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Locomotor responses of juvenile and adult sockeye salmon (Oncorhynchus nerka) to acute changes in temperature… Tolson, Graeme M. 1988

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LOCOMOTOR RESPONSES OF JUVENILE AND ADULT SOCKEYE SALMON (ONCORHYNCHUS NERKA) TO ACUTE CHANGES IN TEMPERATURE AND SALINITY. By GRAEME M. TOLSON B.Sc, The University of V i c t o r i a , 1985 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s thesis as conforming to the required standards THE UNIVERSITY OF BRITISH COLUMBIA May, 1988 ® GRAEME M. TOLSON, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British 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 or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT The locomotor responses of juvenile and adult sockeye salmon (Oncorhynchus nerka) to concurrent changes i n temperature and s a l i n i t y were examined i n a controlled laboratory setting. I hoped to better understand how these environmental factors influence the coastal movements of migrating salmon. Juvenile sockeye were captured during the downstream migration from Great Central Lake on Vancouver Island, B r i t i s h Columbia, Canada. The f i s h were acclimated for 1 wk at 10°C, 20 ppt, and then tested i n annular a c t i v i t y tanks. Spontaneous locomotor movements were recorded during concomitant changes i n temperature and s a l i n i t y using inf r a - r e d photometry. Raising the water temperature by 4°C i n 1 h caused a dramatic increase i n locomotor a c t i v i t y . Decreasing temperature by 4°C or varying s a l i n i t y by 10 ppt from the control l e v e l s did not influence routine swimming speed and there was no i n t e r a c t i o n between factors. Adult sockeye homing to the Fraser River, B r i t i s h Columbia, Canada were captured along the nearshore migration route i n two oceanographically d i s t i n c t regions. Three groups of f i s h were c o l l e c t e d from the cold, saline waters of Queen Charlotte S t r a i t , near the northern end of Vancouver Island. Two groups of sockeye were captured within 60 km of the Fraser River i n the warmer, less saline waters of the S t r a i t of Georgia. The adults were acclimated 2 - 5 days at 12°C, 30 ppt and locomotor a c t i v i t y was tested i n annular a c t i v i t y tanks. Routine swimming speed and turning rate rose when the water temperature was raised by 4°C i n 2 h, however, locomotor a c t i v i t y was not influenced by decreasing temperature. In addition, decreasing s a l i n i t y by 10 ppt i n 2 h had no e f f e c t on swimming a c t i v i t y of adult sockeye and there was no i n t e r a c t i o n between the two factors. Fish taken from the S t r a i t of Georgia generally showed a less dramatic response to increasing temperature than adults captured i n Queen Charlotte S t r a i t . Results indicate that warm coastal temperatures may influence the nearshore migration of both juvenile and adult sockeye salmon. i v TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS . i v LIST OF TABLES v i LIST OF FIGURES ix ACKNOWLEDGEMENTS. . . x i INTRODUCTION 1 LITERATURE REVIEW 5 I. THE LIFE HISTORY OF PACIFIC SALMON 5 A. ENVIRONMENTAL INFLUENCE ON THE BEHAVIOR OF YOUNG SALMON 5 B. JUVENILE MIGRATION 7 (i) LACUSTRINE AND RIVERINE MOVEMENTS... 7 ( i i ) ESTUARINE MOVEMENTS 8 C. OCEAN RESIDENCE OF SALMON 10 D. HOMING MIGRATION 11 (i) OPEN OCEAN MOVEMENTS 11 ( i i ) COASTAL AND RIVERINE MOVEMENTS 13 II. INFLUENCE OF TEMPERATURE AND SALINITY ON METABOLISM AND BEHAVIOR 14 MATERIALS AND METHODS 20 I. JUVENILE EXPERIMENTS 20 A. FISH COLLECTION 20 B. HOLDING CONDITIONS 23 V Page C. EXPERIMENTAL APPARATUS 24 D. DATA COLLECTION 27 E. EXPERIMENTAL PROCEDURE 30 F. TEST CONDITIONS AND STATISTICAL ANALYSIS. 31 II. ADULT EXPERIMENTS 3 5 A. FISH COLLECTION 36 B. HOLDING CONDITIONS 38 C EXPERIMENTAL APPARATUS AND DATA COLLECTION 38 D. EXPERIMENTAL PROCEDURE 43 E. TEST CONDITIONS AND STATISTICAL ANALYSIS. 44 RESULTS 47 I. JUVENILE EXPERIMENTS 47 II. ADULT EXPERIMENTS 62 DISCUSSION 88 LITERATURE CITED 101 v i LIST OF TABLES Page Table 1. Combinations of water sources used to produce test conditions i n the juvenile sockeye a c t i v i t y experiments 28 Table 2. Contributions of sockeye from four Fraser River races to the adult a c t i v i t y tank experiments. Location, date of capture, and t o t a l s from each set are included for male and female f i s h 37 Table 3. Combinations of water sources used to produce test conditions i n the adult sockeye a c t i v i t y experiments 42 Table 4. The number of passes through photo-cell stations recorded for juvenile sockeye during 30 minutes exposure to control conditions 48 Table 5. The average swimming speed of juvenile sockeye salmon exposed for 30 minutes to control conditions i n morning or afternoon tests 48 Table 6. The mean swimming speeds of juvenile sockeye salmon during the f i n a l 60 minutes exposure to test levels 52 Table 7. Results of the two factor ANOVA comparing the mean swimming speeds of juvenile sockeye salmon subjected to experimental conditions for 60 minutes 52 Table 8. The mean swimming speeds of juvenile sockeye salmon during 60 minutes exposure to water of 14 C and 20 ppt 54 Table 9. Mean swimming speeds of juvenile sockeye salmon calculated at 30 minute int e r v a l s during exposure to control conditions, water turnover, test levels 61 Table 10. The number of passes through photo-cell stations recorded for adult sockeye during 60 minutes' exposure to control conditions 63 v i i Page Table 11. The average swimming speed of adult sockeye salmon exposed for 30 minutes to control conditions i n morning or afternoon tests 63 Table 12. The average swimming speed of four races of adult Fraser River sockeye 64 Table 13. The mean swimming speeds of male and female sockeye salmon subjected to control conditions for 30 minutes 64 Table 14. The mean swimming speeds of adult sockeye salmon during the f i n a l 60 minutes' exposure to test conditions 68 Table 15. Results of the two factor ANOVA comparing the mean swimming speeds of adult sockeye salmon subjected to test conditions for 60 minutes 68 Table 16. The average swimming speeds of adult sockeye salmon subjected to 16 C, 20 ppt or 16 , 30 ppt during the f i n a l hour of test i n g 70 Table 17. The mean swimming speeds of adult sockeye during the f i n a l hour of exposure to 16 C water 70 Table 18. Mean swimming speeds of adult sockeye calculated over 30 minute in t e r v a l s i n control conditions, water turnover, and at test l e v e l s 78 Table 19. Average swimming speeds of adult sockeye salmon calculated over 30 minute i n t e r v a l s i n control conditions, water turnover, and at 16 C for salmon from northern and southern areas 81 Table 20. A c t i v i t y of adult sockeye salmon during exposure to control temperature and control s a l i n i t y 83 v i i i Page Table 21. A c t i v i t y of adult sockeye salmon during exposure to decreasing temperature and control s a l i n i t y 84 Table 22. A c t i v i t y of adult sockeye salmon during exposure to control temperature and decreasing s a l i n i t y 85 Table 23. A c t i v i t y of adult sockeye salmon during exposure to increasing temperature and control s a l i n i t y 86 Table 24. The mean swimming speeds, locomotor a c t i v i t y and turning rate of adult sockeye salmon during exposure to 16 C and 30 ppt... 87 ix LIST OF FIGURES Page Figure 1. Locations where juvenile and adult sockeye were c o l l e c t e d for locomotor a c t i v i t y experiments 22 Figure 2. Top and side views of a c t i v i t y tank used to measure locomotor responses of juvenile sockeye salmon to rapid changes i n temperature and s a l i n i t y 26 Figure 3- Experimental apparatus used to measure locomotor responses of adult sockeye to rapid changes i n temperature and s a l i n i t y . . . 40 Figure 4. Average swimming speeds of juvenile sockeye salmon during the f i n a l 60 minutes exposure to test l e v e l s 50 Figure 5. Mean swimming speeds of juvgnile sockeye salmon during exposure to 6 C, 10 ppt; 6°C, 20 ppt; and 6°C, 30 ppt 56 Figure 6. Mean swimming speeds of juvenile sockeye salmon during exposure to 10 C, 10 ppt; 10°C, 20 ppt; and 10°C, 30 ppt 58 Figure 7. Mean swimming speeds of juvenile sockeye salmon during exposure to 14 C, 10 ppt; 14°C, 20 ppt; and 14°C, 30 ppt 60 Figure 8. Average swimming speeds of adult sockeye salmon during the f i n a l 60 minutes exposure to test l e v e l s 67 Figure 9. Mean swimming speeds of adult sockeye salmon during exposure to 8 C, 20 ppt and 8°C, 30 ppt 72 Figure 10. Average swimming speeds of agult sockeye salmon during exposure to 12 C, 20 ppt and 12°C, 30 ppt 74 X Page Figure 11. Mean swimming speeds of adult sockeye salmon during exposure to 16 C, 20 ppt and 16°C, 30 ppt 76 Figure 12. Mean swimming speeds of adult sockeye salmon during exposure to 16 C pooled for f i s h taken from northern and southern sets 80 x i ACKNOWLEDGEMENTS I would l i k e thank Mr. H. Jagger, Mr. G. Wasden, and the crews of the NAFCO and the Cape Canso for t h e i r help i n capturing the adult salmon. I g r a t e f u l l y acknowledge the assistance of Dr. D. Randall, and Dr. L. Mysak for t h e i r help and support of my research. I express warmest thanks to Dr. C. Groot and Dr. T. Quinn, who have provided me with guidance, understanding, and encouragement i n my years as an undergraduate and a graduate student. This research was funded by the Department of Fisheries and Oceans, and by NSERC Strategic Grant G-1485 awarded to L. Mysak, K. Hamilton, and C. Groot. -1-INTRODUCTION The coastal migration i s an important phase i n the l i f e h i s t o r y of anadromous P a c i f i c salmon (Oncorhynchus sp.). Temperature and s a l i n i t y gradients have been proposed to influence the nearshore movements of both juvenile and adult salmon (Baggerman 1960a, Mclnerney 1964, Hurley and Woodall 1968, T u l l y et a l . 1960). However, i t has also been hypothesized that other factors such as t i d a l currents or odor cues exert a greater influence on migration (LaBar et a l . 1979, Stabell 1982). At present, the ways i n which oceanographic conditions a f f e c t the migratory behavior of salmon i s poorly understood (Groot and Quinn 1987). This thesis examined the locomotor responses of juvenile and adult sockeye salmon to acute changes i n temperature and s a l i n i t y . Both of these factors may play a role i n the coastal movements of migrating salmon. With respect to the juvenile migration, Mclnerney (1964) suggested that temporal changes i n s a l i n i t y preference could regulate the seaward migration of young salmon through estuaries. Experiments i n v e r t i c a l gradient tanks led Hurley and Woodall (1968) to conclude that time-varied changes i n preference for temperature and s a l i n i t y d i r e c t juvenile pink salmon (0. gorbuscha) during the outmigration. Si m i l a r l y , Straty and Jaenicke (1980) found that sockeye smolts oriented to s a l i n i t y and temperature gradients while -2-in nearshore waters- Quinn and Groot (1983) concluded that compass orientation and preference for saline water could d i r e c t juvenile chum salmon (0. keta) during the feeding migration. Several researchers have questioned the role of temperature and s a l i n i t y on juvenile salmon migration (e.g. Fried et a l . 1978). LaBar et a l . (1979) concluded that migration patterns of A t l a n t i c salmon smolts were not affected by any environmental variables other than water current. S i m i l a r l y , McCleave (1978) attributed the estuarine movements of juvenile A t l a n t i c salmon to passive d r i f t , dependent on t i d a l flow. Studies r e l a t i n g the return migration of adult salmon to oceanographic variables are often based on s t a t i s t i c a l correlations using f i s h e r i e s catch records (reviewed by Leggett 1977). One of the more recent studies examined the homing migration of sockeye salmon (0. nerka) to the Fraser River, B r i t i s h Columbia (Groot and Quinn 1987). Each year, between 2 and 20 m i l l i o n sockeye salmon return to the Fraser River (IPSFC 1954-1984). Access to the r i v e r i s by one of two possible routes. H i s t o r i c a l l y , the majority of migrants approached the Fraser River from the southern end of Vancouver Island (southern route). The f i s h adopting t h i s route approach south and then east through Juan de Fuca S t r a i t before turning north to the Fraser River -3-(Groot and Quinn 1987). The remainder of the sockeye would return between the northern t i p of Vancouver Island and the mainland coast (northern route) and approach the r i v e r south through Johnstone S t r a i t (Groot and Quinn 1987). Since 1977, greater proportions of returning sockeye have used the northern route than had previously done so (Mysak et a l . 1986, Hamilton 1985). A number of hypotheses have been proposed to explain the interannual v a r i a b i l i t y i n diversions through the northern passage (known as the Johnstone S t r a i t Diversion). T u l l y et a l . (1960) and Royal and T u l l y (1961) suggested that the r e l a t i v e l y high JSD of 1958 (35%) could have been a resu l t of warm water intrusions from the south d e f l e c t i n g migrants farther north so that they migrated through Johnstone S t r a i t . Favorite (1961), on the other hand, hypothesized that Fraser River water emanating north through Johnstone S t r a i t could act as an attractant to returning adults (see also Wickett 1977). Groot and Quinn (1987) showed that from 1953 to 1977 Fraser River discharge was s i g n i f i c a n t l y correlated with sockeye returns through Johnstone S t r a i t , however, since 1977 the re l a t i o n s h i p has broken down. Groot and Quinn (1987) concluded that temperature and s a l i n i t y gradients around the northern t i p of Vancouver Island do not guide the movements of Fraser River sockeye but r e f l e c t ocean conditions that may d i r e c t l y influence behavior during the homing migration ( i . e . -4-preference/avoidance responses) or i n d i r e c t l y , p r i o r to the migration, by a f f e c t i n g food supply. The locomotor responses of migrating sockeye salmon to concurrent changes i n temperature and s a l i n i t y have not been analyzed i n the laboratory. Few experiments have focussed on the e f f e c t s of temperature and s a l i n i t y corresponding to actual conditions that may be encountered i n coastal waters. In addition, i t i s not known how responses to temperature and s a l i n i t y f i t into the general scheme of f i s h migratory mechanisms (e.g. N e i l l 1979, 1984). In t h i s study, I examined the swimming a c t i v i t y of migrating sockeye salmon during concomitant changes i n temperature and s a l i n i t y , within a range that could be encountered i n nearshore waters. The hypothesis I tested was that rapid changes i n temperature and s a l i n i t y have a d i r e c t e f f e c t on locomotor behavior and could thereby influence coastal migration patterns of juvenile and adult sockeye. -5-LITERATURE REVIEW This review w i l l consist of two sections. F i r s t , I w i l l discuss the general l i f e h i s t o r y of P a c i f i c salmon, stressing the influence of environmental factors on migratory behavior. The second section w i l l review the physiological and behavioral responses of migratory f i s h to temperature and s a l i n i t y , including relationships to season and stage of maturation. 1. THE LIFE HISTORY OF PACIFIC SALMON P a c i f i c salmon t y p i c a l l y migrate from freshwater lakes and r i v e r s to oceanic waters, and, after one to seven years, return to spawn and die i n the natal stream. The dramatic environmental changes that salmon encounter require appropriate ph y s i o l o g i c a l and behavioral adaptations. In addition, d i r e c t i o n a l information gained from environmental cues may also guide migratory movements. A. ENVIRONMENTAL INFLUENCE ON THE BEHAVIOR OF YOUNG SALMON The' environment affects the behavior of P a c i f i c salmon soon aft e r the egg has hatched. The f i r s t response of newly emerged salmon i s to wriggle down beneath rocks and gravel (Bams 1969); probably as a reaction to l i g h t (Hoar -6-1955, 1958, Heard 1964). In addition, developing alevins exhibit a 'righting response' that p e r s i s t s through yolk absorption ( D i l l 1982). Hoar (1958) showed that oriented responses to environmental cues lead populations of salmon fry to t h e i r respective rearing areas. However, the early behavior of fry shows marked i n t e r s p e c i f i c and interpopulation differences (Hoar 1958, Brannon 1972) implying genetic control (Raleigh 1971). Pink salmon f r y begin the seaward migration soon afte r yolk absorption (Hoar 1956), and downstream movements re s u l t from a negative rheotaxis i n response to low l i g h t i n t e n s i t y (McDonald 1960). Chum f r y also begin the downstream migration within a few weeks of emergence and r i v e r i n e movements may depend on negative rheotaxis i n response to high water temperature (Keenleyside and Hoar 1953). In addition, a re l a t i o n s h i p may exi s t between compass orientation and rheotactic behavior. Quinn and Groot (1984) showed that chum f r y exhibited unimodal compass orienta t i o n i n high water flow, and bimodal d i r e c t i o n a l tendencies i n low flow. Coho (O. kisutch) f r y remain i n r i v e r systems for approximately 18 to 30 months, during which time d i s t r i b u t i o n i s a function of s o c i a l interactions (Hoar 1958) and rearing channel temperature (Glova 1986). Chinook (0. tshawytscha) may proceed d i r e c t l y to the estuary, or spend up to a year i n the homestream (Reimers 1973, Healey 1980, 1982). Sockeye salmon generally spend the f i r s t year or two of l i f e i n freshwater lakes. The migration to these rearing areas i s probably aided by orientation to odors and water flow (Brannon 1972). V e r t i c a l d i s t r i b u t i o n of sockeye during lake residence appears to be dependent on metabolic responses to temperature i n r e l a t i o n to food a v a i l a b i l i t y (Brett 1971). B. JUVENILE MIGRATION (i) LACUSTRINE AND RIVERINE MOVEMENTS Prior to the downstream migration, salmon undergo a number of morphological, ph y s i o l o g i c a l and behavioral changes that are r e q u i s i t e for an ocean existence. These processes have been c o l l e c t i v e l y termed s m o l t i f i c a t i o n (reviewed by Hoar 1976, Folmar and Dickoff 1980, Wedemeyer et a l . 1980). The smolting process i s p a r t i a l l y under endogenous control and regulated by the neuroendocrine system. In addition, the process appears to be synchronized both by photoperiod (Hoar 1976) and temperature (Clarke and Shelbourn 1985). In p a r t i c u l a r , seasonal fluctuations i n water temperature appear to be important for i n i t i a t i n g the downstream migration (Foerster 1937, 1968, Brett 1983, Rogers 1980). Jonsson and Ruud-Hansen (1985) suggested that temperature changes i n r e l a t i o n to acclimation temperature -8-are important for the development of a migratory d i s p o s i t i o n i n young salmon. The migration of juvenile sockeye salmon out of lake systems appears to be directed by solar and magnetic factors. Groot (1965) found that sockeye smolts exhibit time-varied d i r e c t i o n a l preferences involving c e l e s t i a l orientation (see also Quinn and Brannon 1982), r e s u l t i n g i n an active, well oriented migration out of the lake rearing areas (Groot and Wiley 1965, Groot 1972). Riverine movements of juvenile salmon may be f a c i l i t a t e d by compass orientation (Healey 1967, Quinn and Groot 1983), while passive responses to current may also play a role i n downstream movements, es p e c i a l l y i n the lower reaches of the r i v e r (Fried et a l . 1978, Thorpe et a l . 1981). MacDonald (1960) proposed that decreasing l i g h t levels are important for maintaining negative rheotaxis during the downstream migration (see also Hoar 1958). In addition, temperature may influence migratory behavior i n conjunction with other environmental factors such as water flow (White 1939), climate (Solomon 1978), and lunar cycle (Grau 1982). ( i i ) ESTUARINE MOVEMENTS The environmental conditions encountered i n the r i v e r estuary impose s i g n i f i c a n t p hysiological stress on migrating salmon (Healey 1982, Simenstad et a l . 1982). Exposure of pink and chum f r y to high s a l i n i t y water results i n a t r a n s i t o r y decrease i n swimming a c t i v i t y (Houston 1957) that may i n h i b i t predator avoidance (Houston 1959). The timing of the downstream migration corresponds to high b i o l o g i c a l productivity i n the n e r i t i c zone (Simenstad 1982), however, the f i r s t few weeks i n saltwater probably account for a large proportion of the o v e r a l l salmon mortality (Brett 1983). Estuaries serve several roles for young salmon, and the duration of coastal residence shows marked i n t e r s p e c i f i c differences. Sockeye and chum salmon move s w i f t l y through nearshore areas (Brett 1983, Quinn and Groot 1983), while chinook and pink salmon may inhabit coastal waters for a number of months (Healey 1980, Hurley and Woodall 1968). Progressive changes i n preference for colder temperatures and more saline waters has been c i t e d as a p o t e n t i a l orientation mechanism for migrating smolts (Hurley and Woodall 1968, Mclnerney 1964, Baggerman 1960b). However, i t appears that other environmental factors may be of greater importance for the coastal migration of some salmonid species. Tracking studies of A t l a n t i c salmon (Salmo salar) smolts through estuaries have shown that current plays a major role i n seaward movements (Labar et a l . 1979). Eriksson (1984) found that juvenile A t l a n t i c salmon exhibited negative rheotaxis i n fresh and brackish water, -10-however, migratory behavior was influenced mainly by water current. C. OCEAN RESIDENCE OF MATURING SALMON The coastal migration of young P a c i f i c salmon has been reviewed by Hartt and Dell (1986), while the offshore d i s t r i b u t i o n of maturing sockeye salmon i n the northeast P a c i f i c has been reviewed by French et a l . (1976). Favorite - and Hanavan (1956) noted that sea surface conditions did not s i g n i f i c a n t l y a f f e c t oceanic d i s t r i b u t i o n of salmon, however, s p e c i f i c water masses seemed to delimit t h e i r range i n both a southerly and northerly d i r e c t i o n . Favorite et a l . (1976) suggested that sockeye salmon d i s t r i b u t i o n was bounded by i d e n t i f i a b l e water masses- the Subarctic Boundary i n the north, and the Tr a n s i t i o n a l Domain i n the south. During ocean residence, seasonal changes i n environmental parameters may a f f e c t the d i s t r i b u t i o n of maturing salmon. Royce et a l . (1968) suggested that currents i n the ocean (in p a r t i c u l a r the Alaskan gyre) were responsible for seasonal variations i n the d i s t r i b u t i o n of B r i s t o l Bay sockeye. Burgner (1980) concluded that salmon rearing areas were primarily determined by genetic factors. However, French and Bakkala (1974) found that both temperature and food supply were important i n determining movements and d i s t r i b u t i o n of maturing sockeye. This view was endorsed by Leggett (1977) who suggested that ocean temperatures may af f e c t food a v a i l a b i l i t y and thus influence migratory patterns (see also McAlister 1969, Andrievskaya 1957, Ito 1964). Watanabe (1954) reported that high seas salmon f i s h i n g concentrated at areas bounded by cold northern surface waters, and warm water intrusions from the south. Horizontal gradients of temperature and s a l i n i t y , associated with upwelling, appeared to increase catch e f f i c i e n c y . Similar reports by Nakai and Honjo (1954) related increased salmon catches to areas of high primary production. D. HOMING MIGRATION (i) OPEN OCEAN MOVEMENTS A number of hypotheses have been proposed to explain the homing migration of salmon. Leggett (1977) concluded that salmon may gain d i r e c t i o n a l information from polarized l i g h t , sun, or geomagnetic cues. Hasler (1971) proposed the use of a sun-compass mechanisms during the open-sea migration. Quinn (1984) suggested that salmon may have a bicoordinate map that permits navigation using the sun or magnetic f i e l d s . S a i l a and Shappy (1963) developed a computer model that depicted the homeward migration of P a c i f i c salmon as a random walk accompanied with a s l i g h t d i r e c t i o n a l bias. The -12-authors concluded that well-oriented behavior was not a prerequisite for successful homing. This model was c r i t i c i z e d by Quinn and Groot (1984) who showed that many of the model's assumptions were inaccurate. Quinn and Groot (1984) showed that at the optimum cr u i s i n g speed and observed rate of t r a v e l , salmon must migrate with a high degree of orientation to be consistent with known level s of homing success. Patten (1964) concluded that appropriate 'low-level' behavioral responses to environmental gradients would allow salmon to home with s u f f i c i e n t accuracy. Balchen (1976) extended t h i s view and concluded that migration re s u l t s from a constant attempt to maintain an optimal ph y s i o l o g i c a l state and responses to environmental conditions based on stage of maturation ultimately determine the expression of migratory behavior (see also N e i l l 1979, 1984). Leggett (1977) endorsed the 'optimisation of comfort' hypothesis, but stressed that additional research i s required before applying i t to open-sea migrations. Quinn and Groot (1984) emphasized that any migration mechanism must account for known rates of t r a v e l i n r e l a t i o n to the optimum swimming speeds and the r e l a t i v e l y weak gradients of temperature and s a l i n i t y i n the sea. -13-( i i ) COASTAL AND RIVERINE MOVEMENTS The return migration through nearshore waters once again provides salmon with a wide variety of p o t e n t i a l orientation cues (Quinn and terHart 1987). Hasler and Scholz (1983) showed that homestream odors provide the major d i r e c t i o n a l stimulus during the spawning migration. However, the chemical nature of these odors and the extent of t h e i r influence on movements through coastal waters i s unknown. Stabell (1982) extended the scope of Nordeng's (1977) pheromone hypothesis by suggesting the entire return migration of A t l a n t i c salmon was dependent on orientation to population-specific odors released by migrating juveniles. Evidence indicates that P a c i f i c salmon can i d e n t i f y population-specific odors (Quinn and Tolson 1986, Groot et a l . 1986), however, t h e i r role i n migration remains uncertain. Recent work has shown that environmental gradients may be important for locating odors during the homestream approach. Doving et a l . (1985) proposed that adult A t l a n t i c salmon attempt to gain d i r e c t i o n a l cues by concentrating a c t i v i t y around steep gradients of temperature and s a l i n i t y -the most l i k e l y location for obtaining chemical cues. Quinn and terHart (1987) concluded that the preference of Fraser River sockeye salmon for s t r a t i f i e d depths was a pote n t i a l mechanism for odor location, however, the responses of f i s h -14-to t i d e and horizontal environmental gradients were not e a s i l y characterized. The return migration terminates i n the natal stream, where P a c i f i c salmon spawn and subsequently die. During the spawning migration, d i r e c t i o n a l information i s gained primarily from homestream odors (reviewed by Hasler and Scholz 1983). Other environmental stimuli that control d i f f e r e n t stages of the upstream migration include; waterflow, temperature, photoperiod, and t i d a l action (Gilhousen 1960, Weaver 1963, Banks 1969). The t i g h t energy budget imposed on some migrating salmon (Idler and Clemens 1959), necessitates accurate homing with minimal metabolic cost. Methods to reduce energy expenditure include an a b i l i t y to d i s t i n g u i s h between minor variations i n water flow and choose routes that provide the greatest energetic e f f i c i e n c y (Brett 1983). II. INFLUENCE OF TEMPERATURE AND SALINITY ON METABOLISM AND BEHAVIOR Changes i n temperature and s a l i n i t y often have a dramatic influence on the metabolism and a c t i v i t y of f i s h (reviewed by Brett 1970) and species that undergo diadromous migrations naturally encounter steep gradients of both factors. Physiological stress imposed by the environment has been proposed to a f f e c t the d i s t r i b u t i o n of many f i s h species (reviewed by Leggett 1977). Therefore, i t i s -15-important to review some physiological p r i n c i p l e s of temperature and s a l i n i t y related to behavioral responses and possible influences on migration. Temperature influences the a c t i v i t y of poikilotherms by governing the rate of metabolism (e.g. Brett 1967, 1982). Within the thermal tolerance l i m i t s , f i s h operate within a zone of e f f i c i e n c y i n which i n t e r n a l metabolism accommodates a range of temperature (Crawshaw 1977). Outside of t h i s range, regulatory or compensatory processes are required (Brett 1970). Instances of physiological temperature regulation i n f i s h are rare and apparently li m i t e d to ce r t a i n scombrid species and lamnid sharks (e.g. Carey and Teal 1969, Carey et a l . 1971). In the vast majority of f i s h , responses to adverse temperature are dependent on behavioral thermoregulation (reviewed by Crawshaw 1977), and to a lesser extent, on phy s i o l o g i c a l compensation (Dizon et a l . 1978, reviewed by Hazel and Prosser 1974). Many studies have dealt with the concept of temperature preference and behavioral thermoregulation (see compilation by Coutant 197 7, reviewed by Reynolds and C a s t e r l i n 1979). Fish exposed to rapidly changing temperatures exhibit the least a c t i v i t y at the acclimation temperature (e.g. S u l l i v a n 1954, 011a and Studholm 1971). Ivlev (1960) showed that a c t i v i t y levels of young A t l a n t i c salmon were d i r e c t l y related to the absolute difference between preferred and experimental temperatures. Sim i l a r l y , -16-Peterson and Anderson (1969) found that A t l a n t i c salmon fry exhibited a rapid increase i n a c t i v i t y and oxygen consumption as temperatures departed from acclimation l e v e l s . In a rapid thermal s h i f t , f i s h show the least a c t i v i t y at the preferred temperature. If, however, f i s h are exposed to a gradual temperature change, and can eq u i l i b r a t e with the environment, then spontaneous a c t i v i t y i s greatest over a temperature range that permits the maximum metabolic scope (Fry 1971). In other words, f i s h placed i n a constant heterothermal environment sequentially select and adapt to temperatures that provide optimum physi o l o g i c a l benefits. The point where acclimation and selected temperatures meet represents the spe c i e s - s p e c i f i c f i n a l temperature preferendum (Fry 1971, Reynolds and C a s t e r l i n 1979). Fry (1971) described s a l i n i t y as a masking factor, e s s e n t i a l l y adding to the cost of metabolism through the need for regulation. Rao (1968) showed that the metabolic cost for r e s p i r a t i o n i n rainbow trout (S. gairdneri) increased 20% as s a l i n i t y rose from isosmotic (7.5 ppt) to 15 ppt. However, t o t a l metabolism only increased from 20% to 27% as s a l i n i t y was raised from 15 ppt to 30 ppt. Glova (1972) found that the sustained swimming speed of juvenile coho salmon was affected s l i g h t l y by s a l i n i t i e s ranging from 1 ppt to 20 ppt, but noted that tolerance to s a l i n i t y -17-decreased during s m o l t i f i c a t i o n • Brett (1970) reported that the metabolic rate of sockeye smolts decreased by 20 to 30% upon transfer from fresh to s a l t (28 ppt) water. Although oxygen consumption appears to be lowest at isosmotic concentrations (Farmer and Beamish 1969), selected temperatures may vary considerably with changes i n s a l i n i t y (Beamish 1970). In addition, Job (1959) and Hickman (1959) showed that routine metabolism may also be influenced by s a l i n i t y and thereby a f f e c t spontaneous a c t i v i t y . Early work showed that some f i s h can select very narrow temperature and s a l i n i t y ranges (e.g. Bul l 1938), introducing the p o s s i b i l i t y of a d i r e c t i v e influence (reviewed by Brett 1956, 1970). Recent studies have shown that s a l i n i t y gradients, i n concert with temperature, may provide l o c a l i z e d areas for migrating f i s h to obtain other d i r e c t i o n a l cues (Doving et a l . 1985, Quinn and terHart 1987). In addition, behavioral responses of f i s h to s a l i n i t y may often be dependent on physiological state and can be modified by other external and i n t e r n a l factors (reviewed by Holliday 1971, Woodhead 1975). Temperature and s a l i n i t y may d i r e c t f i s h behavior under the influence of i n t e r n a l drive or environmental stress'( H o l l i d a y 1971). For migratory f i s h , seasonal variations i n environmental stimuli have been shown to influence migrations, often associated with maturational changes (reviewed by Leggett 1977). Laboratory and f i e l d -18-investigations led Norris (1963) to conclude that seasonal temperature changes were d i r e c t l y responsible for the onshore movements of opaleye ( G i r e l l a nigerens). 011a et a l . (1985) tested locomotor responses of juvenile b l u e f i s h (Potatomus s a l t a t r i x ) to v e r t i c a l temperature gradients, and found a temporal s h i f t i n avoidance of cold water that coincided with the southerly f a l l migration. Nyman (1972) determined that yellow (immature) eels (Anguilla anguilla) were attracted to a r i s i n g temperature gradient, whereas s i l v e r (mature) eels were attracted and l a t e r repelled by the same temperature conditions (see also Westin and Nyman 1979). Westin and Nyman (1977) hypothesized that a seasonal change i n the behavioral response to temperature was the single factor that allowed s i l v e r eels to migrate back to the Sargasso Sea. Baggerman (1957, 1960a) noted the influence of maturational stage on the s a l i n i t y preference of sticklebacks (Gasterosteus aculeatus), but could not demonstrate a s i g n i f i c a n t change i n temperature preference. Other studies showed that gulf k i l l i f i s h (Fundulus grandis) exhibit a temporal change i n s a l i n i t y preference, modulated both by the neuroendocrine system ( F i v i z z a n i and Meier 1978) and by temperature ( M i l l e r et a l . 1983). The role of temperature and s a l i n i t y i n the coastal migration of salmon i s not well understood. Both factors could d i r e c t movements i n nearshore areas by influencing -19-preference/avoidance behavior (Straty and Jaenicke 1980, Hurley and Woodall 1968, T u l l y et a l . 1960, Royal and T u l l y 1961). A l t e r n a t i v e l y , migrations may be controlled by other environmental factors not related to nearshore temperature and s a l i n i t y gradients (Groot and Quinn 1987, McCleave 1978, LaBar et a l . 1976, T y t l e r et a l . 1978). In order to gain a better understanding on how environmental conditions influence the coastal migration, I tested the locomotor responses of adult and juvenile sockeye salmon to horizontal gradients of temperature and s a l i n i t y , within a range that could be encountered i n nearshore waters. -20-MATERIALS AND METHODS This study examined the spontaneous locomotor movements of juvenile and adult sockeye salmon during concurrent changes i n temperature and s a l i n i t y . A l l behavioral tests were conducted at the P a c i f i c B i o l o g i c a l Station, Nanaimo, B r i t i s h Columbia, between June 1 and September 20, 1986. I. JUVENILE EXPERIMENTS Sockeye smolts from Great Central Lake, B r i t i s h Columbia were used for the juvenile behavior experiments. This stock leaves the lake between early A p r i l and early June (Groot et a l . 1986). The f i s h migrate through the Stamp and Somass Rivers and into Alberni Inlet, where they encounter seawater for the f i r s t time (Figure 1). A. FISH COLLECTION On May 7, 1986, approximately 450 juvenile sockeye salmon were c o l l e c t e d from a small creek near the head of the Stamp River. The capture s i t e was a shallow area, located approximately 2 km from Great Central Lake (Figure 1). The sockeye were caught using a long-handled dip net and quickly placed i n two 40 1 transport tanks that had been -21-Figure 1. Coastal migration area of Great Central Lake and Fraser River sockeye salmon. Adults used i n a c t i v i t y experiments were c o l l e c t e d at three locations near the northern t i p of Vancouver Island (N-l - N-3), and from two areas near the Fraser River (S-l - S-2). Location where the juvenile sockeye were c o l l e c t e d i s shown i n r e l a t i o n to Alberni I n l e t . -23-f i l l e d with r i v e r water (11.7°C) and connected to a compressed a i r supply. Ice packs were p e r i o d i c a l l y added or removed during transport to maintain the container water temperature at 10°C (+/- 0.5°C). B. HOLDING CONDITIONS At the P a c i f i c B i o l o g i c a l Station, groups of approximately 60 juvenile sockeye were transferred to 8 separate 30 1 holding tanks. The f i s h were acclimated to dechlorinated c i t y water (10°C) for a period of 1 wk. I n i t i a l m o r t a l i t i e s were severe. During the f i r s t day over 100 f i s h succumbed- l i k e l y due to scale loss incurred during c o l l e c t i o n . After 2 d i n c a p t i v i t y m o r t a l i t i e s decreased s i g n i f i c a n t l y and only 5 f i s h died during the remainder of the experimental period. Maintaining sockeye smolts i n freshwater for extended periods of time may resu l t i n extensive m o r t a l i t i e s (C. Groot, P a c i f i c B i o l o g i c a l Station, Nanaimo, B r i t i s h Columbia; pers. comm.); therefore, the juveniles were transferred to d i l u t e d seawater (10°C, 20 ppt) on May 24, and acclimated for a period of 1 wk. I chose acclimation and test conditions that could normally be encountered by sockeye migrating through the Somass River estuary (Tully 1949, Morris and Leany 1980). The temperature and s a l i n i t y of holding tanks were midway between the upper and lower -24-test l e v e l s , and also provided control conditions during the experiments. The juvenile sockeye commenced feeding aft e r 2 d i n c a p t i v i t y and were fed frozen euphausids ad libitum every morning. The tanks were cleaned of feces and food remains once per week. Overhead fluorescent lamps were connected to a timer that was adjusted weekly to simulate the l o c a l photoperiod. C. EXPERIMENTAL APPARATUS Each of the '6 annular a c t i v i t y tanks used i n the present study consisted of 2 PVC rings fixed with fiberglass r e s i n to a waterproofed, plywood bottom (Figure 2). The 2 rings formed a swimming chamber that had an outer circumference of 250 cm, and an inner circumference of 160 cm. External standpipes were used to maintain water depth at 10 cm. Excess glare was eliminated by painting the bottom of the swimming chambers with black, rust-oleum paint. Both control and experimental water was added through 0.63 cm PVC valves connected to the sides of the tanks. Fresh (1 ppt) and s a l t (31 ppt) water was available at temperatures of 4, 10 and 28°C. (+/- 1.0°C for each). The test conditions were produced by premixing 2 or more water sources at d i f f e r e n t rates i n 30 1 fiberglass tanks -25-Figure 2. Top and side views of a c t i v i t y tank used to measure locomotor responses of juvenile sockeye salmon to rapid changes i n temperature and s a l i n i t y . At each photo-cell station, an in f r a - r e d beam was focussed through a plexiglass plate, r e f l e c t e d on a mirror, and c o l l e c t e d by a receiver positioned underneath the emitter. TOP VIEW TO COMPUTER 4 -26-PHOTOCELL STATION INLET OUTLET SIDE VIEW (Table 1). The experimental water was then gravity fed to the test apparatus at a rate of 2 1/min. Sl i g h t fluctuations i n water temperature (up to 1°C) over the 6 wk test period necessitated weekly flow adjustments i n order to maintain consistent levels of temperature and s a l i n i t y . Therefore, the flow rate between tanks varied between 1.9 and 2.1 l/min. However, water flow to the tanks was constant during the experiments. D. DATA COLLECTION Juvenile salmon held i n annular tanks exhibit constant u n i d i r e c t i o n a l swimming behavior (Byrne 1968, Godin et a l . 1978). In preliminary experiments, Great Central Lake smolts exhibited si m i l a r behavior, however, turning and periods of i n a c t i v i t y were also quite common. Locomotor a c t i v i t y data were co l l e c t e d using inf r a - r e d photo-metric sensors (Amseco Ltd, Houston, Texas -model EBP-2503) interfaced with an Apple 11+ microcomputer. There were 2 photo-cell stations per tank (each station consisting of 1 emitter and 1 receiver) positioned on opposite sides; thus, d i v i d i n g the apparatus into equal halves (Figure 2). The in f r a - r e d beam was focussed through a plexiglass window on the outer tank wall, r e f l e c t e d o f f mirrors on the inner and outer tank walls, and c o l l e c t e d by the receiver positioned below the emitter. The i n f r a - r e d T a b l e 1. Combinations o f w a t e r sources used t o produce t e s t c o n d i t i o n s i n the j u v e n i l e sockeye a c t i v i t y e x p e r i m e n t s . Flow r a t e s o f each w a t e r s o u r c e and t o t a l f l o w are i n c l u d e d i n the t a b l e . Ranges o f each parameter were t h e minimum and maximum r e c o r d e d d u r i n g the e x p e r i m e n t a l p e r i o d . T e s t c o n d i t i o n s were produced by m i x i n g water s o u r c e s t o g e t h e r i n 30 L t a n k s . C= C o l d (4 C ) , N= Normal (10°C), H= Hot (28°C), F= F r e s h (1 p p t ) , S= S a l t (31 p p t ) . Temperature S a l i n i t y Flow Rate o f T e s t Water Source T o t a l Flow ( 0.2 C) ( 1 p p t ) ( 0.1 L/min) Rate ( 0.2 l/m i n ) CF CS NF NS HF HS 6.0 10 1.4 - - 0.6 - 2.0 6.0 20 - 1.4 0.6 - - 2.0 6.0 30 - 1.4 - 0.6 - 2.0 10.0 10 - - 1.4 0.6 - 2.0 10.0 20 - - 0.6 1.4 - 2.0 - c o n t r o l 10.0 30 - - - 2.0 - 2.0 14.0 10 0.8 - 0.5 - 0.7 2.0 14.0 20 - 0.8 0.5 0.7 - 2.0 14.0 30 — 0.8 — 0.5 0.7 2.0 -29-f i e l d provided s u f f i c i e n t coverage so that a photo-cell station could not be passed by a juvenile sockeye without t r i g g e r i n g the receiver. A mechanical switch located within the receiver relayed a continuous high ('connected') or low ('broken') signal to the computer. An analog to d i g i t a l converter (12 b i t , 16 channel- Applied Engineering Ltd., Carrollton, Texas).was used to interface the a c t i v i t y recorders with the microcomputer. In t o t a l , 12 photo-cell units (2 for each tank) were used for data c o l l e c t i o n . An Applesoft (Apple Computer Inc., Cupertino, C a l i f o r n i a ) BASIC program was written for data a c q u i s i t i o n and storage. The algorithm involved sequential monitoring of the 12 channels ( i . e . photo-cells) i n a continuous loop. When a 'broken' signal was received, the program branched to a subroutine that recorded the time and channel number to a 1 dimensional array. The subroutine then returned to the main program and continued sequential monitoring. Preliminary experiments showed that f i s h would often change t h e i r v e r t i c a l p o s i t i o n while passing through the i n f r a - r e d f i e l d , causing r e p e t i t i v e signal recordings. Therefore, the program was modified so that once a 'broken' signal was established for a given photo-cell, that unit could not be recorded again u n t i l a period of 2 s had passed (allowing the f i s h to pass through the sta t i o n ) , and the signal had returned to a 'connected' state. -30-Th e recording accuracy of the apparatus was also determined. The number of photo-cell breaks recorded by a single f i s h during 30 min exposure to control conditions was monitored v i s u a l l y and e l e c t r o n i c a l l y . The mean number of counts obtained by the two methods were s t a t i s t i c a l l y compared using chi-square analysis. E. EXPERIMENTAL PROCEDURE The juveniles were not fed 1 d p r i o r to testing, and the experiments were conducted twice d a i l y (morning and afternoon). Prior to the tests, the annular tanks were f i l l e d with control water (10°C, 20 ppt) and maintained at a flow rate of 2 l/min. A single f i s h was introduced into each experimental tank and covered with a transleucent sheet to prevent s t a r t l i n g . The smolts were observed v i s u a l l y through 10 cm wide areas that had been cut over the photo-cell stations. For a period of 1 h, the smolts were allowed to adjust to the experimental tanks. A c t i v i t y during t h i s period was monitored (but not recorded) both v i s u a l l y and on the computer screen. The sockeye often did not move during the f i r s t few minutes aft e r transfer, however, most became mobile within 15 min. Fish that remained immobile for 45 min were removed and that tank was not used i n the t e s t . Each experiment was divided into a 1 h control phase, followed by a 1 h water turnover period and concluding with a 1 h test phase. During the i n i t i a l hour, swimming a c t i v i t y was recorded i n control conditions (10°C, 20 ppt) to determine baseline l e v e l s . At the star t of the second hour, the control water valve was shut o f f and experimental water was introduced into the test apparatus. Overflow samples were obtained at 10 min in t e r v a l s during the turnover phase to determine temperature, s a l i n i t y , and water flow. Although water turnover was not li n e a r , both temperature and s a l i n i t y s t a b i l i z e d at experimental levels within 45 to 50 min. During the f i n a l hour, a c t i v i t y was recorded during exposure to the treatment conditions. Upon completion of the test, fork lengths of the f i s h were recorded. Prior to the next test, tanks were rinsed and r e f i l l e d with control water. F. TEST CONDITIONS AND STATISTICAL ANALYSIS In t o t a l , there were 8 experimental conditions and 1 control (Table 1). The juvenile sockeye were subjected to control conditions for 1 h. In the second hour, temperature was increased to 14°C, decreased to 6°C, or held constant. Thirty minutes afte r introducing warm or cold water, temperature had changed by +/- 1.8°C, and afte r 60 min, water temperature had increased or decreased by 4°C. In the f i n a l hour, temperature remained constant at the treatment -32-l e v e l . After the i n i t i a l 60 min i n control conditions, s a l i n i t y was increased to 30 ppt, decreased to 10 ppt, or held constant at 20 ppt. During the f i r s t 30 min of water turnover, test tank s a l i n i t y was altered by +/- 6 ppt. Sixty minutes a f t e r test water introduction, s a l i n i t y had increased or decreased by 10 ppt. S a l i n i t y remained constant during the f i n a l 60 min of testing. A c t i v i t y of the sockeye smolts was converted into average swimming speed for comparison between treatment groups. Preliminary experiments showed that, even i n control conditions, f i s h would occasionally stop moving for periods of up to 5 min. Therefore, to decrease v a r i a b i l i t y i n the c a l c u l a t i o n of swimming speed, only active behavior was included i n the analysis. This was calculated as follows. There were 2 photo-cell stations for each tank. Preliminary tests showed that i n control conditions active f i s h usually swam 1/2 the distance around the tank ( i . e . between stations) within 10 to 15 s. A c t i v i t y data were recorded when the f i s h swam between stations within 30 s. Intervals of more than 30 s and instances when f i s h turned back through the same station were not included i n the analysis. A c t i v i t y i n each 30 min period was converted to average swimming speed. Total excursions under 30 s were mul t i p l i e d by the average distance for 1 excursion -33-(difference between the outer and inner walls of the swimming chamber). This r e s u l t was divided by the t o t a l time (in seconds) to complete a l l excursions, and divided by the fork length of the f i s h . The value calculated was average routine swimming speed i n fork lengths per second ( f l / s ) . Responses to temperature and s a l i n i t y were the main effects tested by the s t a t i s t i c a l analyses. However, Byrne (1968) showed that juvenile sockeye entrained to a 12:12 L/D cycle exhibited s i g n i f i c a n t diurnal variations i n locomotor a c t i v i t y . While experiments were coordinated with the peak a c t i v i t y period for young sockeye ( i . e . morning and afternoon- Byrne 1968), the time of experiment was also incorporated into the s t a t i s t i c a l analysis. A single factor ANOVA was used to test for differences i n mean swimming speed during the 60 min control ( i . e . pre-treatment) phase, for sockeye tested i n either the morning or afternoon. The mean swimming speed of juvenile sockeye during the f i n a l 60 min exposure to test conditions was analyzed using a two factor ANOVA. The experiment was designed so that treatment e f f e c t s could be compared as well as any possible i n t e r a c t i o n s . When sample sizes were unequal, an F-max tes t (Sokal and Rholf 1969) was used to assess homogeneity of variance p r i o r to the ANOVA. If heterogeneity existed, a ln(x+l) transformation (Zar 1980) was conducted on the data, and the results were then -34-subjected to parametric analyses. Newman-Keuls multiple range test (Zar 1980) was used as an a p o s t e r i o r i comparison of between treatment e f f e c t s . Behavioral responses of young salmon to temperature and s a l i n i t y may change over time (e.g. Hurley and Woodall 1968, Mclnerney 1964). In the present study, experiments were conducted during a 6 wk period. In the event of a s i g n i f i c a n t e f f e c t from the two factor ANOVA, possible temporal changes i n locomotor response were analyzed between f i s h tested i n the f i r s t 3 wk and the f i n a l 3 wk using a single factor ANOVA. In addition to te s t i n g responses i n the f i n a l 1 h of the experiments, a c t i v i t y was also analyzed at 30 min i n t e r v a l s during the control, water turnover, and test phases. Mean swimming speeds of the smolts were s t a t i s t i c a l l y tested using a repeated measures ANOVA (Zar 1980). Unequal sample sizes prohibited the use of 1 large multivariate block analysis. Rather than using s t a t i s t i c a l methods to estimate 'missing data' (e.g. Zar 1980), the experimental r e s u l t s were analyzed separately and interactions were not tested. The analyses were designed such that a single f i s h constituted 1 block and swimming speed was averaged over 30 min periods during exposure to test conditions. In t o t a l there were f i v e 30 min in t e r v a l s (1 control, 2 water turnover, and 2 test) for which mean swimming speed was calculated. -35-II. ADULT EXPERIMENTS From August 10, 1986 to September 20, 1986, the locomotor responses of migrating adult sockeye salmon to rapid changes i n temperature and s a l i n i t y were tested. A l l adult sockeye used i n the present study were assumed to be migrating to the Fraser River. The capture area extended from Queen Charlotte S t r a i t at the northern end of Vancouver Island to the S t r a i t of Georgia near the Fraser River estuary (Figure 1). During the summer months, Queen Charlotte S t r a i t i s s l i g h t l y s t r a t i f i e d , with l i t t l e v e r t i c a l change i n temperature and s a l i n i t y (Thomson et a l . 1985). The S t r a i t of Georgia, however, i s a more strongly s t r a t i f i e d region with d i s t i n c t variations i n temperature and s a l i n i t y over the top 30 m. (Thomson et a l . 1985). Although other l o c a l r i v e r s do contain small sockeye runs, i n 1986 the Fraser River accounted for over 90% of sockeye production i n the study area (B. Tasaka, P a c i f i c Salmon Commission, Vancouver, B r i t i s h Columbia; pers. comm.). The 2 p r i n c i p l e runs that constituted the majority of spawners i n 1986 were from the Adams Lake and Chilko Lake systems. Lesser contributions were made by runs to Birkenhead River and Weaver Creek (B. Tasaka,. P a c i f i c Salmon Commission, Vancouver, B r i t i s h Columbia; pers. comm.). The race of in d i v i d u a l f i s h was determined using discriminate -36-scale sample analysis by s t a f f of the P a c i f i c Salmon Commission, Vancouver, B r i t i s h Columbia (Table 2). A. FISH COLLECTION Adult sockeye were co l l e c t e d at 5 locations along the nearshore migration route (Figure 1, Table 2). Three samples ( t o t a l of 44 f i s h ) were taken from Queen Charlotte S t r a i t (Sets Nl - N3) on August 7th, 14th, and 21st, and two ( t o t a l of 34 fish) from the S t r a i t of Georgia (Sets SI - S2) on September 4th and 10th. The salmon were c o l l e c t e d by purse seine i n areas that were h i s t o r i c a l l y known to be prime f i s h i n g locations. Prior to sampling, surface seawater was pumped into the vessel's hold. After the set was made, the net was brought close to the boat and the adult sockeye were transferred to the hold by dip net. Oxygen was provided for the f i s h using an a i r compressor. Surface temperatures were recorded immediately after capture. The seiner brought the samples to shore within 2 h of c o l l e c t i o n and water was pumped from the hold of the boat into a large f i b e r g l a s s tank (1200 1) located on the back of a truck. In general, most salmon were r e l a t i v e l y docile during transport. Oxygen was provided for the f i s h by adding compressed a i r . Water i n the transport tank was maintained at 12°C (+/- 1°C) by p e r i o d i c a l l y adding or T a b l e 2. C o n t r i b u t i o n s o f sockeye from f o u r F r a s e r R i v e r r a c e s t o t h e a d u l t a c t i v i t y t a n k e x p e r i m e n t s . L o c a t i o n , date o f c a p t u r e , and t o t a l s from each s e t a re i n c l u d e d f o r male (M) and female (F) f i s h . Set Capture L o c a t i o n C h i l k o Date R i v e r Adams B i r k ' h e a d Weaver R i v e r R i v e r Creek ? ? T o t a l M F M F M F M F M F N l 24/07/86 G o l e t a s Channel N2 1/08/86 G o l e t a s Channel N3 21/08/86 Qu'n Ch't 4 S t r a i t 51 4/09/86 Sabine Channel 52 10/09/86 G u l f o f G e o r g i a 2 1 0 0 0 0 0 10 2 5 1 4 1 1 0 2 0 0 16 1 5 2 0 1 1 2 0 18 2 2 4 3 1 1 2 1 1 0 17 2 0 6 5 1 2 0 0 0 1 17 i I -38-removing ice packs during the drive to the P a c i f i c B i o l o g i c a l Station i n Nanaimo. Transport time (seiner plus truck) varied from 7 h for f i s h taken from Queen Charlotte S t r a i t to 2 h for f i s h caught i n the S t r a i t of Georgia. Recovery from capture was excellent; a l l 79 f i s h sampled survived transport and only 1 died after a r r i v a l at the P a c i f i c B i o l o g i c a l Station. B. HOLDING CONDITIONS The sockeye were acclimated for 1 d p r i o r to the experiments and subsequently tested for 2 to 5 d. Twenty f i s h were held i n two 800 1 fiberglass tanks with water (12°C, 30 ppt) flowing at 15 l/min. Overhead fluorescent lamps were connected to a timer (adjusted weekly) corresponding to l o c a l photoperiod. Tanks were covered with PVC sheeting (0.02 cm) to prevent i n j u r i e s caused by jumping. The adult sockeye were not fed at any time during the experiments. C. EXPERIMENTAL APPARATUS AND DATA COLLECTION Three 800 1, c i r c u l a r , fiberglass tanks were f i t t e d with a center fiberglass annulus (diameter= 60 cm) to provide a swimming channel of 60 cm between the outer tank wall and the annulus (Figure 3). The circumference of the - 3 9 -Figure 3. Experimental apparatus used to measure locomotor responses of adult sockeye salmon to rapid changes i n temperature and s a l i n i t y . At each photo-cell station, two emitters were placed end to end i n a plexiglass tube. The infr a - r e d beams were focussed onto two receivers positioned on the opposite side of the swimming channel. outer wall was 570 cm and the circumference of the annulus was 190 cm. External standpipes provided a water depth of 45 cm. Locomotor a c t i v i t y was recorded by 2 photo-cell stations located on opposite sides of the test tanks. Each station consisted of 2 emiters placed end to end i n clear PVC tubes (12 cm diameter) and fixed with marine caulking to the inner side of the tank wall (Figure 3). Si m i l a r l y , tubes containing the 2 receivers were fixed to the outer side of the annulus. The 2 photo-cell units provided s u f f i c i e n t coverage so that at least 1 beam would be broken i f an adult salmon passed by. F i l t e r e d seawater (4, 12, 28°C, 30 ppt) or dechlorinated c i t y water (12, 28°C, 1 ppt) were used as control and experimental sources. Up to 3 water types were combined at d i f f e r e n t rates i n 40 1 mixing containers before being gravity fed to the experimental tanks (Table 3). The experimental design of the adult tests consisted of a f a c t o r i a l combination of 3 temperatures (8°C, 12°C, 16°C) by 2 s a l i n i t i e s (20 ppt, 30 ppt). The a c t i v i t y of the f i s h was monitored both v i s u a l l y and e l e c t r o n i c a l l y for 60 min during exposure to control conditions to determine the recording accuracy of the in f r a - r e d sensors. The mean number of counts obtained by both methods were compared using a single factor ANOVA. Table 3. Combinations of water sources used to produce te s t conditions i n the adult sockeye a c t i v i t y experiments. Flow rates of each water source and t o t a l flow are included i n the table. Ranges of each parameter were the minimum and maximum recorded during the experimental period. Test conditions were produced by mixing water sources together i n 40 L tanks. C= Cold (4 C), N= Normal (12°C), H= Hot (28°C), F= Fresh (1 ppt), S= Salt (31 ppt). Temperature S a l i n i t y Flow Rate of Test Water Source Total Flow ( 0.2 C) ( 1 ppt) ( 1.0 L/min ) Rate ( 1.0 L/min) CF CS NF NS HF HS 8.0 20 - 10.0 3.8 - - 1.2 15.0 8.0 30 - 7.5 - 7.5 - - 15.0 12.0 20 - - 5.0 10.0 - - 15.0 12.0 30 - - - 15.0 - - 15.0 -control 16.0 20 0.8 - - 10.0 4.2 - 15.0 16.0 30 - — — 11.2 3.8 — 15.0 I I -43-D. EXPERIMENTAL PROCEDURE Prior to an experiment, the test tanks were f i l l e d with the same water that was used i n the holding tanks (12°C, 30 ppt). A single f i s h was then transferred from the holding tank to an experimental chamber and acclimated for 1 h. Most adults began swimming immediately and f i s h that did not become active 45 min aft e r introduction were excluded from the t e s t . When the experiment commenced, baseline a c t i v i t y was recorded for 1 h during exposure to control conditions. In the second hour, the control water was shut o f f and experimental water was introduced at 15 l/min. At 30 min i n t e r v a l s , temperature and s a l i n i t y were recorded from the overflow pipe. The turnover phase took approximately 120 min. In the f i n a l hour, a c t i v i t y was recorded during exposure to treatment conditions. After the experiment finished, the t o t a l length of each f i s h was recorded. The tanks were then drained, rinsed, and r e f i l l e d for the next t e s t . During the 5 wk of testing, experimental and ambient temperatures ranged by a maximum of +/- 0.2°C. In addition, s a l i n i t y varied by about 1 ppt, and flow rate was accurate to within +/- 1 l/min (Table 3). In addition to swimming behavior, a c t i v i t i e s such as the number of turns made ( i . e . reversals of d i r e c t i o n ) , the -44-number of 'noses' ( " l i f t i n g the nose or head out of the water as far as the operculars"- see Groot et a l . 1986) and 'fin s ' (moving the dorsal surface out of the water) were recorded for 10 min i n t e r v a l s before, during, and a f t e r introduction of the test water. E. TEST CONDITIONS AND STATISTICAL ANALYSIS The adult experiments were divided into 3 phases. After the i n i t i a l 60 min i n control conditions, water temperature was increased or decreased by 4°C, or held constant at 12°C. Concurrently, s a l i n i t y was decreased by 10 ppt or maintained at 30 ppt. A c t i v i t y was converted into average swimming speed by c a l c u l a t i n g the t o t a l number of excursions between stations, multiplied by the average distance for 1 excursion, and divided by the t o t a l time to complete a l l excursions. The r e s u l t i n g value was divided by the t o t a l body length of the f i s h , giving average swimming speed i n t o t a l lengths per second ( t l / s ) . The time required for swimming between stations was usually 20 - 30 s, however, adults would occasionally stop moving; therefore, the value used as the upper l e v e l for making an excursion was set at 60 s. In the s t a t i s t i c a l analysis, a number of tests were i n i t i a l l y conducted to i d e n t i f y any inherent differences between the experimental animals that may have influenced results of the main design. Mean swimming speeds in control conditions were compared i n r e l a t i o n to sex (single factor ANOVA), race (single factor ANOVA), and time of day (single factor ANOVA). The mean swimming speeds of adult sockeye during the f i n a l 60 min test period were compared using a two factor ANOVA. Tests for homogeneity of variance (F-max test) were used, and the Newman-Keuls multiple range test was u t i l i z e d to examine between group differences using the results of the ANOVA. Fish came from 2 d i s t i n c t oceanographic regions and were acclimated for varying amounts of time p r i o r to te s t i n g . Therefore, when s i g n i f i c a n t e f f e c t s were obtained from the main treatment model, mean swimming speeds were compared during the f i n a l hour of te s t i n g based on area of capture and number of days acclimated to control conditions. A repeated measures ANOVA in a mixed block design ( f i s h as blocks, periods as treatments) was used to test differences i n mean swimming speed between 1/2 hour i n t e r v a l s . The f i r s t 30 min period i n control water was not used i n the analysis. Comparisons were made between the other seven 30 min i n t e r v a l s for each experimental condition. In the event of a s i g n i f i c a n t main e f f e c t , multiple range te s t i n g (Newman-Keuls) was used to compare average swimming speeds between the 30 min periods. Other behaviors ( i . e . nosing, finning, turning) were analyzed between treatment groups using a repeated measures ANOVA. The analyses compared mean events i n 10 min in t e r v a l s during the control period, the f i r s t 30 min of water turnover, and the f i r s t 30 min at test l e v e l s . An alpha l e v e l of 0.05 was used for a l l s t a t i s t i c a l t e s t s . -47-RESULTS JUVENILE EXPERIMENTS In t o t a l , 214 juvenile sockeye were tested over a 6 wk period (mean fork length= 10.39 cm, SD= 0.66 cm). The sample size was o r i g i n a l l y to be 240 (30 f i s h for 8 conditions), however, equipment malfunctions resulted i n the exclusion of 8 tests from the data analysis. In addition, 18 juveniles remained motionless for most of the experiment and were not included i n the s t a t i s t i c a l t e s t s . Analyses were conducted on each of the 6 experimental tanks to determine the accuracy of recording equipment. Chi-square analysis showed no difference between the mean number of photo-cell breaks recorded by v i s u a l or ele c t r o n i c methods i n 30 min tests (Table 4). The experiments were run twice d a i l y - once i n the morning and once i n the late afternoon (~ 4 h difference between t e s t s ) . The average swimming speed of juvenile sockeye from morning experiments was not d i f f e r e n t from f i s h tested i n the afternoon (Table 5). The swimming speeds of juvenile sockeye averaged over the l a s t hour of tes t i n g are shown i n Figure 4. Fish exposed to decreasing temperature, and increasing or decreasing s a l i n i t y had mean swimming speeds that were close to control values. However, f i s h tested i n 14°C showed - 4 8 -Table 4. The number of passes through photo-cell stations recorded for juvenile sockeye during 30 minutes exposure to control (10 C, 20 ppt) conditions. Data c o l l e c t e d by ele c t r o n i c and v i s u a l observations were not s i g n i f i c a n t l y d i f f e r e n t (chi-square= 0.11, P> 0.05). Observation Number of counts Method per 30 minute i n t e r v a l  Tank 1 Tank 2 Tank 3 Tank 4 Tank 5 Tank 6 Electr o n i c 112 86 84 103 91 41 Visual 108 87 86 110 90 39 Table 5. The average swimming speed of juvenile sockeye salmon exposed for 30 minutes to control conditions (10 C, 20 ppt) i n morning or afternoon tests (~ 4 hours di f f e r e n c e ) . S t a t i s t i c a l analysis (single factor ANOVA) showed no s i g n i f i c a n t difference between mean values. Time of Day N Mean Swimming SD F P > F Speed (1/s) (1/s) Morning 107 1.02 0.15 0.11 -Afternoon 107 1.01 0.20 - 4 9 -Figure 4. Average swimming speeds (+/-SEM) of juvenile sockeye salmon during the f i n a l 60 minutes exposure to test l e v e l s . Fish were i n i t i a l l y subjected to control conditions (10 C, 20 ppt) for one hour, and water turnover took approximately 60 minutes. CD 3 CO T 3 <D —\ 3' CO y~t * c»< —1 CD TET 3 SWIMMING SPEED (l/s) o In CT> go>| CO CD I o o o o O 4^ -51-elevated swimming speeds i n each of the 3 salinity-conditions. The highest average speed was found for f i s h exposed to 14°C and 20 ppt. There were an unequal number of juvenile sockeye tested i n each experimental condition (Table 6). In addition, variances were found to be heterogeneous (F-max t e s t - F= 9.00, P< 0.05). The conservative approach suggested by Zar (1980) was adopted, and the swimming speed data were transformed (ln (x+1)). The two factor ANOVA on the transformed data, showed that temperature was the only s i g n i f i c a n t treatment e f f e c t (F= 22.07, P< 0.001). There was no influence due to s a l i n i t y (F= 1.43, P= 0.24) or inter a c t i o n between factors (F= 1.07, P= 0.37). For comparative purposes, I also conducted a two factor ANOVA on the untransformed swimming speeds (Table 7). F values were sim i l a r to those derived from the transformed data, and s t a t i s t i c a l conclusions were the same- temperature was the only factor that influenced locomotor a c t i v i t y . Due to the equivalent r e s u l t s of the two s t a t i s t i c a l tests, I f e l t j u s t i f i e d i n using the untransformed data i n the a p o s t e r i o r i analysis. Newman-Keuls multiple range test showed that increasing temperature was the only factor that affected swimming a c t i v i t y (Table 6). Additional tests were performed to assess changes i n locomotor a c t i v i t y based on the number of weeks i n -52-Table 6. The mean swimming speeds of juvenile sockeye salmon during the f i n a l 60 minutes exposure to test l e v e l s . Fish were i n i t i a l l y subjected to control conditions (10 C, 20 ppt) for one hour, and water turnover took approximately 60 minutes. Results from Newman-Keuls multiple range test are also included i n the table (NS= not s i g n i f i c a n t , *= < 0.05, **= < 0.01). Temperature S a l i n i t y N Mean Swimming SD Newman-Keuls ( c ) (ppt) Speed (1/s) (1/s) 6 10 19 1.04 0.11 NS 6 20 21 1.05 0.19 NS 6 30 25 1.00 0.15 NS 10 10 24 1.07 0.11 NS 10 20 22 1.10 0.18 -c o n t r o l -10 30 29 1.07 0.15 NS 14 10 25 1.31 0.18 * 14 20 26 1.48 0.33 ** 14 30 20 1.20 0.27 * Table 7. Results of the two factor ANOVA comparing the mean swimming speeds of juvenile sockeye salmon subjected to experimental conditions for 60 minutes (see Table 6). Source SS DF MS F P > F Temperature 3.01 2 1.50 18.79 < 0.001 S a l i n i t y 0.22 2 0.11 1.35 0.260 Temp*Sali 0.36 4 0.09 1.13 0.345 Error 15.40 198 0.08 -53-c a p t i v i t y . The previous analysis showed that increasing temperature was the only factor influencing swimming a c t i v i t y (Table 7). Therefore, results were r e s t r i c t e d to f i s h tested i n 14°C, 20 ppt. A single factor ANOVA showed that the mean swimming speed of f i s h tested i n weeks 1 to 3 was not d i f f e r e n t from f i s h tested i n weeks 4 to 6 (Table 8). For each experimental condition, the swimming speeds of juvenile sockeye were averaged over 30 min in t e r v a l s during the control, water turnover, and experimental periods. Juveniles subjected to decreasing temperature and decreasing, constant, or increasing s a l i n i t y maintained a consistent a c t i v i t y l e v e l throughout the experiment (Figure 5, Figure 6). Fish tested i n 14°C water increased locomotor a c t i v i t y i n each of the 3 s a l i n i t y conditions (Figure 7). After introduction of the experimental water, there was an i n i t i a l r i s e i n average swimming speed, followed by a period of r e l a t i v e l y constant a c t i v i t y during temperature s t a b i l i z a t i o n . However, locomotor a c t i v i t y continued to increase somewhat towards the end of the experiments despite constant temperatures. The only e f f e c t detected by the repeated measures ANOVA was due to increasing temperature (Table 9). Newman-Keuls multiple range test showed that swimming a c t i v i t y increased above control levels after 30 min exposure to test conditions. In addition, for f i s h exposed -54-Table 8. The mean swimming speeds of juvenile sockeye salmon during 60 minutes exposure to water of 14 C and 20 ppt. Data was pooled from f i s h tested i n the f i r s t 3 weeks (1 - 3) or the l a s t 3 weeks (4 - 6) of the experimental period. Results from the s t a t i s t i c a l analysis (single factor ANOVA) are included i n the table. Week of Test N Mean Swimming Speed (1/s) SD F (1/s) P > F 1 - 3 13 1.49 0.34 0.35 -4 - 6 13 1.46 0.29 -55-Figure 5. Mean swimming speeds ( + / - S E M q of juvenile sockeye salmon during exposure to (A) 6 C, 10 ppt; (B) 6 C, 20 ppt; and (C) 6°C, 30 ppt. Values were calculated at 30 minute i n t e r v a l s for control conditions (T0), one hour of water turnover (T0 - 60), and one hour at test l e v e l s (T60 - T120). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. -56-TEMPERATURE (°C) SALINITY (ppt) (C) | 0.8 " co 0 30 60 TIME (min) 90 120 -57-Figure 6. Mean swimming speeds (+/-SEM) of juvenile sockeye salmon during exposure to (A) 10 C, 10 ppt; (B) 10°C, 20 ppt; and (C) 10°C, 30 ppt. Values were calculated at 30 minute i n t e r v a l s for control conditions (T0), one hour of water turnover (T0 - 60), and one hour at test levels (T60 - T120). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. SWIMMING SPEED (l/s) TEMPERATURE (°C) o 00 ro cnoooro A T I I I I H T—i—r ^ ro co O o o (idd) A1INI1VS SWIMMING SPEED (l/s) TEMPERATURE (°C) Odd) A1INHVS SWIMMING SPEED (l/s) TEMPERATURE (°C) cnoo o ro (Jdd) A1INI1VS -59-Figure 7. Mean swimming speeds (+/-SEM) of juvenile sockeye salmon during exposure to (A) 14 C, 10 ppt; (B) 14°C, 20 ppt; and (C) 14°C, 30 ppt. Values were calculated at 30 minute i n t e r v a l s for control conditions (T0), one hour of water turnover (T0 - 60), and one hour at test l e v e l s (T60 - T120). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. SWIMMING SPEED (1/s) TEMPERATURE (°C) OJ 00 O M A ^ ro u O o o (Jdd) A1INHVS SWIMMING SPEED (1/s) TEMPERATURE (°C) O -L -L -I bo o ho cnoo oro I 1 1 1 1 I I I I I I — (}dd) A1INI1VS SWIMMING SPEED (1/s) TEMPERATURE (°C) O -L -L -I _ i _ L _ i bo o ho ^ cn OD o ro A — I 1 1 1 1 I I I I I I ~ > Odd) A1INI1VS Table 9. Mean swimming speeds of juvenile sockeye calculated over 30 minute interv a l s during 1/2 hour i n control conditions (T0), one hour of water turnover (T0 - T60) and one hour at test levels (T60 - T120). Results of s t a t i s t i c a l tests (repeated measures ANOVA) are included for each condition. Temperature S a l i n i t y N Mean Swim Speed ( l / s ) per 30 F P > F ( C) (ppt) Minute Interval (SD i n brackets) T0 T30 T60 T90 T120 6 10 19 1.02 (0.14) 1.03 (0.21) 0.98 (0.10) 1.02 (0.10) 1.05 (0.10) 0. 71 0. 468 6 20 21 1.00 (0.17) 0.93 (0.27) 1.00 (0.17) 1.04 (0.21) 1.05 (0.21) 1. 40 0. 253 6 30 25 1.06 (0.10) 0.99 (0.15) 1.08 (0.20) 0.98 (0.17) 1.02 (0.21) 1. 21 0. 321 10 10 24 0.99 (0.13) 1.06 (0.15) 1.08 (0.16) 1.09 (0.18) 1.04 (0.13) 1. 04 0. 290 10 20 22 1.08 (0.19) 1.04 (0.21) 1.08 (0.11) 1.11 (0.26) 1.10 (0.18) 0. 64 10 30 29 1.06 (0.17) 1.02 (0.17) 1.03 (0.21) 1.09 (0.19) 1.05 (0.11) 0. 56 14 10 25 1.03 (0.20) 1.20 (0.20) 1.26 (0.24) 1.28 (0.33) 1.34 (0.29) 9. 28 < 0. 001 14 20 26 0.97 (0.16) 1.28 (0.28) 1.36 (0.23) 1.44 (0.28) 1.52 (0.35) 22. 80 < 0. 001 14 30 20 1.00 (0.23) 1.19 (0.26) 1.20 (0.30) 1.23 (0.25) 1.27 (0.27) 10. 80 < 0. 001 -62-to 14°C, 10 ppt and 14°C, 20 ppt, average swimming speed was higher 120 min aft e r test water introduction, compared to the i n i t i a l 30 min exposure. ADULT EXPERIMENTS The adult experiments were o r i g i n a l l y designed to test 8 sockeye from northern waters, and 8 from the south i n each of the 6 conditions ( t o t a l of 96 f i s h ) . However, only 76 f i s h were used i n the analysis. Of the 79 adults collected, 1 died p r i o r to experiments and 2 were excluded from tests because they f a i l e d to move during the control period. The mean t o t a l length was 61.4 cm (SD= 2.6 cm). The number of passes through photo-cell stations was recorded for 60 min by ele c t r o n i c and v i s u a l means. Results are shown i n Table 10. Chi-square analysis f a i l e d to demonstrate a difference between the two methods of data c o l l e c t i o n . S t a t i s t i c a l tests were performed to i d e n t i f y any variations i n locomotor a c t i v i t y due to time of day, race, or sex. Results showed no difference i n average swimming speed between sockeye tested i n the morning and afternoon (Table 11). In addition, the analyses did not detect a difference i n locomotion between the 4 races of sockeye (Table 12), or between males and females (Table 13). Swimming speeds of adult salmon exposed to -63-Table 10. The number of passes through photo-cell stations recorded for adult sockeye during 60 minutes exposure to control (12 C, 30 ppt) conditions. Data c o l l e c t e d by ele c t r o n i c and v i s u a l observations were not s i g n i f i c a n t l y d i f f e r e n t (chi-square= 0.038, P> 0.05). Observation Number of counts Method per 30 minute i n t e r v a l Tank 1 Tank 2 Tank 3 Electr o n i c 91 96 168 Visual 93 94 163 Table 11. The average swimming speed of adult sockeye salmon exposed for 30 minutes to control conditions (12 C, 30 ppt) i n morning or afternoon tests (~ 4 hours di f f e r e n c e ) . S t a t i s t i c a l analysis (single factor ANOVA) showed no s i g n i f i c a n t difference between mean values. Time of Day N Mean Swimming Speed ( l / s ) SD F (l / s ) P > F Morning 38 0.41 0.23 0.19 -Afternoon 38 0.38 0.21 -64-Table 12. The difference i n average swimming speed between four races of adult Fraser River sockeye. A c t i v i t y of f i s h was recorded during exposure to control conditions (12°C, 30 ppt) for 30 minutes. S t a t i s t i c a l analysis (single factor ANOVA) showed no s i g n i f i c a n t difference between mean values for each of the four groups. Population N Mean Swimming Speed (1/s) SD (1/s) F P > F Chilko River 25 0.38 0.21 0.70 Adams River 32 0.46 0.21 Birkenhead 9 0.46 0.26 Weaver Creek 8 0.40 0.24 Table 13. The mean swimming speeds of male and female sockeye salmon subjected to control conditions (12 C, 30 ppt) for 30 minutes. S t a t i s t i c a l tests (single factor ANOVA) showed no difference between mean values. Sex N Mean Swimming Speed (1/s) SD (1/s) F P > F Male 36 0.38 0. 23 0.29 Female 40 0.39 0.22 -65-decreasing s a l i n i t y or decreasing temperature were comparable to the controls (Figure 8). However, exposure to 16°, 20 ppt and 16°C, 30 ppt caused an elevation i n locomotor a c t i v i t y (Table 14). A two factor ANOVA showed that temperature was the only factor influencing average swimming speed during the f i n a l hour of te s t i n g (Table 15). In addition, Newman-Keuls multiple range test demonstrated that the ef f e c t was so l e l y due to increasing temperature (Table 14). Since f i s h were obtained from oceanographically d i s t i n c t regions and were acclimated for d i f f e r e n t periods of time, additional analyses were required to i d e n t i f y e f f e cts due to area of capture and/or number of days i n c a p t i v i t y . Prior tests had indicated that decreasing temperature did not influence swimming a c t i v i t y (Table 14); thus, the analyses were r e s t r i c t e d to f i s h tested i n 16°C. S a l i n i t y was also found to have no eff e c t on locomotor a c t i v i t y (Table 15); therefore, to increase sample size for tes t i n g e f f e c t s due to days i n c a p t i v i t y , data were pooled from 16°C, 20 ppt and 16°, 30 ppt. The average swimming speeds of adult sockeye tested i n 16°C were compared by area of capture and s a l i n i t y condition. The two factor ANOVA did not detect an ef f e c t on mean speed due to area of capture and there was no int e r a c t i o n between response to s a l i n i t y and sampling -66-Figure 8. Average swimming speeds (+/-SEM) of adult sockeye salmon during the f i n a l 60 minutes exposure to test l e v e l s . Fish were i n i t i a l l y subjected to control conditions (12 C, 30 ppt) for one hour, and water turnover took approximately 120 minutes. -67-42 o L U L U OL C O (3 CO Temperature ( C) Salinity (ppt) -68 Table 14. The mean swimming speeds of adult sockeye salmon during the f i n a l 60 minutes exposure to test l e v e l s . Fish were i n i t i a l l y subjected to control conditions (12 C, 30 ppt) for one hour, and water turnover took approximately 120 minutes. Results from Newman-Keuls multiple range te s t are also included i n the table (NS= not s i g n i f i c a n t , *= < 0.05, **= < 0.01). Temperature S a l i n i t y N Mean Swimming SD Newman-Keuls ( C) (ppt) Speed (1/s) (1/s) 8 20 10 0.37 0.13 NS 8 30 14 0.39 0.19 NS 12 20 15 0.38 0.15 NS 12 30 11 0.36 0.14 -c o n t r o l -16 20 15 0.60 0. 26 ** 16 30 11 0.55 0.18 * Table 15. Results of the two factor ANOVA comparing the mean swimming speeds of adult sockeye salmon subjected to experimental conditions for si x t y minutes (see Table 14). Source SS DF MS F P > F Temperature 8. .11 2 4. .11 7. .49 0.001 S a l i n i t y 0. .26 1 0. .26 0. .47 -Temp*Sali 0. .27 2 0. .14 0. .25 -Error 41. .64 76 0. .55 region (Table 16). Sockeye taken from the northern area were tested i n 16°C water 2 - 5 d af t e r c o l l e c t i o n . Analyses did not detect a difference i n average swimming speed between the 4 d (Table 17). Fish caught i n the southern area were tested i n 16°C water 2 - 4 d af t e r capture and also there was no ef f e c t of days i n c a p t i v i t y on mean swimming speed (Table 17). Locomotor a c t i v i t y was compared between each test condition during control, water turnover, and test phases. Fish tested i n decreasing temperature, and either decreasing or constant s a l i n i t y maintained consistent levels of swimming a c t i v i t y throughout the experiment (Figure 9a-b). Similar r e s u l t s were obtained for f i s h exposed to decreasing s a l i n i t y (Figure 10a) compared to the controls (Figure 10b). The locomotor a c t i v i t y of adult sockeye tested i n 16°C water tended to follow the pattern of temperature change (Figure 11). For f i s h exposed to 16°C, 20 ppt swimming a c t i v i t y increased s t e a d i l y during the f i r s t hour of water turnover, followed by a plateau period, and concluding with a s l i g h t r i s e i n swimming speed during the f i n a l hour of tes t i n g (Figure 11a). Fish exposed to 16°C, 30 ppt exhibited a si m i l a r pattern of locomotor a c t i v i t y (Figure l i b ) , however, the change i n swimming speed did not appear as pronounced. The repeated measures ANOVA demonstrated that the -70-Table 16. The average swimming speeds of adult sockeye salmon subjected to 16 C 20 ppt or 16 C 30 ppt during the f i n a l hour of t e s t i n g . Standard deviations are given i n brackets beside each mean value. Mean speeds were pooled for f i s h taken i n the northern sampling sets (Nl, N2, N3) and the southern sets (SI, S2). Results from the s t a t i s t i c a l analysis (two factor ANOVA) are also included i n the table. Area of Capture N S a l i n i t y Mean Swimming Speed ( l / s ) Source of Variation F P > F North 9 20 0.61 (0.23) Area 0.80 North 7 30 0.58 (0.18) S a l i n i t y 0.36 South 6 20 0.56 (0.17) Area* 0.21 S a l i n i t y South 4 30 0.54 (0.22) Table 17. The mean swimming spegds of adult sockeye during the f i n a l hour of exposure to 16 C water. Average values are pooled for f i s h from northern and southern sets based on the number of days acclimated at control conditions. Results of the s t a t i s t i c a l analyses (single factor ANOVA) conducted on northern and southern samples are also included. Days Acclimated Area Caught N Mean Swimming Speed ( l / s ) SD (l / s ) F P > F 2 North 4 0.62 0.27 0.70 3 North 4 0.55 0.15 4 North 4 0.64 0.23 5 North 4 0.61 0.27 2 South 4 0.47 0.28 0.40 3 South 3 0.60 0.19 4 South 3 0.46 0.34 -71-Figure 9. Mean swimming speeds (+/-SEM) of adult sockeye salmon during exposure to (A) 8 C, 20 ppt; and (B) 8 C, 30 ppt. Values were calculated at 30 minute i n t e r v a l s for control conditions (T0), two hours of water turnover (T0 - 120), and one hour at test l e v e l s (T120 - T180). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. TEMPERATURE {"C) SALINITY (ppt) (A) _ 0.6 Q LU UJ 0.5 1 0.4 0.3 • ' l l I I i _ 0 30 60 90 120 150 180 TIME (min) -73-Figure 10. Mean swimming speeds (+/-SEM) of adult sockeye salmon during exposure to (A) 12 C, 20 ppt; and (B) 12 C, 30 ppt. Values were calculated at 30 minute in t e r v a l s for control conditions (T0), two hours of water turnover (T0 - 120), and one hour at test levels (T120 - T180). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. (A) 16 h 14 12 § 10 CL S 8 1 0 6 Q LU LU 0.5 0.4 0.3 TEMPERATURE (°C) SALINITY (ppt) 40 30 20 i i i i f J I L 16 14 12 10 8 0.6 0.5 -i 0.4 0.3 40 30 20 0 30 _l I l _ 60 90 120 TIME (min) I L_ 150 180 -75-Figure 11. Mean swimming speeds (+/-SEM) of adult sockeye salmon oduring exposure to (A) 16 C, 20 ppt; and (B) 16 C, 30 ppt. Values were calculated at 30 minute i n t e r v a l s for control conditions (T0), two hours of water turnover (T0 - 120), and one hour at test levels (T120 - T180). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. TEMPERATURE (°C) SALINITY (ppt) (A) J 1 1 1 i J 1 1 1 I I L _ 0 30 60 90 120 150 180 TIME (min) -77-average swimming speeds of adult sockeye were not affected by decreasing temperature or by s a l i n i t y (Table 18). However, locomotor a c t i v i t y increased during exposure to 16°C, 20 ppt and 16°C, 30 ppt. Additional a p o s t e r i o r i analysis (Newman-Keuls multiple range test) showed that the average swimming speed of adult sockeye was higher aft e r 60 min exposure to 16°C, 20 ppt, and after 90 min exposure to 16°C 30 ppt (Table 18). The influence of capture area on swimming a c t i v i t y i n 16°C water was also examined. Fish from the northern areas had a more pronounced locomotor response to increasing temperature (Figure 12). Mean swimming speeds of f i s h from each sampling set were subjected to a repeated measures ANOVA. Set Nl had only 2 f i s h tested i n 16°C, and therefore was pooled with set N2. Previous analyses had shown no eff e c t due to s a l i n i t y (Table 15). Therefore, to increase sample size data were pooled from f i s h subjected to 16°C, 20 ppt and 16°C 30 ppt. The ANOVA demonstrated that f i s h from each of the northern sets had highly s i g n i f i c a n t responses to increasing temperature, while f i s h from southern sets did not (Table 19). When sets SI and S2 were pooled together, the ef f e c t of increasing temperature was s i g n i f i c a n t at the 0.05 l e v e l (Table 19). In addition to elec t r o n i c recording of swimming a c t i v i t y , adult salmon were observed v i s u a l l y for 10 min Table 18. Mean swimming speeds of adult sockeye calculated over 30 minute in t e r v a l s after 1/2 hour i n control conditions (T0), two hours of water turnover (T0 - T120) and one hour at test l e v e l s (T120 - T180). Results of s t a t i s t i c a l tests (repeated measures ANOVA) are included for each condition. Temp. S a l i . N Mean Swimming Speed (1/s) for each 30 minute F P > F ( C) (ppt) i n t e r v a l (SD i n brackets) T0 T30 T60 T90 T120 T150 T180 8 20 10 0.46 (0.21) 0.43 (0.25) 0.41 (0.23) 0.42 (0.23) 0.39 (0.21) 0.38 (0.12) 0.37 (0.18) 0. 48 -8 30 14 0.38 (0.13) 0.40 (0.18) 0.40 (0.17) 0.36 (0.15) 0.38 (0.21) 0.41 (0.22) 0.38 (0.14) 0. 55 -12 20 15 0.42 (0.18) 0.37 (0.21) 0.38 (0.18) 0.37 (0.17) 0.38 (0.13) 0.39 (0.18) 0.40 (0.19) 0. 50 -12 30 11 0.40 (0.16) 0.39 (0.16) 0.38 (0.14) 0.39 (0.19) 0.41 (0.20) 0.38 (0.21) 0.37 (0.16) 0. 45 -16 20 15 0.40 (0.15) 0.47 (0.16) 0.54 (0.22) 0.55 (0.18) 0.55 (0.22) 0.60 (0.23) 0.60 (0.26) 7. 75 <0.001 16 30 11 0.42 (0.12) 0.42 (0.12) 0.47 (0.23) 0.49 (0.15) 0.49 (0.17) 0.56 (0.18) 0.55 (0.16) 4. 25 <0.001 -79-Figure 12. Mean swimming spgeds (+/-SEM) of adult sockeye salmon during exposure to 16 C pooled for f i s h taken from (A) northern sets- Nl, N2, N3 (n= 16), and (B) from southern sets SI and S2 (n= 10). Values were calculated at 30 minute i n t e r v a l s for control conditions (T0), two hours of water turnover (T0 - 120), and one hour at test l e v e l s (T120 - T180). Approximate changes i n temperature and s a l i n i t y are included i n the upper portion of each figure. TEMPERATURE (°C) SALINITY (ppt) 30 60 90 120 150 180 TIME (min) Table 19. Average swimming speeds of adult sockeye salmon calculated over 30 minute inter v a l s after 1/2 hour i n control conditions (T0), 2 hours of water turnover (T0 - T120) and 1 hour exposure to 16°C (T120 - T180). Mean values are given for the d i f f e r e n t sampling sets and for pooled data from northern and southern areas. Results from s t a t i s t i c a l tests (repeated measures ANOVA) are included for separate and pooled samples. Set number N Mean Swimming Speed (1/s) for each 30 minute F P > F in t e r v a l (SD i n brackets)  T0 T30 T60 T90 T120 T150 T180 N1/N2 10 0.46 (0.19) 0.46 (0.14) 0.54 (0.24) 0.54 (0.24) 0. 57 (0.22) 0.67 (0.22) 0.60 (0.24) 5 .88 <0. 001 N3 6 0.31 (0.16) 0.36 (0.10) 0.47 (0.16) 0.50 (0.12) 0.41 (0.08) 0.51 (0.13) 0.61 (0.19) 5 .14 <0. 001 SI 5 0.41 (0.17) 0.37 (0.15) 0.50 (0.25) 0.53 (0.22) 0.54 (0.20) 0.45 (0.20) 0.54 (0.27) 2 .00 0. 105 S2 5 0.38 (0.09) 0.43 (0.11) 0.42 (0.21) 0.44 (0.14) 0. 51 (0.14) 0.58 (0.28) 0.53 (0.24) 1 .77 0. 150 North pooled 16 0.39 (0.13) 0.43 (0.13) 0. 52 (0.21) 0.52 (0.18) 0.51 (0.19) 0.61 (0.20) 0.60 (0.22) 10 .60 <0. 001 South pooled 10 0.39 (0.13) 0.41 (0.18) 0.46 (0.22) 0.49 (0.18) 0.52 (0.24) 0.52 (0.24) 0.53 (0.24) 2 .64 0. 025 -82-periods during the control, water-turnover, and test phases. The conditions for which data were recorded include: 8°C, 30 ppt; 10°C, 20 ppt; 10°C, 30 ppt; and 16°C, 30 ppt. This allowed for the main effects (temperature and s a l i n i t y ) to be examined, but interactions between factors were not compared. Fish were not separated by geographical area. Results for f i s h maintained i n control conditions are included i n Table 20. S t a t i s t i c a l tests detected no difference i n the 4 parameters that were recorded. In addition, analyses showed no e f f e c t of decreasing temperature (Table 21) or s a l i n i t y (Table 22) on any of the observed behaviors. Nosing and finning were not influenced by increasing temperature. However, both swimming a c t i v i t y and turning rate increased within 30 min exposure to 16°C water (Table 23). In the f i n a l hour of testing, locomotor a c t i v i t y had s t a b i l i z e d . Turning rate appeared to decrease, however, Newman-Keuls test f a i l e d to detect a s i g n i f i c a n t r e s u l t . The el e c t r o n i c and v i s u a l methods of data c o l l e c t i o n both showed an e f f e c t of increasing temperature on locomotion. However, there was some v a r i a t i o n i n swimming a c t i v i t y recorded by the two methods (Table 24). The swimming speed of sockeye during the i n i t i a l 30 min exposure to 16°C water was low compared to the rate of locomotor a c t i v i t y and turning that was measured by v i s u a l means. -83-Table 20. A c t i v i t y of adult sockeye salmon during exposure to control temperature (12 C) and control s a l i n i t y (30 ppt). There were four a c t i v i t y parameters, each recorded for ten minute i n t e r v a l s , at various times i n the experiment. Data c o l l e c t i o n corresponded to the experimental periods. These included; the i n i t i a l control phase (Time 1), ten minutes during the f i r s t 1/2 hour of water turnover (Time 2), and ten minutes during the f i r s t 1/2 hour at tes t l e v e l s (Time 3). Mean values are events per ten minute i n t e r v a l . Standard deviations (in brackets below means) and re s u l t s from s t a t i s t i c a l (repeated measures ANOVA)_analyses are included i n the table. A c t i v i t y Turns Noses Fins (per 10 min) (per 10 min) (per 10 min) (per 10 min) Time 1 11.78 8.60 1.78 0.67 (11.96) (10.70) (4.30) (2.00) Time 2 15.90 3.22 0.67 1.00 (9.70) (3.07) (1.12) (1.80) Time 3 14.00 3 . 78 0.33 0.22 (14.70) (4.92) (0.50) (0.44) N 9 9 9 9 ANOVA F 0.82 1.55 0.77 0.53 P > F 0.80 0.24 — — -84-Table 21. A c t i v i t y of adult sockeye salmon during exposure to decreasing temperature (8°C) and constant s a l i n i t y (30 ppt). There were four a c t i v i t y parameters, each recorded for ten minutes i n control conditions (Time 1), ten minutes during the f i r s t 1/2 hour of water turnover (Time 2), and for ten minutes during the f i r s t 1/2 hour at test l e v e l s (Time 3). Mean values are events per ten minute i n t e r v a l . Standard deviations (in brackets below means) and resu l t s from s t a t i s t i c a l analyses (repeated measures ANOVA) are included i n the table. A c t i v i t y Turns Noses Fins (per 10 min) (per 10 min) (per 10 min) (per 10 min) Time 1 10. 30 2 .14 1.18 0.43 (10.70) (5.24) (3.21) (1.62) Time 2 14.14 5.42 0.68 0. 91 (11 .05) (8.79) (1.05) (1 .33) Time 3 13.71 2. 28 0.92 1 .26 (14.51) (4.11) (1.83) (1-46) N 7 7 7 7 ANOVA F 0.24 0.80 0.63 0.81 P > F - - - --85-Table 22. A c t i v i t y of adult sockeye salmon during exposure to control temperature (12 C) and decreasing s a l i n i t y (20 ppt). There were four a c t i v i t y parameters, each recorded for ten minutes i n control conditions (Time 1), ten minutes during the f i r s t 1/2 hour of water turnover (Time 2), and for ten minutes during the f i r s t 1/2 hour at test l e v e l s (Time 3). Mean values are events per ten minute i n t e r v a l . Standard deviations (in brackets below means) and results from s t a t i s t i c a l analyses (repeated measures ANOVA) are included i n the table. A c t i v i t y Turns Noses Fins (per 10 min) (per 10 min) (per 10 min) (per 10 Time 1 13.33 4.25 1. 50 1.17 (9.43) (5.07) (3.34) (2.29) Time 2 13 .33 1.83 0. 50 0.67 (9.37) (2.12) (1-45) (1-37) Time 3 16 .08 3 . 25 1 .67 1 .83 (8.50) (5.94) (5.77) (3.61) N 12 12 12 12 ANOVA F 0. 59 0. 76 0.34 1.15 P > F 0.33 -86-Table 23. A c t i v i t y of adult sockeye salmon during exposure to increasing temperature (16°C) and control s a l i n i t y (30 ppt). There were four a c t i v i t y parameters, each recorded for ten minutes i n control conditions (Time 1), ten minutes during the f i r s t 1/2 hour of water turnover (Time 2), and for ten minutes during the f i r s t 1/2 hour at test l e v e l s (Time 3). Mean values are events per ten minute i n t e r v a l . Standard deviations (in brackets below means) and results from s t a t i s t i c a l analyses (repeated measures ANOVA) are included i n the table. A c t i v i t y Turns Noses Fins (per 10 min) (per 10 min) (per 10 min) (per 10 min) Time 1 8.43 5.21 1. 36 1.07 (6.74) (5.45) (3.71) (3.20) Time 2 19.43 18.71 3.93 2 .07 (19.67) (18.13) (6.74) (2.43) Time 3 22.21 10.57 0. 79 0. 93 (8.44) (8.86) (1.81) (1.90) N 10 10 10 10 ANOVA F 22.41 5 .14 2.14 1.33 P > F < 0.001 0.01 0.14 0. 28 -87-Table 24. The mean swimming speeds, locomotor a c t i v i t y and turning rate of adult sockeye salmon during exposure to increasing temperature and control s a l i n i t y . Standard deviations are included i n brackets under each mean. Swimming speed was calculated at 1/2 hour i n t e r v a l s during control (Time 1), water turnover (Time 2), and test (Time 3) i n t e r v a l s . A c t i v i t y and turning rate were recorded v i s u a l l y for 10 minute i n t e r v a l s during each of the three time periods. Time N Mean Swimming A c t i v i t y Turns Period Speed ( l / s ) (per 10 min) (per 10 min) 1 17 0.38 11.4 4.8 (0.12) (5.3) (5.3) 2 17 0.40 18.9 16.4 (0.13) (9.2) (18.0) 3 17 0. 58 23.9 10.2 (0.21) (13.4) (9.1) -88-DISCUSSION This study was undertaken to gain a better understanding of how environmental factors may influence the nearshore migration of sockeye salmon. The only factor that affected the locomotor a c t i v i t y of juvenile and adult sockeye was increasing temperature. Swimming speed was not influenced by s a l i n i t y or decreasing temperature, and there was no in t e r a c t i o n between factors. Differences between test f i s h based on race, sex, area of capture, and time of experiment did not a f f e c t locomotor behavior. Both juvenile and adult sockeye increased swimming speed during exposure to warm water (Figure 7, Figure 11). Because the juvenile behavior was not recorded v i s u a l l y , turning behavior could not be assessed. However, the adults showed an increase both i n turning rate and locomotor a c t i v i t y (Table 23). The behaviors demonstrated by test f i s h were consistent with previously described mechanisms of animal orientation. Fraenkel and Gunn (1961) suggested that an increase i n locomotor a c t i v i t y (orthokinesis) when conditions are poor, coupled with a decrease i n a c t i v i t y when conditions are favourable leads to an aggregation of animals i n a preferred temperature range. Fraenkel and Gunn (1961) also suggested that an elevation i n turning rate (klinekinesis) when an unfavourable environment i s -89-encountered increases the p r o b a b i l i t y of finding the preferred area. When favourable conditions are relocated, turning immediately decreases and the animal maintains po s i t i o n i n the desired f i e l d . If favourable conditions are not located, 'adaptation' occurs and turning rate gradually declines. In t h i s way the animal increases i t s area of search and raises i t s chance of finding the preferred conditions (Fraenkel and Gunn 1961). Few studies have applied the mechanisms described by Fraenkel and Gunn (1961) to salmon orient a t i o n . N e i l l (1979) tested a computer simulation of Fraenkel and Gunn's (1961) hypotheses using Ivlev's (1960) A t l a n t i c salmon data. N e i l l ' s (1979) model f a i l e d to show that s t r i c t orthokinesis allowed adequate avoidance of l e t h a l temperatures. Although k l i n e k i n e t i c responses were more e f f e c t i v e , he showed that a k l i n e k i n e s i s 'with avoidance' produced re s u l t s comparable to those given by Ivlev (1960). In his model, N e i l l (1979) assumed that turning rate was dependent on the i n t e r a c t i o n between two variables- recent temperature stress and rate of thermal change. Thus, turning rate increased when a combination of these parameters exceeded some pre-set tolerance l i m i t . In the present study, turning rates of adult sockeye exposed to 16°C declined during the f i n a l hour of testing, while swimming speeds remained high (Table 19, Table 23). This may have resulted from*'adaptation' s i m i l a r to the -90-mechanism described by Fraenkel and Gunn (1961). However, the results could also be i n accordance with N e i l l ' s (1979) model of k l i n e k i n e s i s based on recent thermal experience and rate of temperature change ( i . e . during tests, the rate of temperature change decreased throughout the water turnover period). The decline i n turning rate was not s t a t i s t i c a l l y s i g n i f i c a n t , and random va r i a t i o n was high (Table 23); therefore, I hesitate to make any conclusions regarding the present data set. Orientation to s a l i n i t y gradients i s considered to involve the k i n e t i c mechanisms described by Fraenkel and Gunn (1961). Mclnerney (1964) hypothesized that juvenile salmon maintain p o s i t i o n i n a s a l i n i t y f i e l d using k l i n e k i n e t i c rather than orthokinetic behavior. Holliday (1971) also suggested that k l i n e k i n e t i c responses allow f i s h to maintain p o s i t i o n i n a s a l i n i t y gradient. In the present study, turning rates of juvenile sockeye were not recorded, however, there was no orthokinetic response to test s a l i n i t i e s (Table 9). S i m i l a r l y , the adult salmon I tested did not exhibit orthokinetic or k l i n e k i n e t i c responses to decreasing s a l i n i t y (Table 22). Both juvenile and adult sockeye were able to withstand a 4°C decrease i n temperature without influencing locomotor a c t i v i t y (Figure 5, Figure 9). The lack of a behavioral response suggests that sockeye salmon may u t i l i z e p h y siological means to deal with decreasing temperatures. -91-One mechanism that has been reported for a number of f i s h species involves molecular temperature compensation (Dizon et a l . 1978, Stevens and Fry 1972, Glova 1972, Conner et a l . 1964). Temperature compensation may involve an enhanced a f f i n i t y of cert a i n enzymes for t h e i r substrate at low temperature ('positive thermal modulation'), as well as the use of enzyme varients (reviewed by Hazel and Prosser 1974, Hochachka and Somero 1970). Other workers have suggested that some eurythermal species have an enhanced a b i l i t y to regulate m y o f i b r i l l a r ATPase a c t i v i t y over a wide range of temperatures (Heap et a l . 1986). Behriger (1969) showed that migrating pink salmon maintained high l e v e l s of energy conversion over an extensive thermal range, and suggested that enzyme/substrate modulation and decreased a l l o s t e r i c i n h i b i t i o n at low temperatures were the most l i k e l y mechanisms involved. In the f i e l d , migrating sockeye swim faster than the f i s h I tested (Quinn and terHart 1987, Quinn 1988), and may show a d i f f e r e n t response to decreasing temperature. However, the results do suggest that some mechanism of adaptation i s involved. The a b i l i t y of sockeye salmon to withstand a wide thermal range i s emphasized by the v e r t i c a l migrations of both juveniles and adults. In summer, the d a i l y v e r t i c a l migration i n lakes may expose sockeye fry to temperature ranges of 10°C (Brett 1971, Barraclough and Robinson 1972), while homing adults may move through thermal -92-gradients of 8°C i n a matter of minutes (Quinn and terHart 1987) . Temperature compensation may be an important component of the salmon migratory strategy. At various stages of t h e i r l i f e h i s t o r y salmon encounter dramatic temperature gradients that could p o t e n t i a l l y compromise locomotor movements. Since adult sockeye migrate on a r e l a t i v e l y t i g h t energy budget (Brett 1983) and at a constant rate (Groot and Quinn 1987), i t would not be conducive to survival i f cold temperatures dramatically decreased swimming a c t i v i t y . Migrating s i l v e r eels that encounter excessively cold autumn temperatures h a l t the migration and hibernate u n t i l the following spring (Westin and Nyman 1977). An alt e r n a t i v e strategy of temperature compensation would allow sockeye a greater degree of freedom i n t h e i r movements, and, i n e f f e c t increase the thermal zone of e f f i c i e n t operation (Crawshaw 1979). Juvenile and adult sockeye responded to elevated temperatures by increasing locomotor a c t i v i t y (Figure 4, Figure 8). This may r e f l e c t a lesser a b i l i t y to compensate at high temperatures compared to low temperatures (eg. Hochachka and Somero 1971, Peterson and Anderson 1969). For a mobile animal, elevated a c t i v i t y with increasing temperature would be an appropriate component of behavioral thermoregulation (Crawshaw 1979), whereas decreasing locomotion with decreasing temperatures would not. -93-When exposed to 16°C, a number of juvenile and adult sockeye continued to increase t h e i r swimming speeds even though temperatures had s t a b i l i z e d (Table 9, Table 18). The res u l t s were sim i l a r to the 'overshoot' reported by Peterson and Anderson (1969). They noted that at low temperatures and a modest rate of water turnover juvenile A t l a n t i c salmon i n i t i a l l y increased a c t i v i t y , followed by a plateau period, and a subsequent r i s e i n swimming speed. At higher rates of water turnover the f i s h tested by Peterson and Anderson (1969) showed a more pronounced overshoot, and a corresponding increase i n oxygen consumption. It appears l i k e l y that a si m i l a r mechanism influenced the locomotion of f i s h I tested; although, the adaptive sig n i f i c a n c e of t h i s behavior i s not known. The juvenile sockeye did not show a locomotor response to s a l i n i t y changes (Figure 6, Table 7), however, there may have been an in t e r a c t i o n between s a l i n i t y and temperature at 14°C (Figure 11). The average speeds of juvenile sockeye tested i n 14°C, 10 ppt and 14°C, 30 ppt, were somewhat lower than for f i s h exposed to 14°C, 20 ppt. It i s possible that s a l i n i t y challenge at higher temperatures may have ccmpromised metabolic functions of the smolts and caused a decrease i n v o l i t i o n a l swimming a c t i v i t y . Brett (1970) reported a 20 - 30% drop i n standard metabolism for sockeye smolts passing from fresh to saltwater. Houston (1959) noted a s i g n i f i c a n t decrease i n -94-locomotor a c t i v i t y of juvenile salmon undergoing seawater t r a n s i t i o n . The adult sockeye taken from the northern area exhibited a more pronounced locomotor response to increasing temperature then did f i s h c o l l e c t e d near the Fraser River (Figure 12). However, the small and unequal sample sizes make inter p r e t a t i o n of the results d i f f i c u l t . It i s possible that acclimation state had some influence on a c t i v i t y responses to increasing temperature. Fish taken from the southern region had access to warmer temperatures, and Quinn et a l . (1988) showed that Fraser River sockeye spend at least some time i n the warmer surface layers of the S t r a i t of Georgia. If acclimation was a factor a f f e c t i n g behavior, then locomotor responses might change as a function of time i n c a p t i v i t y . This was not the case (Table 17); although, conditioning to a new temperature may take weeks (Brett 1970), and the f i s h I tested were only held for a few of days. It i s also conceivable that developmental changes during the homestream approach had some influence on locomotor responses to temperature. A re l a t i o n s h i p between maturational state and behavioral response to environmental gradients has been demonstrated for a number of f i s h species (eg. Norris 1963, Baggerman 1957). The sockeye caught near the Fraser River had s i g n i f i c a n t l y higher levels of sex steroids (unpublished data), however, i t was not possible to -95-separate the influence of other factors such as acclimation state. For the present study, no conclusions can be made regarding the a f f e c t of maturational state on a c t i v i t y responses to test temperatures. It has been hypothesized that estuarine migrations depend on orientation to temperature and s a l i n i t y gradients (Mclnerney 1964, Baggerman 1960b). Hurley and Woodall (1968) concluded that time-varied changes i n preference for nearshore temperature and s a l i n i t y gradients lead pink salmon smolts to ocean feeding areas. Straty and Jaenicke (1980) suggested that the run timing and d i s t r i b u t i o n of B r i s t o l Bay sockeye smolts was influenced by d i r e c t responses to both temperature and s a l i n i t y . Opposing views contend that temperature and s a l i n i t y are not the main factors a f f e c t i n g smolt migrations. Ultrasonic tracking studies (LaBar et a l . 1978) indicated that environmental factors other than temperature and s a l i n i t y influenced the migratory movements of juvenile A t l a n t i c salmon. S i m i l a r l y , McCleave (1978) reported that responses to current were the main factor a f f e c t i n g the estuarine migration of A t l a n t i c salmon smolts. Some of the discrepancy concerning the role of environmental parameters relates to the behavior of the species i n question. For example, pink salmon t y p i c a l l y move downstream soon after yolk absorption, but may spend months i n estuaries p r i o r to migrating offshore (Hurley and -96-Woodall 1968). Therefore, temporal changes i n preference for colder, more saline water could play a role i n the seaward movement of pink salmon (Hurley and Woodall 1968). Orientation to temperature and s a l i n i t y gradients may be of less importance to migrating A t l a n t i c salmon smolts. Telemetry studies have shown that A t l a n t i c salmon move d i r e c t l y seaward and do not require extensive periods of acclimation (McCleave 1978). The smolts tracked by LaBar et a l . (1978) moved from fresh water to 29 ppt i n less than 48 h (see also T y t l e r et a l . 1978). If sequential changes i n temperature and s a l i n i t y preference do influence the migration, i t would be d i f f i c u l t to i d e n t i f y behavioral responses i n such a short t r a n s i t i o n period. The seaward movements of sockeye smolts i s generally d i r e c t and rapid (Brett 1983); thus, the use of nearshore gradients as an orientation mechanism must be r e l a t i v e l y b r i e f . The juvenile sockeye I tested did not exhibit a temporal change i n locomotor response to increasing temperature (Table 8) and the f i s h were able to withstand 10 ppt deviations i n s a l i n i t y . Acclimation to 10°C, 20 ppt for 1 wk p r i o r to the experiments may have increased tolerance to s a l i n i t y challenge, and decreased the need for behavioral avoidance. Otto and Mclnerney (1970) reported that preference/avoidance responses to s a l i n i t y gradients would not be an e f f e c t i v e d i r e c t i n g mechanism for juvenile coho salmon once the f i s h were acclimated to intermediate - 9 7 -s a l i n i t i e s . Changes i n temperature influenced the swimming a c t i v i t y of juvenile and adult sockeye, and locomotor responses were consistent with known k i n e t i c mechanisms of orientat i o n . I w i l l now consider the possible ecological s i g n i f i c a n c e of these results on the coastal migration of sockeye salmon. Great Central Lake sockeye begin the downstream migration i n A p r i l or May (Groot et a l . 1986). Robinson and Barraclough (1972) reported that GCL smolts migrating i n the spring have been exposed to waters of 2 - 6°C for the previous 5 mo. Therefore, p r i o r to the downstream migration i t i s probably safe to assume that the salmon are conditioned to r e l a t i v e l y cold temperatures. The smolts move out of the Somass River (Figure 1) and through the inner estuary, which extends about 5 - 6 km from the r i v e r mouth. T u l l y (1949) showed that sockeye migrating through Alberni Inlet i n spring would encounter temperatures of 13 - 15°C at the surface, and 9 - 10°C at a depth of 10 m (see also Morris and Leany 1980). T u l l y (1949) also reported that maximum surface temperatures were located near the estuary and progressively decreased towards Barkley Sound. Given the behavior of the smolts I tested, and the arrangement of temperature gradients i n Alberni Inlet, i t i s possible that locomotor responses to temperature aid the -98-migration to oceanic waters. However, i t i s unl i k e l y that orthokinesis i s the only factor involved. Pickard (1963) showed that over the length of Alberni Inlet temperatures at 10 m depth d i f f e r e d by only about 3°C. It remains to be seen i f gradients of t h i s magnitude are s u f f i c i e n t to f a c i l i t a t e oriented movements, or i f additional guidance mechanisms are also required. During an E l Nino event, sockeye homing to the Fraser River may be exposed to anomalous coastal temperatures 2°C above normal (Dodimead 1985). The present study showed that adult sockeye respond to temperature changes of t h i s magnitude by increasing locomotor a c t i v i t y and turning rate. Therefore, i t i s possible that orthokinetic and k l i n e k i n e t i c responses to warm temperatures influence the nearshore migration of Fraser River adults. The re s u l t s support the hypothesis of T u l l y et a l . (1960) and Royal and T u l l y (1961) that avoidance of warm waters emanating from the south cause a higher than average diversion of sockeye through Johnstone S t r a i t . Groot and Quinn (1987) hypothesized that the ocean d i s t r i b u t i o n p r i o r to the nearshore approach influences the location where sockeye make l a n d f a l l , and thereby determines the route taken to the Fraser River. If adult sockeye maintain consistent speed and compass d i r e c t i o n while homing (Quinn and Groot 1984), then the location p r i o r to the onset of migration w i l l determine where, when, and i f the f i s h -99-encounter steep environmental gradients- It may be that both oceanic d i s t r i b u t i o n and locomotor responses to gradients encountered enroute act s y n e r g i s t i c a l l y to influence the path taken to the Fraser River. More information on ocean movements i n r e l a t i o n to environmental parameters i s required to better understand the r e l a t i v e importance of each factor. The present study showed that sockeye respond to elevated temperatures by increasing swimming a c t i v i t y , however, additional work i s required to assess the use of v e r t i c a l avoidance as a pot e n t i a l orientation mechanism. Quinn et a l . (1988) found that adult sockeye swam deeper i n the warm waters of Georgia S t r a i t than did f i s h tracked i n colder, northern waters. V e r t i c a l temperature avoidance was also reported by 011a et a l . (1985) who showed that juvenile b l u e f i s h faced with cold temperatures increased t h e i r swimming speed and changed v e r t i c a l d i s t r i b u t i o n . The hypothesis posed i n thi s study was that rapid changes i n temperature and s a l i n i t y have a d i r e c t influence on the behavior of juvenile and adult sockeye and could thereby a f f e c t the nearshore migration. There was no locomotor response to decreasing temperature or changing s a l i n i t y , however, I conclude that warm temperatures could a f f e c t the movements of sockeye i n coastal waters. For Great Central Lake smolts, elevated locomotor a c t i v i t y and avoidance of warm temperatures may f a c i l i t a t e the migration -100-out of Alberni Inlet and Barkley Sound. The homing migration of Fraser River adults could be affected by anomalous temperatures o f f of the B r i t i s h Columbia coast, however, the location where temperature influences migration i s not known. Adults appear to u t i l i z e a combination of orthokinetic and k l i n e k i n e t i c responses to unfavourable temperatures, but p o t e n t i a l v e r t i c a l avoidance mechanisms require greater study. In developing a predictive model of sockeye migration, i t i s important to i d e n t i f y the factors involved, and to understand how these factors may a f f e c t migratory movements. The present study, and concurrent f i e l d investigations (Quinn 1988, Quinn et a l . 1988, Quinn and terHart 1987) have better characterized how a number of environmental parameters may influence the nearshore migration of sockeye salmon. Future work should be directed to oceanic regions to determine when and where these factors exert the greatest influence. LITERATURE CITED -101-Andrievskaya, L. D. 1957. The food of P a c i f i c salmon i n the northeastern P a c i f i c Ocean. J. Fish. Res. Bd. Can. Transl. Ser., 182: 64-75. Baggerman, B. 1957. 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