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Rheotaxis in fish, with particular reference to effects of temperature and some hormones on this reaction… Keenleyside, Miles Hugh Alston 1953

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RHEOTAXIS IN F I S H , WITH PARTICULAR R E F E R E N C E TO E F F E C T S OF TEMPERATURE AND SOME HORMONES ON T H I S R E A C T I O N IN YOUNG P A C I F I C SALMON b y M i l e s Hugh A l s t o n K e e n l e y s i d e A T H E S I S SUBMITTED IN P A R T I A L FULF ILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n t h e D e p a r t m e n t o f ZOOLOGY We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e s t a n d a r d r e q u i r e d f r o m c a n d i d a t e s f o r t h e d e g r e e o f MASTER OF ARTS Members o f t h e D e p a r t m e n t o f Z o o l o g y . T H E U N I V E R S I T Y OF B R I T I S H COLUMBIA A p r i l , 1953 ABSTRACT S e v e r a l s p e c i e s o f f i s h swim u p s t r e a m i n t o t h e a r e a o f g r e a t e s t t u r b u l e n c e i n a r t i f i c i a l l y c r e a t e d c u r r e n t s o f w a t e r . T h i s r e a c t i o n i s most p r o n o u n c e d w i t h y o u n g s a l -mon and t r o u t . T r e a t m e n t w i t h t h y r o x i n e , t e s t o s t e r o n e a n d t h r e e e s t r o g e n compounds s l i g h t l y i n c r e a s e s t h e r a t e a t w h i c h e o h o a n d s o c k e y e s a l m o n s m o l t jump u p s t r e a m o v e r a d a m . E l e v a t e d t e m p e r a t u r e s i n c r e a s e t h e amount o f n e g a t i v e r h e o t a x i s shown b y chum f r y and c o h o s m o l t i n c i r c u l a r c u r r e n t s . TABLE OF CONTENTS Page INTRODUCTION 1 MATERIALS AND METHODS 6 General Responses to Cu r r e n t s of Water 6 Preference of Turbulent or Quiet Water 8 M o d i f i c a t i o n of Rheotaxis by Hormone Treatment 9 E f f e c t s of Temperature Changes on Rheotaxis 11 RESULTS 14 General Responses t o Cur r e n t s 14 Preference f o r Flowing or Quiet Water 15 Hormones and Rheotaxis 17 Temperature and Rheotaxis 21 DISCUSSION 23 Sensory B a s i s o f Rheotaxis 23 General R h e o t a c t i c Reactions 26 Hormones and Rheotaxis 30 T h y r o i d Hormone and A c t i v i t y 32 Gonad Hormones and A c t i v i t y 34 Temperature and a c t i v i t y 36 SUMMARY 3d ACKNOWLEDGMENTS 39 LITERATURE CITED 40 APPENDIX 45 1 INTRODUCTION In order not to be carr i e d about passively by currents, aquatic animals are variously adapted to maintain p o s i t i o n i n t h e i r p a r t i c u l a r ecological niches. Many i n -vertebrates can l i v e i n fast-flowing waters, and some f i s h e s have well developed ventral sucking structures which enable them to l i v e i n highly turbulent mountain streams (Hora, 1930). The P a c i f i c lamprey uses i t s sucking mouth to hold onto rocks as i t moves into fresh water from the ocean to spawn. Some f i s h , such as chum and pink salmon f r y , are highly active i n fres h water and exhibit a strong tendency to swim vigorously against f a s t currents, thus holding p o s i t i o n i n p a r t i c u l a r areas during daylight. Other active f i s h l i k e coho salmon f r y show t e r r i t o r i a l behaviour and tend to stay i n quieter waters where they remain close to p a r t i c u l a r objects i n the environment (Hoar, 1951 a). Swimming against the current i s the method used by most f i s h e s to hold p o s i t i o n i n flowing streams. This i s not a novel idea. Such a c t i v i t y has been recognized by f i s h e r -men and nature lovers f o r a very long time, and i s now usually r e f e r r e d to i n the s c i e n t i f i c l i t e r a t u r e as rheotaxis. A t a x i s i s a directed o r i e n t a t i o n reaction i n which movement i s towards or away from a source of stimulation (Fraenkel and Gunn, 1940). Thus, p o s i t i v e and negative phototaxis are move-ments by an animal straight towards and away from a l i g h t 2 source. It i s suggested here that p o s i t i v e rheotaxis i s the movement by f i s h upstream against a current of water, and negative rheotaxis i s swimming movements with the current. It should be emphasized that rheotaxis i s not confined to the f i s h e s , but i s also exhibited by r e p t i l e s and many inverte-brates. Buddenbrock (1952) presents a b r i e f outline of the occurrence of rheotaxis throughout the animal kingdom. One of the aims of t h i s thesis i s to determine how widespread among fishes i s the tendency to swim a c t i v e l y with or against currents of water and to determine how uniform the type of response i s among several species. As many species as possible were u t i l i z e d , and, although a large number of experiments was not performed with each species, the answers to several questions were sought by observing t h e i r behaviour i n a r t i f i c i a l l y created turbulent flows i n long narrow troughs. Some of these questions are: Do these f i s h swim against the current a l l or most of the time ? I f so, i s there v a r i a t i o n i n the rate of i n i t i a l response, and i s the response consistent? Do they prefer turbulent or quiet water when both are a v a i l -able ? Is there v a r i a t i o n i n the degree of a c t i v i t y shown by the d i f f e r e n t species when i n turbulent waters ? Do some f i s h , but not others, jump out of the water ? Some c o r r e l a t i o n was also sought between the a c t i v i t y of the animals i n these currents and the natural habitat i n which they are found. In other words, do young salmon that swim about i n lakes and r i v e r s show a higher degree of p o s i t i v e response i n a r t i f i c i a l currents 3 than sculpins and eels, which l i v e mostly on the bottom ? Many of these questions may be important i f we are eventually to understand the mechanisms governing long-dis-tance movements of some f i s h . Russell (1937) has shown that some marine fi s h e s regularly move with or against the d i r e c -t i o n of flow at d i f f e r e n t times during t h e i r l i f e h i s t o r i e s . Such generalizations do l i t t l e to further our understanding of the basic fac t o r s involved i n the d e l i c a t e balance .. between f i s h e s and t h e i r environment; factors which i n i t i a t e , d i r e c t and control such outstanding movements of f i s h as those occurring i n some diadromous (Myers, 1949) species. However, Russell's ideas do serve to emphasize that the movements of f i s h e s i n d i r e c t r e l a t i o n to currents are not uncommon. The metabolism, a c t i v i t y and d a i l y l i f e of p o i k i l o -thermic animals are probably governed to a greater extent by temperature than by any other variable i n t h e i r external en-vironment. Such a generalization need not be elaborated on here. The r e l a t i o n s h i p of temperature to the reactions of f i s h e s to currents i s of more p a r t i c u l a r i n t e r e s t , however, when dealing with species such as the P a c i f i c salmon that have complicated l i f e h i s t o r i e s . Of perhaps greater importance i n understanding the complex of events that leads to these f i s h moving successfully from fresh to salt water and back again i s the r o l e played by hormones. Tinbergen (1950) has described the reproduction of the male three-spined stickleback, starting with migration and ending with the reproductive act, as an example of the 4 h i e r a r c h i c a l pattern i n which the nervous mechanisms under-l y i n g i n s t i n c t i v e behaviour i s l a i d out. Emphasis i s placed on the f a c t that appetitive behaviour (or, i n t h i s case, migration from s a l t or deep, fresh water into shallow, fresh water) i s the highest or primary l e v e l of the i n s t i n c t i v e re-productive act. This behaviour i s i n i t i a t e d by the action of the gonad hormone l e v e l of the blood on nervous centres i n the brain. The gradual increase i n length of day i n springtime acts on the p i t u i t a r y gland, which i n turn activates the go-nads of the stickleback to secrete increasing amounts of t h e i r hormones. This i n i t i a t e s , through the brain, the most gene-r a l i z e d type of appetitive behaviour, i . e . migration, which continues u n t i l c e r t a i n sign s t i m u l i (or r e l e a s e r s ) , of which higher temperatures i s one, release a more specialized type of appetitive behaviour', i n t h i s case, holding and defence of a t e r r i t o r y . Wandering about the t e r r i t o r y continues u n t i l further sign s t i m u l i release the next most specialized act, either f i g h t i n g or nest building. Thus, hormone l e v e l i s of prime importance i n the i n i t i a t i o n of the most generalized type of appetitive behaviour, and temperature i s one of the external releasers helping to direct the behaviour of the f i s h along proper l i n e s . Such an analysis i s , i n part, similar to Fontaine's (1948) theory that hormonal changes i n f i s h create i n t e r n a l stresses which lead to a movement out of one area into another. It has been suggested that the spawning migrations of adult P a c i f i c salmon are b a s i c a l l y no more complicated than t h i s 5 r e p r o d u c t i v e m i g r a t i o n o f t h e s t i c k l e b a c k ( H o a r , 1951 b ) « I t m i g h t n o t be t o o r a s h , t h e n , t o p r o p o s e t h a t t h e d o w n s t r e a m movement o f y o u n g s a l m o n i s a l s o due t o t h e p r e s e n c e o f a h i e r a r c h i c a l l y o r g a n i z e d s y s t e m o f n e r v o u s c e n t r e s i n t h e b r a i n w h i c h a r e a c t i v a t e d i n t u r n by i n t e r n a l m e d i a s u c h a s h o r -mones a n d b y e x t e r n a l s t i m u l i s u c h a s t e m p e r a t u r e . A d e t a i l e d a n a l y s i s s i m i l a r t o T i n b e r g e n ' s w o r k o n t h e s t i c k l e b a c k h a s n o t b e e n a t t e m p t e d w i t h P a c i f i c s a l m o n ; h o w e v e r , H o a r (1951a) h a s made many c o n t r i b u t i o n s t o o u r k n o w l e d g e o f t h e c o m p a r a -t i v e b e h a v i o u r o f t h e s e y o u n g f i s h a n d i t i s i n t h e h o p e o f f u r t h e r i n g o u r u n d e r s t a n d i n g o f t h e p a r t p l a y e d b y s u c h f a c -t o r s a s h o r m o n e s a n d t e m p e r a t u r e o n t h e r e a c t i o n s o f t h e s e f i s h t o c u r r e n t s t h a t t h e l a t t e r p a r t o f t h i s s t u d y h a s b e e n c o n d u c t e d . I n s u m m a r y , t h e n , t h e p u r p o s e o f t h i s t h e s i s i s t h r e e f o l d . F i r s t l y , a n a t t e m p t was made t o d e t e r m i n e , w i t h s e v e r a l s p e c i e s , how w i d e s p r e a d r h e o t a x i s i s among f i s h e s , t o w h a t e x t e n t t h e a c t i v i t i e s o f f i s h e s v a r y i n f l o w i n g s t r e a m s , a n d w h e t h e r b o t h p o s i t i v e a n d n e g a t i v e r h e o t a x i s o c c u r . S e c o n d l y , t h e e f f e c t s o f t h y r o x i n e , t e s t o s t e r o n e and t h r e e e s t r o g e n c o m p o u n d s o n t h e a c t i v i t y o f c o h o a n d s o c k e y e s m o l t i n t u r b u l e n t w a t e r w e r e s t u d i e d . T h i r d l y , t h e p o s s i b i l i t y was c o n s i d e r e d o f s u d d e n t e m p e r a t u r e c h a n g e s r a d i c a l l y m o d i f y -i n g t h e r h e o t a c t i c r e a c t i o n o f c o h o and s o c k e y e s m o l t . 6 M A T E R I A L S AND METHODS E x p e r i m e n t s w e r e c a r r i e d o u t a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a f r o m May 1952 t o A p r i l 1953. F i s h w e r e h e l d i n c e m e n t h a t c h e r y t r o u g h s i n t h e b a s e m e n t o f t h e B i o l o g i c a l S c i e n c e s b u i l d i n g . W a t e r e n t e r i n g t h e h a t c h e r y was r u n t h r o u g h g r a v e l and c h a r c o a l f i l t e r s s e t u p a t t h e h e a d o f e a c h t r o u g h . M o r t a l i t y f r o m c h l o r i n e i n t h e w a t e r was t h u s a v o i d e d . F o o d , i n g e n e r a l , c o n s i s t e d o f c a n n e d s a l m o n m i x e d w i t h p a b l u m and c o m m e r c i a l f i s h m e a l . Some f i s h , s u c h a s e e l s , f e d more r e a d i l y o n a d i e t o f e a r t h w o r m s , w h i t e w o r m s ( E n c h y t r a e u s ) . D a p h n i a o r m e a l worms ( T e n e b r i o ) . T a b l e I l i s t s t h e common a n d s c i e n t i f i c names o f t h e s p e c i e s u s e d , t o g e t h e r w i t h t h e l o c a l i t y w h e r e e a c h was c a u g h t . U n d e r e a c h g r o u p o f e x p e r i m e n t s t o be d e s c r i b e d b e l o w , t h e s p e c i e s u t i l i z e d a r e l i s t e d , w i t h c o r r e s p o n d i n g s i z e d a t a . G e n e r a l R e s p o n s e s t o C u r r e n t s o f W a t e r . T h e f i s h e s s t u d i e d i n t h i s and t h e n e x t s e r i e s , and t h e i r mean l e n g t h s , a r e l i s t e d i n T a b l e I I . T h e e x p e r i m e n t a l p e r i o d l a s t e d f r o m A u g u s t 1 t o D e c e m b e r 15, 1952, d u r i n g w h i c h t i m e t h e t e m p e r a t u r e i n t h e h a t c h e r y t r o u g h s f e l l f r o m 18 t o 8 ° C . M e t a l t r o u g h s 242 c m . l o n g , 26 c m . w i d e a n d 19 c m . d e e p w e r e e m p l o y e d f o r o b s e r v a t i o n s o f f i s h e s i n l i n e a r c u r r e n t s . F i g u r e 1 shows two o f t h e s e t r o u g h s s e t up f o r t h e hormone e x -p e r i m e n t s t o be d e s c r i b e d l a t e r . A n o v e r f l o w p i p e 2 c m . i n T a b l e I. S p e c i e s O n c o r h y n c h u s k i s u t c h (Walbaum) 0 . t s h a w y t s c h a (Walbaum) 0. k e t a (Walb aum) 0 , n e r k a (Walbaum) Sa lmo gairdnerii k a m l o o p s J o r d a n C o t t u s asper R i c h a r d s o n A m e i u r u s n e b u l o s u s ( L e S u e u r ) A n g u i l l a b o s t o n i e n s i s L e S u e u r u s e d f o r s t u d y i n g r h e o t a x i s . Common name Where o b t a i n e d c o h o s a l m o n B r u n e t t e and A l o u e t t e R i v e r s , B . C . s p r i n g s a l m o n N i l e C r e e k h a t c h e r y , B . C . chum s a l m o n it it s o c k e y e s a l m o n M a r b l e m o u n t h a t c h e r y , W a s h . k a m l o o p s t r o u t S m i t h F a l l s h a t c h e r y , C u l t u s L a k e , B . C . p r i c k l y s c u l p i n D e e r L a k e , B . C . b r o w n c a t f i s h S t a v e R i v e r , B . C . a m e r i c a n e e l B e c a g u i m i c R i v e r , N . B , Table I I Names and fork lenths of fishes studie f o r general response to currents. Common name Mean length Standard deviation cm. cm. coho salmon 7.7 + O.67 spring salmon 6 .2 _+ 0.5& brown c a t f i s h 4.5 ±0.71 p r i c k l y sculpin 4 .3 + 0 .99 a t l a n t i c eel 29.7 +10.26 kamloops tro u t 6 .2 +1.15 Figure 1 . Apparatus f o r observing jumping of young salmon. Troughs were a l s o used f o r studying general res-ponses t o c u r r e n t s , and preference of f i s h f o r f l o w i n g or quiet water. P , 1/4 horsepower cen-t r i f u g a l pump; F, f r e e z i n g u n i t ; B, s l o p i n g metal catc h - b a s i n r e t u r n i n g water from e x p e r i -mental troughs t o c o o l i n g r e s e r v o i r below f r e e z i n g u n i t . 7 d i a m e t e r , a t one e n d , h e l d t h e w a t e r l e v e l a t 8" c m . , w h i l e w a t e r was pumped i n a t t h e o t h e r end t h r o u g h 1.2 c m . g l a s s t u b i n g , a t t h e r a t e o f 8" t o 10 l i t e r s p e r m i n u t e . A G e n e r a l E l e c t r i c 1/4 h o r s e p o w e r c e n t r i f u g a l pump o r t w o s m a l l e r E a s t e r n c e n t r i f u g a l pumps w e r e u s e d t o m a i n t a i n a c o n s t a n t a n d i d e n t i a l f l o w o f w a t e r i n t h e two t r o u g h s . T h e o v e r f l o w was s c r e e n e d o f f s o t h e s p a c e a v a i l a b l e t o t h e f i s h was 225 c m . l o n g . A l l s u r f a c e s i n c o n t a c t w i t h w a t e r w e r e c o v e r e d w i t h a l u m i n u m p a i n t . B y u s i n g f o u r o f t h e s e t r o u g h s a t one t i m e a g r e a t e r number o f e x p e r i m e n t s was p o s s i b l e . T h e p r o c e d u r e was t o p l a c e 12 f i s h o f one s p e c i e s i n t h e c e n t r a l t h i r d o f a n y t r o u g h b e t w e e n t w o p e r f o r a t e d p a r t i t i o n s w i t h no w a t e r c u r r e n t i n t h e t r o u g h . A f t e r one h o u r pumps w e r e t u r n e d o n , t h e i n f l o w r e g u l a t e d t o t h e d e s i r e d v o l u m e , t h e p a r t i t i o n s r e m o v e d , and o b s e r v a t i o n s o f t h e f i s h e s ' movements i m m e d i a t e l y b e g u n f r o m a p o s i t i o n w h e r e t h e f i s h w e r e n o t s t a r t l e d . R e d wax p e n c i l l i n e s marked t h e d i v i s i o n o f t h e a r e a o f t h e t r o u g h i n t o t h r e e e q u a l s e c t i o n s . T h e number o f f i s h i n e a c h o f t h e s e s e c t i o n s was n o t e d e v e r y 30 s e c o n d s f o r 15 m i n u t e s . T h i s r e c o r d i n g p r o c e d u r e was r e p e a t e d a f t e r one h o u r a n d a g a i n two h o u r s l a t e r . The f i s h were t h e n r e t u r n e d t o t h e h o l d i n g t r o u g h s . W a t e r t e m p e r a t u r e s w e r e t a k e n a n d t h e l i g h t i n t e n s i t y a t t h e w a t e r s u r f a c e i n t h e c e n t r e o f e a c h t r o u g h was r e c o r d e d w i t h a W e s t o n L i g h t M e t r e a f t e r e a c h e x -p e r i m e n t . A t o t a l o f s i x e x p e r i m e n t s f o r e a c h s p e c i e s Was p e r f o r m e d w i t h c o h o and s p r i n g s a l m o n , s c u l p i n s and e e l s , w h i l e c a t f i s h w e r e u s e d f o r e i g h t r e p l i c a t i o n s . 8 I n a l l e x p e r i m e n t s i n v o l v i n g e e l s and y o u n g s a l m o n p l a s t i c s c r e e n i n g c o v e r e d t h e t r o u g h t o p r e v e r t t h e f i s h f r o m e s c a p i n g . I n a n a l y s i n g t h e d a t a , t h e mean p e r c e n t o f f i s h i n t h e i n f l o w t h i r d o f t h e t r o u g h s e v e r y 30 s e c o n d s was d e t e r m i n e d f o r e a c h s p e c i e s . P r e f e r e n c e f o r T u r b u l e n t o r Q u i e t W a t e r . A m o d i f i c a t i o n o f t h e a b o v e a p p a r a t u s was d e s i g n e d t o d e t e r m i n e w h e t h e r f i s h w i l l move i n t o t u r b u l e n t o r q u i e t w a t e r . A p i e c e o f p l y w o o d 75 cm. l o n g a n d 2 4 c m . w i d e was p l a c e d i n t h e i n f l o w e n d o f t h e t r o u g h t o f o r m a c e n t r a l l o n g i t u d i n a l p a r t i t i o n down one t h i r d o f i t s l e n g t h . I n f l o w i n g w a t e r c o u l d be d i r e c t e d i n t o e i t h e r s i d e o f t h e p l y w o o d , t h u s c r e a t i n g t u r b u l e n c e o n one s i d e o n l y . A d d i t i o n o f m e t h y l e n e b l u e d y e showed, t h a t movement o f i n f l o w i n g w a t e r t o t h e o p p o s i t e s i d e o f t h e p a r t i t i o n was n e g l i g i b l e . The v o l u m e o f w a t e r pumped i n t o t h e t r o u g h was h e l d a t 1 0 l i t e r s p e r m i n u t e . I n a n y e x p e r i m e n t t h e i n f l o w o f w a t e r was s t a r t e d o n one s i d e o f t h e p a r t i t i o n . T w e l v e f i s h w e r e p l a c e d i n t h e o u t l e t e n d a n d p e r m i t t e d t o r o a m f r e e l y i n t h e t r o u g h . A f t e r one h o u r t h e numbers o f f i s h o n e a c h s i d e o f t h e p l y w o o d w e r e r e c o r d e d e v e r y 3 0 s e c o n d s f o r 15 m i n u t e s . The i n f l o w was t h e n s w i t c h e d t o t h e o t h e r s i d e and one h o u r l a t e r s i m i l a r r e c o r d s made f o r a n o t h e r 1 5 - m i n u t e p e r i o d . W a t e r t e m p e r a t u r e s and i l l u m i n a t i o n w e r e r e c o r d e d a f t e r e a c h e x p e r i m e n t . Goho s a l m o n , k a m l o o p s t r o u t , e e l s , s c u l p i n s and c a t f i s h w e r e u s e d i n t h e s e p r e f e r e n c e t e s t s . S i x e x p e r i m e n t s 9 w e r e c a r r i e d o u t w i t h t h e s a l m o n a n d t r o u t , and f i v e w i t h e a c h o f t h e o t h e r s p e c i e s . T h e mean p e r c e n t a g e o f f i s h o n e a c h s i d e o f t h e p a r t i t i o n a t t h e e n d o f one h o u r and a g a i n a t t h e e n d o f t w o h o u r s was c a l c u l a t e d f o r e a c h s p e c i e s . t a n d P v a l u e s w e r e c a l c u l a t e d t o show t h e s i g n i f i c a n c e o f t h e d i f f e r e n c e b e t w e e n means ( S n e d e c o r , 1946) . M o d i f i c a t i o n o f R h e o t a x i s b y Hormone T r e a t m e n t . C o h o and s o c k e y e s a l m o n s m o l t w e r e i m m e r s e d f o r v a r y i n g p e r i o d s o f t i m e i n hormone s o l u t i o n s t o d e t e r m i n e w h e t h e r o r n o t t h i s w o u l d a l t e r t h e i r r e a c t i o n s t o f l o w i n g w a t e r . The f o l l o w i n g h o r m o n e s w e r e u s e d : 2,500,000 2 , 0 0 0 , 0 0 0 1 , 6 0 0 , 0 0 0 1 , 6 0 0 , 0 0 0 2 0 , 0 0 0 , 0 0 0 s y n t h e t i c t h y r o x i n e - s o d i u m (BDH) 1 m e t h y l t e s t o s t e r o n e (BDH) 1 D i e n o e s t r o l (BDH) 1 S t i l b o e s t r o l (BDH) 1 E t h i n y l O e s t r a d i o l ( N y l e s t i n ) ( B D H ) 1 T h e c o n c e n t r a t i o n s o f t h y r o x i n e and t e s t o s t e r o n e u s e d w e r e b a s e d o n p r e v i o u s e x p e r i m e n t s w i t h s a l m o n ( H o a r e t a l , 1952) . C o n c e n t r a t i o n s o f t h e t h r e e e s t r o g e n s w e r e d i c t a t e d b y a v a i l -a b i l i t y and b y some p o t e n c y d a t a s u p p l i e d b y t h e B r i t i s h D r u g H o u s e s , b u t w e r e n o t b a s e d o n p r e v i o u s w o r k w i t h f i s h . G r o u p s o f 20 f i s h w e r e i m m e r s e d i n 20 l i t e r s o f a e r a t e d s o l u t i o n i n 22 l i t r e g l a s s b a t t e r y j a r s . T h e y w e r e f e d t w i c e d a i l y , e x c e p t o n week e n d s , and t h e s o l u t i o n s c h a n g e d e v e r y s e c o n d d a y . C o n t r o l g r o u p s w e r e k e p t u n d e r i d e n t i c a l c o n d i t i o n s i n h a t c h e r y t a p w a t e r . T o c o n t r o l t e m p e r a t u r e s t h e 10 j a r s were s e t i n one of t h e cement hatchery troughs and s u r -rounded by ru n n i n g water. Experiments were c a r r i e d out from January t o A p r i l , 1953, and temperatures i n the hatchery v a r i e d from 6 t o 9° C. F i s h t r e a t e d w i t h hormones were coho salmon smolt (£.9 + 0.54 cm.) and sockeye salmon smolt (£.2 _+ 0.53 cm.) Measurements were mean f o r k l e n g t h s . Jumping behaviour was s e l e c t e d as a t e s t f o r studying changes i n a c t i v i t y f o l l o w i n g hormone treatment. The l o n g metal troughs d e s c r i b e d p r e v i o u s l y were a g a i n u t i l i z e d . I n these t e s t s a c e n t r a l l y p l a c e d v e r t i c a l dam d i v i d e d them i n t o e q u a l - s i z e d upper and lower p o o l s . Water was r e c i r c u l a t e d by a l / 4 horse-power G.E. pump from a r e s e r v o i r , where a Parmetic f r e e z i n g u n i t ( u s i n g f r e o n gas) maintained the temperature equal to t h a t i n the hatchery. From the o u t l e t ends of t h e troughs water was r e t u r n e d t o the c o o l i n g r e s e r v o i r ( f i g u r e s 1 and 2 ) . The heig h t o f the dam above the lower p o o l was r e g u l a t e d by changing the h e i g h t of the o v e r f l o w p i p e . Coho were made t o jump over a 2 cm. dam, and sockeye, being s m a l l e r f i s h , had t o jump 1.5 cm. t o r e a c h the upper p o o l . The water volume e n t e r i n g each t r o u g h was h e l d at 14 l i t e r s per minute and p l a s t i c s c r e e n i n g prevented f i s h e s c a p i n g over the s i d e s . A l l p a r t s o f the appa-r a t u s were covered w i t h aluminum p a i n t and p e r i o d i c a l l y thoroughly c l e a n e d t o remove s l i m e . I n any experiment f i s h from two b a t t e r y j a r s were p l a c e d i n separate c o n t a i n e r s i n q u i e t water f o r one hour. Water c i r c u l a t i o n was s t a r t e d i n t h e troughs, water l e v e l s were adj u s t e d so the dams were the a p p r o p r i a t e h e i g h t , and one group F i g u r e 2 . A p p a r a t u s used t o pump a c o n s t a n t volume o f w a t e r o f r e q u i r e d t e m p e r a t u r e t h r o u g h e x p e r i -m e n t a l t r o u g h s . P , 1/4 horsepower G . E . c e n -t r i f u g a l pump; I , i n t a k e p i p e ; N , n o z z l e s ; F , t w i n c o i l P a r m e t i c f r e e z i n g u n i t . 11 o f f i s h was p u t i n t h e l o w e r p o o l o f e a c h t r o u g h . O b s e r v a t i o n s w e r e b e g u n a t o n c e f r o m a p o i n t o u t o f s i g h t o f t h e f i s h and t h e t i m e n e c e s s a r y f o r 50 p e r c e n t (10 f i s h ) t o jump t o t h e u p p e r p o o l was r e c o r d e d . F i s h w e r e t h e n r e t u r n e d t o t h e a p p r o p r i a t e b a t t e r y j a r . W a t e r t e m p e r a t u r e s , l i g h t i n t e n s i t y a n d c u r r e n t s p e e d w e r e r e c o r d e d a t t h e c o n c l u s i o n o f e a c h f e x p e r i m e n t . F i g u r e 3 shows a g r o u p o f t r o u t i m m e d i a t e l y b e l o w a d a m . E x p e r i m e n t s commenced a t t h e b e g i n n i n g o f t h e s e c o n d week o f t r e a t m e n t a n d w e r e r e p e a t e d f i v e o r s i x t i m e s a w e e k . A f t e r f o u r w e e k s of t r e a t m e n t e x p e r i m e n t s w e r e d i s c o n t i n u e d . F i s h were t h e n p l a c e d i n t h e m e t a l t u b s d e s c r i b e d l a t e r t o o b s e r v e t h e i r b e h a v i o u r i n c i r c u l a r c u r r e n t s f o l l o w i n g hormone t r e a t m e n t . T h e n t h e f i s h w e r e a n e s t h e t i z e d i n e t h y l u r e t h a n e s o l u t i o n , m e a s u r e d a n d p r e s e r v e d i n 10 p e r c e n t f o r m a l i n . T h e p e r i o d o f e x p e r i m e n t a t i o n was a r b i t r a r i l y d i v i d e d i n t o t h r e e w e e k l y s t a g e s a n d mean t i m e s ( i n m i n u t e s ) f o r 50 p e r c e n t o f t h e f i s h t o jump o v e r t h e dam w e r e c a l c u l a t e d f o r e a c h s t a g e . A t - t e s t was u s e d t o d e t e r m i n e t h e s i g n i f i -c a n c e o f t h e d i f f e r e n c e b e t w e e n t h e mean v a l u e s f o r e x p e r i -m e n t a l a n d c o n t r o l f i s h . T h e c a l c u l a t i o n s f o r t h y r o x i n e and t e s t o s t e r o n e t r e a t e d f i s h c o v e r p o o l e d r e s u l t s f r o m two s e r i e s o f e x p e r i m e n t s , w h i l e o n l y one s e r i e s was c o m p l e t e d w i t h t h e t h r e e d i f f e r e n t e s t r o g e n s . E f f e c t s o f T e m p e r a t u r e C h a n g e s o n R h e o t a x i s . Chum s a l m o n f r y (4 *9 + 0.43 c m . ) and c o h o s a l m o n s m o l t (8.9 + 0.54 c m . ) w e r e u s e d i n t h i s s e r i e s . T h e s e F i g u r e 3 » Kamloops t r o u t swimming i n t u r b u l e n t water below v e r t i c a l dam. Most f i s h are f a c i n g c u r r e n t . D, dam. 12 species were chosen because they show strong positive rheotaxis and changes occurring i n the response to d i r e c t i o n of flow were e a s i l y detected i n the apparatus described below. Experiments with chum salmon were carr i e d out during the summer of 1952 and those with coho i n the spring of 1953. The apparatus consisted of two galvanized i r o n wash tubs 68 cm. i n diameter across the top, 212 cm. i n circumference and 27 cm. deep. These were placed side by side to f a c i l i t a t e comparative observations (figure 4 ) . A v e r t i c a l pipe 1 cm. i n diameter attached to the inside of each tub was perforated along i t s length so that water entering at the top was forced out the series of holes, i n a d i r e c t i o n p a r a l l e l to the side of the tub and produced a comparatively uniform c i r c u l a r current. A c e n t r a l overflow pipe maintained the water l e v e l at 19 cm. and drained water back into a reservoir while an Eastern c e n t r i f u g a l pump forced i t up again into the perforated i n l e t pipe. Tubs and r e s e r v o i r s were set i n deep cement troughs where water, surrounded the r e s e r v o i r s to maintain appropriate temperatures. The surface speed of the current i n each tub was held at 25 - 30 cm. per second, measured at the periphery. Aluminum paint covered the inner surfaces of both tubs and r e s e r v o i r s . The procedure followed i n any experiment was to hold two groups of one species separately f o r an hour i n quiet water at the temperature of the hatchery water. Currents as described above were started i n the tubs, the temperature i n Figure 4 . Rheotaxis tubs with kamloops trout orienting i n c i r c u l a r currents. R, reservoir surrounded by water to control temperature; P , Eastern centrifugal pump. 13 one tub being equal to the holding temperature, and that in the other 4 or 5° C, above or below. A group of fish was placed in each tub and observations begun immediately from behind a screen. Chum salmon were observed in groups of 12 and coho in groups of 10. No attempt was made to obtain a quantitative measure of the activity of the f i s h in this apparatus, but over a 10 to 15-minute period careful ob-servations were made of the rheotactic response of each group. Fish were described as showing negative rheotaxis when they swam faster than the surface flow, and in the same direction. If the f i s h faced the current, swimming into i t or holding position in the flow, they were said to be showing positive rheotaxis. Occasionally an individual drifted with the current. This i s not referred to as negative rheotaxis. Fish behaving in this way were classed with those showing positive rheotaxis. Light intensity at the water surface was recorded after every experiment. Thirty-six separate experiments were carried out with chum salmon and 12 with coho. 14 RESULTS General Responses to Currents. Figure 5 shows the proportion of f i v e species i n the area of greatest turbulence of the long troughs f o r 15 minutes a f t e r the flow was started. Each point on any curve represents the mean percentage of f i s h i n the inflow t h i r d of the trough over a number of experiments. These f i v e curves have been presented together to emphasize the f a c t that, although there are variations among species, a l l of these f i s h move close to the inflow and stay there at least 50 percent of the time. On removal of the p a r t i t i o n s holding the f i s h at the centre of the trough, the immediate response was usually a general movement by a l l f i s h toward the outflow end. The length of time f o r movement toward the i n l e t tube from t h i s p o s i t i o n varied among the species (figure 5 ) . Both eels and c a t f i s h showed a rapid i n i t i a l response, moving into the most turbulent area within one minute of release from the centre of the trough. In contrast the spring salmon moved into the inflow end i n an average of four minutes and the coho i n seven minutes. Throughout these experiments the spring salmon f r y showed the greatest a c t i v i t y . They svram most consistently into the turbulent zone and jumped out of the water i n t h i s area more often than any other species except the eels. When the spring f r y moved away from the inflow, they swam quickly i n F i g u r e $ . Mean p e r c e n t o f f i v e s p e c i e s o f f i s h i n t h e i n f l o w e n d o f t h e l o n g m e t a l t r o u g h s a t i n -t e r v a l s o f 30 s e c o n d s o v e r a 1 5 - m i n u t e p e r i o d . See t e x t . EEL I I O IO 20 30 TIME - 1/2 MINUTE INTERVALS 15 c l o s e aggregates t o t h e o u t l e t end of t h e trough and back a g a i n . Coho f r y , o n the o t h e r hand, showed a l e s s c o n s i s t e n t p o s i t i v e response to the i n f l o w i n g water. They moved back and f o r t h from i n f l o w t o o u t l e t more o f t e n t h a n the s p r i n g f r y , and i n l o o s e r a g g r e g a t i o n s . Jumping near the i n f l o w o c c u r r e d l e s s o f t e n w i t h coho than w i t h s p r i n g salmon. Nipping and defence of t e r r i t o r y (Hoar, 1951 a; S t r i n g e r , 195 2) by the coho were o c c a s i o n a l l y seen, but n e i t h e r r e a c t i o n was shown by the s p r i n g f r y . In g e n e r a l , c a t f i s h , s c u l p i n s and eels behave l i k e the two s p e c i e s of salmon d i s c u s s e d above. The percent of these t h r e e s p e c i e s i n the i n f l o w end i s more c o n s i s t e n t t han t h a t o f coho. T h i s i s p a r t l y e x p l a i n e d by the f a c t t h a t the former moved s i n g l y o r i n small groups, and over the f i r s t 15 minutes t h e r e were some f i s h at t h e i n f l o w end most of the time, while others were s c a t t e r e d throughout the t r o u g h . On the other hand, the coho moved about i n aggregates and t h e r e were o f t e n no f i s h near th e i n f l o w . The e e l s were the most d i f f i c u l t t o h o l d i n the t roughs. They are a c t i v e f i s h and escaped over the s i d e s by jumping and working under the p l a s t i c s c r e e n i n g . A l l s p e c i e s showed much the same response to the i n f l o w over a two hour p e r i o d as they d i d d u r i n g the f i r s t 15 minutes. F i g u r e 6 shows the response t o c u r r e n t demonstrated by coho and s p r i n g salmon f r y over two hours. S i m i l a r data f o r the o t h e r three s p e c i e s are g i v e n i n the appendix. Preference f o r Flowing or Quiet Water. The r e s u l t s of t h e experiments u s i n g the l o n g troughs F i g u r e 6. Mean p e r c e n t o f t w o s p e c i e s o f s a l m o n i n t h e i n f l o w e n d o f t h e l o n g m e t a l t r o u g h s ; r e c o r d s w e r e t a k e n a t t h e t i m e i n t e r v a l s s h o w n . S o l i d c i r c l e s , s p r i n g s a l m o n f r y ; o p e n c i r c l e s , c o h o s a l m o n f r y ; v e r t i c a l b r o k e n l i n e s , one h o u r p e r i o d s d u r i n g w h i c h no o b s e r v a t i o n s w e r e m a d e . IOO 75 50 •••• •• o • • • • •• • •••• •••• •• • •••••• • • • • • o o o o o o — o O o o o o o o o o • o o • • o o ° • ° o O O o o o 0 oo ° o oo ° ° oo o • o o oo o • • • o • • o • ° • • o o o o ° ° ° o o o o o o o o 0 o ooo oo - O O o oo o • o • o - 1 o 1 OQOO 1 1 1 30 150 270 TIME - 1/2 MINUTE INTERVALS 16 with l o n g t i t u d i n a l p a r t i t i o n s at the inflow end are given i n Table I I I . Figures shown are for average percentages of f i s h i n the turbulent and the quiet areas over a series of experi-ments. With one exception, the sculpin, these figures i n -dicate that a greater proportion of each species w i l l move into a strong flow of water than into a quiet area. Coho salmon are most marked i n t h e i r preference for turbulence. The experiments were carried out i n the l a t e f a l l when spring salmon were no longer a v a i l a b l e , and there was no p o s s i b i l i t y of comparing coho with spring f r y . Kamloops trout f r y were used instead for comparison with coho. Various observations were made on the behaviour of the f i s h during these experiments. The kamloops trout f r y usually remained i n aggregations, but some evidence of t e r -r i t o r i a l behaviour was seen. This sometimes led to confusing r e s u l t s . T e r r i t o r i a l behaviour and occasional nipping i n the turbulent water by several trout during the f i r s t hour of some experiments led to inconsistent r e s u l t s and a r e l a t i v e l y high P value compared to that for the second observation period. As before, the coho f r y moved about i n loose ag-gregations. They moved a c t i v e l y up and down the length of the trough and entered the inflow side of the p a r t i t i o n more con-s i s t e n t l y than the other species. The young c a t f i s h also moved into turbulent rather than quiet water, but more frequently stayed i n groups near the outlet screen. The eels were d i f f i c u l t to keep i n the trough. Some eels t r i e d vigorously Table I I I . Mean percent of f i s h on each side of p a r t i t i o n . Flow changed to opposite side of trough after one hour. Percent f i s h before change Percent f i s h a f t e r change Species No. of experiments turbulent quiet water water t turbulent quiet water water t P coho 6 37.8 5.0 6.934 <0.01 39.5 9.2 5.499 < 0 . 0 1 trout 6 27.3 12.4 1.242 O.25 28.8 11 .0 2.438 0.04 c a t f i s h 5 20.4 12.2 1.206 0.27 24.1 4 . 8 3.O63 0.016 eel 5 24.4 11.6 1.123 0.30 21.1 14.1 0.986 O.36 sculpin 5 27.9 16.7 1.349 0.22 10.3 11.3 0.400 0.5 17 t o work t h e i r way out under t h e s c r e e n i n g , e s p e c i a l l y when i n the most t u r b u l e n t water. T h i s "escape" behaviour l e d to i n c r e a s e d a c t i v i t y on the i n f l o w s i d e of the p a r t i t i o n and the p r o p o r t i o n of e e l s on t h i s s i d e was decreased. S c u l p i n s tended t o s t a y near the c o r n e r s of the troug h . During the f i r s t , hour the p r o p o r t i o n of s c u l p i n s was s l i g h t l y higher i n the t u r b u l e n t t h a n i n the q u i e t a r e a . By the second hour no p r e f e r e n c e was seen. S c u l p i n s and c a t f i s h d i d not jump out of the water i n the t u r b u l e n t a r ea. Hormones and Rheotaxis The e f f e c t s of t e s t o s t e r o n e and t h y r o x i n e on the r a t e at which coho smolt jump over a 2 cm. dam are summarized i n f i g u r e 7. The f o u r week treatments were d u p l i c a t e d w i t h d i f f e r e n t f i s h and the graphs are the r e s u l t s o f lumping the two s e t s o f d a t a . The d i f f e r e n c e i n jumping time between t r e a t e d f i s h and c o n t r o l s v a r i e s . The s i g n i f i c a n c e of t h i s d i f f e r e n c e f o r each week has been determined s t a t i s t i c a l l y and t and P v a l u e s are presented i n Table IV. I n only one case, the 3rd week o f t e s t o s t e r o n e treatment, i s t h i s d i f f e r e n c e s t a t i s -t i c a l l y s i g n i f i c a n t at the 0 .G1 l e v e l f o r coho. However, the tendency o f experimental f i s h t o move over the dam f a s t e r than c o n t r o l s i s c o n s i s t e n t , except f o r the f i n a l week of treatment w i t h t h y r o x i n e , where the t r e a t e d f i s h seemed i n poor con-d i t i o n . F i g u r e 8 g r a p h i c a l l y p r e s e n t s data f o r an i d e n t i c a l s e r i e s u s i n g sockeye smolt. Here aga i n the o v e r a l l r e s u l t i s F i g u r e 7. H i s t o g r a m s s h o w i n g t h e e f f e c t s of two h o r m o n e s o n t h e r a t e a t w h i c h c o h o s a l m o n s m o l t jump u p s t r e a m o v e r a 2 c m . d a m . Open b a r s , c o n t r o l e x p e r i m e n t s . 25 15 TESTOSTERONE 1 I 21 I A THYROXINE • • • ••• • • m • "I •« • % • •. • • 3 4 2 3 4 DURATION OF TREATMENT - WEEKS T a b l e IV T i m e t a k e n f o r 50 p e r c e n t o f c o h o s m o l t t o jump f r o m l o w e r t o u p p e r p o o l d u r i n g t h y r o x i n e a n d t e s t o s t e r o n e t r e a t m e n t . Week o f t r e a t m e n t T h y r o x i n e C o n t r o l N o . o f e x p e r i m e n t s Mean t i m e m i n u t e s N o . o f e x p e r i m e n t s Mean t i m e m i n u t e s s e c o n d 4 2 1 . 9 4 2 3 . 3 0.179 > 0 . 5 t h i r d 8 2 2 . 4 8 2 5 . 6 O . 9 4 I O . 3 6 f o u r t h 8 2 6 . 4 8 18.7 2 . 4 0 6 0 . 0 3 Week o f t r e a t m e n t T e s t o s t e r o n e C o n t r o l N o . o f Mean t i m e e x p e r i m e n t s m i n u t e s N o . o f e x p e r i m e n t s Mean t i m e m i n u t e s s e c o n d 4 17.3 t h i r d 9 17.5 f o u r t h 9 14.9 4 2 4 . 8 3 . 0 0 0 0 . 0 2 9 2 6 . 9 3 . 3 5 7 < 0 . 0 1 9 18.1 1 . 0 6 7 0 . 3 Figure 8 . Histograms showing the ef f e c t s of two hormones on the rate at which sockeye salmon smolt jump upstream over a 1 . 5 cm. dam. Open bars, con-t r o l experiments. TESTOSTERONE I THYROXINE • • • ... * I*. • » »• • • • DURATION OF TREATMENT - WEEKS 18 for treated f i s h to move upstream fa s t e r than controls. A notable exception occurs with testosterone treated f i s h i n the second week of treatment. The t and P values are calculated for sockeye and presented i n Table V. The r e s u l t s of i d e n t i c a l experiments with sockeye smolt using three estrogen compounds are shown i n figure 9» A l l three hormones stimulated the a c t i v i t y of the f i s h , but the change was most pronounced with one group. Those immersed i n S t i l b o e s t r o l were the most active f i s h seen i n t h i s appara-tus. This increase i n a c t i v i t y was also noticeable i n the battery j a r s , -and when the f i s h were carried i n p a i l s . N y l e s t i n , on the other hand, seemed to have a detrimental e f f e c t . Fish immersed i n solutions of t h i s compound appeared to be under stress and t h e i r movements i n the troughs were e r r a t i c ; while i n the battery j a r s they were l e s s active than controls. It. i s i n t e r s t i n g to note, however, that the mean time for h a l f of t h i s group to cross the dam i s s t i l l l ess than for controls. Table VI presents the t and P values f o r significance of the difference between mean values. Figures 7, 8 and 9 show that with few exceptions, both control' and experimental sockeye and coho move upstream fa s t e r i n the -later stages of treatment than at f i r s t . This was especially noticeable af t e r the f i r s t two or three ex-periments with each group. The p o s s i b i l i t y of a learning process being involved i n t h i s increase i n jumping rate w i l l be discussed l a t e r . During the many hours of observations necessary Table V Time taken f o r 50 percent of sockeye smolt to jump from lower to upper pool during thyroxine and testosterone treatments. Thyroxine Control Week of treatment No. of Mean No. of Mean experiments time experiments time min. min. second t h i r d fourth 5 8 8 18.7 10.9 9.9 5 8 8 21.9 14.2 11.1 0.561 1.100 0.857 >0.5 0.3 0.4 Week of treatment Testosterone No. of Mean experiments time min. Control No. of Mean experiments time min. second t h i r d fourth 6 9 7 21.8 10.8 7.9 6 13.8 9 12.1 7 10.5 1.951 0.929 1.857 0.08 0.37 0.09 F i g u r e 9. H i s t o g r a m s s h o w i n g t h e e f f e c t s o f t h r e e e s t r o g e n s o n t h e r a t e a t w h i c h s o c k e y e s a l m o n s m o l t jump u p s t r e a m o v e r a 1.5 c m . d a m . O p e n b a r s , c o n t r o l e x p e r i m e n t s . DURATION OF TREATMENT - WEEKS T a b l e V I . T i m e t a k e n f o r 50 p e r c e n t o f s o c k e y e s m o l t t o jump f r o m l o w e r t o u p p e r p o o l d u r i n g t h r e e e s t r o g e n t r e a t m e n t s , t and P v a l u e s show t h e d i f f e r e n c e i n t i m e b e t w e e n e a c h t r e a t e d g r o u p a n d t h e same c o n t r o l . C o n t r o l S t i l b o e s t r o l D i e n o e s t r o l N y l e s t i n Week o f t r e a t m e n t N o . o f Mean N o . o f Mean N o . o f Mean N o . o f Mean e x p e r i m e n t s t i m e e x p e r i m e n t s t i m e e x p e r i m e n t s t i m e e x p e r i m e n t s t i m e m i n . m i n . m i n . m i n . s e c o n d 3 15.8 4 10.3 4 19.9 3 2 0 . 3 t 2.037 0.569 0 . 8 0 3 P 0 .1 > 0 . 5 0.46 t h i r d 6 8.2 6 7.5 6 11.9 6 11.4 t 0.854 3.08*3 1.975 P 0 . 4 0.01 0 . 0 8 f o u r t h 5 13 .0 5 6.1 5 10 .0 5 9 .2 t 3.833 1.667 2.000 P < 0 . 0 1 0.12 0 . 0 8 19 t o c o m p i l e the d a t a p r e s e n t e d h e r e some c o n t r a s t s i n b e h a v i o u r o f sockeye and coho were e v i d e n t . A l t h o u g h b o t h s p e c i e s moved about t h e t r o u g h s i n a g g r e g a t e s , t h e young sockeye s t a y e d i n more compact groups t h a n t h e coho. One c h a r a c t e r i s t i c of both s p e c i e s d u r i n g the f i r s t few minutes o f any experiment was f o r a l l f i s h t o swim back and f o r t h i n c l o s e groups f r o m t h e out-l e t s c r e e n t o t h e f a c e of t h e dam. T h i s movement was a t f i r s t r a p i d and r e g u l a r l y t i m e d , the f i s h s t a y i n g below t h e dam f o r a few seconds o n l y . However, w i t h i n a few minutes the t i m e spent s t r u g g l i n g i n t h e t u r b u l e n t w a t e r below t h e f a l l s g r a d u a l l y i n c r e a s e d . The c l o s e r g r o u p i n g by sockeye was t h e n emphasized as t h e coho a g g r e g a t e s broke up more r e a d i -l y , some f i s h s t a y i n g i m m e d i a t e l y below t h e dam and o t h e r s swimming t o the; o u t l e t . I n t h e a r e a above t h e f a l l s t h i s more compact group-i n g among sockeye was a g a i n e v i d e n t . Whereas some o f t h e coho i n t h e upper p o o l o f t e n r e s t e d near the b o t t o m i n f r o n t o f t h e dam, t h e sockeye s t a y e d m o s t l y i n the a r e a o f g r e a t e s t t u r b u l e n c e , and when swimming t o t h e dam and back a g a i n moved as a group. Another f e a t u r e of t h e b e h a v i o u r o f t h e s e young salmon i s t h e marked t e n d e n c y o f s e v e r a l f i s h t o jump over t h e dam-together. I t was r e p e a t e d l y n o t i c e d t h a t s e v e r a l minutes would pass w i t h no f i s h j umping, t h e n f i v e o r s i x f i s h would move over t h e b a r r i e r w i t h i n s e v e r a l seconds. T h i s happened more o f t e n w i t h sockeye t h a n coho. Two f u r t h e r p e c u l i a r i t i e s o f qpho b e h a v i o u r i n t h i s a p p a r a t u s a r e worthy o f comment. One i s t h e movement o f 20 f i s h back over the vertical face of the dam from the upper to the lower pool. This activity was seen in 26 different coho experiments of which 15 were with treated fis h and 11 with con-tr o l s . The other activity peculiar to coho was chafing, which has been described previously for a species of c'yprinid (Keenleyside, 1952) and was seen in 10 separate experiments in this study. Chafing occured both above and below the dam, among control and test coho, and by f i s h that were either facing or moving with the current. Neither downstream move-ment over the dam nor chafing was seen among sockeye. The prolonged, 4-week treatment with hormones produced evidence of stress. The fis h often showed erratic movements in the later stages of treatment. For example, coho smolt during the fourth week of treatment with thyroxine, were very slow to move over the barrier. Their jumping below the f a l l s was weak and erratic and the same fi s h often had to jump six or eight times to cross the dam. Controls usually reached the upper pool on the f i r s t try. Furthermore, at this stage many coho stayed at the outlet end of the trough and did not attempt to jump. In contrast, some of the treated sockeye showed increased, but more erratic, general activity, swimming speed and jumping. The fish jumped vigorously, but in various directions below the dam and the result was slower movement to the upper pool than the degree of activity warranted. Such erratic behaviour was not consistent with any one group, but appeared occasionally among a l l treated sockeye. 2 1 When these ..experiments were ter m i n a t e d each group of f i s h was p l a c e d i n the/rotating c u r r e n t i n one of the r h e o t a x i s tubs d e s c r i b e d e a r l i e r . The c o n t r o l coho smolt stayed i n a c l o s e group and h e l d p o s i t i o n i n the f a s t e s t f low. Those coho from t h y r o x i n e s o l u t i o n s showed e r r a t i c movements and much d a r t i n g about. T h i s l e d t o a s c a t t e r e d d i s t r i b u t i o n both i n f a s t and slow water. T e s t o s t e r o n e t r e a t e d coho, however, d i s p l a y e d v i g o r o u s p o s i t i v e r h e o t a x i s i n the f a s t e s t f l o w . The e n t i r e group moved as a l o o s e a g g r e g a t i o n around the tub a g a i n s t the c u r r e n t . No negative r h e o t a x i s was observed among coho. I n t h e s e c i r c u l a r c u r r e n t s the sockeye e x h i b i t e d more i n c o n s i s t e n t behaviour. P o s i t i v e r h e o t a x i s dominated, but both t r e a t e d and c o n t r o l sockeye o c c a s i o n a l l y darted about and the grouping behaviour was l e s s marked than expected. Those t r e a t e d w i t h S t i l b o e s t r o l were the most a c t i v e sockeye. They aggregated more c l o s e l y than the o t h e r s and showed a hi g h e r degree of p o s i t i v e r h e o t a x i s . Sockeye d i d not show a c t i v e n e gative r h e o t a x i s i n these t u b s . I t was not p o s s i b l e t o c a r r y out t e s t s i n t h i s apparatus d u r i n g e a r l i e r stages of treatment of sockeye and coho salmon. Temperature and Rheotaxis At e l e v a t e d temperatures both chum f r y and coho smolt show c o n s i s t e n t n e g a t i v e r h e o t a x i s i n the c i r c u l a r t u b s . In water c o l d e r than the h o l d i n g temperature the dominant a c t i v i t y i s p o s i t i v e r h e o t a x i s . F i g u r e 1 0 summarizes the r e s u l t s f o r 36 experiments w i t h chum salmon. These were c a r r i e d out from May t o J u l y , 1 9 5 2 when temperatures i n the F i g u r e 1 0 . H i s t o g r a m s s h o w i n g r e s p o n s e o f . chum s a l m o n f r y t o c i r c u l a r c u r r e n t s a t d i f f e r e n t t e m p e r a t u r e s . V a l u e s shown a r e p e r c e n t e x p e r i m e n t s a t e a c h t e m p e r a t u r e r a n g e . C r o s s - h a t c h e d b a r s , p o s i t i v e r h e o t a x i s ; o p e n b a r s , n e g a t i v e r h e o t a x i s ; s o l i d c i r c l e s , p r o p o r t i o n o f e x p e r i m e n t s i n e a c h b a r t h a t w e r e c o n t r o l s . See t e x t . 22 h a t c h e r y i n c r e a s e d from 10 t o 16° C. Most of the chum f r y showed negative r h e o t a x i s d u r i n g J u l y when c o n t r o l temperatures were h i g h . The f o u r c e n t r a l bars i n f i g u r e 10 c o n t a i n s o l i d c i r c l e s . The p r o p o r t i o n of the bar below the c i r c l e marks the p r o p o r t i o n of experiments i n c l u d e d i n t h a t bar that were c o n t r o l s . The 6 - 9 ° and 18 - 21° bars which i n c l u d e no c o n t r o l s show most c l e a r l y the d i f f e r e n t . r e s p o n s e t o c u r r e n t s w i t h e l e v a t i o n and l o w e r i n g of temperature. The r e s u l t s of 12 i d e n t i c a l experiments i n February and March, 1953, w i t h coho smolt are shown i n f i g u r e 1 1 . Because the p e r i o d of experimentation w i t h coho covered about f i v e weeks d u r i n g e a r l y s p r i n g , the c o n t r o l temperatures were c o n s i s t e n t at 9° C. F i g u r e 11 covers only the e x p e r i -mental r e s u l t s , thus emphasizing the response at extreme temperatures. Some c o n t r o l coho showed negative r h e o t a x i s a l s o . I t was found t h a t s t a r t l i n g the f i s h suddenly a f t e r the o b s e r v a t i o n p e r i o d by waving a white handkerchief over both tubs immediately enhanced the p o s i t i v e r e a c t i o n r e g a r d -l e s s of the dominant response d u r i n g the experiment. F i g u r e 1 1 . H i s t o g r a m s s h o w i n g r e s p o n s e o f c o h o s a l m o n s m o l t t o c i r c u l a r c u r r e n t s a t d i f f e r e n t t e m -p e r a t u r e s . V a l u e s shown a r e p e r c e n t e x p e r i -m e n t s a t e a c h t e m p e r a t u r e r a n g e . C r o s s - h a t c h e d b a r s , n e g a t i v e r h e o t a x i s ; o p e n b a r s , p o s i t i v e r h e o t a x i s . 23 DISCUSSION The widespread occurrence o f r h e o t a x i s among a q u a t i c animals has been mentioned and t h i s f a c t i s emphasized many-times i n the l i t e r a t u r e ( F r a e n k e l and Gunn, 1940; Buddenbrock, 1952) . Among f i s h e s , the phenomenon i s u n i v e r s a l l y r e c o g n i z e d and, i n some cases, i s of d i r e c t importance t o the f i s h i n g i n d u s t r y , and i n the c o n s e r v a t i o n of f i s h as a food and r e c -r e a t i o n a l r e s o u r c e . With some commercially v a l u a b l e s p e c i e s the spawning m i g r a t i o n i s the o n l y time when the f i s h are con-c e n t r a t e d i n an area small enough t o make f i s h i n g p r o f i t a b l e . Since i t i s b e l i e v e d t h a t the a b i l i t y o f f i s h e s , s u c h as salmon, to o r i e n t themselves i n c u r r e n t s i s o f fundamental importance i n t h e i r spawning m i g r a t i o n upstream, a d e t a i l e d knowledge of t h e i r movements i n r e l a t i o n t o the water masses along t h e i r m i g r a t i o n r o u t e s i s d e s i r a b l e . F u r t h e r , i t i s becoming i n -c r e a s i n g l y d e s i r a b l e t o d i r e c t the downstream movements of young salmon around power dams without great l o s s e s t o the p o p u l a t i o n , and here a g a i n knowledge of the a b i l i t y of f i s h t o o r i e n t i n a f a s t stream i s important. Sensory B a s i s of R h e o t a x i s . In attempting t o understand an innate r e a c t i o n such as r h e o t a x i s one must be f a m i l i a r w i t h the sensory mechanisms i n v o l v e d . There are d e s c r i p t i o n s i n the l i t e r a t u r e of ex-periments designed t o determine what sense organs are p r i m a r i l y i n v o l v e d i n r h e o t a x i s . A b r i e f review of some of the more p e n e t r a t i n g o f these w i l l not be out of p l a c e here. 24 f Lyon (1904) p l a c e d s e v e r a l f i s h i n an enclosed b o t t l e of water and suspended i t i n a r i v e r . When the b o t t l e d r i f t e d w i t h the c u r r e n t , the f i s h crowded t o the upstream end, and when p u l l e d upstream the f i s h / q u i c k l y moved t o the downstream end. When the apparatus was h e l d s t a t i o n a r y , t h e r e was a l a c k of o r i e n t a t i o n . T h i s experiment was c a r r i e d out i n shallow water where the bottom was v i s i b l e t o the f i s h , and i t was c l e a r t h a t the observed r e a c t i o n was due to l o s s of v i s u a l con-t a c t w i t h o b j e c t s on the bottom. Lyon f u r t h e r demonstrated the importance of the o p t i c a l s timulus by p l a c i n g f i s h i n an aqua-r i u m w i t h a movable background along each s i d e . The f i s h swam alo n g beside the moving f i e l d although no c u r r e n t was pr e s e n t . He l a t e r showed (1909) t h a t b l i n d i n g both eyes of the f i s h d e s t r o y e d the l a t t e r r e a c t i o n , but wit h only one eye b l i n d e d swimming w i t h the background o c c u r r e d as b e f o r e . Lyon concluded t h a t the eyes were of prime importance i n h o l d i n g p o s i t i o n i n a stream. Other workers have a l s o emphasized the important r o l e of the eyes i n o r i e n t a t i o n t o f l o w i n g waters (Garrey, 1904; Clausen, 1931) . The r o l e o f t a c t i l e organs i n r h e o t a x i s has a l s o been s t r e s s e d . Lyon (1904) found t h a t b l i n d e d f i s h o r i e n t e d i n c u r r e n t s when they touched the bottom. Dykgraaf (1933) showed t h a t f i s h e s u t i l i z e the sense o f touch t o maintain p o s i t i o n i n a stream by p l a c i n g b l i n d e d f i s h i n an aquarium w i t h a moving f l o o r . When the f i s h touched the bottom they moved along w i t h i t , thus swimming through the s t i l l water. Others have argued t h a t t a c t i l e s t i m u l a t i o n i s of prime importance.in e n a b l i n g the f i s h t o de t e c t p r e s s u r e changes i n c u r r e n t s of water. Buddenbrock (1952) reviews t h i s l i t e r a t u r e . The function of the l a t e r a l l i n e i n rheotaxis has been emphasized. Dykgraaf (1933) showed that blinded f i s h could detect f i n e j e t s of water directed against t h e i r sides through a pipette, and that t h i s detection ceased when the l a t e r a l l i n e nerves were cut. He stressed the f a c t , however, that the cutaneous sense organs w i l l detect sudden differences i n water pressure i n larger masses of water such as the f i s h meets i n i t s natural habitat and thus overshadow stimulation of the l a t e r a l l i n e . Dykgraaf concluded that sight and touch are the primary senses of orientation for fishes i n currents, while the l a t e r a l l i n e may be important i n some sit u a t i o n s . The part played by the ear i n rheotaxis i s not yet c l e a r l y understood. Gray (1937) found blinded f i s h could orient i n r o t a t i n g but not l i n e a r currents and attributed t h i s "pseudo-rheotropism" to asymmetrical stimulation of the semicircular canals. In a review of the sensory c a p a b i l i t i e s of the lab y r i n t h Lowenstein (1950) concluded that the canals are sensitive to angular accelerations while the o t o l i t h s are capable of responding to any movement involving a change i n momentum. Not a l l workers are agreed, however, that the semi-c i r c u l a r canals cannot also detect l i n e a r movements (Lowenstein, 1950). Jordan (1917) has observed the grouper Epinephelus  s t r i a t u s orienting to a stream of water by pointing i t s t a i l toward the flow. Cutting the l a t e r a l l i n e nerves had no eff e c t bn t h i s response, but anesthetizing the l i p s resulted i n lack 26 o f o r i e n t a t i o n . The l i p s of t h i s f i s h are the most s e n s i t i v e p a r t of the body and Jordan argues t h a t o r i e n t a t i o n w i t h the head p o i n t i n g away a f f o r d s the g r e a t e s t p r o t e c t i o n f o r 'the mouth r e g i o n . T h i s seems t o be an u n j u s t i f i e d c o n c l u s i o n , as the most s e n s i t i v e area of any f i s h ' s body i s probably some p a r t of the head, but the grouper seems t o be the o n l y one showing t h i s type of o r i e n t a t i o n . A f t e r r e v i e w i n g some of the l i t e r a t u r e on the sense organs i n v o l v e d i n r h e o t a x i s of f i s h e s , i t i s evident t h a t the m a j o r i t y of workers i n t e r e s t e d i n t h i s problem today be-l i e v e the v i s u a l s t i m u l u s t o be the s t r o n g e s t , although t a c -t i l e and l a b y r i n t h i n e s t i m u l i are a l s o important. The l a t e r a l l i n e may be c a l l e d i n t o p l a y i n some s i t u a t i o n s . General R h e o t a c t i c R e a c t i o n s . Experiments i n v o l v i n g d i f f e r e n t s p e c i e s i n the l o n g metal troughs have brought out s e v e r a l s i g n i f i c a n t p o i n t s . Coho and s p r i n g salmon, t r o u t , s c u l p i n s , c a t f i s h and e e l s move towards the i n f l o w when water i s pumped through the troughs. However, the i n t e n s i t y of t h i s p o s i t i v e r h e o t a x i s v a r i e s among the f i v e s p e c i e s . Such v a r i a t i o n i s not un-expected, and d i f f e r e n c e s can probably be c o r r e l a t e d w i t h n a t u r a l h a b i t s o f the s p e c i e s . Spring salmon f r y are u s u a l l y found i n r i v e r s d u r i n g t h e i r f i r s t y ear of l i f e , and many of them move out to sea . b e f o r e t h e i r second y e a r . T h i s movement i s g r a d u a l , however, and i n some areas many s p r i n g salmon stay i n t h e i r home streams 27 u n t i l t h e i r second summer. A c a r e f u l a n a l y s i s o f the me-chanisms r e s p o n s i b l e f o r downstream movement of young s p r i n g salmon has not been p u b l i s h e d . However, i t i s t e n t a t i v e l y suggested here t h a t those f i s h which show the s t r o n g e s t t e n -dency to move i n t o f a s t water are those most l i k e l y t o be swept away at night when v i s u a l s t i m u l i d i s a p p e a r . A s i m i l a r e x p l a n a t i o n has been o f f e r e d f o r the seaward movement of chum salmon f r y (Hoar, 1951a). MacKinnon (1950) found t h a t coho f r y move i n t o the f a s t e r o f two f l o w s , but t h a t t h i s p r e f e r e n c e i s g r e a t e s t d u r i n g the f i r s t two hours of o b s e r v a t i o n s , a f t e r which the response to f a s t e r f l o w changes to an i n d i f f e r e n c e . The coho used f o r t h i s study moved r e a d i l y i n t o the i n f l o w end of the l o n g troughs, but d i d not show a c o n s i s t e n t response, i . e . they moved up and down the l e n g t h of the trough more o f t e n t h a n d i d the s p r i n g salmon. I t i s suggested t h a t t h i s type o f response would not l e a d coho f r y i n t o s t r o n g c u r r e n t s where they would be swept away r e a d i l y at n i g h t . However, i n the experiments where t u r b u l e n t and q u i e t areas on e i t h e r s i d e of a p a r t i t i o n are a v a i l a b l e , coho almost i n v a r i a b l y move i n t o the t u r b u l e n t water. I n these experiments, r e c o r d s of the p o s i t i o n s of the f i s h were made one hour a f t e r the f l o w s t a r t e d on one s i d e o f the p a r t i t i o n . I f coho show i n -d i f f e r e n c e to f a s t e r f l o w only a f t e r two or t h r e e hours (MacKinnon, 1950), these r e s u l t s may not g i v e a t r u e p i c t u r e of the r h e o t a c t i c r e a c t i o n . F i g u r e 6 shows t h a t whereas 28 s p r i n g f r y continue t o move i n t o the i n f l o w end over a two hour p e r i o d , the coho response decreases more r a p i d l y . I t i s suggested t h a t c o n s i s t e n t p o s i t i v e r h e o t a x i s c o n t r i b u t e s t o the e a r l y downstream movement of many s p r i n g salmon f r y . The f a c t t h a t most coho f r y s t a y i n f r e s h water l o n g e r i s due i n p a r t t o t h e i r l e s s c o n s i s t e n t p o s i t i v e r h e o t a x i s . Kamloops t r o u t were s t u d i e d only i n the troughs w i t h p a r t i t i o n s at the i n f l o w end, where they p r e f e r r e d the t u r -b u l e n t s i d e . However, they moved i n t o t h e q u i e t area more o f t e n than coho. These f i s h are hatched i n streams l e a d i n g i n t o or out of l a k e s . While some stay permanently i n streams, o t h e r s may move i n t o l a k e s as f r y . From the few experiments performed here no c o n c l u s i o n s can be drawn as t o the l i k e l y f a t e o f these p a r t i c u l a r f i s h i n t h e i r n a t i v e h a b i t a t . The l a r g e r percentage o f f i s h i n the i n f l o w s i d e suggests move-ment i n t o f a s t water. There t h e y would e i t h e r be c a r r i e d downstream i n t o l a k e s at n i g h t or t h e y would swim v i g o r o u s l y upstream i n t o l a k e s d u r i n g the day. The high r h e o t a c t i c response shown by young c a t f i s h i s noteworthy. The f i s h used i n t h i s study were t a k e n from a shallow, q u i e t p a r t of the Stave R i v e r , t y p i c a l of the waters a n g l e r s u s u a l l y a s s o c i a t e w i t h c a t f i s h . Both l a r g e and s m a l l c a t f i s h were t a k e n i n the same h a u l s . Thus, t h e r e i s no evidence t h a t the d i f f e r e n t age groups p r e f e r d i f f e r e n t hab-i t a t e s . The small f i s h seem t o be more a c t i v e g e n e r a l l y t han the l a r g e r ones and t h i s a c t i v i t y may r e s u l t i n the younger f i s h moving i n t o c u r r e n t s . However, the l a c k of c a t f i s h i n 2 9 f a s t c u r r e n t s i n nature suggests s t r o n g p o s i t i v e r h e o t a x i s may be o n l y temporary. The p r i c k l y s c u l p i n i s a bottom d w e l l i n g f i s h t h a t i s w i d e l y d i s t r i b u t e d i n f r e s h water. In the experiments w i t h a s t r a i g h t f l o w o f water about 5 0 percent of the f i s h were i n the i n f l o w end over a two hour p e r i o d . In the p a r t i t i o n apparatus they showed about equal p r e f e r e n c e f o r t u r b u l e n t and q u i e t a r e a s . The f i s h used i n these experiments were caught on sandy s l o p i n g bottom immediately o f f .the mouth of a s m a l l stream f l o w i n g i n t o Deer Lake, Burnaby. I t i s suggested t h a t s c u l p i n s p r e f e r q u i e t water near f l o w i n g streams i n t o which they d a r t f o r f o o d . These f i s h o f t e n r e s t i n c o n t a c t w i t h o b j e c t s on t h e bottom and i n cor n e r s of the troughs (thigmotaxis) and i t i s p o s s i b l e t h a t i n t u r b u l e n t r i v e r s they s t a y i n q u i e t p o o l s o r behind r o c k s . S c u l p i n s are known t o descend r i v e r s d u r i n g the night at the time of seaward m i g r a t i o n of young salmon. A c t i v e f e e d i n g behaviour may l e a d the s c u l p i n s i n t o f a s t water where they are c a r r i e d downstream. The A t l a n t i c e e l l i v e s on t h e bottom of r i v e r s and estuar r i e s of the east coast o f North America, where i t h i d e s under cover d u r i n g d a y l i g h t and moves about more d u r i n g the n i g h t . F i g u r e 5 shows t h a t about 50 percent of the e e l s are i n the i n f l o w end of the trough over a f i f t e e n minute p e r i o d . T h i s p r o p o r t i o n i s maintained over a two hour p e r i o d (see appen-d i x ) . With a p a r t i t i o n at the i n l e t end, they show s l i g h t p r e f e r e n c e f o r the t u r b u l e n t over the q u i e t area. For a 30 s p e c i e s l i v i n g i n t u r b u l e n t waters a g r e a t e r p o s i t i v e response f o r s t r o n g f l o w might be expected, but i t i s p o s s i b l e t h a t the e e l s , which r e p e a t e d l y t r i e d t o escape, were under s t r e s s i n t h i s apparatus and t h a t a t r u e p i c t u r e o f t h e i r response t o c u r r e n t s was not o b t a i n e d . Comparisons can be made on the l e n g t h o f time a f t e r the flow i s s t a r t e d i n the long troughs b e f o r e the f i s h move towards the i n f l o w . The t h r e s h o l d f o r t h i s i n i t i a l response i s lower w i t h c a t f i s h and e e l s t h a n w i t h the other t h r e e s p e c i e s . The meaning of t h i s d i f f e r e n c e i s not e n t i r e l y c l e a r , but i t may be t h a t c a t f i s h and e e l s are l e s s s e n s i t i v e t o d i s t u r b a n -ces such as shadows and v i b r a t i o n s . I t was evident t h a t coho and s p r i n g salmon and s c u l p i n s were more e a s i l y d i s t u r b e d by movements o f the obs e r v e r . Data from experiments on the gen e r a l r h e o t a c t i c r e a c t i o n o f s e v e r a l s p e c i e s p a r t l y e x p l a i n s the behaviour of these f i s h i n nature. The s p r i n g and coho salmon data i s most c o n s i s t e n t w i t h the r e l a t i o n between the s e f i s h and c u r r e n t s of water i n t h e i r environment. Hormones and Rheotaxis. Hormone treatment b r i n g s about changes i n the responses of sockeye and coho salmon smolt t o f l o w i n g water. The i n t e r -p r e t a t i o n of these changes, however, i s not a simple matter. One o f the c h i e f d i f f i c u l t i e s l i e s i n the apparatus, which was designed to determine whether or not treatment w i t h hor-mones a f f e c t s the r a t e at which f i s h jump upstream over a dam. T h i s change i n r a t e o f jumping should be a rough measure of 31 the change i n g e n e r a l a c t i v i t y of the animals. The anomaly i n t h i s s i t u a t i o n i s t h a t a change i n a c t i v i t y of the f i s h does not n e c e s s a r i l y l e a d to an i n c r e a s e d number of s u c c e s s f u l jumps, even though the swimming speed may be i n c r e a s e d . Some of the t r e a t e d sockeye o c c a s i o n a l l y showed i n c r e a s e d swimming speed, and an i n c r e a s e i n numbers o f jumps, but the l a t t e r were o f t e n more e r r a t i c t h a n the jumps of the c o n t r o l f i s h , l e a d i n g t o slower movement of the group i n t o the upper p o o l . An a c c u r a t e q u a n t i t a t i v e d e s c r i p t i o n of t h e e f f e c t s of hormone treatment on a c t i v i t y of young salmon w i l l g r a d u a l l y be b u i l t up by the use of d i f f e r e n t t y p e s of apparatus u n t i l the most s u i t a b l e i s found. Another obvious f e a t u r e of t h e s e experiments was the g r a d u a l decrease over a p e r i o d of f o u r weeks i n jumping time among c o n t r o l as w e l l as experimental f i s h . T h i s change i s most apparent d u r i n g the f i r s t t h r e e or f o u r o b s e r v a t i o n s . Each group of f i s h shows a s i m i l a r p a t t e r n , namely, moving over t h e dam v e r y s l o w l y f o r the f i r s t few t r i a l s , t h e n g r a d u a l l y d e c r e a s i n g t h i s jumping time. I t i s suggested t h a t t h i s speeding up of jumping time by a l l f i s h , i n c l u d i n g c o n t r o l s , i s due t o h a b i t u a t i o n t o the presence of the dam and t o the h a n d l i n g i n v o l v e d i n t r a n s f e r r i n g f i s h to the t e s t t r o u g h . The tendency f o r sockeye and coho salmon smolt t o move toward an area of i n c r e a s e d flow i s s t r o n g and i t i s f e l t t h a t the adverse e f f e c t of the dam on t h i s r h e o t a c t i c r e a c t i o n i s soon decreased due to h a b i t u a t i o n (Thorpe, 1 9 5 0 ) . 32 T h y r o i d Hormone and A c t i v i t y . The r e l a t i o n s h i p between the t h y r o i d g l a n d and a c t i v i t y of f i s h i s not c l e a r . Treatment w i t h t h y r o x i n e i n c r e a s e s the metabolic r a t e of h i g h e r animals ( B a r r i n g t o n , 1952, Schneider, 1 9 3 9 ) , but many workers have f a i l e d t o demonstrate a change i n metabolism, as measured by d i f f e r e n c e i n oxygen consumption,in f i s h e s t r e a t e d w i t h mammalian t h y r o i d e x t r a c t (Root and E t k i n , 1937 ; H a s l e r and Meyer, 1 9 4 2 ; Smith and E v e r e t t , 1 9 4 3 ) . The t h y r o i d i n h i b i t i n g drug, t h i o u r e a , has been shown t o have no e f f e c t on oxygen consumption of Fundulus (Matthews and Smith, 1 9 4 7 ) . One author (Fleischmann, 1951) has concluded t h a t most f i s h are very i n s e n s i t i v e t o t h y r o x i n e . However, at l e a s t one e x c e p t i o n to t h i s l a c k of metabolic s t i m u l a t i o n has been p u b l i s h e d . Smith and Matthews (1948) i n c r e a s e d t h e oxygen consumption of specimens o f Bathystoma over 15 grams i n weight by treatment w i t h p a r r o t f i s h t h y r o i d e x t r a c t . The su g g e s t i o n i s made by these authors t h a t t h y r o x i n e from f i s h t h y r o i d i s more e f f e c t i v e than that from the mam-malian g l a n d . The t h y r o i d i s known t o be i n t i m a t e l y asso-c i a t e d w i t h metamorphosis of amphibia and does modify some phases o f f i s h metabolism (Hoar, 1951b). In s p i t e of the l a c k of c o n c l u s i v e evidence t h a t t h y -r o x i n e i n c r e a s e s a c t i v i t y of f i s h through a change i n r a t e o f oxygen consumption, t h e r e i s at l e a s t one example of i n c r e a s e d a c t i v i t y of f i s h e s a f t e r treatment w i t h t h y r o x i n e . Hoar et a l ( 1 9 5 2)found t h a t chum salmon f r y t r e a t e d f o r one week.with s y n t h e t i c t h y r o x i n e showed an i n c r e a s e i n swimming speed, 33 and the swimming o f those immersed i n t h i o u r e a s o l u t i o n slowed markedly a f t e r two weeks. No attempt was made t o measure the oxygen consumption of these f i s h . I t i s now becoming i n c r e a s i n g l y evident t h a t the t h y r o i d gland i s r e l a t e d i n some way to f i s h m i g r a t i o n s (Hoar, 1951 b ) . The change from parr t o smolt stage i s c h a r a c t e r i s t i c of young m i g r a t i n g salmonoids, and heightened a c t i v i t y of the t h y r o i d has been r e c o g n i z e d at t h i s stage i n some salmon and t r o u t (Hoar, 1 9 3 9 , Robertson, 1 9 4 8 ) . F u r t h e r , Robertson ( 1 9 4 9 ) , Smith (1949) and Hoar (1951b) have i n c r e a s e d s i l v e r i n g among salmonoid p a r r by treatment w i t h t h y r o i d d e r i v a t i v e s . No c l e a r evidence of i n c r e a s e d s i l v e r i n g was seen i n e i t h e r coho or sockeye smolt t r e a t e d w i t h t h y r o x i n e i n t h i s study. T h i s may be due t o the f a c t t h a t the p a r r marks were a l r e a d y p a r t l y covered b e f o r e treatment commenced and s l i g h t changes i n the guanine d e p o s i t i o n were d i f f i c u l t t o d e t e c t . Hoar and B e l l (1950) r e l a t e i n c r e a s e d t h y r o i d a c t i v i t y i n chum salmon f r y h e l d i n f r e s h water past t h e i r normal m i g r a t i o n time with an upset osmotic balance at t h i s t i m e . There i s evidence i n the l i t e r a t u r e of a r e l a t i o n between t h y r o x i n e and r h e o t a x i s . Fontaine (1948) t r e a t e d e l v e r s o f t h e European e e l m i g r a t i n g i n t o f r e s h water w i t h p h e n y l t h i o u r e a . A f t e r s e v e r a l days o n l y 20 percent of these f i s h showed p o s i t i v e r h e o t a x i s , while 9 0 percent of the con-t r o l s s t i l l e x h i b i t e d t h i s r e a c t i o n . V i l t e r ( 1 9 4 4 ) , however } attempted t o show by h i s t o l o g i c a l i n s p e c t i o n t h a t the t h y r o i d 34 gland of m i g r a t i n g e l v e r s i s i n the same s t a t e as t h a t of e l v e r s r a i s e d i n c a p t i v i t y . He concluded t h a t the t h y r o i d p l a y s no p a r t i n r h e o t a x i s . I t i s c o n s i d e r e d t h a t V i l t e r ' s c o n c l u s i o n i s not based on adequate experimental evidence. The d a t a on the r a t e a t which t h y r o x i n e t r e a t e d coho and sockeye salmon smolt jump upstream over a dam does not demonstrate c l e a r l y t h a t such treatment r e s u l t s i n a l t e r e d r h e o t a x i s . The r e s u l t s suggest, however, i n c o n j u n c t i o n with q u a l i t a t i v e o b s e r v a t i o n s , t h a t t h e r e may be an i n c r e a s e i n r h e o t a x i s which can be demonstrated by more r e f i n e d apparatus. A method of q u a n t i t a t i v e l y measuring the swimming r a t e of f i s h s i m i l a r t o t h a t used by F r y and Hart (1948) might be advantageous i n t h i s r e s p e c t . Gonad Hormones and A c t i v i t y . There are many accounts i n the l i t e r a t u r e of treatment of f i s h e s w i t h male and female sex hormones (Hoar, 1951b) • Most of these d e s c r i b e t h e premature i n d u c t i o n of secondary sex c h a r a c t e r i s t i c s (Berkowitz, 1937; B r e t s c h n e i d e r and Duyvene de Wit, 1947; E v e r s o l e , 1941) o r sex r e v e r s a l ( B u l l o u g h , 1940; ,Taylor, 1948"). However, th e r e are some examples of change i n a c t i v i t y of f i s h e s a f t e r treatment. S t a n l e y and Tescher (1931) g r e a t l y i n c r e a s e d the a c t i v i t y of g o l d f i s h by f e e d i n g them mammalian t e s t i c u l a r substance, and Hoar et a l (1952) showed t h a t the swimming speed of chum salmon f r y was i n c r e a s e d a f t e r one week o f treatment w i t h methyl t e s -t o s t e r o n e . The treatments of sockeye and coho smolt i n t h i s study show t h a t i n g e n e r a l the gonad hormones i n c r e a s e d the 35 a c t i v i t y of the f i s h . This increase was expecially marked i n those f i s h treated with S t i l b o e s t r o l . The significance of the coincident change i n rheotaxis i s not e n t i r e l y c l e a r . The increasing size of the gonads and the appearance of secondary sexual c h a r a c t e r i s t i c s are well known features of adult salmon during t h e i r spawning migration. Increased a c t i v i t y of the gonads i s not to be expected i n young salmon moving to sea. However, i n t e r r e l a t i o n s between the endocrine organs may be very complex. It has been shown that maturation of the gonads of f i s h may reduce a c t i v i t y of the thyroid gland (Olivereau, 1949; Hoar, 1951). Barrington (1952) found that immersion of Lebistes i n thiourea solution f o r several months resulted i n f a i l u r e of development of the germ c e l l s and secondary sex characters. The l a t t e r appeared when the f i s h were fed thyroid. The p i t u i t a r y i s recognized as the s i t e of production of both gonadotrophic and thyrotrophic hormones (Hoar, 1951), but the true picture of t h i s complex i n t e r r e l a t i o n s h i p among p i t u i t a r y , thyroid and gonads i n f i s h e s i s l i t t l e understood. It should be stressed that the concentrations of estrogen solutions used varied widely and potency of the three compounds also varies. The differences that these variati o n s might produce i n the a c t i v i t y of the f i s h should not be overlooked. Another variable i n the sex hormone experiments was the sex r a t i o among the treated f i s h . The gonads of yearling P a c i f i c salmon are well d i f f e r e n t i a t e d , but no method has yet 36 been d e v i s e d f o r d i f f e r e n t i a t i n g the sexes from e x t e r n a l c h a r a c t e r i s t i c s . Temperature and A c t i v i t y . The r o l e of temperature i n t h e seaward movement of young salmon i s s t i l l u n c e r t a i n . Some workers are o f the o p i n i o n t h a t i t i s important as a departure s t i m u l u s ( F o e r s t e r , 1 9 3 7 ) . Hoar ( 1 9 5 1 ) found t h a t chum f r y show i n c r e a s e d a c t i v i t y and a marked tendency t o swim w i t h the c u r r e n t as hatchery temperatures i n c r e a s e d u r i n g the summer months. On the o t h e r hand, Huntsman (1948)- s t a t e s t h a t at no time do salmon swim a c t i v e l y downstream wi t h the c u r r e n t . On the b a s i s of many o b s e r v a t i o n s of chum f r y and eoho smolt i n the r h e o t a x i s tubs used f o r temperature experiments, i t i s concluded t h a t n e gative r h e o t a x i s does occur at h i g h temperatures, and t h a t a c t i v e downstream movement i n these tubs i s not simply a f a i l u r e o f p o s i t i v e r h e o t a x i s . F o e r s t e r ( 1 9 3 7 ) has shown that sockeye salmon migrate from C u l t u s Lake at temperatures of 4 . 4 t o 5 « 0 ° C, As the warmer s p r i n g temperatures cause an o v e r t u r n of the waters i n the l a k e , the mean temperature i n c r e a s e s , and at the above range, sockeye smolt move out of the l a k e . From the evidence i n the l i t e r a t u r e and as a r e s u l t of the experiments performed here i t i s suggested t h a t sudden e l e v a t i o n i n temperature may l e a d t o a c t i v e n e g a t i v e r h e o t a x i s by coho smolt and chum f r y i n r i v e r s , thus h a s t e n i n g t h e i r downstream movement. In c o n c l u s i o n , p o s i t i v e r h e o t a x i s has been shown i n 3 7 s e v e r a l s p e c i e s o f f r e s h water and diadromous f i s h . The degree of a c t i v i t y i n c u r r e n t s of water v a r i e s , those f i s h normally l i v i n g i n the f a s t e s t f l o w i n g waters showing the most c o n s i s t e n t response. Sustained p o s i t i v e r h e o t a x i s , however, i s not the o n l y method used t o maintain p o s i t i o n i n a stream. Some f i s h e s , such as s c u l p i n s , h o l d p o s i t i o n through strong p o s i t i v e t h i g m o t a x i s . A c t i v e p o s i t i v e r h e o t a x i s may l e a d some young salmon and t r o u t i n t o f a s t waters where they w i l l be swept downstream at n i g h t when v i s u a l s t i m u l i aire l o s t . The r e l a t i o n of t h y r o x i n e , t e s t o s t e r o n e and t h r e e estro' gen compounds t o r h e o t a x i s i s s t i l l not d e f i n i t e , but i n d i c a -t i o n s are t h a t a l l of these hormones i n c r e a s e g e n e r a l a c t i v i t y and l e a d t o more a c t i v e p o s i t i v e r h e o t a x i s . I t i s suggested t h a t the a p p e t i t i v e behaviour l e a d i n g t o r e s t l e s s movements o f such f i s h as sockeye y e a r l i n g s about a l a k e may be i n i t i a t e d by the hormonal l e v e l i n the b l o o d . Temperature i s probably an environmental r e l e a s e r l e a d i n g t o a more s p e c i a l i z e d form of a c t i v i t y , which i n some s p e c i e s at l e a s t takes t h e form of an a c t i v e swimming downstream. 38 SUMMARY 1 . T h e t e n d e n c y o f s e v e r a l s p e c i e s o f f i s h t o move i n t o a f l o w i n g s t r e a m o f w a t e r h a s b e e n m e a s u r e d . 2 . Some c o r r e l a t i o n h a s b e e n s u g g e s t e d b e t w e e n t h e n a t u r a l h a b i t a t o f e a c h s p e c i e s a n d t h e d e g r e e o f a c t i v i t y i n a r t i f i c i a l l y c r e a t e d c u r r e n t s . 3. T h e r e i s some e v i d e n c e t h a t i n c r e a s e i n t h y r o x i n e and s e x h o r m o n e ; l e v e l e n h a n c e s t h e r h e o t a c t i c r e s p o n s e i n s o c k e y e and c o h o s a l m o n s m o l t . T h i s i n c r e a s e i s r e f l e c t e d i n t h e s h o r t e r t i m e r e q u i r e d b y f i s h t o jump u p s t r e a m o v e r a d a m . A n e s t r o g e n , S t i l b o e s t r o l , h a s t h e most m a r k e d e f f e c t . Q u a l i t a t i v e o b s e r v a t i o n s c o n f i r m t h e s e r e s u l t s . 4 . S u d d e n e l e v a t i o n i n t e m p e r a t u r e 4 t o 5 ° C . a b o v e t h e h o l d i n g t e m p e r a t u r e p r o d u c e s n e g a t i v e r h e o t a x i s i n chum s a l m o n f r y a n d c o h o s a l m o n s m o l t . 5 . M i g r a t i o n d o w n s t r e a m o f y o u n g P a c i f i c s a l m o n may be a p p e t i t i v e b e h a v i o u r w h i c h i s i n i t i a t e d b y i n c r e a s e i n some b o d y h o r m o n e s , c o n t r o l l e d , i n p a r t , b y t e m p e r a t u r e and d i r e c t e d b y w a t e r c u r r e n t s . 39 ACKNOWLEDGMENTS F i n a n c i a l a s s i s t a n c e i n the form of a summer s c h o l a r s h i p from the N a t i o n a l Research C o u n c i l i s greatly-a p p r e c i a t e d . Thanks are extended t o F.P. Maher and G.E. S t r i n g e r o f the F i s h e r i e s Management D i v i s i o n of the B.C. Game Com-m i s s i o n f o r a i d i n c o l l e c t i n g f i s h . The w r i t e r i s p a r t i c u l a r l y indebted t o Dr. W.S. Hoar of the Department of Zoology f o r a s s i s t a n c e , guidance and i n s p i r a t i o n throughout the course of the p r o j e c t . Thanks are extended t o Dr. W.A. Clemens, Head of the Department of Zoology, f o r c o n s t r u c t i v e c r i t i c i s m s of t h e manuscript. 40 L I T E R A T U R E C I T E D B a r r i n g t o n , E . J . W . T h e T h y r o i d g l a n d : a p r o b l e m i n c o m -p a r a t i v e p h y s i o l o g y . New B i o l o g y , 13 : 61 - 7 9 , 1 9 5 2 . B e r k o w i t z , P . E f f e c t s o f e s t r o g e n i c s u b s t a n c e s i n L e b i s t e s r e t i c u l a t u s ( G u p p y ) . P r o c . S o c . E x p . B i o l . M e d . , 36 : 416 - 4 1 8 , 1 9 3 7 . B r e t S c h n e i d e r , L . H . and J . J . D u y v e n e de W i t . S e x u a l e n d o c -r i n o l o g y o f n o n - m a m m a l i a n v e r t e b r a t e s . E l s e i n e r , 1 9 4 7 . B u d d e n b r o c k , W. v o n . Y e r g l e i c h e n d e P h y s i o l o g i e . B a n d I, S i n n e s p h y s i o l o g i e . V e r l a g B i r k h a u s e r , B a s e l , 1 9 5 2 . B u l l o u g h , W . S . A s t u d y o f s e x r e v e r s a l i n t h e minnow ( P h o x i n u s  l a e v i s L . ) . J . E x p . Z o o l . , 85 : 475 - 5 0 1 , 1 9 4 0 . C l a u s e n , R . G . O r i e n t a t i o n i n f r e s h w a t e r f i s h e s . E c o l o g y , 12 : 541 - 5 4 6 , 1 9 3 1 . D y k g r a a f , S . F u n c t i o n d e r S e i t e n o r g a n e a n F i s c h e n . Z . v e r g l . P h y s i o l . , 20 : 162 - 2 1 4 , 1 9 3 3 . E v e r s o l e , W . J . T h e e f f e c t s o f p r e g n e n i n o l o n e and r e l a t e d s t e r o i d s o n s e x u a l d e v e l o p m e n t i n f i s h ( L e b i s t e s r e t i c u l a t u s ) . E n d o c r i n o l o g y , 28 : 6 O 3 - 6 I O , 1 9 4 1 . F l e i s c h m a n n , W. C o m p a r a t i v e p h y s i o l o g y o f t h e t h y r o i d and p a r a t h y r o i d g l a n d s . A m e r . L e c t u r e S e r i e s , 1 1 8 , 1 9 5 1 . F o e r s t e r , R . E . 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Stringer, G.E. An experimental study of some v i s u a l l y r e-leased behaviour patterns i n young coho salmon and kamloops trout. M.A. t h e s i s , Dept. of Zoology, Univ. of B r i t i s h Columbia, 1952. Taylor, A.B. Experimental sex reversal i n the red swordtail hybrid Xiphophorus-Platypoecilus. Trans. Amer. Micr. S o c , 6? : 155-164, 1948. Thorpe, W.H. The concepts of learning and t h e i r r e l a t i o n to those of i n s t i n c t . Symp. Soc. Exp. B i o l . , 4 : 387 - 408, 1950. Tinbergen, N. The h i e r a r c h i c a l organization of nervous mechanisms underlying i n s t i n c t i v e behaviour. Symp. Soc. Exp. B i o l . , 4 : 305-312, 1950. V i l t e r , V. Rheotropisme de l a C i v e l l e et a c t i v i t e thyroidienne CR. Soc. B i o l . Paris, 138 : 668-669, 1944. 45 APPENDIX Page D a t a o n G e n e r a l R e s p o n s e t o C u r r e n t s . T a b l e 1. S c u l p i n s i T a b l e 2. E e l s i i T a b l e 3 . C a t f i s h i i i i T a b l e 1 . P e r c e n t s c u l p i n s i n i n f l o w e n d d u r i n g s e c o n d a n d t h i r d h o u r s o f f l o w . F i g u r e s a r e mean P e r c e n t a g e s f o r s i x e x p e r i m e n t s . S e c o n d h o u r T h i r d h o u r i ; i T i m e - 3 0 s e c o n d P e r c e n t f i s h T i m e - 3 0 s e c o n d P e r c e n t f i s h i n t e r v a l s i n t e r v a l s 1 5 5 . 6 1 6 5 . 3 2 5 9 . 7 2 5 9 . 7 3 4 7 . 2 3 5 0 . 0 4 5 0 . 0 4 5 5 . 6 5 5 0 . 0 5 5 4 . 2 6 5 4 . 2 6 . 5 5 . 6 7 5 8 . 3 7 5 4 . 2 8 5 1 . 4 ' 8 . 5 5 . 6 9 4 7 . 2 9 51 .4 1 0 - 3 3 . 3 1 0 5 6 . 9 1 1 4 8 . 6 1 1 . 5 1 . 4 1 2 5 1 . 4 1 2 5 6 . 9 13 4 4 » 4 1 3 5 0 . 0 1 4 5 0 . 0 1 4 4 0 . 3 1 5 4 3 . 1 1 5 4 4 * 4 1 6 3 4 . 7 1 6 51 .4 1 7 4 4 * 4 1 7 5 4 . 2 18 4 5 . 8 18 5 0 . 0 1 9 3 3 - 3 1 9 4 8 . 6 2 0 3 6 . 1 2 0 5 8 . 3 2 1 5 6 . 9 2 1 5 6 . 9 2 2 5 2 . 8 2 2 5 4 . 2 2 3 3 4 . 7 2 3 6 5 . 3 2 4 4 5 . 8 2 4 61 .1 2 5 4 1 . 7 2 5 5 0 . 0 2 6 5 4 . 2 2 6 5 6 . 9 2 7 5 2 . 8 2 7 6 3 . 9 28 3 4 . 7 28 5 6 . 9 2 9 3 7 . 5 2 9 6 6 . 7 3 0 4 5 . 8 3 0 5 6 . 9 1 1 T a b l e 2 . P e r c e n t e e l s i n i n f l o w e n d d u r i n g s e c o n d a n d t h i r d h o u r s o f f l o w . F i g u r e s a r e mean p e r c e n t a g e s f o r s i x e x p e r i m e n t s . S e c o n d h o u r T h i r d h o u r T i m e - 30 s e c o n d P e r c e n t f i s h T i m e - 30 s e c o n d P e r c e n t f i s h i n t e r v a l s i n t e r v a l s 1 4 3 . 1 2 4 1 . 7 3 4 0 . 3 4 4 4 . 4 5 5 4 . 2 6 5 4 . 2 7 51 .4 8 4 5 . 8 9 4 8 . 6 1 0 5 5 . 6 1 1 4 0 . 3 12 5 8 . 3 13 5 9 . 7 14 6 1 . 1 15 6 3 . 9 16 • 5 4 . 2 17 5 4 . 2 18 51 .4 1 9 5 5 . 6 20 5 6 . 9 21 5 6 . 9 22 5 5 . 6 23 4 5 . 8 24 5 9 . 7 25 • 5 5 . 6 26 5 9 . 7 27 5 6 . 9 28 5 5 . 6 29 5 6 . 9 30 6 1 . 1 1 51.4 2 55.6 3 52.8 4 52.8 5 4 8 . 6 6 5 0 . 0 7 58.3 8 52.8 9 52.8 10 50.0 11 52.8 12 48.6 13 50.0 14 5 6 . 9 15 5^.3 16 55.6 17 59.7 18 54.2 1 9 55.6 20 55.6 21 56.9 22 54.2 23 54.2 24 5 6 . 9 25 52.8 26 6 8 . 1 27 53.3 28 58.3 29 61.1 30 62.5 i i i Table 3, Percent c a t f i s h i n inflow end during second and t h i r d hours of flow. Figures are mean percentages for eight experiments. Second hour Third hour Time - 30 second Percent f i s h Time - 30 second Percent f i s h i n t e r v a l s i n t e r v a l s 1 87.5 1 61.5 2 74.0 2 71.9 3 71.9 3 70.8 4 77.1 4 64.6 5 72.9 5 62.5 6 70.8 6 71.9 7 7 6 . 0 7 6 0 . 4 8 58.3 8 6 7 . 7 9 69.8 9 69.8 10 76.0 10 58.3 11 55.2 11 6 I . 5 12 65.6 12 65.6 13 63.5 13 7 4 . 0 14 65.6 14 6 7 . 7 15 70.8 15 7 5 . 0 16 69.8 16 7 5 . 0 17 74.0 17 71 .9 IS 77.1 18 71 .9 19 63.5 19 7 4 . 0 20 6 6 . 7 20 72.9 21 80.2 21 77.1 22 79.2 22 80.2 23 78.1 23 6 6 . 7 24 80.2 24 74.0 25 81.3 25 76.0 26 76.0 26 8 I . 3 27 79.2 27 7 6 . 0 28 6 I . 5 28 78.1 29 74.0 29 76.1 30 83.3 30 83.3 

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