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Effects of variability in space and time on the production dynamcis of salmonid fishes Tautz, A. F. 1977

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EFFECTS OF VARIABILITY IN SPACE AND TIME ON THE PRODUCTION DYNAMICS OF SALMONID FISHES ARTHUR FREDRICK TAUTZ B . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1968 M . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF. THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA .JULY -1977'r O ) Arthur Fredrick Tautz, 1977 by (DEPARTMENT OF ZOOLOGY) In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of Brit ish Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of S2~<s-c /o 17 The University of Brit ish Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i ABSTRACT •Detailed studies of the spawning behavior of chum salmon (Oncorhynchus keta) and rainbow trout (Salmo gairdneri) in laboratory-flumes were conducted. The behavioral a c t i v i t i e s , quivering, probing, and crossing over increase in frequency as a function of time prior to spawning whereas digging remains constant or decreases slightly. Maps of digging locations and movie films suggest nest shape and current pattern are monitored by the female, allowing her to intensify her digging activity near the center of the nest. Probing appears to be a signal to the male indicating approach of oviposition and also provides information to the female regarding the space and s u i t a b i l i t y of the nest site. The probing act i s also used in the synchronization of. the male and female spawning acts. Changes in velocity do not appear to markedly affect nest construction either in terms of number of digs to ovipoistion or in size of nest constructed. It i s inferred that velocity and gravel size are important insofar as they influence the construction of a suitable nest depression. Nest sites would appear to be selected on the basis of acceleration of flow rather than velocity per se though high limits must obviously exist. Simulation studies, f i e l d observations of sockeye salmon (Oncorhynchus nerka) spawning in spawning channels, and laboratory studies were used to estimate optimal spawning densities for salmonids. Optimum density was found to be a function of redd size, territory size, temporal distribution of the run and ocean survival rate. Pattern of t e r r i t o r i a l defense in sockeye i s consistent with maximizing protection of the redd from superimposition, and provides a quantitative value for the benefits of t e r r i t o r i a l behavior. i i A comparison of the t h e o r e t i c a l optimum with current operating channels in d i c a t e s a possible over-escapement of up to 50 percent, representing a s u b s t a n t i a l annual commercial l o s s to the f i s h e r y . i i i TABLE OF CONTENTS Page TITLE PAGE i ABSTRACT i i TABLE OF CONTENTS i i i LIST OF FIGURES v i LIST OF TABLES x GENERAL INTRODUCTION 1 H i s t o r i c a l Aspects 1 Problem D e f i n i t i o n 3 PART 1 4 Behavioral and Environmental Components of Spawning 4 Introduction 4 Materials and Methods 5 I Chum Salmon Behavior 6 II Rainbow Trout Behavior 9 Results 1 3 I Description of Basic Behavior 13 II D i e l A c t i v i t y 1 5 III Selection of Spawning Site 16 IV Construction of the Nest 21 V E f f e c t s of Altered V e l o c i t i e s 2 7 VI Female-Male Interactions During Spawning 28 VII Female Nest Interactions 32 i v Page VIII Nest Construction i n Relation to Gravel Composition 34 Summary 40 PART II 4 3 U t i l i z a t i o n of the Spawning Area 1 + 3 Introduction 1 + 3 Methods 1 + 5 I Laboratory Studies of Area Disturbed During Nest Construction ^5 II F i e l d Studies of Spacing and Residence Time 45 III Simulation Studies 47 Results 51 I Laboratory Studies. 51 i ) Nest Size Estimates 51 i i ) Estimates of Overlap Between Successive Nests BO i i i ) Estimates of Redd Size 63 II . F i e l d Studies 65 i ) General Patterns of Behaviour 65 i i ) Temporal D i s t r i b u t i o n and Residence Time 68 i i i ) Spacing of Females 72 i v ) Area Disturbed During Nest Construction 74 V Page III Simulation Studies , . . , 75 i ) Simple Models of Super-imposition and Packing 75 i i ) T e r r i t o r i a l Model Incorporating Variation 79 a) Effects of T e r r i t o r i a l Behavior on Production • • 79 b) Effects of Normalized Distribution of Maturation 81 c) Effects of Nest Locations Within Redd 82 d) Effects of Waiting Time. . 85 e) Effects of Various Types of T e r r i t o r i a l Defence. . . 89 A CASE STUDY .• 90 SUMMARY 95 DISCUSSION AND RECOMMENDATIONS 99 ACKNOWLEDGEMENTS 104 LITERATURE CITED 105 LIST OF FIGURES FIGURE 1. Plywood flume used for studying chum salmon spawning behavior. 2. Indoor tank used for studying rainbow trout spawning behavior. 3. Chum salmon digging activity. Arrows indicate egg deposition. 4-. Diagram showing nest locations, flow pattern and orientation of the flume. 5. Definition of variables used in describing dig position relative to the location of the egg pocket. 6. Comparison of average upstream-downstream (Y) and lef t - r i g h t (X) distances from the egg pocket in relation to probing intensity. 7. Average distance from nest and probing intensity (with +1 standard deviations) as a function of digs prior to spawning. 8. Records of two females showing distance of dig from egg pocket under high and low velocity regimes as well as phases of digging activity. 9. Reconstruction of dig tracings for three females under high and low velocity regimes. Number of digs is indicated in the bottom right hand corner of each set. 10. Average frequency/2 minutes +1 S.E. of male and female chum spawning behaviors.. 11. Average frequency/2 minutes+1 S.E. of male and female rainbow trout spawning behaviors. 12. Diagram comparing an early crouch sequence ( l i f t ) with one resulting in egg deposition (spawn). 13. Body position relative to gravel bed during probing in chum salmon and rainbow trout. v i i FIGURE PAGE 1*4. Comparison of number and l o c a t i o n of digs with and 36 without p r i o r excavation of the nest s i t e . 15. a) Diagramatic representation of the r e l a t i o n s h i p between number of p a r t i c l e s above c r i t i c a l s i z e and depth of nest. 38 b) Patterns of flow through a n a t u r a l redd demon-s t r a t i n g e f f e c t s of high and low permeability-areas. 38 16. A e r i a l view of Fulton spawning channels and adjacent r i v e r (D.O.E. Annual Report, 1966). 46 17. Flow chart f o r simulation model assessing rates of superimposition. 48 18. D i s t r i b u t i o n s of X and Y co-ordinates of d i g s t a r t l o c a t i o n s and angle f o r a representative nest. 53 19. Percentage of d i g end points located at various X and Y co-ordinate p o s i t i o n s r e l a t i v e to a nest center of (50, 50). 58 20. Diagramatic representation of method of c a l c u l a t i n g length of Y axis f o r an average nest, and an approximate d e s c r i p t i o n of the s i z e of area disturbed i n r e l a t i o n to f i s h s i z e . 59 21. Diagramatic representation of area of overlap f o r an average distance between nests and the minimum distance between nests. The former r e s u l t e d i n an overlap of 18 percent while the l a t t e r r e s u l t e d i n 38 percent. 62 22. Percent frequency d i s t r i b u t i o n s of t o t a l residence time and paired residence time f o r females i n the study area. _ 69 23. Temporal d i s t r i b u t i o n of numbers of paired females and t o t a l number of females i n the study area i n d i -c ating the timing of the two waves of f i s h . 70 Locations o f redds f o r wave 1 and wave 2 i n the study s e c t i o n demonstrating the e f f e c t o f t e r r i -t o r i a l i t y on the p o s i t i o n o f redds on the second wave. D a i l y mean, p a i r e d minimum and minimum observed nearest neighbour d i s t a n c e s measured f o r females spawning i n the study s e c t i o n , over the d u r a t i o n of the spawning run. Three methods of packing uniform spheres i n a f i x e d area. Random packing provides 60% coverage, columnar 79%, and hexagonal 91%. Log number of attempts (base 10) r e q u i r e d t o l o c a t e a spawning s i t e r e l a t i v e t o the percentage of the area u t i l i z e d . Values are from a s i n g l e monte c a r l o s i m u l a t i o n run. Percentage increases i n production measured r e l a t i v e t o a n o n - t e r r i t o r i a l model f o r v a r i o u s d e n s i t i e s (percent commitment) and d i s t r i b u t i o n s o f the run over time. Percentage increases i n production f o r v a r i o u s d e n s i t i e s measured f o r a normalized d i s t r i b u t i o n o f maturation times r e l a t i v e t o a 40 day uniform d i s t r i b u t i o n . Arrangements of nest l o c a t i o n s w i t h i n the redd used t o examine e f f e c t s of nest spacing on s u p e r i m p o s i t i o n r a t e s . Mean w a i t i n g times c a l c u l a t e d f o r v a r i o u s d e n s i t i e s and temporal d i s t r i b u t i o n s . Maximum w a i t i n g times obtained i n 8 and 20 day s i m u l a t i o n s i n r e l a t i o n t o d e n s i t y . Comparison of the percentage of the t o t a l number of nests superimposed i n r e l a t i o n t o d e n s i t y f o r the 40 day and 8 day s i m u l a t i o n s f o r three p a t t e r n s of redd defence. FIGURE 34. Relationship between fry production and spawner numbers for Fulton Channel #2, for a variety of redd sizes and a 16 day maturation period (100% run matures within 16 days). 35. Estimates of optimal number of females for a variety of fry to adult survival rates. Maximum sustained catch indicated by maximum distances between production and replacement lines. LIST OF TABLES TABLE PAGE I Comparison of methods used i n salmon and trout 14 i n v e s t i g a t i o n s . II Distances of f i r s t and second nest from mound f o r high and low v e l o c i t i e s . 20 III C o r r e l a t i o n s among X and Y co-ordinates of s t a r t i n g l o c a t i o n s , d i g angle, and distance from nest. 54 IV Nest s t a t i s t i c s f o r X and Y co-ordinates of s t a r t i n g l o c a t i o n s f o r excavation (E) and couching (C) d i g s , d i g angle, pooled variance estimates f o r X, Y and angle, plus o v e r a l l averages. 55 V Summary of data and weighting procedures f o r c a l c u l a t i o n of average d i g length from excavation (E) and covering (C) digs. 56 VI Locations of successive nests spawned by s i x females i n flume experiments. (Female 4 spawned 3 nests, nest 3 measured r e l a t i v e to nest 2) and average distance between successive nests. 61 VII Number of eggs spawned i n i n d i v i d u a l nests f o r each female used i n the spawning behavior experi-ments. Figures i n brackets i n d i c a t e percentages of the t o t a l number of eggs. 64 VIII Comparison of t h e o r e t i c a l redd s i z e estimates with measured values reported by Burner (1951). Percent deviations i n brackets. 66 x i ACKNOWLEDGEMENTS I wish to thank the Ford Foundation, the B r i t i s h Columbia Fish and W i l d l i f e Branch and the F i s h e r i e s and Marine Service of Canada who a l l provided assistance i n the form of funds, l i v i n g accommodations and t e c h n i c a l support. Thanks are also due to P.A. Lark i n , C. Groot, R. L i l e y and C.J. Walters who edited the manuscript, D. McKay and I. Sanson who decoded and typed the o r i g i n a l d r a f t and P. Henderson who prepared the f i g u r e s . S p e c i a l thanks are also due to my supervisor, C S . H o l l i n g , who helped i n so many ways, and whose patience serves as an i n s p i r a t i o n to us a l l , and f i n a l l y a s p e c i a l acknowledgement to P.A. Larkin who, several years ago, rescued me from the peace and s e c u r i t y of a law degree. GENERAL INTRODUCTION 1 HISTORICAL ASPECTS The behavior of most b i o l o g i c a l systems and c e r t a i n l y most managed b i o l o g i c a l systems such as f i s h e r i e s , i s c h a r a c t e r i z e d by v a r i a t i o n i n space and time. Yet de s p i t e i t s obvious importance i n salmonid management, l i t t l e a t t e n t i o n has been given t o s t u d i e s of sources of v a r i a t i o n i n production or t o techniques of d e c i s i o n making i n the face of such v a r i a b i l i t y . R i c k e r (1958), Tautz et a l . (1969) and others considered v a r i a b i l i t y i n stock recruitment systems (the r e l a t i o n s h i p between number of spawners and t h e i r progeny r e t u r n i n g as a d u l t s ) but the general t h e o r e t i c a l conclusions obtained were of l i m i t e d value i n determining d e s i r a b l e escapements f o r p a r t i c u l a r f i s h e r i e s . In p r a c t i c e , d e s i r a b l e escapements are estimated by the a n a l y s i s of h i s t o r i c a l d a t a , but even i n s i t u a t i o n s not complicated by changes i n spawning or r e a r i n g c a p a c i t y , the i n t e r p r e t a t i o n of catch and e x p l o i t a t i o n r a t e s can be complex (Ricker 1975). How such i n t e r p r e t a t i o n s are a f f e c t e d by environmental v a r i a t i o n i s a matter f o r c o njecture, but i t i s p o s s i b l e that s e v e r a l generations would be r e q u i r e d t o describe f u l l y the r e l a t i o n s h i p between escapement and production f o r a p a r t i c u l a r system. F u r t h e r , i f environmental con-d i t i o n s are g r a d u a l l y and c o n s i s t e n t l y changing, the task would appear t o be impossible. One concludes t h e r e f o r e t h a t current management p r a c t i c e s u t i l i z e d f o r n a t u r a l systems are l i k e l y sub-optimal i n the sense of o p t i m i z i n g catch or some d i r e c t f u n c t i o n of 2 catch, and that p o t e n t i a l b e n e f i t s to be derived from improvements on these techniques are s u b s t a n t i a l . Two general approaches have been used to upgrade the performance of managed systems: (1) environmental c o n t r o l during r a t e l i m i t i n g stages of the l i f e h i s t o r y (2) increasing manageability by development of p r e d i c t i o n techniques f o r r e l a t i n g p h y s i c a l and b i o l o g i c a l parameters to production. In f i s h e r i e s the former approach, which includes hatcheries, spawning channels, r e a r i n g ponds, flow c o n t r o l , etc. has a long h i s t o r y characterized by spectacular successes and spectacular f a i l u r e s , while the l a t t e r approach has been f r u s t r a t e d by problems associated with the analysis of complex i n t e r a c t i v e systems. At present, the r e l a t i v e merits of the two approaches are d i f f i c u l t to a s c e r t a i n . For example, in t r o d u c t i o n of methods of a r t i f i c i a l pro-pagation i n t o a n a t u r a l system, trades one set of u n c e r t a i n t i e s f o r another, i . e . whereas i n n a t u r a l systems, flow r a t e s , s i l t a t i o n , temperatures, etc. influence production, i n hatcheries, disease, feeding, timing and s i z e at release l i k e l y r e l a t e to r a t e of r e t u r n . Also, while hatcheries provide f o r s u b s t a n t i a l increases over n a t u r a l production, they also contain the p o t e n t i a l f o r producing s u b s t a n t i a l d e c l i n e s . V i r a l i n f e c t i o n s , losses of genetic f i t n e s s , water contamination, and other catastrophies p e c u l i a r to hatchery programs a l l can contribute to the p o s s i b l e extermination of n a t u r a l runs. Spawning channels, which represent an intermediate condition between hatcheries and n a t u r a l systems provide uniform conditions f o r the deposition and incubation of eggs, yet there i s some doubt as to whether conditions are uniformly good or uniformly bad, or perhaps 3 uniform at a l l . Some "channels have been q u i t e s u c c e s s f u l , others have not and the key v a r i a b l e s have not been adequately d e f i n e d . I n c r e a s i n g manageability which i n essence simply provides a b e t t e r understanding- o f the l i f e h i s t o r y , i s a l s o not without d i f f i c u l t i e s . While b e t t e r l e v e l s of p r e d i c t a b i l i t y should be p o s s i b l e through a more d e t a i l e d understanding o f the system dynamics, the i n f o r m a t i o n requirements of such a system might be c o s t l y enough to outweigh gains on p r e c i s i o n . I t i s perhaps t r i v i a l t o suggest t h a t an o v e r a l l management pla n should i n c l u d e a d i v e r s i t y o f the above approaches, w i t h ongoing e v a l u a t i o n s , but i n many agencies t h i s has not been the case. D e t a i l e d e v a l u a t i o n s and b a s i c r e s e a r c h have r e c e i v e d low p r i o r i t y o f t e n because b e n e f i t s appeared marginal. Thus, the i m p l i c a t i o n s f o r r e s e a r c h i n these areas are q u i t e c l e a r , namely t h a t programs should be developed which provide some t a n g i b l e b e n e f i t s i n terms of management g o a l s , perhaps at the expense of d e t a i l e d s t u d i e s of p a r t i c u l a r phases of the l i f e h i s t o r y which do not in c r e a s e manageability of s t o c k s . PROBLEM DEFINITION For many species of P a c i f i c coast salmonids, i n c l u d i n g sockeye (Onchorynchus nerka)3 chum ' ('Onchorynchus keta) and pink (Onchorynchus gorbuscha), amount of a v a i l a b l e spawning area i n many areas has been assumed t o l i m i t f r y production and consequently the number of r e t u r n i n g a d u l t s . The b a s i c management problem a s s o c i a t e d w i t h these species l i e s i n the e s t i m a t i o n of escapements c o n s i s t e n t w i t h o p t i m a l f r y p r o d u c t i o n , which from an o p e r a t i o n a l s t a n d p o i n t , 4 require (1) a methodology for estimating the quantity and quality of available spawning area and (2) an understanding of mechanisms which determine how that area w i l l be u t i l i z e d by escapements of various sizes. The thesis presented herein is therefore of two parts--the f i r s t dealing with physical and behavioral factors relevant to the development of a classification of spawning environments, and secondly the pattern of u t i l i z a t i o n of a given area for runs of various sizes and temporal distributions of escapement. PART I BEHAVIORAL AND ENVIRONMENTAL COMPONENTS OF SPAWNING INTRODUCTION Survival of eggs deposited in spawning gravel is dependent on presence of a flow of water bearing sufficient oxygen, and absence of mechanical disturbance resulting from floods, spawning f i s h , etc. The "problem" facing female spawners consists of selecting a site which over a period of some months w i l l consistently provide these conditions. Several investigators have observed that d i s t r i -bution of spawners in any stream is not random, and that in general there is a positive relationship between size of f i s h , water velocity, and size of gravel in which they spawn (Burner 1951). However, this does not necessarily imply larger fish require these conditions since differences in migratory behavior combined with non-random distributions of gravel and flow within a stream could produce similar 5 r e s u l t s , i . e . a large f i s h may simply have a greater range of acceptable spawning environments. Of the various experimental methods a v a i l a b l e f o r the determination of desirable conditions, none are without problems. Choice experiments i n which f i s h are presented with various v e l o c i t y and gravel a l t e r n a t i v e s are i m p r a c t i c a l to carry out on a large s c a l e , and r e s u l t s would l i k e l y be equivocal i n any event. Studies u t i l i z i n g eggs deposited i n various mixtures of gravel could produce s i m i l a r r e s u l t s over a wide range of conditions. A remaining approach and the one u t i l i z e d i n t h i s study, consists of an examination of spawning behavior, with p a r t i c u l a r reference to the importance of environmental cues i n the development of behavior patterns leading to s u c c e s s f u l o v i p o s i t i o n , and subsequently to determine how changes i n these conditions might influence the s u i t a b i l i t y of a s i t e . Therefore the objectives of the fol l o w i n g study were: 1) Identify and quantify behavioral sequences which are p r e r e q u i s i t e to completion of spawning. 2) Compare these sequences f o r two rather d i f f e r e n t salmonids, the chum salmon (Onchorhynohus keta) and rainbow t r o u t (Salmo gairdneri) to d i s t i n g u i s h features which may represent general c h a r a c t e r i s t i c s from those which are s i t e or species s p e c i f i c . 3) Examine changes i n behavioral sequences when environmental conditions are a l t e r e d , and thereby gain some i n s i g h t into the importance of gravel s i z e and v e l o c i t y . While only the behavior of i s o l a t e d p a i r s of spawning adults i s considered i n t h i s s e c t i o n , i t i s not the only information r e l a t e d 6 to the development of classification.of spawning habitats. Such a classification might in addition be based on: 1. Quantitative descriptions of redd micro-environments produced by different species digging in different water velocities and substrate types. 2. Responses of eggs and alevins to the various redd micro-environments. 3. Responses of the redd micro-environment to macro-environ-mental changes, e.g. s i l t a t i o n , temperature, scouring, etc. A l l of these factors are important in salmonid reproductive biology and further insights are l i k e l y dependent upon a consideration of the inter-relationships among these various components. However for present purposes, they are perhaps too detailed to be useful in any practical scheme of classification and w i l l be ignored in the following discussion. MATERIALS AND METHODS I. Chum Salmon Behavior This investigation was undertaken during October 15, 1970 to January 1, 1971 at the Big Qualicum development project of the Fisheries Service (Pacific Region), situated on the east coast of Vancouver Island, British Columbia. In these experiments, pairs were isolated in a stream flume to eliminate v a r i a b i l i t y arising from agonistic behavior and to allow a clearer picture of the f i s h -environment interaction to emerge. 7 The apparatus ( F i g . 1) consisted of a 4.9 x 1.2 m plywood flume with a 1.8 m periscope b u i l t i n t o one side. The f r o n t of the periscope box consisted of a 1.8 x 0.6 m piece of 1.3 cm ( t h i c k ) plate glass and i n s i d e were placed two 1.8 x 0.3 m mirrors. Neutral buoyancy was obtained by p a r t i a l l y f i l l i n g the periscope with water. An observer was thus able to view spawning a c t i v i t y at an apparent underwater distance of 30-60 cm from the spawning p a i r , and so long as the viewing area was darkened, was able to move f r e e l y about without d i s t u r b i n g the f i s h . The apparatus was placed i n an unused re a r i n g channel supplied with water from the main r i v e r system. A small dam across the width of the channel was employed to create a head s u f f i c i e n t to produce desired v e l o c i t i e s . F i s h were captured during t h e i r upstream migration i n a large trap and counting fence f a c i l i t y operated by the F i s h e r i e s Service. F i s h entered the trap overnight, and next morning a mature male and female were selected. (A female was considered mature i f eggs were exuded a f t e r gentle pressure was applied to the abdomen.) The p a i r was transported to the flume i n a f i b r e g l a s s tank on the back of a pick-up truck. Capture, tran s p o r t a t i o n and release of the f i s h required 10 to 15 minutes. Complete records of digging a c t i v i t y were obtained by combining an LC-10 transducer ( A t l a n t i c Research Corp. Ser - 1286), a Uher tape recorder, an Acoustomat t r i g g e r , and a Rustrak 4 channel event recorder. The Acoustomat was adjusted so that the sound of gravel moving during digging a c t i v i t y would cause the tape recorder FIG. 1. Plywood flume used f o r studying chum salmon spawning behavior. g to turn on and then off at each dig. The Rustrack~ih turn, was triggered each time the tape recorder was activated, thus providing the desired record. The equipment could function unattended in excess of 24 hours and would accurately record digging activity under almost a l l circumstances. Velocities in the flume fluctuated with changes in river l e v e l . Temperature and photoperiod were those experienced by the f i s h under natural conditions. II Rainbow Trout Behavior Experiments with rainbow trout were conducted during the period April 5 - June 5, 1971, at the Pacific Biological Station, Nanaimo, B.C. Twelve pairs of trout were obtained in late April from Loon Lake Outlet (described in Hartman et a l . , 1962), and transported to Nanaimo in an aluminum holding tank. Water was periodically re-oxygenated using a series of airstones connected to an oxygen cylinder, and temperature was maintained at 6 - 10 C° by addition of crushed ice. Prior to use in the spawning tank, the maturing trout were kept outdoors in a circular fibreglass tank for up to thirty days. Hatchery food was added, but no feeding was observed. No attempt was made to duplicate water temperatures at Loon Lake Outlet, which vary dramatically during the course of the spawning season (Hartman et a l . , 1962). The f i s h were exposed to normal Nanaimo (50° latitude) photoperiods for the season, which do not d i f f e r significantly from those at Loon Lake (51° latitude). The experimental apparatus consisted of a 7.0 x 2.4 x 1.2 m 10 tank with p l a t e glass windows along one side and divided lengthways in t o two channels to provide a c i r c u l a r , continuous flow of water. The f i s h were r e s t r i c t e d by net p a r t i t i o n s to the area near the glass window, which contained a gravel box f o r spawning, a ramp and pool area ( F i g . 2). Water depth was maintained at 20 cm over the gravel area and 35 cm i n the r e s t of the tank. A continuous supply of f r e s h water maintained temperature at 14° C which was w e l l within the range of normal spawning conditions. V e l o c i t i e s i n these experiments were s t r i c t l y c o n t r o l l e d . Two 2 horsepower Pumps and Power c e n t r i f u g a l , enclosed impeller pumps operating at 1725 rpm were used s i n g l y or together to produce two d i f f e r e n t flow regimes. Water from each pump was d i r e c t e d to a manifold containing a s e r i e s of 1.3 cm diameter nozzles. With two pumps, the increased nozzle v e l o c i t i e s plus the change i n depth over the gravel area produced turbulent v e l o c i t i e s of 60 cm/sec, and v e l o c i t i e s of 37 cm/sec i n laminar regions. With.one pump, laminar flows of 24 cm/sec were obtained. Flows experienced by the f i s h during s e l e c t i o n and e a r l y construction of the nest were measured 5 cm from the bottom with an Ott current meter. Gravel consisted of commercially a v a i l a b l e "pea g r a v e l " (9 mm d i a ) over which 40 l a r g e r rocks of d i f f e r e n t s i z e s (12 - 50 mm dia) were arranged i n a g r i d pattern. These rocks were painted various colours f o r i d e n t i f i c a t i o n and i n d i c a t e d how gravel p a r t i c l e s moved during the construction of the nest. Data on p a r t i c l e movements and d i g l o c a t i o n s were recorded OUTLET FIG. 2. Indoor tank used f o r studying rainbow trout spawning behavior. 12 through use of a mirror suspended at 45 degrees over the gravel area, and a Bolex 16 mm film camera with single frame exposure capability. Each dig was recorded on film and a l l other behavioral a c t i v i t i e s monitored with an Esterline-Angus 20 channel event recorder. In this manner a record of most behavior was obtained for several complete spawnings. Films were analyzed with a Vanguard Motion Analyzer (Model m-16 CW), and IBM 1130 and IBM 360 computing machines. To i n i t i a t e an experiment, a pair of f i s h was moved from the outdoor holding pond into the flume. If no spawning activity was observed within 3 - 4 hours, the fi s h were returned to the holding f a c i l i t y . The procedure was repeated, usually the next day, u n t i l a suitable pair was found. Because variation in behavior within females was expected to be larger than variation within velocities or nest number ( f i r s t , second, etc.,), each female was allowed to construct two nests, one under a high and the other under a low velocity regime. Assignment of a high or low velocity for the f i r s t nest was alternated for each successive pair, and for each pair the switch from high to low or low to high occurred 50 digs after the f i r s t oviposition. After two spawnings were completed, the pair was removed and the female stripped of her remaining eggs. Eggs deposited in the gravel were allowed to remain there u n t i l the next morning whereupon the tank was drained sufficiently to allow complete excavation of the redd. Eggs in each nest were counted and preserved in Stockner's solution. After levelling the gravel area and f i l l i n g 13 the tank with f r e s h water, a new p a i r was introduced. A summary of methods i s included i n Table I. RESULTS I Description of Basic Behavior Spawning behavior i n both chum salmon and rainbow trout consists of a combination of nest b u i l d i n g by the female and courtship d i s p l a y by the male, leading to deposition of f e r t i l i z e d eggs i n the nest. Three c h a r a c t e r i s t i c a c t i v i t i e s performed by the female during nest b u i l d i n g are: 1. Digging - which c o n s i s t s of a s e r i e s of strong body flexures while turned on one side . This digging creates a nest depression i n the gravel i n which eggs are eventually deposited (see Breder and Rosen [1966] f o r an extensive review). 2. Probing - described by Jones and B a l l [1954] as a crouch which occurs during the l a t t e r stages of nest preparation. Jones (1959) describes t h i s crouch as a behavior " i n which the female, at f i r s t poised a few inches above the deepest p o r t i o n of the bed, drops slowly and v e r t i c a l l y downward with her anal f i n e r e c t , u n t i l i t touches or s l i p s between the l a r g e r stones at the bottom; on contact the downward movement i s reversed and she returns to her o r i g i n a l p o s i t i o n " . Each such movement i s considered to be a probe i n t h i s paper while crouch i s used to describe the p o s i t i o n of the female at o v i p o s i t i o n . TABLE I. Comparison of methods used i n salmon and trout investigations, Species Study S i t e Duration of Study Home Stream Maximum Holding Time Transport Time Maturity (at c o l l e c t i o n ) Apparatus Holding F a c i l i t y Size Range (fork length) Ve l o c i t y SALMON Onoorhynchus keta Big Qualicum Development Project October 15 - January 1, 1971 Big Qualicum River Overnight 10 - 20 minutes Mature Stream Flume, Periscope, Hydrophone, Event Recorder Counting Trap 65 - 75 cm 60 cm/sec TROUT Salmo gairdneri F i s h e r i e s Research Board of Canada, Nanaimo, B.C. A p r i l 5 - June 4, i.971 Loon Lake (Outlet) 30 days 10 hours Immature Indoor Tank, E l e c t r i c Pumps, Movie Camera, Event Recorder Fibreglass Tank (outdoor) 2 m (diameter) 23.5 - 32.5 cm 15 and 28 cm/sec (average) 15 3. Covering - a different type of digging which is initiated immediately after oviposition and gradually blends into the digging of the next nest. It is characterized by an increased frequency (Sheridan, 1960) and, except for the f i r s t few digs, by an increased number of flexures per dig. During courtship display the male's position is usually to one side of the female with his head at the level of her caudal f i n . Two characteristic a c t i v i t i e s shown by the male are: 1. Quivering - which is described in several species as a high frequency low amplitude undulation of the body. 2. Crossing over - which is a side to side movement by the male over the caudal peduncle region of the female (Hartman, 1969). Courtship display and nest building culminate in oviposition and release of sperm. Immediately prior to oviposition, the female drops down into the nest in a crouch position and the male moves into the nest beside her. The female opens her beak, immediately followed by the male, and at this point the reproductive products are released with both vibrating caudal peduncle and anal f i n s . The eggs are then usually visible at the bottom of the redd and covering begins immediately. The f i r s t few covering digs are very gentle and do not normally move any gravel. However, the resulting currents serve to lodge the eggs in the interstices of the larger rocks which have accumulated in the bottom of the nest. This appears effective in preventing damage resulting from moving gravel, etc. Digging then becomes more vigorous, and gradually the female 16 moves the location of digging upstream. This f i l l s in the existing nest and at the same time creates another. II Diel Activity Before quantitative aspects of nest building and courting behavior were considered, i t was necessary to determine d i e l periodicity of spawning behavior. Figure 3 shows digging records for 6 pairs of chum salmon as recorded on the hydrophone apparatus. Abrupt peaks in digging activity (marked by arrows) indicate coverin of the nest immediately after spawning. Visual confirmation of spawnings was obtained for those peaks occurring during the day-light period. Clearly chum salmon are capable of spawning at any time during the day or night. Activity seems to be associated more close with time to next spawning than with the light cycle, i.e., there is a repeated sequence of events leading to oviposition, and i n i t i a t i o n of each sequence is independent of the light cycle. The data are in disagreement with Hartman (1969) who observed a d i e l pattern of digging in the Gerrard rainbow stock. However, i t must be borne in mind that these records were obtained for isolated pairs and effects of factors such as aggressive behavior were not considered. III Selection of the Spawning Site The early chum salmon investigations fortuitously TIME (HRS.) FIG. 3. Chum salmon d i g g i n g a c t i v i t y . Arrows i n d i c a t e egg d e p o s i t i o n . 18 demonstrated the types of stimuli important in selection of a spawning site. As indicated ea r l i e r , the flume contained a gravelled area located between two areas covered by plywood which were intended to locate the female in front of the periscope. However, the f i r s t pair initiated spawning activity at the extreme back end of the tank completely within the boundaries of the plywood sheet. Digging and quivering were observed over a period of several hours and no obvious attempt was made to move upstream to the gravel. A few small rocks were present on the plywood near the female but since they were quite inconspicuous, i t was f e l t that another cue must have determined the choice. Upwelling patterns associated with the end of the tank appeared to play some role in increasing the desirability of the location. Therefore, a number of rocks was placed at the back of the gravel area, creating a similar upwelling and accelerating flow. From that point a l l pairs initiated spawning near the back of the gravel area, immediately in front of the row of rocks. These observations are in agreement with those of White (1942). Since velocities were not manipulated in the chum salmon studies, i t was impossible to distinguish a choice of upwelling, accelerating current from that of a faster velocity. However, data collected for rainbow trout did distinguish between these p o s s i b i l i t i e s . Figure 4 shows the locations of nests constructed by rainbow trout under two velocity regimes with a mound of gravel (4 cm high) located at the extreme back of the box. A l l i n i t i a l nests were built immediately in front of the mound indicating that velocity had l i t t l e effect on the location of the f i r s t nest (Table II). N E S T 1 N E S T 2 0 o U P W E L L I N ® Y A X I S FIG. 4. Diagram showing nest l o c a t i o n s , flow pattern and o r i e n t a t i o n of the flume. 20 TABLE II.- Distances of f i r s t and second nests of rainbow trout from mound for high and low velocities. Female Nest No. Distance (cm) Velocity (cm/sec) Velocity 1 2' 2 3 3 4 4 5 5 6 6 Second First Second First Second First Second First Second First Second 72.8 15.04 56.41 10.44 61.31 20.79 82.39 21.33 65.46 16.30 58.97 21.94 27.43 15.84 15.24 18.28 12.80 35.35 28.34 17.67 12.80 35.35 High High Low Low High Low High High Low Low High S.E. High Low 27.78 14.87 6.92 2.09 6 5 21 As a fu r t h e r t e s t , the mound was moved upstream with the r e s u l t that the f i r s t nest of the next s e r i e s was again located i n front of the mound. F i n a l l y , the f i s h e s ' behavior suggested that the a c c e l e r a t i n g -upwelling condition rather than v e l o c i t y per se determined the choice of l o c a t i o n . Slow, passive, downstream, d r i f t i n g with anal and p e l v i c f i n s touching the gravel was u s u a l l y abruptly terminated when the f i s h encountered the a c c e l e r a t i n g current. On these occasions the f i s h would begin a c t i v e l y swimming upstream, or, quite often, a d i g would be made. This was observed i n low and high water v e l o c i t i e s . One a d d i t i o n a l complexity remains with regard to the se l e c t i o n of a s i t e . Because of the hydrodynamic properties of the flume, the v e l o c i t y range of the two flow conditions overlapped to some degree, i . e . , areas i n the high flow regime exhibited v e l o c i t i e s which were i d e n t i c a l to those exhibited by some other areas i n the low flow regime and v i c e versa. Therefore, i n order to eliminate the p o s s i b i l i t y that f i s h were i n f a c t choosing the same v e l o c i t y , i r r e s p e c t i v e of flow regime, i t was necessary to consider the i n i t i a l v e l o c i t i e s at each nest s i t e (Table I I ) . These data, again, suggest that v e l o c i t y i s of secondary importance i n the i n i t i a l s e l e c t i o n of a s i t e . IV Construction of the Nest Construction of a nest with a s u i t a b l e environment f o r eggs and al e v i n s constitutes the major focus of adult spawning behavior. In t h i s s e c t i o n , d e t a i l e d aspects of nest b u i l d i n g are 22 considered f o r rainbow t r o u t . _ Distance parameters r e q u i r e d f o r d e s c r i b i n g the l o c a t i o n s of each d i g r e l a t i v e t o the eventual l o c a t i o n of the egg pocket are d e f i n e d i n Figure 5. Y d i s t a n c e r e f e r s t o the d i s t a n c e upstream or downstream, X d i s t a n c e to the d i s t a n c e r i g h t or l e f t , and t o t a l d i s t a n c e t o the d i s t a n c e from the l o c a t i o n of the f i s h ' s t a i l t o the eventual l o c a t i o n of the egg pocket. The average p a t t e r n of d i g g i n g observed d u r i n g the c o n s t r u c t i o n of the v a r i o u s nests i s summarized i n F i g u r e s 6 and 7. Figure 6 shows: (1) a s m a l l average movement of the female upstream du r i n g the c o n s t r u c t i o n of the nest. (2) no s i g n i f i c a n t l e f t or r i g h t b i a s . "(3) an apparent r e d u c t i o n i n the estimated standard d e v i a t i o n of both X and Y as spawning approaches. Figure 7 i n d i c a t e s t h a t as spawning proceeds, d i g g i n g was not only c l o s e r t o the eventual egg pocket ( F i g . 6) but a l s o t h a t successive d i g s were c l o s e r t o each other. A d d i t i o n a l i n f o r m a t i o n was obtained from a study of i n d i v i d u a l d i g g i n g records ( F i g . 8). Here, l o c a l i z a t i o n of d i g g i n g was not obscured by averaging and was c l e a r l y d i s c e r n e d as a r a p i d decrease i n t o t a l d i s t a n c e ( i . e . , the combination of the X and Y Footnote - These are i n f a c t estimates of cf^ , not <f\ , and t h e r e -f o r e are not adjusted f o r sample s i z e . This i s necessary because a few nests may have r e q u i r e d only say, 180 d i g s and these numbers would not be i n c l u d e d i n the 200 d i g s p r i o r t o spawning est i m a t e s . Consequently, the s t a t i s t i c s should be considered only as rough estimates of v a r i a b i l i t y . FIG. 5. Analysis of digging behavior indicated that there was a small average movement of the female upstream during nest c o n s t r u c t i o n , and that digging could be characterized as three separate phases--exploratory, l o c a l i z e d and covering. 24 —20 I I i I ! : 1 0 0 50 100 150 200 DIGS PRIOR TO SPAWNING FIG. 6. Comparison .of - average upstream-downstream (Y) and l e f t - r i g h t (X) d i s t a n c e s from the egg pocket i n r e l a t i o n t o probing i n t e n s i t y . DISTANCE FROM N E S T ( C m ) I—I CD cx- > CD < < CD p . 4 -OJ cu r t OP p- ro o 3 Cb cn (-•• w cn r+ CU OJ cn 3 O OJ CD Hi Hi C H 3 O O 3 r t H- 3 CD cn r t O 3 O Hi OJ 3 CL, CL. H-OP cn H H O cr 3 O OP H 3 O r t CD cn 3 X) cn OJ r t 3 ^ 3 OP s: H-r+ 1 + cn r t OJ 3 CL. OJ H CL. P R O B E S / ; ? .5 MIN. 52 UJ 60 O z < H 1/1 20 exp lo ra to ry 11 l o c a l i z a t i o n cover ing I |\|W FEMALE I NEST Z VELOCITY LOW 40 BO 120 160 ZOO 2«0 DIGS 28 0 320 160 400 exDlorntory i t , i l l o c a l i z a t i o n FEMALE 2 NEST I VELOCITY LOW cover ing mm 40 BO 160 200 200 2 8 0 3 2 0 360 400 DIGS o z exp lo ra to ry l o c a l i z a t i o n cover ing FEMALE 2 NEST 2 VELOCITY HIGH 160 200 DIGS 240 280 320 360 400 cn FIG 8. Probing appeared to serve as a s i g n a l to the male i n d i c a t i n g the approach of o v i p o s i t i o n and i n a d d i t i o n provided the means of coordinating the release of sexual products. 27 components in Figures—6 and 7) and a decrease in digging location v a r i a b i l i t y . Covering i s also clearly indicated by the rapid increase (upstream) in distance from nest. In summary, there appear to be at least three phases of digging: (1) Exploratory - characterized by large variation in digging location, often occurring at large distances from the egg pocket. Probing occurred infrequently during this stage. (2) Localized - characterized by small variation in digging location, occurring at small distances from the egg pocket. Probing was intensive during this phase. (3) Covering - characterized by increased v a r i a b i l i t y and an obvious movement of the female upstream. Further, i t was apparent that increased probing activity and localized digging were associated with development of the nest depression which, in turn, suggest female interaction with current patterns and/or nest shape. V Effects of Altered Velocities A two-way analysis of variance was performed on the number of digs completed prior to-spawning for the f i r s t and second nest of a spawning sequence, under conditions of high and low velocity. The average number of digs required was 267 (S.E. 32), and no main effects were significant. However, since number of observations in each c e l l was small (3), no firm conclusions should be drawn. The data do suggest that number of digs required for nest 2 was slightly 28 more than for nest 1 (279 vs 255) and that more digging was required for nests constructed under conditions of high flow (275 vs 255). Data obtained by estimating the distance traversed in each dig and reconstructing the nest from the film records indicated that there were no differences observed in angle of dig relative to current in the high and low flow condition, nor was any consistent difference apparent in size of area disturbed during construction of the nests (Fig. 9). VI Female-Male Interactions during Spawning Frequencies per 2-minute interval of male and female spawning behaviors as a function of time prior to spawning are provided for chum salmon and rainbow trout in Figures 10 and 11 respectively. The sequences are similar in that: 1. Probing was initiated between 100 and 130 minutes prior to spawning. 2. A small but consistent decrease in digging frequency was observed as spawning approaches. 3. The largest increase in frequency of male courtship behavior coincided with i n i t i a t i o n of probing in the female. The patterns d i f f e r in that male quivering i s not as closely associated with probing activity in the trout as in the chum salmon, and that the frequency of probing in chum salmon was approximately one-half that observed for trout. These behavior a c t i v i t i e s were seen to occur in a usually FIG. 9 . Reconstruction of dig tracings for three females under high and low velocity regimes. Number of digs i s indicated in the bottom right hand corner of each set. 12 CJCHUM "CROSS OVER • QUIVER Q CHUM ° PROBE • DIG 1 ° . 2 0 3 0 4 0 5 0 6 0 ™ 80 90 ,00 ,10 120 130 MIN. PRIOR TO SPAWNING FIG. 10. Average frequency/2 minutes +1 S.E. of male and female chum spawning behaviors. o 20 30 40 50 60 70 80 90 100 120 MIN. PRIOR TO SPAWNING FIG. 11. Average frequency/2 minutes +1 S.E. of male and female rainbow trout spawning behaviors. • 32 predictable order as oviposition approached. After completing a dig, the female would d r i f t backwards so that her vent was over the egg pocket and i n i t i a t e a probe. Immediately thereafter, the male would approach the female from his position behind and to one side of her, quivering as he did so. At this point, the female would usually complete the probe, i.e., l i f t herself out of the crouch, and the male would begin to d r i f t backwards to his original location, often crossing over the back of the female (Fig. 12). A sequence which culminated in oviposition appeared similar except that the female would remain in the crouch, thereby allowing the male to assume a similar position beside her (Fig. 12). VII Female-nest Interactions The close temporal association of probing and quivering suggested that probing served as a signal to the male., indicating an increased readiness to spawn on the part of the female. In addition to this function however, i t also seemed l i k e l y that probing was a means by which the female could monitor the structure of the nest. To support this hypothesis, i t was desirable to show that: 1. some component of probing behavior changes with change in nest structure, and/or 2. digging behavior changes in response to alterations in nest structure. In order to satisfy the former condition, cine films recording a number of probes and spawnings were studied. For each probe, the angle of anterior-posterior body axis were measured FIG. 12. Diagram comparing an e a r l y crouch sequence ( l i f t ) with one r e s u l t i n g i n egg deposition (spawn). OJ 34 relative to the gravel bed, e.g., i f fi s h were monitoring depth of nest, the deeper the bed, the larger would be the angle recorded. These data are plotted for three separate spawnings (Fig. 13) (spawnings indicated by arrows), but since the sequences were taken at random intervals ( i . e . , not every 5th, 10th, etc., probe was photographed), the data cannot show the gradual change in probing angle that would be expected i f the female was continually monitoring nest shape. Never-theless, the angle does become larger as spawning approaches, thus suggesting that probing could convey information to the female concerning the structure of the nest. The second condition is more d i f f i c u l t to demonstrate since without knowing exactly which nest cue(s) is responsible for e l i c i t i n g oviposition, one cannot be certain of the degree to which any experi-mental manipulations have altered the c r i t i c a l stimuli. Nevertheless, a depression was constructed in the shape of a nest, and a mature and unspawned female was directed to that area. The'number of digs com-pleted prior to spawning in this case (75), was substantially less than average for an i n i t i a l l y level substrate (228), and the digging locations and v a r i a b i l i t y were characteristic of the f i n a l stages of spawning (Fig. 14). The same female went on to construct a second nest, which required close to the average number of digs to complete. VII Nest Construction in Relation to Gravel Composition If, as indicated in the previous section, a nest of a particular shape and depth provides the key environmental cue leading CHUM TROUT 10 FRAME 20 F I G . 1 3 . r a i n b o r t r o iu?. r e l a t i V e ^ ^ d U r i n g i n c h u m s a l m o n a n d DIGS PRjOR TO SPAWNING FIG. 14. Compar ison of number and l o c a t i o n of digs with and without p r i o r excavation of the nest s i t e . 37 to spawning, the a b i l i t y of the female to construct such a depression given various combinations of gravel and velocity provides the mechanism for assessing gravel "quality" in relation to the spawners' requirements. Observations made on the movements of the colored particles as nests were constructed, indicated -1) there were two patterns of movement,, particles below a certain size were removed entirely from the nest area, while larger particles tended to migrate to the center of the excavation. 2) velocity appeared to play only a minor role in the ease with which particles were dislodged, i.e. that the primary forces causing movement resulted from the digging behavior of the female. The weight at which particles were dislodged from the nest area was between 20 and 40 gms which, i f a spherical shape was assumed, represented particle diameters of 2.4 to 3.1 cm. Thus, by making an assumption concerning the depth and shape of the nest, the tolerances for the grading curve could be established in that only a certain percentage of the material could be of the c r i t i c a l size or larger. For example, i f nest shape was approximated as in Figure 15 and a depth of 7 cm was required, the percentage of material of the total nest volume of diameter greater than 3.1 cm must be less than 11 per cent. If porosity is calculated, then a grading curve may be evaluated. A f i n a l and important result of this phenomenon was that a structure with unique hydraulic properties was created. The effect of the large material moving to the bottom of the nest was that then an area of high permeability was created which was surrounded by areas of 38 10 0 CPcpo FIG. 15a. Diagramatic r e p r e s e n t a t i o n of the r e l a t i o n s h i p between number of p a r t i c l e s above c r i t i c a l s i z e and depth of nest. FIG. 15b. Patterns of flow through a n a t u r a l redd demonstrating e f f e c t s of high and low p e r m e a b i l i t y areas. 39 lower permeability. This s t r u c t u r e , combined with the mound created above the nest surface from covering a c t i v i t y , d e f l e c t e d s u r f i c i a l and subgravel flows through the area i n which the eggs were located. Thus, even with diverse i n i t i a l substrates and v e l o c i t i e s , the f i n a l micro environment f o r the eggs i s l i k e l y to be very s i m i l a r as a r e s u l t of the nest digging process. 40 SUMMARY C h a r a c t e r i s t i c behavior of the male during nest b u i l d i n g consisted of quivering and crossing over. There were two types of digging exhibited by the female, excavation and covering. Covering digging was characterized by an increased frequency of flexures per d i g and number of digs per unit time. Covering digging occurred upstream of the nest pocket. Spawning i n chum salmon occurred during most hours of the day and night and d i d not appear to depend on the l i g h t c y c l e . However, the presence of other spawners would influence t h i s r e s u l t i n a n a t u r a l system i f aggressive behavior was reduced during dark hours. Upwelling flows appeared to provide an important cue i n the l o c a t i o n of a spawning s i t e . The observation -"that spawning behavior occurred over plywood while gravel areas were a v a i l a b l e upstream suggested that v i s i o n played only a minor r o l e . Pattern of flow rather than rate of flow was demonstrated as important i n experiments where a number of v e l o c i t i e s were a v a i l a b l e to the spawner. Analysis of digging' behavior indicated that there was a small average movement of the female upstream during nest c o n s t r u c t i o n , and that digging could be characterized as three separate phases --exploratory, l o c a l i z e d and covering. 41 6. A n a l y s i s o f v a r i a n c e o f d i g s t o n e s t c o m p l e t i o n i n d i c a t e d no s i g n i f i c a n t e f f e c t s o f v e l o c i t y o r n e s t number. No d i f f e r e n c e s i n a n g l e o f d i g g i n g o r n e s t shape were a p p a r e n t f o r t h e d i f f e r e n t v e l o c i t i e s . 7. I n t e n s i v e p r o b i n g was i n i t i a t e d between 100 and 130 m i n u t e s p r i o r t o s p a w n i n g , w h i c h c o i n c i d e d w i t h an i n c r e a s e i n t h e f r e q u e n c y o f male c o u r t s h i p b e h a v i o r . 8. P r o b i n g a p p e a r e d t o s e r v e as a s i g n a l t o t h e male i n d i c a t i n g t h e a p p r o a c h o f o v i p o s i t i o n and i n a d d i t i o n p r o v i d e d t h e means o f c o - o r d i n a t i n g t h e r e l e a s e o f s e x u a l p r o d u c t s . 9. P r o b i n g a l s o a p p e a r e d as a means by w h i c h t h e f e m a l e o b t a i n e d i n f o r m a t i o n r e g a r d i n g t h e shape and s u i t a b i l i t y o f t h e n e s t p o c k e t . 10. Nest shape p r o v i d e d a key s t i m u l u s i n t h e i n t e r a c t i o n between t h e f e m a l e and t h e e n v i r o n m e n t , inasmuch as amount o f c o u r t s h i p b e h a v i o r was r e d u c e d c o n s i d e r a b l y i f t h e n e s t p o c k e t was e x c a v a t e d p r i o r t o t h e i n t r o d u c t i o n o f t h e spawning. 11. The r e l a t i o n s h i p between n e s t d e p t h , s i z e o f f e m a l e and s i z e o f p a r t i c l e s "the f e m a l e c o u l d d i s l o d g e p r o v i d e d a means o f q u a n t i t a t i v e l y a s s e s s i n g v a r i o u s g r a v e l m i x t u r e s as spawning s u b s t r a t e s . Females o f 31 cm ( f o r k l e n g t h ) were c a p a b l e o f d i s l o d g i n g m a t e r i a l o f up t o 40 gms o r 3.1 cm ( d i a ) . From t h e s e e s t i m a t e s i t was p o s s i b l e t o e v a l u a t e a v a r i e t y o f p o s s i b l e g r a d i n g c u r v e s f o r r a i n b o w t r o u t . 42 The construction of the nest r e s u l t e d i n a structure with unique h y d r o l o g i c a l p r o p e r t i e s . Flows were d i r e c t e d towards the area containing the eggs by the j u x t a p o s i t i o n of layers of d i f f e r e n t p e r m e a b i l i t i e s and the cr e a t i o n of surface roughness. 43 PART I I UTILIZATION OF THE SPAWNING AREA INTRODUCTION Once area a v a i l a b l e f o r spawning has been determined, the second aspect of production o p t i m i z a t i o n r e l a t e s to u t i l i z a t i o n o f t h a t area by escapements of v a r i o u s s i z e s and w i t h v a r i o u s d i s t r i b u t i o n s i n time. The d e s i r e d r e l a t i o n s h i p between p o p u l a t i o n parameters and f r y production i s a problem w e l l s u i t e d to- process modeling, the approach adopted i n t h i s s e c t i o n , as important components of the d e n s i t y dependent mechanisms can be r e a d i l y i d e n t i f i e d , and the process takes place over a r e l a t i v e l y s h o r t p e r i o d of time. Fry s u r v i v a l i s the r e s u l t of two types of processes, those r e l a t e d t o (1) the i n t r i n s i c c a r r y i n g c a p a c i t y of the g r a v e l and (2) d e p o s i t i o n success. The former i s a f u n c t i o n of the average q u a l i t y of the g r a v e l environment, w h i l e the l a t t e r i s a f u n c t i o n of d e n s i t y dependent processes o p e r a t i n g d u r i n g the spawning run. I t i s p o s s i b l e t h a t , subsequent t o the d e p o s i t i o n of eggs, there are a l s o d e n s i t y dependent e f f e c t s w i t h i n the g r a v e l , e.g. competition f o r oxygen, space, e t c . but recent work i n d i c a t e s t h a t high s u r v i v a l s can be r e a l i z e d u s i n g egg d e n s i t i e s higher than those normally encountered under c o n d i t i o n s of n a t u r a l spawning (Thomas 1975). The d e n s i t y dependent process e n v i s i o n e d i s one i n which i n d i v i d u a l females move i n t o the spawning a r e a , b u i l d redds of a given s i z e each c o n t a i n i n g a number of n e s t s , defend t h a t area f o r a p e r i o d o f time, and then d i e . The eggs are then exposed t o a m o r t a l i t y from 44 l a t e r females which mechanically d i s t u r b or "superimpose" the o r i g i n a l eggs. For a given spawning are a , t h i s m o r t a l i t y i s a f u n c t i o n of number of females, area d i s t u r b e d , s i z e , d u r a t i o n , and p a t t e r n o f t e r r i t o r i a l defence, and d i s t r i b u t i o n i n time of the spawning run. Thus, o b j e c t i v e s of f o l l o w i n g s t u d i e s were: 1. o b t a i n estimates of the f o r e g o i n g parameters. 2. develop a t h e o r e t i c a l model, which by i n c o r p o r a t i n g these es t i m a t e s , would a l l o w f o r s i t e s p e c i f i c estimates of o p t i m a l p r o d u c t i o n to be obtained. Three separate s t u d i e s were conducted: 1. l a b o r a t o r y s t u d i e s of nest b u i l d i n g , t o o b t a i n estimates of nest s i z e (area d i s t u r b e d ) . 2. f i e l d s t u d i e s , t o o b t a i n estimates of p a t t e r n of s p a c i n g , type of t e r r i t o r i a l defence, and residence time. 3. s i m u l a t i o n s t u d i e s , t o determine the s e n s i t i v i t y of the parameters and s i t e s p e c i f i c optima. 45 METHODS I Laboratory Studies of Area Disturbed During Nest Construction Data relevant to the c a l c u l a t i o n of redd s i z e were c o l l e c t e d f o r rainbow trout (Salmo gairdneri,) during the previously described studies of spawning behavior. S t a r t i n g l o c a t i o n s and angle of each dig were recorded f o r several spawning sequences, after.which i t was possible to reconstruct the area disturbed f o r each nest using an estimate of average distance traversed during the execution of a d i g . A d d i t i o n a l f i l m sequences of complete digs were c o l l e c t e d f o r both chum salmon (Onchorynchus keta) and rainbow trout to obtain estimates of d i g length, and analyzed with a Vangard motion analyzer. II F i e l d Studies of Spacing and Residence Time The r e l a t i v e l y uniform c h a r a c t e r i s t i c s of spawning channels make them i d e a l f a c i l i t i e s f o r the study of t e r r i t o r i a l behavior and spacing i n salmonids. The channel u t i l i z e d ( F i g . 16) was developed f o r sockeye (Onchorhynehus nerka) and was located on the Fulton River, a major t r i b u t a r y of the Babine Lake - Skeena River system i n c e n t r a l B r i t i s h Columbia. It 'is one of three channels which together compose the Babine Lake enhancement program. A 15.25 x 9.4 m section of Fulton channel #2 was designated as a study area and an observation tower 6 m high was constructed immediately upstream of the s i t e . The p o s i t i o n i n g of the tower was d i c t a t e d by v i s i b i l i t y considerations, and although located i n the center of the channel, d i d not appear to influence the p o s i t i o n i n g of the spawners downstream. 46 ^ B A BINE LAKE JBfgg, l i f e U M 1 i:t ™-fmnii,»aii n»r>Mitii,iti; COUNTING FENCE a LAB FISHERIES CAMP FIG. 16. A e r i a l view of F u l t o n spawning channels and adjacent r i v e r . 47 The channel was 5182 m (1700TT f t ) in length, 15.24 m (50 f t ) in width and at a discharge of 4248 1/sec (150 cfs) produced an average velocity of .67 m/sec (2.2 ft/sec). The design escapement of 151,000 adults entered the channel from early August to late September and was distributed among various sections by a series of bypass structures and fences. The channel f i l l e d from the "top down", each section being closed off when the desired escapement level was achieved. Therefore, because the study site was in the upper leg of the channel, fis h in the study area were among the earliest entering the f a c i l i t y . Detailed observations of the spacing and behavior of the fis h commenced on August 23, 1972, when the f i r s t f i s h were observed digging in the section, and continued u n t i l September 31. Observations consisted of mapping locations of females twice daily, u t i l i z i n g a surveyor's transit mounted in the observation tower, as well as notes on behavior of individual females. These included whether or not she was attended by a male, digging or engaged in t e r r i t o r i a l defence. Duration of stay was estimated by assuming that the fi s h arrived mid-way between the time the female was f i r s t observed and the previous observation period and died mid-way between the last recorded sighting and the succeeding observation period. I l l Simulation Studies To examine effects of changes in various parameters on overall production, a simulation model (Fig. 17) was devised which provided for variation i n : SPAWNERS ON DAY 1 RESIDENCE T IME O DAY= i+1 SEARCH MODEL UPDATE AREA DEFENCE SPAWNERS ON i th DAY PERCENT COMMITMENT, ADD TO DAY i + 1 UNSUCCESSFUL SPAWNERS AREA SUPERIMPOSED FIG. 17. Flow chart f o r simulation model assessing r a t e s ' o f superimposition. X T C O 49 1. temporal distribution of the spawning run 2. territory size as a function of time on the spawning bed 3. locations of nests within the area disturbed 4. residence time Operationally, the model behaved as follows; for each simulated day the model was provided with the number of fis h maturing and seeking a territory. An area of arbitrary size was then searched randomly un t i l either a territory was found or a maximum number of attempts consistent with maximum density was encountered. If the former, the process was repeated u n t i l a l l f i s h for that particular day obtained t e r r i t o r i e s ; i f the latt e r , the remaining spawners were added to the total for the forthcoming day. For each f i s h , the location of the redd center and the day of arr i v a l was stored. Centers of five nests were assumed to be distributed uniformly within a circular t e r r i t o r i a l area, and i f any or a l l of these points were incorporated within the t e r r i t o r i a l boundaries of later f i s h , the eggs in that nest were assumed to be destroyed. For the i n i t i a l runs of the model, maximum territory size was equated to the area disturbed during redd construction, residence time was a r b i t r a r i l y assigned to be twelve days, and during the last 6 days the radius of the territory was decreased by a constant amount each day (12.5 per cent of the original value). It was also useful to use a new term "percent commitment" which allowed for a general treatment of results. Specifically, i t was defined as the product of the area of disturbance created by each female and the number of females, divided by the area of the spawning grounds, 50 times 100. Thus, i f area available was 100 m2, and each female required-1 m2, 100 percent commitment would consist of 100 females. An alternative way of viewing the concept i s that i f maximum channel production was a direct function of the density of eggs within a redd, 100 percent commitment would correspond to 100 percent of the possible production, i f no superimposition took place and egg pockets were uniformly distributed in the spawning area. 51 RESULTS I Laboratory Studies The redd i s generally considered as the area disturbed by a female spawner during the construction of sev e r a l nests, each nest containing a portion of the female's complement of eggs. Thus redd s i z e i s , by d e f i n i t i o n , a product of the area of each i n d i v i d u a l nest and the number of nests spawned, adjusted f o r the amount of overlap among nests. Estimates of each of these parameters were obtained as described i n the following sections. i ) Nest Size Estimates Nest s i z e was a function of the s t a r t i n g l o c a t i o n s of each d i g , the angle of each d i g r e l a t i v e to the current and distance traversed by the female during the execution of a d i g . However, estimation of an area which would best describe a f u n c t i o n a l nest proved troublesome, p r i m a r i l y because of the d i f f i c u l t i e s i n s e l e c t i n g appropriate c r i t e r i a . There were two a t t r i b u t e s of importance i n t h i s respect, area disturbed and i n t e n s i t y of disturbance. Thus, the nest could be best considered analogous to b i v a r i a t e normal d i s t r i b u t i o n , i n which the height of the surface represented the i n t e n s i t y of disturbance and the p r o j e c t i o n on the h o r i z o n t a l plane represented the area containing that l e v e l of disturbance. The problem thus became one of obtaining estimates of the parameters of the d i s t r i b u t i o n , and the method f i n a l l y u t i l i z e d incorporated a monte c a r l o simulation which provided d i s t r i b u t i o n s of the perimeter points of the digs. 52 Analysis of the distribution of the starting locations indicated that the X and Y co-ordinates were each approximately normal (Fig.. 18), that the distribution of the angle of the dig was bimodal, but could be considered normal i f the absolute value was used, and that there were no consistent correlations between parameters (Table III). Covering and excavation digs were analyzed separately for each nest (Table IV), and pooled to obtain an estimate of variance for starting locations. Results of analysis of dig lengths (Table VA) indicated that the average excavation dig for both chum salmon and rainbow trout was approximately 56 percent of the body length (fork length). Covering digging was significantly longer for rainbow trout (82.4 percent) but comparisons could not be made for chum salmon, as suitable films were not available. Average dig length was calculated for each nest, as the weighted average of the number of covering digs and excavation digs (Table VB) which were then averaged over a l l nests to obtain an estimate of 61.22 percent of the body length. The simulation model, selected starting locations from a bivariate normal distribution (mean (0.0)), a dig angle from a normal distribution (mean 21°) and used average dig length for a 31 cm female (the average length used in the experiments), to calculate locations of dig end points. X and Y co-ordinates of these points were then calculated for use in estimation of nest area. As expected, variances of end point locations for X. and Y (13.26 and 11.89 S.D.) were larger than variances of the starting locations (9.47, 11.77 S.D.). Both 53 22.5 35.0 47.5 60.0 X C O O R D I N A T E 72.5 •3.0 12.0 27.0 42.0_ . Y C O O R D I N A T E 57.0 20 10H •35.0 -17.5 17.5 35.0 A N G L E FIG. 18. D i s t r i b u t i o n s of X and Y co-ordinates of d i g s t a r t l o c a t i o n s and angle f o r a r e p r e s e n t a t i v e nest. 54 TABLE III.Correlations among X and Y co-ordinates of starting locations, dig angle and distance from nest. X WITH Y X WITH ANG. Y WITH ANG. ANG. WITH : Nest 7 - .201 .108 - .234 .251 7C . 330 .307 - .102 .141 8 .124 - .235 - .056 .240 8C 0.075 - .159 .037 .086 9 . 365 .335 - .032 .170 9C . 538 .186 .177 - .025 10 . 338 .222 . 302 - .265 10C .244 .203 .499 - .116 11 .111 .339 - .067 .078 11C - .460 .490 - .320 .152 12 .243 .226 .226 .110 12C .307 .373 .075 .115 13 .158 - .491 -0.004 .477 13C .425 . - .132 -0.044 .192 18 .181 - .247 -2.39 .075 18C - .041 - .142 -0.251 .197 19 - .059 - .363 - .045 .059 19 C - .063 .333 - .052 - .048 20 .016 - .195 .095 .101 20C .116 .248 - .231 .103 21 .016 - .267 .336 .063 21C - .219 .126 - .102 .129 TABLE IV. Nest S t a t i s t i c s f o r X and Y co-ordinates of s t a r t i n g locations f o r excavation (E) and covering (C) digs, d i g angle, pooled variance estimates f o r X, Y and angle, plus o v e r a l l averages.  INDIVIDUAL COMBINED tfEST TYPE 1 SDX SDY MEAN AVG. SDA SDX SDY MEAN AVG. SDA 7 E 11.56 13.89 25.20 12.12 13.53 16.80 25.68 12.68 7 C 18.26 10.22 27.43; 14.47 8 E 12.26 10.98 25.49 12.71 13.46 13.59 24.48 12.72 8 C 16.19 10.04 21.36 12.34 9 E 4.80 8.20 18.46 12.87 5.25 10.24 18.69 12.54 9 C 6.35 10.22 19.56 11.16 10 E 6.17 13.03 17.56 11.65 7.06 14.24 18.70 11.80 10 C 9.65 6.15 23.65 11.30 11 E 7.25 6.64 17.33 ' 12.18 7.63 8.91 18.07 12.88 11 C 7.39 6.55 22.55 15.94 12 E 7.42 10.76 20.01 11.70 9.60 13.76 19.06 11.64 12 C 14. 54 13.82 14.91 10.50 13 E 10.48 8.94 21.89 12.29 10.46 9.25 21.59 12.02 13 C 9.30 5.52 10.35 9.66 14 E 7.17 13.07 17.29 8.80 18 E 9.50 9.95 19.90 8.60 9.44 12.13 20.15. 8.59 18 C 9.22 9.86 20.80 8.84 19 E 8.70 12.26 19.53 10.91 9.83 14.14 21.26 11.65 19 C 13.41 7.14 28.02 12.08 20 E 14.28 10.47 23.14 10.46 13.88 11.47 24.56 11.88 20 C 11.40 7.64 32.65 15.76 21 E 7.39 11. 53 21.16 14.65 8.20 13.23 20.58 14.07 21 C .10.53 11.56 18.65 11.83 OVERALL AVERAGES 9.85 12.52 21.17 12.04 56 TABLE V. Summary of data and weighting procedures f o r c a l c u l a t i o n of average d i g length from excavation (E) and covering (C) digs. SPECIES Salmo gairdnerii Salmo gairdnerii Oncorhynchus keta TYPE OF DIGGING Excavation Covering Excavation % OF BODY LENGTH 55.96 82.40 57.90 S.E. 3.51 7.32 5.26 NO. OF DIGS 25 6 10 B. NEST TYPE NO. OF DIGS WEIGHTED AVERAGE 7 E 223 61.71 7 C 62 8 E 166 62.35 8 C 53 9 E 215 61.18 9 C 53 10 E 195 60.92 10 C 45 11 E 292 59.69 • 11 C 48 12 E 200 60.90 12 • C 46 13 E 249 59.13 13 C 34 18 E 276 61.49 18 C 73 19 E 184 61.33 19 C 47 20 E 457 59.89 20 C 80 21 E 179 64.87 21 C 54 OVERALL AVERAGE 61.22 57 X.and Y components of the end points were approximately normal . (Fi g . 19) s i m p l i f y i n g the q u a n t i t a t i v e d e s c r i p t i o n of the nest. Nest shape was assumed e l l i p t i c a l , though i n f a c t i t was narrower at the downstream end due to the o r i e n t a t i o n and angle of the digs upstream. Lengths of the semi-major and semi-minor axis of an e l l i p s e which contained 95 percent of the perimeter points were estimated as: X minor = 1.96 * SD,, . Xstop • = 1.96 * 11.92 = 23.36 cm Y major = 0.5 * (1.96 SD t (X Bar,,, ^ + 1.96 * SD„ ^ . Ystart (Ystop Ystop) = 0.5 * (1.96 * 11.72 + (18.1 + 1.96 * 11.,84) = 32.14 cm X minor = 1/2 the length of the x (cross-stream) axis Y major = 1/2 the length of the upstream-downstream axis SD,, ^ = standard d e v i a t i o n of the X end point co-ordinates Xstop SDyg-f-Qp = standard deviation of the Y end point co-ordinates SD,, . . = standard d e v i a t i o n of the Y s t a r t i n g co-ordinates Ystart & The cumbersone estimation of the Y axis wastthe:.'resu±t _o'f perimeter points on the downstream edge being composed of s t a r t i n g points ( F i g . 20). The appropriate e l l i p s e area was estimated as n*X minor:':Y major or 2358cm2 f o r an average female ( F i g . 20). Estimates of areas f o r f i s h of d i f f e r e n t s i z e s were obtained as Area disturbed = ( F L ) 2 ... where ;|p * 2358 cm2 58 20 >-O 23.0 34.5 46.0 57.5 69.0 80.5 X COORDINATE >-O 2 UJ =) O UJ rr 51.0 66.0 Y COORDINATE 81.0 96.0 FIG. 19. Percentage of d i g end points located at various X and Y coordinate p o s i t i o n s r e l a t i v e to a nest center of (50, 50). , , , 1 1 ;— i 2 SD 1 SD (23) (0,0) 2 SD NEST CENTER MEAN END + 1 g E POINT + F I G . 2 0 . Diagramatic r e p r e s e n t a t i o n of method o f c a l c u l a t i n g l e n g t h of Y a x i s f o r an average n e s t , and an approximate d e s c r i p t i o n of the s i z e o f area d i s t u r b e d i n r e l a t i o n t o f i s h s i z e . 60 where FL = fork length of the spawner for which the nest size i s to be estimated. i i ) Estimates of Overlap Between Successive Nests While the foregoing gives an indication of nest size in relation to body size, i t provides no information regarding tolerable overlap between the nests which comprise the redd. Estimates of overlap were obtained by examining the distance between successive nest centers for the rainbow trout described in the spawning behavior section, on the assumption that a female in isolation would be unlikely to behave so as to excavate or disturb her own eggs. These distances showed a f a i r degree of v a r i a b i l i t y (Table VI) with an average of 45.05 cm (10.45 SD) and a range of 26.04 - 55.58 cm. Ut i l i z i n g both average and minimum figures, the amount of overlap for the two ellipses containing 95 percent of the perimeter end points was determined by solving the equations of the two ellipses simultaneously and integrating to obtain the area of overlap (Fig. 21). The shaded area was estimated by integrating the equation of the ellipse for a = 23.36, b = 32.14 over the range X = - 8.5 to X = 21.8. Rearranging and collecting terms, and substituting values for a and b, which is the form C / a 2 - x 2 dx = C*l/2 (X v'a2 - x 2 + a 2 s i n _ 1 .X.) 61 •TABLE VI. Locations of successive nests spawned by 6 females i n flume experiments. (Female 4 spawned 3 nests, nest 3 measured r e l a t i v e to nest 2 ) and average distances between successive nests. NEST II DISTANCE BETWEEN FEMALE NEST I X . .. Y NESTS (cm) 1 ( o , 0 ) 3 9 . 3 3 9 . 3 5 5 . 5 8 2 ( o , o ) 4 . 7 4 3 1 . 8 8 3 2 . 2 3 3 ( o , 0 ) 9 . 3 0 4 5 . 3 0 4 6 . 2 4 4 ( o , o ) 5 . 0 4 2 5 . 5 5 2 6 . 04 ( o , 0 ) 4 . 1 4 3 8 . 6 8 3 8 . 90 3 2 ' 4 7 5 ( o , 0 ) 1 5 . 7 0 5 2 . 5 6 5 4 . 8 5 6 ( o , 0 ) 5 . 9 3 4 8 . 5 1 4 8 . 87 X Bar 1 3 . 2 6 4 1 . 6 1 4 5 . 0 4 S D 1 3 . 4 3 8 . 6 2 1 0 . 4 5 (Mean) minimum d i s t a n c e between nes t s . The former r e s u l t e d i n an overlap of 18 .per cent while the l a t t e r r e s u l t e d i n 38 per cent. 63 Recognizing that the area contained within the rectangle (-8.5, 0), (21.8, 0) and 21.8, 41.6) was equal to twice the shaded area minus the overlap, the overlap was calculated as 2(845.85) - 1260.5 = 431.7 cm (18 percent). Using the minimum average value for the female demonstrating the closest packing (female 4) and repeating the procedure, an estimate of 902.9 cm was obtained. This represented a 38 percent overlap, but did not indicate that the eggs for this nest were disturbed, since normally they are located nearer the downstream part of the nest. However, this appeared close to the minimum allowable distance between nests. i i i ) Estimates of Redd Size Because females in the flume experiments were not permitted to spawn more than two or three nests, i t was necessary to obtain estimates of the number of nests normally spawned, from counts of eggs deposited in the f i r s t two nests relative to the total complement of eggs per female. An average of 76.9 percent of the eggs-was-deposited in the f i r s t two nests with no significant differences observed between nest one and two (t = 1.76). However, in a l l cases except one, nest two contained fewer eggs than nest one, (34.6 vs 42.3 percent) (Table VII). In one case where three nests were spawned only 18 percent of the eggs were deposited in the third nest. These data indicated that at least three nests are spawned, and that together, contain between 7 5 to 90 percent of the eggs. However, i t is quite possible that two or three additional nests could be 64 TABLE VII. Number of eggs spawned i n i n d i v i d u a l nests f o r each female used i n the spawning behavior experiments. Figures i n brackets indi c a t e percentages of the t o t a l number of eggs.  FEMALE NEST I NEST II NEST III RESIDUAL TOTAL 1 338 (48) 307 (44) - 51 ( 8) 696 2 324 (54) 161 (27) - 112 (19) 597 3 187 (25) 260 (35) - 304 (40) 751 4 428 (50) 276 (32) - 148 (28) 852 5 300 (36) 228 (28) 151 (18) 148 (18) 825 6 247 (41) 244 (40) - 111 (18) 602 7 253 (42) 215 (36) - 151 (22) 599 X (42.3) (34.6) (18) S.E. 3.68 S.E. 2.33 65 constructed. Mathisen (1955) i n studies of sockeye reported a range of 3 to 7 nests spawned per female, with a d i s t i n c t mode at 5. He also observed that a greater proportion of the eggs were deposited i n the f i r s t two nests. Thus i t appears that at l e a s t f o r Onchorynchus . that 4 or 5 nests would contain most (90%+) of the female's complement of eggs. Using the nest s i z e and overlap areas c a l c u l a t e d i n the previous sections, redd s i z e s were estimated f o r various species and compared with measured redds reported by Burner (1951). Reasonable agreement was obtained, though i n a l l cases the computations based on 5 nests per redd were l a r g e r (10 - 60%) than the measured values (Table V I I I ) . II F i e l d Studies The objectives of t h i s s e ction include obtaining f i e l d estimates of (1) general pattern of behavior i n the channel (2) residence time and temporal d i s t r i b u t i o n of the t o t a l (3) spacing between females and (4) area disturbed during nest construction. i ) General Pattern of Behavior Movement into the study_area commenced on August 23, 1971, but as these f i s h were among the f i r s t entering the r i v e r system . and were l a r g e l y immature, aggressive behavior or digging a c t i v i t y was not observed u n t i l September 4, 1971. During t h i s i n i t i a l p e riod, f i s h were observed to e i t h e r remain i n r e s t i n g areas i n large schools 66 TABLE V I I I . Comparison of t h e o r e t i c a l redd s i z e estimates w i t h measured values repo r t e d by Burner (1951). Per cent d e v i a t i o n s i n d i c a t e d i n b r a c k e t s . NO. SIZE OF NESTS AVERAGE SIZE SPECIES (cm) MEASURED (m 2) THEORETICAL ESTIMATE 4 NESTS 5 NESTS 0. kisutch 61 65 2.83 2.56(-10) 3.10(+10) 0. keta 66 66 2.26 2.99(+32) 3.63(+60) 0. nerka 51 68 1.76 1.79(+ 2) 2.17(+23) 0. tschawytscha 91.5* 41.8 6.18 5.74(- 8) 6.91(+12) 67 or migrate up and down the length of the closed channel se c t i o n . However a f t e r t h i s i n i t i a l p e riod, s e l e c t i o n of s i t e s and i n i t i a t i o n of spawning a c t i v i t y proceeded r a p i d l y and within 10 days near maximum d e n s i t i e s were observed i n the study s e c t i o n . In t o t a l , observations were made on 69 females which represented 86 per cent of the number of females expected to spawn i n the study area on a random b a s i s . Since unspawned females were s t i l l observed i n the channel subsequent to the termination of observations, i t was concluded that study s e c t i o n density was representative of the complete population. The i n i t i a l l y observed pattern of spacing suggested that s e l e c t i o n of s i t e s appeared random i n that no obvious preferences were observed f o r various sections of the study area nor were there contagious d i s t r i b u t i o n s r e s u l t i n g from s o c i a l aggregation. Aggressive behavior was observed more frequently as d e n s i t i e s increased, but attempts to define patterns of aggression over time were abandoned. Several f a c t o r s played a r o l e i n the i n i t i a t i o n of an attack, and included a) distance between females b) behavior of the attacked female (e.g. i f a female was close to the gravel i n a digging p o s i t i o n , she was more l i k e l y to be attacked) c) sex, males were u s u a l l y attacked by males, females by females d) immediate behavior, e.g. females i n a c t i v e courtship were l e s s l i k e l y to attack e) temporal sequences, e.g. females which had j u s t been attacked would more r e a d i l y attack the other female. Thus, q u a n t i t a t i v e measures of aggressiveness were d i f f i c u l t to obtain without some 68 method of standardizing the attack stimulus. However, there were two identifiable phases of spawning, an i n i t i a l period during which the female deposited' her eggs, and a subsequent period where she only defended the redd area. Aggressive behavior was high during the i n i t i a l stages and declined during the latter. The two phases were differentiated operationally by the presence of a male, but could also be recognized by loss of coloration, development of fungus infections, etc. i i ) Temporal Distribution and Residence Time The two behavioral phases discussed in the previous section together comprised total residence time. The duration of the i n i t i a l spawning period was 5.3 (- 2.3 SD) days and ranged between 3 and 8 days while t o t a l residence time ranged between 3 and 13 days with a mean of 9.36 days (Fig. 22). Significance of the small total residence times was d i f f i c u l t to estimate, but they are l i k e l y the result of f i s h which moved to another area or perhaps were omitted in the daily census. Temporal distribution of numbers of spawners in the study area was d i s t i n c t l y bimodal and represented two "waves" of females (Fig. 23). The distinction between the two waves was reasonably clear since the colonization of the second wave occurred at a time when the majority of the f i r s t wave was in the post spawning phase. Thus, there were a number of spent females s t i l l defending te r r i t o r i e s between which were located new paired females (Fig. 24). This again suggests a decline in area defended during the post spawning phase. G9 40 i PAIRED R E S I D E N C E TIME O z UJ 3 O LU GC UJ o cc LU 0_ 30H 20 H 10-4 0 - T O T A L R E S I D E N C E TIME O z LU o LU rr r-Z LU O rr LU CL 30H 20-10-10 DAYS FIG. 22. Per cent frequency d i s t r i b u t i o n s of t o t a l residence time and paired residence time f o r females i n the study area, measured from the time t e r r i t o r i a l behavior was f i r s t observed. FIG. 23. Temporal distribution of numbers of paired females and total number of females in the study area indicating the .timing of the two waves of fi s h . 72 The above pattern of u t i l i z a t i o n did not necessarily reflect the distribution of maturation within the population, since i t appeared that- the area became "saturated" and females were required to wait in order to obtain a place to spawn. However, by assuming a normal distribution of maturation time, estimates of the percentage of the run maturing on individual days were obtained by using rates of colonization for the f i r s t 6 days, and adjusting these values to obtain a normal distribution. This resulted in a distribution of maturation in which 100 per cent of the run was estimated to mature by 16 days. i i i ) Spacing of Females Nearest neighbor distances were dependent on several factors, but primarily were determined by female behavioral state and density. During parts of the run, average nearest neighbor distances were large, declined to a constant level for the f i r s t wave, declined slightly for wave two and increased as spawning neared completion (Fig. 25). Three parameters were estimated each day, mean nearest neighbor distance for paired females, mean minimum nearest neighbor distance for paired females (i.e. average of the two smallest daily observed values), and minimum nearest neighbor including unpaired females. Mean nearest neighbor distance averaged between 1.5 and 2 m during periods of high densities, paired minimum between 1 and 1.5 m, while minimum nearest neighbor distance remained constant between 1 and 1.2 m. Comparing these values to the theoretical redd size of a • MEAN I l i 1 SEPT 10 15 20 • • 25 FIG. 25. Daily mean, paired minimum and minimum observed nearest neighbour distances w measured for females spawning in' the study section, over the duration of the spawning run. 60 cm f i s h , (assuming f i v e nests per redd) of 3 m2, the nearest neighbor distance which would correspond to no overlap between redds was 2 m. Recognizing that the average value included l a r g e r values r e s u l t i n g from random spacing, i t appeared that a reasonable correspondence was obtained between redd s i z e and t e r r i t o r y s i z e , i f t e r r i t o r i e s were defined as non-overlapping areas. However, i f the minimum nearest paired neighbor distances were used, the c a l c u l a t e d redd s i z e s appeared to be too large to prevent overlap. i v ) Area Disturbed during Nest Construction From laboratory studies and the l i t e r a t u r e (Burner 1951) i t was expected that females on the spawning bed would gradually move upstream as successive nests were constructed. T h i s , however, di d not occur. In most cases, f i s h movements as measured by d a i l y mapping, were confined to a r e l a t i v e l y small area, and there appeared to be no consistent d i r e c t i o n a l movement. Time di d not permit prolonged observations of i n d i v i d u a l females, and d a i l y observations were subject to considerable v a r i a b i l i t y . However, i n d i c a t i o n s of area disturbed were a v a i l a b l e as e a r l i e r f i s h "cleaned" areas of the channel which contrasted f a i r l y w e ll against undisturbed sections. These were measured with the t r a n s i t and found to range between .86 and 1.73 m2 with an average of 1.22 m2. Thus, a nearest neighbor distance of 1,24 ra would r e s u l t i n redds not overlapping i n the average case. These measured areas contrast markedly with the t h e o r e t i c a l estimates and those of Burner (1951). 75 II I Simulation Studies i ) Simple Models of Superimposition and Packing An e a r l y model d e s c r i b i n g e f f e c t s of superimposition u t i l i z e d a g r i d arrangement of spawning s i t e s (McNeil 1964), each s i t e representing the area disturbed by a s i n g l e female. Females were d i s t r i b u t e d randomly within the g r i d and i t was assumed that successive females spawning on a s i n g l e s i t e would destroy a l l eggs deposited by a previous female. Thus, maximum density of eggs per square meter was a function of fecundity i n r e l a t i o n to area disturbed and the proportion of c e l l s containing 0, 1 . . . N females was described by a Poisson d i s t r i b u t i o n , P(r) = where P(r) = the proportion of females i n a given c e l l type i . e . those containing r f i s h X = the average number of females per c e l l Since the proportion of c e l l s with 0 females i s e \ the proportion of c e l l s i n production i s 1 - e \ I f S/L i s defined as the r a t i o of the number of u t i l i z e d s i t e s (S) to the t o t a l number a v a i l a b l e ( L ) , and the f r a c t i o n of the area committed i s N/L = X, then the proportion of the t o t a l number of females " s a f e l y " depositing eggs i s S = (1 - e - N / L ) 76 A d i f f e r e n t method of conceptualizing the problem i s one i n which the proportion of an area A occupied by P randomly placed c i r c l e s of area r i s - P r r r 2 PR = 1~ 6 ~A which provides f o r the same d i s t r i b u t i o n function as ind i c a t e d by McNeil. Both models assumed no t e r r i t o r i a l e f f e c t s , i . e . the presence of a female i n an area d i d not a f f e c t the p r o b a b i l i t y of that area being superimposed, and that the t o t a l area was a v a i l a b l e f o r the deposition of eggs. This i s c l e a r l y i n c o r r e c t i f t e r r i t o r i a l behavior a f f e c t s the d i s t r i b u t i o n of spawners. I t was d e s i r a b l e therefore to consider some simple models of packing, which be t t e r represented t e r r i t o r i a l e f f e c t s . Three cases, hexagonal, columnar and random packing were selected to r e l a t e amount of area u t i l i z e d to d i f f e r e n t methods of packing. The f i r s t method, hexagonal packing, represented the t i g h t e s t p o s s i b l e instantaneous arrangement and r e s u l t e d i n 91 per cent - u t i l i z a t i o n . Columnar packing, an u n l i k e l y b i o l o g i c a l arrange-ment, but nevertheless a conceptually u s e f u l intermediate stage, u t i l i z e d 79.5 per cent of the a v a i l a b l e area, while random packing produced estimates of 60 per cent (Fig. 26). Estimates of random packing were generated by a monte c a r l o simulation i n which the X 6 Y coordinates of the center of a c i r c l e of a r b i t r a r y area were selected and the p o s i t i o n recorded. The process was repeated f o r s e v e r a l c i r c l e s , with the constraint that c i r c l e s 77 HEXAGONAL FIG. 26. Three methods of packing uniform spheres in a fixed area. Random packing provides 60% coverage, columnar 79%, and hexagonal 91%. 78 not overlap. The number of attempts required to locate a site increased exponentially as the area u t i l i z e d increased over 10 per cent, and reached a maximum near 60 per cent (Fig 27). The area was then checked manually to determine i f additional sites could be located, and i t was thus determined that 60 per cent was very close to the theoretical maximum. i i ) T e r r i t o r i a l Model Incorporating Variation Most biological situations are not well represented by the foregoing models since territory size appears to change as a function of time and most runs neither arrive instantaneously nor over such an extended period of time that females do not interact at a l l . The simple models provided a means of locating boundary conditions but the quantitative effects of variation in temporal distribution, territory size, redd size, etc., remain to be resolved. a) Effects of T e r r i t o r i a l Behavior on Production For obvious reasons, effects of t e r r i t o r i a l i t y must be considered in the context of density and temporal v a r i a b i l i t y . At very high and very low densities, effects on production were minimal (though not on survival rate) since at high "saturated" densities, the number of nests added by an individual female was less than or equal to the number of nests destroyed, while at low densities the probability of superimposition was so low that the consequences of area defence were t r i v i a l . At intermediate densities, however, 79 FIG. 27. Log number of attempts (base 10) required to lo c a t e a spawning s i t e r e l a t i v e to the percentage of the area u t i l i z e d . Values are from a s i n g l e monte c a r l o simulation run. 80 effects were significant. The relationship between per cent commit-ment and the percentage increase in production over that obtained from the non-territorial model (Fig. 28) demonstrated that increase in production of up to 50 per cent could be obtained as a result of t e r r i t o r i a l behavior. Uniform distributions' of maturation times were used in this set of simulations, so that, for example, in the 8-day simulation, 100 per cent of the run would mature in 8 days and an equal percentage (12.5) of the run would mature on each day. The results are consistent with expectations, since the av a i l a b i l i t y of a large number of mature f i s h after the i n i t i a l t e r r i t o r i e s began to decrease in size, resulted in the second wave of spawners distributing themselves at a maximum distance from the f i r s t wave thereby minimizing the probability of superimposition. Also since each wave occupied only 60 per cent of the t o t a l area, benefits from compact temporal distributions were most dramatic between 60 and 120 per cerit commitment. Fish seeking t e r r i t o r i e s after 120 per cent comitment located in the areas occupied by the f i r s t wave, and superimposition rates were correspondingly high. The effect of this was particularly apparent in the 8-day simulations, to such a degree that slightly lower production was obtained at the higher densities. b) Effects of Normalized Distributions of Maturation While uniform distributions of maturation were convenient and therefore used in the previous s i m u l a t i o n s i t was debatable what distributions are common in natural populations. On the one 81 • 8 DAYS O 12 DAYS A 20 DAYS 20 40 60 80 100 120 140 PERCENT COMMITMENT 28. Percentage i n c r e a s e s i n pr o d u c t i o n measured n o n - t e r r i t o r i a l model f o r v a r i o u s d e n s i t i e s and d i s t r i b u t i o n s o f the run over time. r e l a t i v e (percent t o a commitment) 82 hand, i f the run was considered as a single population, a normalized distribution of maturation would be appropriate; on the other, i f the t o t a l run were composed of a number of smaller populations, each normally distributed, a pulsed or even uniform distribution would be preferred. A comparison of production for a 40-day uniform and a normalized .distribution over that same period (Fig. 29) indicated that a 12 per cent increase in production was obtained at 150 per cent commitment. For the 20-day run only marginal increases (3%) were indicated and no increases were obtained for the more constrained temporal distributions. Results were not easily generalizable, since threshold effects played an important role. In particular, the pattern of colonization was almost identical for those normally distributed populations where sufficient numbers were present to saturate the available space in the f i r s t six days. The remainder simply accumulated and occupied t e r r i t o r i e s as they became available, providing results identical to high density uniform distributions. c) Effect of Nest Locations within the Redd Effects of distribution of nests within the redd on super-imposition rate, were largely a function of how individual nests were located relative to the t e r r i t o r i a l boundary. Three arrangements were used in the simulations: (1) uniform, (2) linear, and (3) hexagonal (Fig. 30) even though they were not s t r i c t l y comparable. The hexagonal and uniform arrangements provided for distances between nests to be equal and the size of the area defended to remain constant. This was clearly not possible for the linear arrangement i f the 83 P E R C E N T C O M M I T M E N T FIG. 29. Percentage increases in production for various densities measured for a normalized distribution of maturation times relative to a 40 day uniform distribution. 84 ^ UNIFORM FIG. 30. Arrangements of nest locations within the redd used to examine effects of nest spacing on superimposition rates. 85 constraint of a circular territory of a constant size was maintained, and consequently the distances between nests were reduced. Only•small differences were "observed between the linear and hexagonal arrangements, a result of the nests becoming exposed at approximately the same rate. Lower rates of superimposition for the uniform pattern (maximum of 10 per cent) were observed however, as a l l nests were protected for a longer period of time. d) Effects of Waiting Time To this point i t has been assumed that eggs deposited by later f i s h were of equivalent v i a b i l i t y to those deposited early in the run. However, work on hatchery brood -stocks suggests that maximum f e r t i l i z a t i o n rates occur over a relatively short period of the female maturation cycle (quantitative estimates not available) from which i t follows that undue waiting could seriously affect production rates. Average waiting times were therefore calculated as a function of temporal distribution and density (Fig. 31). For the 40-day simulation, no waiting was observed while for the 8-day run, females waited an average of 5.15 days at 150 per cent commit-ment. Twelve and 20-day runs were intermediate, and in a l l cases where waiting was observed, i t increased as a simple function of density. The average values did not provide a good representation of the various situations however, since a considerable proportion of the run (up to 60 per cent commitment) experienced no waiting (irrespective of temporal distribution) as sites were always available. Thus? at say, 120 per cent commitment the average waiting times for 8 DAYS PERCENT COMMITMENT FIG. 31. Mean waiting times calculated for various densities and temporal distributions. 87 the second half of the run were double those values indicated. Maximum possible waiting time, calculated as the number of days between the f i r s t f i s h waiting and the last f i s h obtaining a site (Fig. 32) also increased as a function of density and reached a maximum of 17 days at 150 per cent commitment with an 8-day temporal distribution. However, there appeared to be only small differences between the 8-day and the 20-day simulations, suggesting that the distribution of waiting time rather than the range, underwent the most change for the various.temporal distributions. It i s the distribution which is perhaps of most potential interest, since the detrimental effects may only be apparent for f i s h waiting longer than a given number of days, but additional work on the subject i s required before this data would be of value. e) Effects of Various Types of T e r r i t o r i a l Defence Pattern of t e r r i t o r i a l defence was another variable altered in the simulations. Three patterns were used which encom-passed the range of theoretical p o s s i b i l i t i e s : (1) maximum defence, in which the size of the area defended remained constant and at a maximum level u n t i l death, (2) gradual decline, in which the radius of the area defended decreased uniformly during the post spawning period, (3) uniform, in which the radius contracted immediately to just encompass the nest pockets and remained at that level. In case (1) the average area defended per day was 100 per cent of the territory size, while in cases (2) and (3), the area defended was 39 per cent of the original area in both cases, the latter two differing only in 88 25A PERCENT COMMITMENT FIG. 32. Maximum waiting times obtained in 8 and 20 day simulations in relation to density. 89 the pattern of defence. Comparing the superimposition rates for the various cases, i t was apparent that maximum defence was least desirable from the point of view of minimizing superimposition rates, and that the remaining two cases were similar in their effectiveness (Fig. 33). The reason for this result is that by reducing territory size during the post spawning period, a second "wave" of spawners was located in the areas between the original set of redds, with the effect that they provided an additional period of protection after the original females had died. The effects were quite significant in some cases (15 per cent difference in superimposition rate) and most prevalent at intermediate densities of runs with constrained temporal distributions. The effects were less dramatic at higher densities since as the third wave of f i s h entered the spawning area, the same process tended to force them directly onto the locations of the i n i t i a l spawners. A CASE STUDY The major emphasis in any management problem related to the optimization of some quantity, and in salmonid management, this quantity is usually related to catch. Consequently, i t was useful to examine the relationship between spawner density and fry production, using the foregoing model, in an effort to derive optimal densities for existing f a c i l i t i e s . To accomplish thi s , i t was necessary to make some assumptions regarding various l i f e history stages, the most important being that spawning area is the rate limiting factor in the l i f e cycle and that lake and ocean mortality rates are constant and independent of density. However, even i f this were not 90 O LU o cc UJ 40 H 30-T Q LU CO o 1 cc LU Q. 3 co co 2 0 -LU 10-0 4 0 DAY SIMULATION X MAXIMUM DEFENCE V GRADUAL DECLINE • UNIFORM DEFENCE -V-50 100 PERCENT COMMITMENT 150 40-O LU CO o CL I 30 -LU D_ 3 co CO to 2 0 -LU U_ O LU o cc LU 0_ io H 0 FIG. 33. 8 DAY SIMULATION X MAXIMUM DEFENCE V GRADUAL DECLINE • UNIFORM DEFENCE 100 PERCENT COMMITMENT 150 Comparison of the percentage of the t o t a l number of nests superimposed i n r e l a t i o n to density f o r the 40 day and 8 day simulations f o r three patterns of redd defence. 91 the case and the ocean or lake environments were limiting production, the relationship would s t i l l be required in the management program since the manipulation of spawner density via regulation of catch is the only control variable in the system. The parameters of the model were altered to describe the operation of channel #2. The t o t a l area was 78,902 m2, females averaged 60 cm in length (fork length) and contained an estimated 3200 eggs (Withler 1950). The area disturbed during the construction of the redd was in doubt as theoretical and measured estimates differed. Consequently, three different areas were u t i l i z e d 3.2, 2.2 and 1.2 m2 per female. The temporal distribution of maturation was also estimated from f i e l d data as outlined in previous sections. The basic survival rate .of eggs in the channel (without considering any superimposition effects) was set at 85 per cent which corresponded to the rate observed for channel 1 from an eyed egg plant in 1966 ( f i r s t year of operation) (1966 Ann. Rept. D.O.E.). Maximum production for channel 2 based on that figure was therefore estimated as 178.8, 97.6 and 67.1 million fry with 1.2, 2.2 and 3.2 m2 per female respectively. The relationship between female numbers and production is indicated in Fig. 34. Estimates of optimal fry production were dependent upon the.fry to adult survival rate, and again estimates of this parameter reported in the literature vary considerably. Four different values were therefore used to estimate replacement—0.01, 0.25, 0.5 and 1.0 per cent and optimal densities determined by estimating the 20 40 60 80 NO. OF F E M A L E S X 103 U3 FIG. 34. Relationship between fry production and spawner numbers for Fulton Channel #2, for a variety of redd sizes and a 16 day maturation period (100% run matures within 16 days). 93 maximum distance between production and replacement, using an average area per female of 2.2 m2. The most recent estimates for average survival rates for the Babine system were 10 per cent from fry to smolt and 4 per cent escapement from smolt to adult. This would suggest an optimal escapement of between 50,000 and 55,000 females assuming an 0.4 per cent survival from fry to adult (Fig. 35) or an area of 1.6 m2 per female. Current operating levels are 1.05 m2 per female, indicating an overescapement of approximately 50 per cent. It must be stressed however that the optimum is quite sensitive to redd size and i t is possible that 2.2m2 i s slightly large, (no more than 20% however). Were this the case, current densities could approach optimum. How-ever, this can only be determined by more detailed measurements of nest size in a competitive situation, and a determination of whether females at high densities would superimpose their own eggs. FIG. 35. Estimates of opt i m a l number of females f o r a v a r i e t y of f r y t o adult s u r v i v a l r a t e s . . Maximum sustained catch i n d i c a t e d by maximum di s t a n c e s between production and r e p l a c e -ment l i n e s . 95 SUMMARY 1. . Distributions of X and Y coordinates of dig starting locations for nest construction were normally distributed and independent. Dig angle was also normally distributed about a mean of 21° with equal numbers of digs being oriented towards the l e f t and right sides of the nest. 2. Average length of an excavation dig was 56 per cent of the fork length for both chum salmon.and rainbow trout. Covering digs were longer in rainbow trout, 82 per cent of the fork length. 3. The nest was described both in terms of area disturbed and intensity of disturbance. The nest was e l l i p t i c a l in shape and for a 31 cm female, an area of. 2358 cm2 contained 95% of the dig end points. In general, the relationship between nest size and f i s h size was (FL) 2 * 2358 cm2. (31) 4. Distance between nests for rainbow trout showed considerable v a r i a b i l i t y and the amount of overlap ranged between 18% and 38%. 5. Redd size was estimated as the product of nest size and nest number adjusted for overlap. Rainbow trout and sockeye salmon appeared to spawn 3 to 7 nests, with 4 or 5 nests being most common. Most of the eggs appeared to be deposited in the f i r s t two nests. 6. Comparisons of calculated nest sizes and measured nest sizes showed reasonable agreement for 4 nests per redd. For 5 nests 96 per redd the calculated values produced overestimates of between 10 and 60 per cent. 7. Studies of aggressive behavior of sockeye in spawning channels indicated that attacks were initiated under a variety of conditions and not subject to analysis without a standardization of stimuli. Nevertheless, two distinct phases of spawning were observed, a paired phase in which the eggs were deposited and aggressive levels remained high, and an unpaired phase where aggressive levels gradually declined u n t i l the female died. 8. The i n i t i a l paired phase of spawning lasted 5.3 days while the total time on the spawning ground averaged 9.4 days. 9. Fish arrived in the study section in two "waves", the second wave of spawners arriving after most of the f i r s t wave were in the post spawning phase. The second wave located'their redds between the areas u t i l i z e d by the f i r s t wave. 10. It was estimated that most of the run would mature in 16 days, provided maturation was normally distributed within the population. 11. " Mean nearest neighbor distance averaged between 1.5 and 2 m during periods of high densities, paired minimum ranged between 1.5 and 2 m, and the minimum nearest neighbor distance was 1 to 1.2 m. 12. Comparing territory size and redd size for a 60 cm fi s h (5 nests per redd), a nearest neighbor distance of 2 m would result in 97 non-overlapping redds. 13. . Estimates of area disturbed were obtained for the early part of the run by measuring "cleaned" areas in the channel. These estimates ranged between .8 m2 and 1.7 m2 with an average of 1.2 m2, and did not compare well with theoretical estimates. 14. Early models of the effects of superimposition u t i l i z e d Poisson or analagous distribution to describe superimposition rates. They did not consider effects of t e r r i t o r i a l behavior nor losses of potential spawning area resulting from inefficient packing of t e r r i t o r i e s . 15. Three packing models were considered which, on an instantaneous basis allowed for per cent u t i l i z a t i o n of between 60% (random) and 90% (hexagonal). 16. Simulation studies indicated that over a wide range of densities and temporal distribution, t e r r i t o r i a l models resulted in substantial increases in production over non-territorial models. The maximum effect of 50% increase occurred under conditions of constrained maturation times and medium to high densities (120% of the area theoretically in use). 17. Effects of pattern of maturation were d i f f i c u l t to generalize, but were most apparent when comparing wide distributions of maturation times, with normalized distributions. 18. Effect of nest locations within the redd were important relative 98 to the decline in size of the territory. Patterns which resulted in nests being unprotected at a faster rate allowed more nests to be superimposed. 19. Waiting time was found to vary as an increasing function of density. 20. Comparing possible methods of t e r r i t o r i a l defence, i t was deter-mined that maintaining a protected area which would encompass the nests u n t i l death was least desirable. Rather, by reducing territory size to allow additional f i s h to spawn nearby afforded a substantial degree of protection. 21. A case study of the Babine Channel suggested that optimum densities of females ranged between 34,000 and 60,000 females depending upon estimates of fry to adult survival. 99 DISCUSSION AND RECOMMENDATIONS Salmonids spawn in environments characterized by va r i a b i l i t y . Streams which during spawning provide only enough flow to allow f i s h to remain upright can change into torrential rivers during the time in which the eggs are in the gravel. It is not surprising therefore that salmonids can and w i l l spawn in what appears to be a wide range of conditions. However, i t i s clear from the preceding studies that even though the i n i t i a l range of conditions may be diverse, the physical and behavioral attributes of spawning fi s h provide the means by which original substrates are altered to produce a uniform environment for the incubation of eggs. Maximum size of spawning gravel for fis h of a given size was determined primarily by the force of the vortex created by movement of the t a i l , not by the velocity of the water flowing over the gravel. This was particularly true during later stages of nest preparation when the velocity within the nest was reduced. Minimum size was likewise determined by the in a b i l i t y of the fis h to create the right form of depression. For example, excavations in sand would not remain stable in a flowing stream, and would not provide the appropriate cue to allow for deposition. Thus, the interaction of the cohesive properties of gravel mixtures combined with the physical attributes of the spawning female together defined limits of acceptable spawning gravel. The study also indicated the means by which the female obtained cues regarding the s u i t a b i l i t y of the nest site and provided 100 information to the male which enabled synchronization of release of sexual products. Probing was most important in this respect since intensity increased as spawning approached, angle of the probe increased as the depression became deeper, and the responsive-ness of the male increased as a function of probing intensity. Actual synchronization of spawning resulted from the female remaining in a crouched position at the end of a probe and allowing the male to assume a similar position beside her. While many details of spawning behavior varied between species, the major components of the process would appear general among salmonids. Probing, quivering, digging and crossing are the most important behaviours, although other less frequently observed patterns may also be of importance. The interaction of the spawner with i t s environment was also well demonstrated in that the deposition of eggs could be accelerated by the excavation of a nest site. Thus salmonids are quite flexible in terms of the pattern of behaviour required to allow successful deposition of eggs. The implications of these' results are quite clear in terms of design of gravel and flow characteristics of spawning channels, namely that from the point of view of satisfying adult requirements, tolerances can be quite large. However, i f specifications are to be designed to optimize egg survival and alevin condition factors, then the standard method of incubating eggs in a variety of flow gravel combinations is inappropriate. Rather, the micro environment produced by females digging in various substrates must be considered to be of primary importance. 101 F i n a l l y , i n assessing the amount of spawning gravel a v a i l a b l e i n any p a r t i c u l a r stream, i t i s important to describe the variance i n the. d i s t r i b u t i o n of p a r t i c l e s i n various sections of the reach. There i s a tendency f o r the t o t a l area i n which f i s h are observed to spawn to be described as s u i t a b l e f o r spawning, any deviations from what could be considered as maximum density, a t t r i -buted to underescapement. While t h i s i s undoubtedly true i n some cases, one should also consider that many of these areas are simply unsuitable f o r spawning, even i f the average c h a r a c t e r i s t i c s of the spawning gravel f a l l within s u i t a b l e tolerances. By comparison with d e f i n i t i o n of s u i t a b l e spawning g r a v e l , estimation of optimal d e n s i t i e s was found to be a complex problem, r e q u i r i n g estimates of several parameters. These included redd s i z e , fecundity, female s i z e , area a v a i l a b l e , d i s t r i b u t i o n of maturation, t e r r i t o r y s i z e , residence time, density independent s u r v i v a l i n the grav e l , and f r y to adult s u r v i v a l i n lakes and oceans ( f o r sockeye). It was also c l e a r that r e l i a b l e estimates of seve r a l of these parameters are d i f f i c u l t to obtain. The system was found to be p a r t i c u l a r l y s e n s i t i v e to redd s i z e i n that there was a d i r e c t l i n e a r r e l a t i o n s h i p between redd s i z e and production. I d e n t i f i c a t i o n of changes i n redd s i z e a r i s i n g from the presence of neighbouring f i s h would appear to be a f r u i t f u l avenue f o r fu r t h e r research, since t h i s f a c t o r i s l i k e l y responsible f o r discrepancies i n ca l c u l a t e d and measured values. In p a r t i c u l a r , i t i s possible that high d e n s i t i e s may r e s u l t i n females digging up t h e i r own eggs, a p o s s i b i l i t y not considered i n 102 the present model. Suggested studies would include a d e t a i l e d monitoring of i n d i v i d u a l females under various d e n s i t i e s i n order to accurately determine redd s i z e , and i n a d d i t i o n to determine the e f f e c t of v e l o c i t y on l e v e l s of aggressive behavior among females. Another shortcoming of the model r e l a t e s to the assumption t h a t . t e r r i t o r i a l defence i s the only mechanism responsible f o r the d i s t r i b u t i o n of females i n the spawning area. In f a c t , as was in d i c a t e d i n the spawning behavior s t u d i e s , upwelling flow patterns do provide a mechanism by which females would avoid superimposition of n ests, independent of any t e r r i t o r i a l e f f e c t s . This would serve to diminish the importance of v a r i a t i o n i n temporal d i s t r i b u t i o n s , but o v e r a l l would not l i k e l y have a major e f f e c t on production. A more important area of research would r e l a t e to the e f f e c t s of waiting time on deposition success and egg v i a b i l i t y , since i n species l i k e sockeye which have a l a r g e r variance maturation time, the r e s u l t s of superimposition combined with high d e n s i t i e s and decreased v i a b i l i t y of l a t e eggs could be dramatic. Another area r e q u i r i n g c l a r i f i c a t i o n r e l a t e s to the r e l a t i o n s h i p between t e r r i t o r y s i z e , density and variance i n temporal d i s t r i b u t i o n . For example, s u r v i v a l s recorded f o r chum spawning channels can be i n excess of 80 per cent, while those f o r sockeye channels at Babine Lake are nearer to 40 per cent. Chum populations are characterized by a short temporal d i s t r i b u t i o n with most of the f i s h spawning i n a given s e c t i o n within 10 - 15 days. Furthermore, i t was apparent that chum tended to pack c l o s e r 103 together, despite the fact that they are the same size or larger than sockeye. The situation is possibly similar to that described by Van Den Assem (1967) in which differences in territory size were apparent for groups of sticklebacks which "settled" either simultaneously or successively. Thus, there may be benefits from selecting groups of f i s h which a l l mature at approximately the same time, particularly i f there is a waiting time effect on egg v i a b i l i t y . Finally, i t is clear that further work must be undertaken to separate mortality related to density dependent effects from those related to gravel quality. It is recognized that .spawning channels double as effective settling basins for sediment, which may produce variable effects from year to year. Assessment of the baseline carrying capacity of the gravel, and i t s v a r i a b i l i t y from year to year, is also an essential but inactive area of research. 104 Sheridan, W: L. 1960. Frequency of digging movements of female pink salmon before and a f t e r egg deposition. Anim. Behaviour 8:3-4, July-October, 1960. Tautz, A. F., P. A. Larkin and W. E. Ricker, 1969. Some e f f e c t s of simulated long-term environmental f l u c t u a t i o n s on maximum sustained y i e l d . J. F i s h . Res. Bd. Canada 26:2715-2726. Thomas, A. E. 1975. E f f e c t of egg concentration i n an incubation channel on s u r v i v a l of chinook salmon f r y . Trans. Amer. F i s h . S o c , 1975, No. 2, p. 335-337. Van Den Assem, J. 1967. T e r r i t o r y i n the three-spined s t i c k l e b a c k Gastevosteus aculeatus L. An experimental study i n i n t e r - s p e c i f i c competition. Leiden, E. J . B r i l l , E d i t o r . White, H. C. 1942. A t l a n t i c salmon redds and a r t i f i c i a l spawning beds. J. F i s h . Res. Bd. Canada 6(l):37-44. Whithler, F. C. 1950. Egg Content of Babine Sockeye. F i s h . Res. Bd. Canada, P a c i f i c Prog. Rept. No. 74, p. 9-12. 105 LITERATURE CITED Breder, CM. Jr., and D.E. Rosen 1966. Modes of reproduction in fishes. Published for American Museum of Natural History by the Natural History Press, Garden City, N.Y. Burner, C.J. 1951. Characteristics of spawning nests of Columbia River salmon. Fish. Bull. 61, U.S. Fish and Wildlife Serv. Vol. 52:97-110. Hartman, G.F. , T.G. Northcote and CC. Lindsey 1962. Comparison of inlet and outlet spawning runs of rainbow trout in Loon Lake, Bri t i s h Columbia. J. Fish. Res. Bd. Canada, 19(2): 173-200. Hartman, G.F. 1969. Reproductive biology of the Gerrard stock rainbow trout. In_ T.G. Northcote [Ed.] Symposium on salmon and trout in streams, H.R. MacMillan Lectures in Fisheries, Univ. of Brit. Col. 388 p. Jones, J.W. and J.H. Ball 1954. The spawning behavior of brown trout and salmon. Brit. Jour. Anim. Behaviour, 2:103-114. Jones, J.W. 1959. The Salmon. Willmer Bros, and Hanem Ltd., London, 190 p. Leggett, J.W. 1969. The reproductive biology of the Dolly Varden char (Salvelinus malma) Walbaum. MSc. Thesis, Univ. of Vict. 110 p. McCart, P. 1969. Digging behaviour of Oncovhynchus nerka spawning in streams at Babine Lake, British Columbia. In T.G. Northcote [Ed.] Symposium on salmon and trout in streams, H.R. MacMillan Lectures in Fisheries, Univ. of Brit. Col. 388 p. Mathisen, O.A. MS, 1955. Studies on the spawning biology of the red salmon, Oncovhynchus nerka, in Bri s t o l Bay, Alaska, with special reference to the effect of sex ratios, Ph.D. Thesis. Univ. of Washington, 1955, 285 p. McNeil, W.J. 1964. Redd superimposition and egg capacity of pink salmon spawning beds. J. Fish. Res. Bd. Canada, 21(6): 1385-1396. Ricker, W.E. 1958. Maximum yields from fluctuating environments and mixed stocks. J. Fish. Res. Bd. Canada, 15:991-1006. Ricker, W.E., and H.D. Smith 1975. A revised interpretation of the history of the Skeena River sockeye salmon (Oncovhynchus nevka). J. Fish. Res. Bd. Canada, 32:1369-1381. 

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