i t s behavior i s fun-damentally p r i m i t i v e . In a d i s c u s s i o n of the spawning h a b i t s of the species Royce (1951) s a i d i t was the only member of the salmon f a m i l y i n which the male d i d not de-velop hooked jaws at the time of spawning. More s i g n i f -i c a n t l y , perhaps, females lacked the redd-digging be-hav i o r found i n other members of the f a m i l y . Females were never observed to t u r n on t h e i r s i d e s and d i s p l a c e g r a v e l by undulating t h e i r t a i l s . However, a stand i s not being made that there i s a l i n e a r e v o l u t i o n a r y r e l a t i o n s h i p among these salmonids but only an e v o l u t i o n a r y progression i n t h e i r behavior from a s o l i t a r y e x i s t e n c e to a s o c i a l one. The e v o l u t i o n of downstream migratory behavior i n j u v e n i l e P a c i f i c salmon has been discussed by Hoar (1958b) who b e l i e v e s the behavior of coho f r y i s p r i m i t i v e to that of the others. The sequence can be envisaged i n terms of the e x i s t i n g s p e c i e s . Coho f r y are a c t i v e i n the daytime and aggressive i n behavior. Their sides have c r y p t i c markings which make them inconspicuous during t h e i r year of stream r e s i d e n c e , a f t e r which they undergo a s i l v e r y smolt and migrate to the sea. Sockeye f r y are n o c t u r n a l , p r e f e r saltwater to f r e s h yet r e t a i n t h e i r p a r r marks u n t i l they undergo a smolt t r a n s f o r m a t i o n . Chum f r y are noc-t u r n a l and not only p r e f e r s a l t w a t e r but are o b l i g a t o r y - 2 7 8 -e a r l y migrants which w i l l d i e i f they d o not reach the sea w i t h i n a few months of emergence. They are s i l v e r y to begin w i t h and do not undergo smolting but r e t a i n parr marks. Pink f r y are the most s p e c i a l i z e d of a l l i n the p r e c i s e timing of t h e i r e a r l y m i g r a t i o n , t h e i r n o c t u r n a l a c t i v i t y , t h e i r complete l a c k of pa r r marks, t h e i r e a r l y dependence upon salt w a t e r and the compactness of t h e i r schools. Chinook salmon, though not f u l l y s t u d i e d , were b e l i e v e d to be intermediate between coho and sockeye salmon i n the development of t h e i r migratory behavior. From the p o i n t of view of t h i s study the r e s i d e n t i a l behavior of j u v e n i l e P a c i f i c salmon shows a p r o g r e s s i v e degeneration f r o m that of coho f r y t o that of pink f r y whereby the well-developed a g o n i s t i c d i s p l a y s of coho are represented i n chum and p o s s i b l y C h i n o o k f r y by ves-t i g i a l behavior patterns no longer i n f u n c t i o n a l context. Hoar ( 1 9 5 8 b ) has remarked that though n i p p i n g behavior among chum f r y has been observed i n the l a b o r a t o r y i t has not been seen i n nature. The f a i r l y i n t e n s e n i p p i n g we have observed among four chum f r y i n a ten g a l l o n tank was p o s s i b l y brought about by the r e s t r i c t i o n to a small and f a m i l i a r space i s o l a t e d from the dangers of predation and the alarm s t i m u l i normally operating on m i g r a t i n g f r y . P o s s i b l y under w i l d c o n d i t i o n s these outsid.e f a c t o r s i n -t e n s i f y s c h o o l i n g , decrease aggressive i n t e r a c t i o n s and f a c i l i t a t e m i g r a t i o n of these a c t i v e l i t t l e f i s h . -279-While the a g o n i s t i c behavior patterns of chum fry-were poorly developed they were not observed at a l l i n e i t h e r sockeye or pink f r y . SUMMARY 1. The j u v e n i l e r e s i d e n t i a l behavior of ten species of salmonids, comprising three genera, was compared i n f i e l d and l a b o r a t o r y s t u d i e s . 2. Three l e v e l s of adjustment t o a new environment were described: p h y s i o l o g i c a l , b e h a v i o r a l and s o c i a l . The establishment of a s t a b l e r e s i d e n t i a l r e l a t i o n s h i p was dependent upon the attainment of these three l e v e l s . 3. Aggregating tendency of l a k e t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t , coho salmon and chum salmon was compared using tanks of three lengths: i 5 0 cm,,213 cm and 427 cm. Chum f r y aggregated more than coho f r y . While the degree of aggregation was low i n i n t r a s p e c i f i c groups of j u v e n i l e l a k e t r o u t , rainbow f r y , c u t t h r o a t f r y and coho f r y , they were not completely dispersed and there may have been some mutual a t t r a c t i o n expressed at a low l e v e l . 4. The response of young salmonids to va r i o u s environmental f a c t o r s was s t u d i e d . No simple a t t r a c t i o n resembling a t a x i s was observed. Rainbow t r o u t parr were not a t t r a c t e d to a small w a t e r f a l l at one end of -280-t h e i r tank but when food was int r o d u c e d v i a the w a t e r f a l l the l a r g e s t one became agg r e s s i v e , remained near the w a t e r f a l l and f r e q u e n t l y chased the others away. Both rainbow and c u t t h r o a t t r o u t tended to s e l e c t shadowed p o r t i o n s of t h e i r c o n t a i n e r s . I n the presence of food the l a r g e s t c u t t h r o a t t r o u t chased smaller ones away from the shadow and remained there i t s e l f . Chum f r y swam back and f o r t h over shallow and deep water but rainbow t r o u t s e l e c t e d the deepest water under the same c o n d i t i o n s . The presence of a predatory f i s h i n the deep water caused, both chum and rainbows t o remain i n shallower water. The presence of a l a r g e r member of t h e i r own species tended to d i s p l a c e s m a l l rainbows i n t o more shallow water but the e f f e c t of dominance was not as great as the e f f e c t of a predator. The i n t r o d u c t i o n of food caused dispersed coho f r y to group together. As the food was consumed they began f i g h t i n g and once more separated. From these experiments i t was concluded that s p e c i e s - s p e c i f i c p r e f -erences f o r c e r t a i n environmental c o n d i t i o n s e x i s t and th a t the preference of r e s i d e n t i a l t r o u t and coho f r y f o r shadowed pools c o n t r a s t e d w i t h those of migrant chum f r y . The grouping of salmonids i n a stream represents a balance between inn a t e preference f o r p a r t i c u l a r en-vironmental c o n d i t i o n s and e x t e r n a l modifying f a c t o r s such as the presence or absence of food, predators and dominant i n d i v i d u a l s . -281-5. The average r a t e of locomotion of l a k e t r o u t , rainbow f r y , c u t t h r o a t f r y , coho f r y , chum f r y and spent rainbow a d u l t s was compared i n a 427 cm trough. Chum f r y moved continuously at a r e l a t i v e l y r a p i d r a t e . The others swam d i s c o n t i n u o u s l y at a much slower average r a t e although l a k e t r o u t were intermediate between chum f r y and the remaining s p e c i e s . 6 . Standard observations were made i n the l a b o r -a t o r y of l a k e t r o u t , d o l l y varden, brook t r o u t , rainbow t r o u t , c u t t h r o a t t r o u t and coho salmon i n i n t r a s p e c i f i c groups of f o u r f i s h each. These s t u d i e s e n t a i l e d de-s c r i p t i o n s of movements, a c t i v i t i e s and d i s p l a y s ; com-p a r a t i v e t a b u l a t i o n s of n i p p i n g , threatening and gaping; and a n a l y s i s of the p r o p o r t i o n of time devoted to various a c t i v i t i e s by each s p e c i e s . 7. Salmonids responded to danger by ceasing to move, adopting a " g e n e r a l i z e d alarm posture" and d a r t i n g away as the alarming stimulus reached a p a r t i c u l a r threshold.. 8. Movements of feeding were s i m i l a r i n species observed. Feeding was i n t e n s e l y s o c i a l i n character and was i n f l u e n c e d by the behavior of other f i s h nearby. 9. J u v e n i l e t r o u t and salmon c o u l d be separated i n t o two d i s t i n c t groups: those which nipped r a r e l y , i f a t a l l , and those which nipped f r e q u e n t l y . The f i r s t -282-group included lake trout, pink salmon and sockeye salmon. The second dolly varden, brook trout, rainbow trout, cutthroat trout, coho salmon, Chinook salmon and chum salmon. In those species which developed dominance-subordinance relations a l l of the act i v i t i e s of the sub-ordinates were influenced and modified by the presence of the dominant. Most nipping was performed by dominant f i s h . It was not continuous but occurred more frequently at some times than at others. Nipping was associated with feeding and was usually more frequent after feeding than before. In most cases more fish were involved i n nipping after feeding than before. 10. Agonistic displays were well developed in brook trout, rainbow trout, cutthroat trout and coho salmon but poorly developed, incompletely expressed or not oriented in the other species. 11. The principal behavioral characteristics de-termining the formation of residence are summarized in Table LXXII. 12. Experiments with coho fry indicated that dom-inant residents usually attack strange individuals more than they do familiar subordinates. New f i s h often died as a result of being steadily attacked. 13. A group of juvenile rainbows tended to behave as a unit in the defense of their territory and attacked new arrivals more vigorously than they did each other. Table LXXII P r i n c i p a l b e h a v i o r a l d i f f e r e n c e s a f f e c t i n g the formation of res i d e n c e . Lake Trout D o l l y Varden Brook Trout Rainbow Trout Cut-t h r o a t Trout Coho Fry- C h i -nook Fry Chum Fry Sock-eye Fry Pink Fry Orient t o s t a t i o n a r y o b j e c t s no yes yes yes yes yes • no no no S t a r t and stop swimming no yes yes yes yes yes « no 9 • no Schooling no no no no no no 9 • yes yes yes Immobile response t o alarm yes yes yes yes yes yes ? ? ? 9 • Aggressive no yes yes yes yes yes yes yes no no Oriented d i splays no no yes yes yes yes ? no no no -284-14. Rainbow t r o u t were moved from one place i n a stream to an enclosure i n another. They were d i f f i c u l t to confine because of continuous r a p i d swimming up and down the e n c l o s i n g screens and u l t i m a t e escape. Thi6 "escape behavior" was one of the c h a r a c t e r i s t i c s which i d e n t i f i e d new f i s h among r e s i d e n t i a l f i s h and probably contributed, to t h e i r being attacked by p r i o r r e s i d e n t s . 15. A stream was s t u d i e d i n which there were many young coho salmon and a few young rainbows. Coho f r y d i d not r e s t r i c t themselves to a p a r t i c u l a r l o c a t i o n but swam about w i t h i n a l a r g e r area. The home range appeared to be more s i g n i f i c a n t than the t e r r i t o r y . I n the winter the stream f l o o d e d and the coho congregated i n pools along the edge. I n the s p r i n g the newly emerged coho f r y were subject to p r e d a t i o n by pre-migrant coho smolt. The s e l e c t i o n of very shallow margins of the stream ap-peared to be an avoidance of the smolts which remained i n deeper pools. 16. Various species were observed i n i n t e r s p e c i f i c combinations. Despite d i f f e r e n c e s i n t h e i r d i s p l a y s each recognized and responded to the aggressiveness of the other. Although l a k e t r o u t were unaggressive i n i n t r a -s p e c i f i c groups, they showed more aggressiveness when kept w i t h aggressive s p e c i e s . They defeated d o l l y varden. Rainbow t r o u t were the most aggressive of a l l species -285-observed and defeated l a k e t r o u t , brook t r o u t , c u t t h r o a t t r o u t and coho salmon. I n t e r s p e c i f i c dominance r e s u l t e d i n the r e p r e s s i o n of feeding of one species by the other and i n t e r f e r e n c e i n a l l the a c t i v i t i e s of the subordinate s p e c i e s . The harmful e f f e c t s on coho salmon r e s u l t i n g from t h e i r being subordinate to rainbow t r o u t was com-pensated by t h e i r being s w i f t e r i n ob t a i n i n g food. 17. Reproductive behavior of rainbow t r o u t and s e v e r a l species of salmon was s t u d i e d i n the f i e l d and the Aquarium. The aggressive s o c i a l behavior of the a d u l t s was very s i m i l a r to that of the j u v e n i l e s but the a c t u a l r e p r o d u c t i v e movements were unique to the a d u l t s . 18. While defense of p o r t i o n s of t h e i r environments was often observed, i t was b e l i e v e d that t e r r i t o r i a l i t y was l e s s s i g n i f i c a n t t o r e s i d e n t i a l f i s h than t h e i r r e -l a t i o n s h i p to a l a r g e r home area. Aggressive exchanges among o l d i n h a b i t a n t s of a home area are f o r m a l i z e d i n t o more or l e s s d e f i n i t e dominance orders w h i l e i n t r u d e r s , recognized by t h e i r d i f f e r e n t behavior, are dr i v e n out. I n t e r s p e c i f i c dominance may a f f e c t the s u r v i v a l of the subordinate species but, as i n the r e l a t i o n s h i p between j u v e n i l e rainbow t r o u t and coho salmon, greater feeding e f f i c i e n c y may compensate f o r lower aggressiveness. 19. Ontogeny of a g o n i s t i c behavior i s a s s o c i a t e d w i t h changes i n l i f e h i s t o r y of the speci e s . -286-20. The phylogenetic d i s t r i b u t i o n of a g o n i s t i c behavior p a t t e r n s r e v e a l s i n c r e a s i n g complexity i n the genus S a l v e l i n u s from l a k e t r o u t through d o l l y varden to brook t r o u t w i t h s p e c i f i c v a r i a t i o n s i n the p a t t e r n s i n rainbow t r o u t , c u tthroat t r o u t and coho salmon and a gradual subsidence of them i n the genus Oncorhynohus. They are best c o r r e l a t e d w i t h those species having a j u v e n i l e p e r i o d of stream residence and p a r t i a l l y present or absent i n those species whose f r y migrate q u i c k l y t o the sea. -287-LITERATURE CITED A l l e e , W.C. 1946. Animal behaviour. I n : Encyclopaedia B r i t a n n i c a . . 1947. Animal s o c i o l o g y . I n : Encyclopaedia B r i t a n n i c a . . 1951. Cooperation Among Animals, With Human I m p l i -c a t i o n s . Schuman. New York. . 1952. 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