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The response of rainbow trout Salmo gairdneri to lures with special references to color preference Dooley, Robert H. A. 1989

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T H E R E S P O N S E O F R A I N B O W T R O U T (Salmo g a i r d n e r i ) TO L U R E S WITH S P E C I A L R E F E R E N C E TO COLOR  PREFERENCE  by  Robert H . A . Dooley B . E d . , U n i v e r s i t y of B r i t i s h C o l u m b i a ,  1971  A THESIS S U B M I T T E D IN P A R T I A L F U L F I L M E N T O F THE REQUIREMENTS FOR THE D E G R E E OF MASTER OF SCIENCE  i n the D e p a r t m e n t of  Zoology  W e a c c e p t this t h e s i s as c o n f o r m i n g to the r e q u i r e d standard  T H E UNIVERSITY O F BRITISH C O L U M B I A S e p t e m b e r , 1974  In p r e s e n t i n g t h i s t h e s i s  in p a r t i a l  f u l f i l m e n t o f the requirements  an advanced degree at the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree the L i b r a r y  s h a l l make i t f r e e l y a v a i l a b l e f o r  thesis  f o r s c h o l a r l y purposes may be granted by the Head of my Department It  i s understood that c o p y i n g o r  permission.  Depa rtment The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  or  publication  of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my written  that  r e f e r e n c e and study.  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s  by h i s r e p r e s e n t a t i v e s .  for  ii  ABSTRACT  The r e s p o n s e of r a i n b o w t r o u t (Salmo g a i r d n e r i ) to l u r e s was i n v e s t i g a t e d i n t r o l l i n g e x p e r i m e n t s at L o o n L a k e , B r i t i s h C o l u m b i a .  The " a c t i o n " of a l u r e  was found to be an i m p o r t a n t p a r a m e t e r i n d e t e r m i n i n g i t s e f f i c i e n c y : a c t i o n s tested, the f l a t f i s h caught the g r e a t e s t n u m b e r of f i s h .  of four  A l t h o u g h the  c o l o r of l u r e was not significant, r e d l u r e s w e r e m o r e efficient than y e l l o w , green, and blue, and m o r e efficient than v a r i o u s c o l o r p a t t e r n s of r e d and white. The p r e s e n c e of a dodger w i t h l u r e s d i d not affect t h e i r e f f i c i e n c y , but l a r g e r f i s h w e r e caught.  N o s i z e s e l e c t i o n o c c u r r e d w i t h e i t h e r c o l o r s or a c t i o n s of l u r e s .  In l a b o r a t o r y feeding e x p e r i m e n t s using dyed t r o u t eggs as food, was s e l e c t e d f i r s t or second m o r e often than y e l l o w , green,  or b l u e .  red  The c o l o r  of b a c k g r o u n d against w h i c h the f i s h were fed, and i n d i v i d u a l d i f f e r e n c e s among f i s h c a u s e d s i g n i f i c a n t changes i n the p r e f e r e n c e shown for v a r i o u s c o l o r s of food. C o m b i n i n g two c o l o r s a l s o affected the s e l e c t i o n i n t e n s i t y , depending upon the c o n t r a s t between the two c o l o r s .  P r e f e r e n c e s for different c o l o r s of food were  not influenced by the hunger l e v e l of the fish,  m e a s u r e d i n t e r m s of the quantity  of food i n the f i s h ' s gut. In the c o u r s e of the e x p e r i m e n t s it was i n c i d e n t a l l y o b s e r v e d : ( 1 ) that r a i n b o w t r o u t p o s s e s s a s t r i k i n g a b i l i t y to m a t c h the hue of t h e i r s k i n ( m a i n l y i n the d o r s a l region) to that of the b a c k g r o u n d i n w h i c h they ar e kept; (Z) the c o l o r of b a c k g r o u n d affects the a c t i v i t y l e v e l of r a i n b o w trout: the highest l e v e l of a c t i v i t y and g r e e n the l o w e s t .  yellow produces  iii T A B L E OF  CONTENTS Page  TITLE PAGE  i  ABSTRACT  «  T A B L E OF CONTENTS  iii  LIST O F FIGURES LIST O F T A B L E S ACKNOWLEDGMENTS  v v  i  viii  INTRODUCTION  1  PARTI.  TROLLING EXPERIMENTS  5  A.  C l a s s i f i c a t i o n of L u r e s  5  B. C.  G e n e r a l Methods Trolling Experiment I 1. Methods 2. R e s u l t s T r o l l i n g E x p e r i m e n t II 1. Methods 2. R e s u l t s T r o l l i n g E x p e r i m e n t III 1. Methods 2. R e s u l t s T r o l l i n g E x p e r i m e n t s -- D i s c u s s i o n  D.  E.  F.  P A R T II. F E E D I N G E X P E R I M E N T S A. B. C.  D.  Introduction G e n e r a l Methods Feeding Experiment I 1. Methods 2. R e s u l t s 3. D i s c u s s i o n F e e d i n g E x p e r i m e n t II 1. Methods 2. Results 3. D i s c u s s i o n  INCIDENTAL A.  OBSERVATIONS  Effect 1. 2. 3.  of Background C o l o r on A c t i v i t y L e v e l of T r o u t Methods Results Discussion  7 1° 10 10 12 1  2  1  3  15 15 I 17 7  24 24 24 28 28 29 36 43 43 46 46 54 54 54 55 55  iv Page B.  A d a p t a t i o n of S k i n of T r o u t to B a c k g r o u n d C o l o r  DISCUSSION A.  B.  Background Literature 1. Color vision in fish 2 . T r a n s m i s s i v i t y of l i g h t i n water 3 . R e l e v a n c e to t r o l l i n g and feeding e x p e r i m e n t s I n t e r p r e t a t i o n of R e s u l t s  R E F E R E N C E S CITED  57 61 61 61 66 68 68 74  V  LIST OF FIGURES FIGURE  1  2  3  4  5  6  Page  C h e c k e r e d and s t r i p e d flatfish, and dodger f r o m t r o l l i n g e x p e r i m e n t III, L o o n L a k e , B . C . , A u g u s t 25 to September 1, 1972  1  6  C u t a w a y v i e w of e x p e r i m e n t a l tank used i n feeding e x p e r i ments I and II at the U n i v e r s i t y of B . C . , M a y 22 to June 6, 1973; and J u l y 23 to A u g u s t 3, 1973  26  G r a p h of mean s e l e c t i o n i n t e n s i t i e s of c o l o r s of food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B . C . , M a y 22 to June 6, 1973  33  G r a p h of mean s e l e c t i o n i n t e n s i t i e s of c o l o r s of food among different f i s h . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B . C . , M a y 22 to June 6, 1973  35  P r e p a r a t i o n of food for feeding e x p e r i m e n t I I - - a r r a n g e m e n t of eggs i n the gelatine; p l a n v i e w . F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 22 to A u g u s t 3, 1973  44  R e g i o n s of s k i n for s k i n c o l o r o b s e r v a t i o n s . observations  59  Incidental  vi LIST OF T A B L E S TABLE I  II  III  IV  V  VI  VII  VIII  IX  X  XI  Page C l a s s i f i c a t i o n of l u r e action b a s e d on a test t r o l l of 3 5 d i f f e r e n t l u r e s i n a f i s h pond at the U n i v e r s i t y of B r i t i s h C o l u m b i a , s p r i n g of 1972  6  N u m b e r s of f i s h caught on l u r e s f r o m t r o l l i n g e x p e r i m e n t I, L o o n L a k e , B.C., J u l y 10-17, 1972  11  N u m b e r s of f i s h caught on l u r e s f r o m t r o l l i n g e x p e r i m e n t II, L o o n Lake, B.C., A u g u s t 5 to 9, 1972  14  N u m b e r s of f i s h caught on l u r e s f r o m t r o l l i n g e x p e r i m e n t III, L o o n L a k e , B.C., A u g u s t 25 to September 1, 1972  18  M e a n lengths (cm) of f i s h caught on l u r e s f r o m t r o l l i n g e x p e r i ment III, L o o n Lake, B.C., on the b a s i s of c o l o r p a t t e r n of l u r e and on the b a s i s of whether o r not a dodger was used. A u g u s t 25 to September 1, 1972 19 S e l e c t i o n i n t e n s i t i e s of c o l o r s of food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B.C., M a y 22 to June 6, 1973  31  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects f o r c o l o r s of food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B.C., M a y 22 to June 6, 1973  32  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects f o r c o l o r s of food among d i f f e r e n t f i s h . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y o f B.C., M a y 22 t o June 6, 1973  " v  34  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects f o r c o l o r s of food among d i f f e r e n t f i s h , f o r e a c h r e p l i c a t e . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B.C.,. M a y 22 to June 6, 1973  38  V a r i a b i l i t y i n s e l e c t i o n o r d e r between r e p l i c a t e s and between tanks. F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B.C., M a y 22 to June 6, 1973  40  I n t e r a c t i o n effects f o r s e c o n d - o r d e r i n t e r a c t i o n (food c o l o r x tank c o l o r x i n d i v i d u a l d i f f e r e n c e s ) -- average f o r two r e p l i c a t e s . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B.C., M a y 22 to June 6, 1973  42  vii TABLE XII  XIII  XIV  XV  XVI  XVII  XVIII  Page S e l e c t i o n i n t e n s i t i e s of b i - c o l o r e d food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973  47  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects for c o l o r s of food w i t h v a r i o u s c o l o r s of tag. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973  48  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects for c o l o r s of food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973  50  Effect of wide s p e c t r a l s e p a r a t i o n of food c o l o r and tank c o l o r on food c o l o r x tank c o l o r i n t e r a c t i o n effects of feeding e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973  51  S e l e c t i o n i n t e n s i t i e s f r o m feeding e x p e r i m e n t II grouped a c c o r d i n g to s i m i l a r i t y of c o l o r s of tank, tag egg, and food egg. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973  53  M e a s u r e s of a c t i v i t y l e v e l s of f i s h i n different c o l o r e d habitats  56  D e s c r i p t i o n of s k i n c o l o r of f i s h f r o m different t a n k s . Incidental o b s e r v a t i o n s  60  colored  viii ACKNOWLEDGMENTS  I would like to thank D r . P. A . L a r k i n who proposed the p r o b l e m for investigation, gave helpful advice and encouragement throughout the f i e l d work and analysis phases of this study, and p r o v i d e d f i n a n c i a l a s s i s t a n c e when it was s o r e l y needed.  Thanks are also due to D r . N. J. W i l i m o v s k y and Dr. T. G.  Northcote, who r e v i e w e d the manuscript. I a m indebted to M r . H. S p a r r o w and M r . A . M i t c h e l l of the B r i t i s h C o l u m b i a F i s h and W i l d l i f e B r a n c h for their cooperation in providing the f i s h used i n the experiments at the U n i v e r s i t y of B r i t i s h Columbia.  A l s o i n the  F i s h and W i l d l i f e Branch, M r . G. Halsey, M r . D. Smith, and other m e m b e r s of the L o o n Lake R e s e a r c h Group helped by providing accommodation at L o o n  Lake  and allowing me to use their r e s e a r c h boat and other equipment. The able a s s i s t a n c e of M r . J. Blackburn, Mr.S.Simms, and M r . A . Belshaw, made it possible to c a r r y out the t r o l l i n g experiments at L o o n Lake. F i n a l l y , I s i n c e r e l y thank my wife, Mary, who accepted the r o l e of a student wife for many y e a r s and who never lost faith i n me throughout this time.  1  INTRODUCTION  The s e l e c t i v i t y and e f f i c i e n c y of f i s h i n g gear i s a v i t a l c o n c e r n of f i s h e r m e n and f i s h e r i e s m a n a g e r s thoughtout the w o r l d .  The f i s h e r m a n , of  c o u r s e , wants to use the m o s t e f f i c i e n t l e g a l gear i n o r d e r to r a i s e h i s c a t c h per unit effort.  On the other hand, by r e g u l a t i n g the l e v e l of gear e f f i c i e n c y ,  a f i s h e r i e s manager c a n m a x i m i z e h a r v e s t ,  thus, i n the long run,  allowing  g r e a t e r n u m b e r s to share i n the r e s o u r c e . S e l e c t i v i t y and e f f i c i e n c y embody two separate concepts, be r e d u c e d to t e r m s of one of t h e m .  but they can  The e f f i c i e n c y of a unit of f i s h i n g g e a r  r e f e r s to i t s a b i l i t y r e l a t i v e to other gear to c a t c h f i s h .  It i s r e a l l y the s a m e  concept as R i c k e r ' s "fishing power", w h i c h he defines as "...the c a t c h taken by the g i y e n apparatus, d i v i d e d by the c a t c h of a standard apparatus f i s h i n g at n e a r l y the same t i m e and p l a c e . "  (Ricker,  1958)  S e l e c t i v i t y r e f e r s to the  c h a r a c t e r i s t i c of a unit of f i s h i n g gear w h e r e b y it catches f i s h of a c e r t a i n weight or length i n g r e a t e r amounts than would be expected on the b a s i s of the abundance of f i s h of that weight or length i n the t o t a l stock.  F o r instance,  a  seine net of a c e r t a i n m e s h s i z e may a l l o w 50 per cent of the f i s h of l e s s than 70 c m length to pass t h r o u g h i t .  It i s s a i d to s e l e c t for f i s h of g r e a t e r than  70 c m length. A l a r g e r m e s h s i z e may a l l o w 50 per cent of the f i s h of l e s s than 80 c m to s l i p t h r o u g h . than the f i r s t net.  It i s s a i d that the second net s e l e c t s for l a r g e r f i s h  But t h i s c a n a l s o be e x p l a i n e d as a change i n e f f i c i e n c y - -  the efficiency of the two nets to c a t c h f i s h of 70-80 c m (and p e r h a p s f i s h of other s i z e s also) i s not the same.  It i s not n e c e s s a r y to l i m i t the concept of  s e l e c t i v i t y to length and weight of f i s h .  G e a r c a n be s a i d to s e l e c t on the b a s i s  of other c h a r a c t e r i s t i c s s u c h as s p e c i e s or s e x . A change i n e f f i c i e n c y does not n e c e s s a r i l y i n v o l v e a change i n s e l e c t i v i t y , although it often d o e s .  It i s at l e a s t t h e o r e t i c a l l y p o s s i b l e to have s o m e  change i n fishing gear, p r o d u c i n g an i n c r e a s e or d e c r e a s e i n e f f i c i e n c y that is p r o p o r t i o n a l l y d i s t r i b u t e d over the range of the v a r i a b l e c o n c e r n e d .  2 The l i t e r a t u r e on gear e f f i c i e n c y i s s i z a b l e , but it tends to c o n s i s t f o r the g r e a t e r part of p a p e r s d e a l i n g w i t h e f f i c i e n c y of n e t s .  The scope of  f a c t o r s found to influence the s e l e c t i v i t y and e f f i c i e n c y of nets is. great; of the m o r e p r o m i n e n t f a c t o r s a r e :  some  s i z e of m e s h (Davis, 1929). s i z e d i s t r i b u -  t i o n of f i s h stock ( B o r o w i k , 1930), m a t e r i a l of which, the net i s made ( B o e r e m a , 1956; P y c h a ,  1962), s i z e of c a t c h ( M c C r a c k e n ,  1963), and c o l o r of net ( J e s t e r ,  1973). - I n c o m p a r i s o n w i t h the l i t e r a t u r e on nets, rather sparse.  the l i t e r a t u r e on l u r e s i s  W h i l e c a t c h per unit effort ( C P U E ) v a l u e s are f r e q u e n t l y  determined f r o m c r e e l censuses,  t h e r e i s often no attempt made to c a t e g o r i z e  these v a l u e s under different types of l u r e ( E m i g ,  1971).  E s p i n o s a , e t a l . , (1971)  c o n t r a s t e d s u c c e s s of l i v e bait f i s h e r m e n w i t h that of f i s h e r m e n u s i n g a r t i f i c i a l l u r e s , but d i d not attempt any s u b d i v i s i o n of the a r t i f i c i a l l u r e s .  In some  studies w h e r e the type of l u r e i s c a t e g o r i z e d p r e c i s e l y , l i t t l e attempt has been made to c o n t r o l other f a c t o r s that m i g h t influence the f i s h i n g s u c c e s s s u c h as a n g l e r s k i l l and technique, l o c a t i o n of f i s h i n g a r e a , (Larkin,  1949).  and t i m e of y e a r of f i s h i n g  In other studies that have p a i d m o r e attention to the  " e n v i r o n m e n t a l " f a c t o r s , the c a t e g o r i e s of l u r e have been few and b r o a d .i  ( B e u k e m a , 1970; B o y d s t u n , 1972).  C e r t a i n l y , t h e r e have b e e n few e x p e r i -  m e n t a l studies a i m e d s p e c i f i c a l l y at d e t e r m i n i n g the c h a r a c t e r i s t i c s of a good lure. Of the studies done on e f f i c i e n c y and s e l e c t i v i t y of l u r e s , m o s t have been designed along the l i n e s of pilot studies for m a n a g e m e n t p u r p o s e s . F r e q u e n t l y they have been p r o m p t e d by o b s e r v a t i o n s that a s u b s t a n t i a l n u m b e r of u n d e r s i z e d f i s h w e r e being s a c r i f i c e d as a r e s u l t of t r a d i t i o n a l f i s h i n g methods ('Pitre, 1970; Boydstun,  1972), or by the d e s i r e to a s s e s s the  effectiveness of c u r r e n t r e g u l a t i o n s (Shetter,  et a l . , 1965).  R e g a r d l e s s of  whether or not t h e i r purpose was to be a t o o l for management,  m o s t studies  have accepted t h e i r f i e l d of r e s e a r c h as c o v e r i n g the l u r e s that ar e c u r r e n t l y used by most f i s h e r m e n . 1973; P y c h a ,  In c o n t r a s t to the studies on net f i s h i n g  (Jester,  1962; and Z u p a n o v i c , 1 9 6 3 ) , - s e l d o m has an i n v e s t i g a t i o n attempted  3 to d e t e r m i n e the effect of m o d i f i c a t i o n s of gear on i t s s e l e c t i v i t y or e f f i c i e n c y . What c o m p a r i s o n s have been made w e r e u s u a l l y made among b r o a d c a t e g o r i e s of l u r e (e.g., f l i e s v e r s u s spoons v e r s u s plugs v e r s u s gang t r o l l s ) . A c c o r d i n g l y , there i s often no effort made to s t a n d a r d i z e techniques of f i s h i n g or even t i m e s of y e a r at w h i c h f i s h i n g o c c u r s ; the a s s u m p t i o n being made, perhaps i m p l i c i t l y , that this w i l l balance out i f enough s a m p l e s ar e taken. T h i s is a dangerous a s s u m p t i o n to make, as it is g e n e r a l l y accepted that f i s h e r m e n using c e r t a i n types of gear e x c l u s i v e l y are m o r e e x p e r i e n c e d and p r o b a b l y m o r e s k i l f u l than f i s h e r m e n using other types of gear ( E s p i n o s a , 1971; Shetter,  1965).  A l s o , l u r e s that are used i n a w i n t e r f i s h e r y , or that s e l e c t  for l a r g e r older f i s h , cannot be expected to y i e l d so high a c a t c h p e r unit effort ( C P U E ) as those used at the height of the f i s h i n g season, or those that s e l e c t for s m a l l e r f i s h . The f o r e g o i n g r e m a r k s a r e not meant to be d i s p a r a g i n g s i n c e the bulk of these studies have been d i r e c t e d to the question, "What effect have the v a r i o u s c l a s s e s of l u r e had on a f i s h e r y ? ", and it i s perhaps not n e c e s s a r y to separate out the effects of f i s h e r m a n s k i l l and other f a c t o r s f r o m the inherent e f f i c i e n c y of th.^ l u r e when d e a l i n g w i t h this question.  But I was m o r e c o n c e r n e d  w i t h identifying the c h a r a c t e r i s t i c s of an efficient l u r e , and it was t h e r e f o r e i m p e r a t i v e that I c o n t r o l as m a n y confusing f a c t o r s as p o s s i b l e .  It i s f o r this  r e a s o n that a c a r e f u l attempt was made to m a t c h the l u r e s for s i z e and to paint t h e m i n toto w i t h standard c o l o r s of paint. S i n c e a multitude of f a c t o r s i n t e r a c t to d e t e r m i n e the s u c c e s s of l u r e s , a f i s h i n g technique was sought that would be most amenable to s t a n d a r d i z a t i o n . B o t h f l y - f i s h i n g and s p i n - c a s t i n g depend s u b s t a n t i a l l y on the s k i l l and technique of the i n d i v i d u a l a n g l e r ; use of l i v e bait makes s t a n d a r d i z a t i o n at the other end of the line d i f f i c u l t .  T h e r e f o r e , the type of f i s h i n g was r e s t r i c t e d to t r o l l i n g  w i t h a r t i f i c i a l l u r e s , for w h i c h i t i s r e l a t i v e l y easy to s t a n d a r d i z e technique. L o c a t i o n and b e h a v i o r of the f i s h l o o m p r o m i n e n t i n the d e t e r m i n a t i o n  of c a t c h a b i l i t y to v a r i o u s types of l u r e , yet are a l m o s t i m p o s s i b l e to standardize experimentally.  N e v e r t h e l e s s , some degree of c o n t r o l c a n be  a c h i e v e d by f i s h i n g the same a r e a i n the same p a t t e r n for the extent of e a c h t r i a l , and a s t a t i s t i c a l c o m p a r i s o n is p o s s i b l e by a s s u r i n g that e a c h l u r e c o m b i n a t i o n i s f i s h e d a number of t i m e s throughout an e x p e r i m e n t . In the second half of this t h e s i s feeding e x p e r i m e n t s are d e s c r i b e d w h i c h w e r e p e r f o r m e d in an attempt to c o n f i r m apparent c o l o r f r o m the l u r e e x p e r i m e n t s .  preferences  It was a s s u m e d that trout s t r i k e l u r e s because  they m i s t a k e t h e m for potential food; i f this i s so, then o b s e r v i n g t h e i r p r e ference for food of different c o l o r s under c o n t r o l l e d c o n d i t i o n s might help to c l a r i f y t h e i r r e s p o n s e s to the c o l o r e d l u r e s used i n the t r o l l i n g e x p e r i m e n t s . F o r purposes of c o m p a r i s o n , t h e r e i s v e r y l i t t l e l i t e r a t u r e on the p r e f e r e n c e of f i s h for different c o l o r s of food.  Some of the e a r l i e r w o r k on  c o l o r v i s i o n i n f i s h sought to prove that c e r t a i n s p e c i e s of f i s h d i s t i n g u i s h hue by d e m o n s t r a t i n g that an a s s o c i a t i o n of food w i t h a c o l o r e d object c o u l d be developed (White, 1919; B r o w n ,  1937).  B u t this a s s o c i a t i o n was developed  a r t i f i c i a l l y through a c o n d i t i o n i n g p r o g r a m and d i d not r e f l e c t " n a t u r a l " p r e f e r e n c e s of the f i s h .  A s far as r a i n b o w trout are c o n c e r n e d , the only w o r  of w h i c h I a m aware that p u r p o r t s to m e a s u r e these " n a t u r a l " p r e f e r e n c e s (albeit i n a l a b o r a t o r y setting) i s that of Ginetz and L a r k i n (1973), and perhap: that of Wolf and W a l e s (1953).  5 P A R T I.  TROLLING EXPERIMENTS  R e a c t i o n of r a i n b o w t r o u t (Salmo g a i r d n e r i ) to l u r e s was i n v e s t i g a t e d i n t r o l l i n g e x p e r i m e n t s at L o o n L a k e , B r i t i s h C o l u m b i a , d u r i n g the s u m m e r of 1972.  A n attempt to c l a r i f y c o l o r p r e f e r e n c e s was made w i t h feeding  e x p e r i m e n t s at the U n i v e r s i t y of B r i t i s h C o l u m b i a i n the s p r i n g and s u m m e r of 1973.  A.  C l a s s i f i c a t i o n of L u r e s T h i r t y - f i v e different l u r e s w e r e " t r o l l e d " i n a f i s h pond at the U n i v e r s i t y  of B r i t i s h C o l u m b i a by dragging t h e m through the water on a l i n e attached to a fishing rod.  The action'' of e a c h l u r e was o b s e r v e d and c l a s s i f i e d .  appeared to be, at the most,  only a half dozen d i s t i n c t types of a c t i o n s ,  individual l u r e s exhibiting slight v a r i a t i o n s .  with  These are d e s c r i b e d i n Table I.  O f these a c t i o n s , four types o c c u r r e d most frequently: spoon and "dead".  There  flatfish,  spinner,  The "dead" l u r e showed no wobbling or spinning a c t i o n .  A l l the l u r e s that w e r e tested r e l i e d i n some way on the f l u i d d r a g of water s t r i k i n g the l u r e to give it whatever " a c t i o n " it had (i.e., t h e r e w e r e no b a t t e r y - o p e r a t e d m o t o r s i n the l u r e i t s e l f to p r o v i d e the action). Therefore, at some m i n i m u m speed of t r o l l i n g where the d r a g was low, each l u r e e x h i b i t e d no action, i . e . , it followed i t s point of attachment to the l i n e w i t h no s i d e w a y s or v e r t i c a l m o t i o n of any p a r t of the l u r e and w i t h no r o t a t i o n of the l u r e i t s e l f , or of any p a r t of the l u r e . A s the speed of t r o l l i n g i n c r e a s e d (and t h e r e f o r e the p r e s s u r e of the water on the l u r e ) , some of the l u r e s s t a r t e d to e x h i b i t a sideways or v e r t i c a l m o t i o n of the whole l u r e or part of the l u r e , i n conjunction w i t h its f o r w a r d m o t i o n . Other l u r e s e x h i b i t e d r o t a t o r y m o t i o n . These " a c t i o n s " began at different speeds for different l u r e s . a n d continued q u a l i t a t i v e l y unchanged throughout a c e r t a i n upward range of t r o l l i n g speeds. 1  A t a s t i l l g r e a t e r speed this m o r e or l e s s o r d e r l y m o t i o n of the l u r e was b l o c k e d a n d / o r e c l i p s e d by an e r r a t i c movement of the l u r e t h r o u g h the water, c o n s i s t i n g of a s e r i e s of j e r k s f o r w a r d three or four t i m e s the length of the l u r e . A t this speed the l u r e c o u l d be s a i d to " c a v i t a t e " as the flow of water over its surface changed f r o m a l a m i n a r to turbulent flow. Frequently the l u r e would r i s e and b r e a k the surface of the w a t e r .  TABLE  I.  C l a s s i f i c a t i o n of l u r e a c t i o n b a s e d on a t e s t t r o l l of 35 d i f f e r e n t l u r e s i n a f i s h pond at the U n i v e r s i t y of B r i t i s h C o l u m b i a ,  s p r i n g of 1972.  u s e d i n t r o l l i n g e x p e r i m e n t I a r e m a r k e d w i t h an a s t e r i s k (*), d i m e n s i o n s are given in  T y p i c a l Shape  Action  Flatfish  Lures and  their  millimeters.  De s c r i p t i o n  F r o n t end  p l a n e s d o w n w a r d i n the  w a t e r and  moves rapidly f r o m  side  to s i d e i n a d i r e c t i o n p e r p e n d i c u l a r to the l i n e .  T h i s g i v e s the r e a r  of the l u r e a s i m i l a r m o t i o n due  end to  the point of a t t a c h m e n t of l i n e . R e q u i r e s f a i r l y s l o w (=^2 of  ft/s) speed  tow.  Spinner  T h e b o d y of the l u r e (B) f o l l o w s i n the p a t h of the l i n e w i t h a m i n i m u m of m o t i o n . A l l the a c t i o n c o m e s f r o m the s p i n n e r (S) w h i c h i s a t t a c h e d to the w i r e g o i n g t h r o u g h the c e n t e r of the b o d y of the l u r e . It s p i n s a r o u n d the b o d y and d e s c r i b e s a c o n e w h o s e a p e x i s at the point of a t t a c h m e n t of the s p i n n e r . Requires a f a i r l y fast tow (>1.7 f t / s ) to m a k e s p i n n e r w o r k .  Spoon  T h e f r o n t end of the l u r e f o l l o w s the l i n e w i t h l i t t l e a c t i o n w h i l e the r e a r of the l u r e m o v e s s i d e w a y s b a c k a n d f o r t h , o r up and d o w n quite r a p i d l y R e q u i r e s a m e d i u m speed.  13 34  S h a p e i s v a r i a b l e but,  Dead  regardless  of  shape t h e r e i s a v e r y m i n i m u m of action,  T  33  the l u r e f o l l o w i n g  almost  d i r e c t l y i n the p a t h of the l i n e . d e a d a c t i o n l u r e that I u s e d  The  was  o b t a i n e d by c l i p p i n g the s p i n n e r off of a s p i n n e r l u r e .  Propeller  action  Two  or t h r e e l u r e s u s e d the f o r c e  of  the w a t e r s t r i k i n g ( u s u a l l y ) t h r e e f o i l s to c a u s e t h e m to r o t a t e a r o u n d a c e n t r a l a x i s c o i n c i d e n t w i t h the l i n e .  These  l u r e s t r o l l e d at a w i d e r a n g e of s p e e d s , and,  to the h u m a n eye,  l i k e n e s s to the s p i n n e r  had  a great  action.  7 B.  General Methods  T h r e e t r o l l i n g e x p e r i m e n t s w e r e p e r f o r m e d at L o o n L a k e , C o l u m b i a between J u l y . 10 and September 1 ,  1972.  British  L o o n L a k e i s situated in a  n a r r o w v a l l e y at an e l e v a t i o n of 2 8 2 0 f e e t a p p r o x i m a t e l y 1 2 m i l e s e a s t of Clinton,  It i s a b o u t 9 . 5 m i l e s long,  British Columbia.  o n e - q u a r t e r and one-half mile, i n width. was  and v a r i e s between  The mean depth i s 9 0 feet.  Trolling  done f r o m two v e s s e l s : a n 1 8 f o o t m o t o r l a u n c h o w n e d b y the B r i t i s h  C o l u m b i a F i s h and W i l d l i f e Branch, m o t o r boat.  a n d a s m a l l ( 1 0 foot) a l u m i n u m o u t b o a r d  W h e n b o t h b o a t s w e r e used,  t h e s p e e d of the s m a l l e r b o a t  was  s y n c h r o n i z e d to that of the l a r g e r b y r u n n i n g a l o n g s i d e a n d n o t i n g t h r o t t l e settings. course,  A s the s m a l l b o a t n o r m a l l y f o l l o w e d t h e m o t o r l a u n c h a r o u n d a s e t a p p r o x i m a t e s y n c h r o n y c o u l d be m a i n t a i n e d q u i t e e a s i l y by k e e p i n g t h e  d i s t a n c e b e t w e e n the b o a t s r o u g h l y c o n s t a n t .  The  s p e e d c h o s e n f o r t r o l l i n g was  d e t e r m i n e d b y t a k i n g into c o n s i d e r a -  t i o n the a c t i o n s of e a c h t y p e of l u r e a s d e s c r i b e d i n T a b l e I.  Picking a speed  that w o u l d g i v e t h e p r o p e r t r o l l i n g c h a r a c t e r i s t i c s f o r e a c h l u r e w a s c r i t i c a l b e c a u s e t h e r e was a m o n g the l u r e s .  n o t a w i d e o v e r l a p i n the a c c e p t a b l e s p e e d r a n g e s  S p e e d was  b o a t a n d t i m i n g how  moderately  the  m e a s u r e d b y d r o p p i n g a w o o d e n b l o c k out of  l o n g i t t o o k to f a l l b e h i n d the b o a t 3 2 feet,  p i e c e of s t r i n g a t t a c h e d to the b l o c k .  One  the l e n g t h of a  speed c h e c k r e a d i n g was  the a v e r a g e  footnote 1 c o n t i n u e d The the  s p e e d at w h i c h a l u r e f i r s t e x h i b i t s d e f i n i t e a c t i o n i s s a i d to be  " m i n i m u m t r o l l i n g s p e e d " f o r that l u r e .  The fastest speed b e f o r e it  s t a r t s t h e e r r a t i c m o v e m e n t i s c a l l e d the " m a x i m u m t r o l l i n g s p e e d " ; a n d b e t w e e n t h e s e two i s the r a n g e f o r the " i n t e n d e d " or " p r o p e r " a c t i o n of t h e lure. T o the e x t e n t that the p r o p e r a c t i o n of the l u r e i s a s s u m e d to be that action existing before cavitation, jective determination, Nevertheless, d i s t i n c t i o n was  it was  i t c o u l d be c h a r g e d t h a t t h i s i s a r a t h e r  sub-  and not b a s e d o n any k n o w n i n t e n t i o n of t h e m a n u f a c t u r e r . o n l y at s p e e d s b e l o w t h i s c r i t i c a l s p e e d that a c l e a r  e v i d e n t to the h u m a n eye b e t w e e n the v a r i o u s a c t i o n s e x h i b i t e d  b y the d i f f e r e n t l u r e s .  8 of t h r e e m e a s u r e m e n t s .  T h e p r e c i s i o n of t h i s m e t h o d w a s  r e a d i n g s s e l d o m d i f f e r e d by m o r e than t h r e e  As  s u c h t h a t the t h r e e  seconds.  t h e m o t o r l a u n c h w o u l d not go s l o w e n o u g h f o r t r o l l i n g at m i n i m u m  throttle, l a r g e plastic drogues w e r e dragged.  W i t h one d r o g u e a t t a c h e d f r o m  t h e b o w a n d one f r o m the s t e r n , the s p e e d a t t a i n e d w a s  1.75 f t / s _+ 0.25 f t / s .  T h i s s p e e d w a s w i t h i n the r a n g e of t r o l l i n g s p e e d f o r a l l f o u r a c t i o n s t e s t e d , a n d w a s the s p e e d u s e d f o r e x p e r i m e n t s I a n d II. d r o g u e w a s d r a g g e d f r o m the bow, 1.5 f t / s +0.25 f t / s.  I n e x p e r i m e r t III a t h i r d  a n d t h i s f u r t h e r r e d u c e d the s p e e d to  T h i s speed was  m o r e t o t h e c e n t e r o f the r a n g e f o r  f l a t f i s h a c t i o n and w a s the b a r e m i n i m u m s p e e d n e c e s s a r y f o r p r o p e r a c t i o n of the d o d g e r 2.  I n e x p e r i m e n t I, i n w h i c h o n l y the m o t o r l a u n c h w a s u s e d , f o u r r o d h o l d e r s w e r e a t t a c h e d at the s t e r n of the b o a t to h o l d the t i p s of the r o d s a b o u t f o u r f e e t a p a r t i n a l i n e p e r p e n d i c u l a r to the p a t h of t r a v e l . assigned a position number  E a c h r o d was  (1, 2, 3, 4) s t a r t i n g w i t h t h e f a r r i g h t - h a n d r o d a n d  ending w i t h the f a r l e f t - h a n d rod, and these n u m b e r s w e r e m a i n t a i n e d throughout t h e e x p e r i m e n t . at r a n d o m .  Two  The four l u r e s used in a given fishing period were a s s i g n e d  men  i n the b o a t t o o k t u r n s e i t h e r d r i v i n g o r a t t e n d i n g the l i n e s .  In e x p e r i m e n t II a n d III two b o a t s w e r e u s e d r a t h e r t h a n one. a s s i s t a n t f i s h e d f r o m the s m a l l o u t b o a r d b o a t w i t h two l i n e s , l i n e s f r o m the launch.  An  a n d I f i s h e d two  P o s i t i o n s 3 a n d 4 w e r e a s s i g n e d to the o u t b o a r d boat,  a n d the l u r e s w e r e a g a i n a s s i g n e d at r a n d o m .  The fishing line and leader were 6 lb nylon monofilament. of l i n e t e r m i n a t e d i n a b r a s s s w i v e l c l i p , f o u r f e e t of l e a d e r ,  a n d the l u r e .  Ninety feet  attached to w h i c h was a b r a s s swivel,  T h e s i n k e r w e i g h t w a s a t t a c h e d to the l i n e  j u s t b e s i d e the s w i v e l c l i p on the r o d - s i d e .  D e s c r i b e d i n T r o l l i n g E x p e r i m e n t III m e t h o d s .  S e e a l s o F i g u r e 1.  9  E a c h h o u r of f i s h i n g w a s d i v i d e d i n t o p e r i o d s of 20 o r 30 m i n u t e s , d e p e n d i n g on the e x p e r i m e n t , w i t h a l i n e c h e c k ( r e e l i n g i n t h e l i n e s a n d checking for fouled lures,  etc.) at the e n d of e a c h p e r i o d .  A new p e r i o d  s t a r t e d w h e n the l a s t c h e c k e d l i n e w a s b a c k i n f i s h i n g p o s i t i o n . four l i n e s n o r m a l l y took 8 - 1 0 out  minutes,  T o check the  so t h a t i n e a c h p e r i o d a l u r e w a s  of i t s f i s h i n g p o s i t i o n f o r 2 - 2 . 5 m i n u t e s .  If a f i s h was caught v e r y c l o s e  to the t i m e of the n e x t l i n e c h e c k ( w i t h i n a b o u t 5 m i n u t e s of i t ) , the l i n e on w h i c h t h e f i s h w a s c a u g h t w a s n o t c h e c k e d f o r that p e r i o d .  T o r e e l i n the line,  r e m o v e the f i s h ,  a n d r e t u r n the l u r e to i t s f i s h i n g p o s i t i o n t o o k a b o u t 3.5  m i n u t e s at l e a s t ,  a n d up to 5 m i n u t e s .  Whenever a p r o b l e m o c c u r r e d  such  t h a t one l i n e m i s s e d o u t o n a s i g n i f i c a n t a m o u n t of f i s h i n g (due to b a d f o u l i n g of the l i n e ,  or breakage,  or f o r some other reason),  c o m p e n s a t e f o r t h i s by f i s h i n g e x t r a t i m e .  a n attempt was m a d e to  U s u a l l y this was added on to the  e n d o f a f i s h i n g p e r i o d , b u t o n c e o r t w i c e d u r i n g the t h r e e t r o l l i n g  experiments  it h a d to b e done t h e n e x t d a y .  In e x p e r i m e n t s I a n d II the l u r e s w e r e p a i n t e d r e d , y e l l o w , g r e e n a n d 3 blue.  T h e c o m p l e t e l u r e was painted,  p r e v i o u s l y painted parts.  covering both metallic parts and  N o r m a l l y a l u r e w a s g i v e n t w o c o a t s of p a i n t a n d  l e f t 48 h o u r s t o d r y , b u t a s p r e l i m i n a r y t r i a l s s h o w e d no d e t r i m e n t a l e f f e c t s due to f r e s h paint, l u r e s w e r e u s e d that h a d a s h o r t e r c u r i n g t i m e .  This  h a p p e n e d o c c a s i o n a l l y w h e n t h e r e w a s a h i g h l o s s of a p a r t i c u l a r c o l o r of l u r e . T h e f i s h i n g p e r i o d f o r a l l t h r e e e x p e r i m e n t s w a s of t h r e e h o u r s d u r a t i o n o c c u r r i n g b e t w e e n 6:00 a n d 10:00 a.m. i n t h e m o r n i n g , 10:00  a n d b e t w e e n 6:00 a n d  p.m. i n the e v e n i n g ( a l l t i m e s P a c i f i c D a y l i g h t S a v i n g ) .  e a c h f i s h caught was m e a s u r e d ,  and its sex was d e t e r m i n e d .  T h e l e n g t h of F i s h caught and  f i s h h o o k e d b u t n o t l a n d e d w e r e c o u n t e d i n the e v a l u a t i o n of a l u r e . as a v a l i d strike,  T o count  t h e f i s h e i t h e r h a d to be s e e n o n the l i n e o r h a d to m a k e i t s  presence indisputably obvious.  A  s i n g l e j e r k o n the l i n e w a s u s u a l l y d i s r e g a r d e d  due to t h e p o s s i b i l i t y of i t b e i n g a r e l e a s e d  snag.  T e s t o r s h o b b y e n a m e l paint, n u m b e r s : 3 r e d , 14 y e l l o w , 24 g r e e n , a n d 8 b l u e . 1  10 C.  T r o l l i n g E x p e r i m e n t I.  1.  Methods  F o u r a c t i o n s a n d f o u r c o l o r s of l u r e w e r e t r o l l e d b e h i n d a n 18 f t m o t o r l a u n c h at L o o n L a k e ,  B r i t i s h C o l u m b i a a t two d i f f e r e n t t i m e s of d a y t h r o u g h -  out the p e r i o d J u l y 10 to J u l y 17, 1972. spinner,  spoon,  green.and blue. was  a n d d e a d ( s e e T a b l e I);  T h e four  actions were flatfish,  a n d the f o u r c o l o r s w e r e r e d , y e l l o w ,  A No. 10 n i c k e l t r e b l e h o o k (point to p o i n t d i s t a n c e of 11  mm)  s u b s t i t u t e d f o r the h o o k s that c a m e w i t h t h e l u r e s ( t h e s e w e r e u s e d f o r a l l  t h r e e e x p e r i m e n t s ) , a n d a 5.5 g r a m r u b b e r c o r s i n k e r w a s a t t a c h e d to t h e l i n e .  A f i s h i n g r o u t e w a s p l a n n e d that w o u l d t a k e t h r e e h o u r s a n d p a r a l l e l t h e s h o r e l i n e a r o u n d the s o u t h w e s t e n d of the l a k e a p p r o x i m a t e l y 100-150 f e e t o f f shore. feet.  F r o m a s e r i e s of s o u n d i n g s a l o n g the r o u t e , the a v e r a g e d e p t h w a s 55 A n e f f o r t w a s m a d e t o k e e p a s c l o s e a s p o s s i b l e to t h e p l a n n e d r o u t e .  T h e unit of t i m e f o r f i s h i n g w a s 20 m i n u t e s , end of e a c h p e r i o d .  Morning  w i t h l i n e c h e c k s at t h e  and evening runs were treated as separate  e x p e r i m e n t s f o r t h e p u r p o s e of a s s i g n i n g l u r e s -- 16 c o m b i n a t i o n s of a c t i o n s with c o l o r s - - t o each r o d .  B e f o r e the e x p e r i m e n t started,  these combinations was r a n d o m l y runs,  t h e o r d e r of f i s h i n g  d e t e r m i n e d f o r b o t h the m o r n i n g  and evening  a n d a f t e r the f i r s t r e p l i c a t e w a s c o m p l e t e d t h e o r d e r of f i s h i n g w a s  s i m i l a r l y d e t e r m i n e d f o r the s e c o n d r e p l i c a t e .  T h e n u m b e r of s t r i k e s a n d l a n d i n g s f o r e a c h l u r e w a s r e c o r d e d f o r each fishing period,  a n d t h i s t o t a l w a s u s e d as a d a t u m p o i n t .  Data were  a n a l y z e d i n a 3-way a n a l y s i s of v a r i a n c e wither, the c h a n c e of m a k i n g a T y p e I error,  =.0 5.  2. R e s u l t s  I n t r o l l i n g e x p e r i m e n t I o v e r h a l f of the f i s h w e r e c a u g h t w i t h the f l a t f i s h l u r e ; o n l y t w o w e r e c a u g h t w i t h the d e a d l l u r e (see T a b l e II).  T h e spoon  TABLE  II. N u m b e r s of f i s h c a u g h t o n l u r e s f r o m t r o l l i n g e x p e r i m e n t I, L o o n B.C.,  J u l y 10 - 17, 1972.  Lake,  A N O V A t a b l e f r o m the a n a l y s i s of t h i s d a t a .  E a c h g r o u p of n u m b e r s r e a d i n g f r o m top to b o t t o m r e p r e s e n t s t h e numb e r of f i s h caught i n the f i r s t a n d s e c o n d r e p l i c a t e s , a n d the t o t a l f o r both r e p l i c a t e s .  Color Action  Red  Total fish  of L u r e  Yellow  caught f o r Green  each action  Blue  Dead  0  1 2  0  ..Morning  1_  1 2  Fishing  2  3  1  3  1 0  2 0  0 0  0 3  1  2  0  3  3 4  2 3  1 0  7  1 1 2  5  1  10  8  7  7  32  0 0  0 0  0 0  0 0  0  0  0  0  0  3  0  1  1  0 3  0  2  0  3  1 2  0  2 0  1 2  0  0 0  2  3  2  2  3  2  2  Spoon  2  9  Period Spinner  Flatfish  Dead  Spoon Evening Fishing  6  15  8  Period Spinner  Flatfish  5  2  1_  2  7  4  3  4  10  6  9  8  20  14  16  15  7  18  33  T o t a l fish caught for  each color  ANOVA  TABLE  Source Color Action  df 3 3  .  65  MS  Prob.  0.43 10.31 0.02  .50< p<.75 p«.001 p ».7 5  T i me  1  Color x Action  1.56  .10<p<.25  Color x Time  9 3  0.18  p>.75  Action x Time  3  0.31  p>.75  1.09 0.92  .10<p<.25  Color x Action x Time Error  9 32  Total  63  12 was  s l i g h t l y m o r e s u c c e s s f u l t h a n the s p i n n e r , t h e f o r m e r h a v i n g a b o u t o n e -  h a l f the e f f i c i e n c y of t h e f l a t f i s h . c a n t (p •< .001).  T h i s action effect was shown to be s i g n i f i -  N o d i f f e r e n c e w a s f o u n d b e t w e e n the m o r n i n g a n d e v e n i n g  fishing periods, approximately  50 p e r c e n t of the f i s h b e i n g c a u g h t d u r i n g e a c h  period.  Red  l u r e s c a u g h t the m o s t f i s h ,  but f a i l e d to s h o w a s t a t i s t i c a l l y  s i g n i f i c a n t s u p e r i o r i t y o v e r the o t h e r c o l o r s . up b e t w e e n the y e l l o w , runs.  green and blue lures,  V e r y little difference showed e i t h e r i n the m o r n i n g o r e v e n i n g  T h e d a t a s u g g e s t the p o s s i b i l i t y of a n i n t e r a c t i o n b e t w e e n the c o l o r a n d  a c t i o n of the l u r e , fishing,  although  b o t h i n the a b s o l u t e s e n s e a n d r e l a t i v e to the t i m e  of d a y of  the e f f e c t w a s n o t s i g n i f i c a n t .  N o s e l e c t i o n o c c u r r e d f o r s i z e o r s e x of f i s h e i t h e r o n t h e b a s i s of c o l o r o r a c t i o n of t h e l u r e . 27 cm,  T h e a v e r a g e l e n g t h ( f o r k length) of f i s h w a s  w i t h a r a n g e of f r o m 13 c m t o 34 c m ( s t a n d a r d d e v i a t i o n = 3.75).  The  o v e r a l l s e x r a t i o w a s 1:1, w i t h no s i g n i f i c a n t d e v i a t i o n s o c c u r r i n g f o r a n y of the c l a s s e s of l u r e f o r w h i c h a s e x r a t i o c o u l d b e d e t e r m i n e d . s e x e d f o r e i t h e r the d e a d l u r e s o r t h e y e l l o w l u r e s .  No f i s h w e r e  A l s o , t h e r e w e r e no  s e x e s r e c o r d e d f o r the r e d s p i n n e r , b e c a u s e t h e s o l e f i s h h o o k e d o n t h a t l u r e was  D.  not landed.  T r o l l i n g E x p e r i m e n t II  1.  Methods  In. a f u r t h e r a t t e m p t to s h o w a s i g n i f i c a n t c o l o r p r e f e r e n c e ,  the b e s t  a c t i o n f r o m e x p e r i m e n t I (flatfish) was chosen, a n d four l u r e s w e r e painted red,  yellow,  green and blue.  E a c h l u r e w a s t h e n f i s h e d t h r e e t i m e s i n the  m o r n i n g a n d t h r e e t i m e s i n the e v e n i n g b e t w e e n A u g u s t 5 a n d A u g u s t 9, 1972. A  f i s h i n g r o u t e w a s m a p p e d out at the n o r t h e a s t e n d of the l a k e s u c h t h a t one  c i r c u i t c o u l d be m a d e e a c h h o u r . boats made approximately  Therefore,  three circuits.  i n o n e p e r i o d of f i s h i n g t h e  The route entailed fishing a  13 U - s h a p e d p a t t e r n along the s h o r e l i n e and then c r o s s i n g the lake, the a r m s o f t h e U.  connecting  T h e s h o r e l i n e f i s h i n g m a d e up a p p r o x i m a t e l y 7 5 p e r cent  of the f i s h i n g t i m e i n a n a v e r a g e d e p t h o f w a t e r of 21 f e e t (6.4 m e t e r s ) ,  while  the o p e n - w a t e r f i s h i n g t o o k the r e m a i n i n g 25 p e r c e n t of t h e t i m e a n d w a s i n v a r y i n g d e p t h s n o t e x c e e d i n g 50 f e e t (15.2 m e t e r s ) .  A s t h e r e h a d b e e n l i t t l e f o u l i n g of l i n e s i n t r o l l i n g e x p e r i m e n t I, t h e u n i t of f i s h i n g t i m e w a s i n c r e a s e d t o 30 m i n u t e s .  T h e w e i g h t of the s i n k e r  w a s d e c r e a s e d f r o m 5.5 g r a m s t o 3.0 g r a m s a s r e p e a t e d d e p t h  sounder  r e a d i n g s i n d i c a t e d the f i s h w e r e c l o s e to the s u r f a c e .  L u r e s w e r e a s s i g n e d at r a n d o m to t h e f o u r r o d s i n a s i m i l a r to that f o r e x p e r i m e n t I. l u r e was r e c o r d e d ,  manner  A g a i n , the n u m b e r s of s t r i k e s a n d l a n d i n g s f o r e a c h  a n d t h e d a t a w e r e a n a l y z e d i n a t w o - w a y a n a l y s i s of  v a r i a n c e w i t h a = .0 5.  2. R e s u l t s  The (see  m o r n i n g f i s h i n g p e r i o d gave a g r e a t e r y i e l d than the evening p e r i o d  T a b l e III).  T h e r e w a s no e v i d e n c e f o r t h e e x i s t e n c e of a c o l o r p r e f e r e n c e .  A l t h o u g h no c o l o r c a u g h t m o r e t h a n r e d ,  y e l l o w c a u g h t a s many, a n d g r e e n a n d  b l u e w e r e o n l y t h r e e f i s h b e h i n d the l e a d e r s .  T h e r e was no i n t e r a c t i o n  b e t w e e n the e f f e c t s of c o l o r a n d t i m e of f i s h i n g .  Lengths  of f i s h c a u g h t w e r e d i s t r i b u t e d o v e r the f o u r c o l o r s s u c h that  t h e r e w a s no s e l e c t i o n by any one c o l o r .  A s s o m e of t h e f i s h c a u g h t w e r e '  m e a s u r e d as to l e n g t h a n d t h r o w n b a c k i m m e d i a t e l y ,  i t i s n o t p o s s i b l e to  r e p o r t on the s e x of e v e r y f i s h caught; b u t of t h o s e f i s h c a u g h t a n d l a t e r 22 out o f 32 w e r e f e m a l e s .  T h e r e w e r e no s u b s t a n t i a l d e v i a t i o n s f r o m  r a t i o a m o n g the f o u r c o l o r s of l u r e t e s t e d .  sexed, this  TABLE  III.  Number s of fish caughton lures f r o m trolling experiment II, Loon Lake, B.C., August 5 to 9, 1972. A N O V A table f r o m the analysis of this data. Each group of three numbers reading f r o m top to bottom represents the number of fish caught in the first, second, and third replicates. Colors of Lures  Fishing Period  Red  Yellow 3 5 2  Morning  Evening  Green  1 1 4  2 4 0  16  16  Blue  Totals  4 5 3  41  o5 4  17 13  58  13  ANOVA T A B L E Source  df  MS  Prob.  Color Time Color x Time Error Total  3 1 3 16 23  0.50 24.00 1.89 2.54  p > .75 .005 < p < .01 .5 < p < .75  15 E.  T r o l l i n g E x p e r i m e n t III  1.  Methods  T h e b e s t c o l o r f r o m t r o l l i n g e x p e r i m e n t II (red) w a s  c h o s e n and  com-  b i n e d w i t h white i n v a r i o u s p a t t e r n s : s o l i d r e d , c h e c k e r e d r e d a n d white, s t r i p e d r e d a n d white, was  fished f r o m August  -- a 5 c m 1).  a n d s o l i d w h i t e ( F i g u r e 1). 25 to S e p t e m b e r  long chrome-plated  The dodger spun around  1,  1972,  E a c h of t h e s e p a t t e r n s w i t h and without a  "dodger"  s p i n n e r f r o m a D a v i s g a n g t r o l l l u r e (see F i g u r e a s i x i n c h l e n g t h of w i r e a t t a c h e d at e i t h e r e n d to  the l i n e and l e a d e r w i t h b r a s s s w i v e l s n a p s .  A t h i r d f i s h i n g route was  m a p p e d out a p p r o x i m a t e l y o n e - h a l f w a y  down  the l a k e c o n s i s t i n g of a p p r o x i m a t e l y 55 p e r c e n t s h o r e l i n e f i s h i n g and the r e s t open water fishing. (16.25 m e t e r s ) ,  The  a v e r a g e d e p t h f o r the s h o r e l i n e s e c t i o n w a s  w h i l e open water depths e x c e e d e d  50 m e t e r s .  The  53 f e e t  route  was  p l a n n e d so that a p p r o x i m a t e l y t h r e e c i r c u i t s c o u l d be m a d e i n the t h r e e - h o u r fishing period.  As  the l m e s b e c a m e f o u l e d f a i r l y f r e q u e n t l y i n t r o l l i n g e x p e r i m e n t II  ( a l t h o u g h t h i s was f i s h i n g t i m e was sounder  m o s t l y c a u s e d b y f i s h i n g i n s h a l l o w w a t e r s ) , the u n i t of d e c r e a s e d f r o m 30 m i n u t e s to 20 m i n u t e s .  From  echo-  r e a d i n g s i t a p p e a r e d that f i s h w e r e at g r e a t e r d e p t h s i n t h i s p a r t of  the l a k e ,  and t h e r e f o r e a 23 g r a m s i n k e r w a s  u s e d i n p l a c e of the 3.0  gram  s i n k e r of e x p e r i m e n t II.  Two  assistants helped with this e x p e r i m e n t  w e r e done by one of the a s s i s t a n t s a n d m y s e l f . the t h i r d r e p l i c a t e c o u l d not be c o m p l e t e d did  h a l f of i t .  The  -- the f i r s t two  replicates  B e c a u s e of a s h o r t a g e of t i m e  by the s e c o n d a s s i s t a n t a l o n e ,  so I  data f r o m the t h i r d r e p l i c a t e w e r e p o o l e d and a n a l y z e d as  i f the w h o l e r e p l i c a t e h a d b e e n done by a s i n g l e p e r s o n .  E a c h l u r e c o m b i n a t i o n was of  a s s i g n e d at r a n d o m to a l i n e a n d the n u m b e r  s t r i k e s and l a n d i n g s w e r e r e c o r d e d .  The  data were analyzed in a four-way  F i g u r e 1.  C h e c k e r e d and s t r i p e d flatfish, t r o l l i n g e x p e r i m e n t III, to S e p t e m b e r  1,  1972.  and d o d g e r f r o m  L o o n Lake,  B.C.,  August  25  17  analysis  of v a r i a n c e w i t h m a i n e f f e c t s b e i n g c o l o r p a t t e r n ,  of a d o d g e r , t i m e of day,  and  to d i f f e r e n t f i s h e r m e n ) .  C h a n c e of m a k i n g a T y p e I e r r o r  2.  investigator  p r e s e n c e or  e f f e c t (the i n d i v i d u a l d i f f e r e n c e s was  s e t at a  w i t h w h i t e or the a l l - w h i t e l u r e , T a b l e IV).  n o t u s i n g one,  The and  i t s s u p e r i o r i t y was  not  t h e r e was  no  s i g n i f i c a n t e f f e c t due  p e r s o n s d o i n g the f i s h i n g (the i n v e s t i g a t o r 40  fisherman,  c o m b i n a t i o n of  5.  by a n o t h e r ,  and  28  effect):  by the t h i r d .  46  T h e r e was l u r e and  one  when  to the t i m e of day.  The  the e f f e c t of d i f f e r e n t f i s h w e r e c a u g h t by  W i t h t h e s e r e s u l t s , the  the i n v e s t i g a t o r  pro0.25.  and  no  effect.  s e l e c t i o n f o r l e n g t h of f i s h on the b a s i s  of c o l o r  pattern  However, l u r e s t r o l l e d with dodgers caught significantly l a r g e r  t h a n t h o s e w i t h o u t d o d g e r s (see difference  i n m e a n s of 2.3  The  one  s i g n i f i c a n t i n t e r a c t i o n e f f e c t b e t w e e n the c o l o r p a t t e r n of the  T h e r e was of l u r e .  red  statistically significant  b a b i l i t y of r e j e c t i n g the n u l l h y p o t h e s i s i n c o r r e c t l y i s b e t w e e n 0.1  5.  = .0  s a m e n u m b e r of f i s h w e r e c a u g h t u s i n g a d o d g e r as  f a c t o r that c a m e c l o s e s t to s t a t i s t i c a l s i g n i f i c a n c e was  a-.0  due  Results  A l t h o u g h the a l l - r e d l u r e c a u g h t m o r e f i s h t h a n any  (see  absence  o v e r a l l sex  important deviations  T a b l e V).  The  fish  length d i s t r i b u t i o n s show a  w h i c h i s s h o w n to be  s i g n i f i c a n t by the t - t e s t at  r a t i o of f i s h c a u g h t was  3$:  If/,  and  there were  f r o m t h i s r a t i o a m o n g the v a r i o u s l u r e s ,  no  e i t h e r w i t h or  without d o d g e r s .  F.  Trolling Experiments —  The  Discussion  d a t a f r o m e x p e r i m e n t I s h o w a c l e a r e f f e c t o f a c t i o n of l u r e on  n u m b e r of f i s h caught, the l u r e s d i f f e r i n g i n b o t h q u a n t i t y and The  e x t e n t of v e r t i c a l and  s m o o t h n e s s of i t s a c t i o n , the r a t i o of r o t a t o r y  horizontal  q u a l i t y of a c t i o n .  m o t i o n of the l u r e , the j e r k i n e s s  or  the d e g r e e of r e g u l a r i t y o r r a n d o m n e s s i n the  m o t i o n to l i n e a r m o t i o n :  a l l these are  w h i c h h e l p to d e s c r i b e the q u a l i t a t i v e a c t i o n of the l u r e s .  the  action,  characteristics In  contradistinction  18  TABLE  IV.  N u m b e r s of f i s h caught on l u r e s f r o m t r o l l i n g e x p e r i m e n t III, L o o n L a k e , B . C . , A u g u s t 2 5 to S e p t e m b e r 1 , 1 9 7 2 . A N O V A table f r o m the a n a l y s i s of this data.  MORNING FISHING PERIOD ; No D o d g e r  Investigator A B C  With D o d g e r  A B C  C o l o r P a t t e r n of L u r e A l l - r e d All-white Striped Checkered  F i s h caught per investigator  7  5  6  2  2  4  1  1  0  2  0  2  _4  9  11  7  5  32  20  8  4  0  1  3  8  0  4  4  0  3  3  3  8  4  13  7  7  8  7  29  16  18  15  12  61  A B  3  0  3  2  8  3  2  0  2  7  C  4  1  3  2  10  10  3  6  6  25 10  E V E N I N G FISHING PERIOD No D o d g e r  With Dodger  A B  4  1  4  1  1  3  1  0  C  4  0  3  6  9  4  8  7  28  =  =  =  =  =»  19  ANOVA  TABLE  7  Source Color pattern Dodger Time Inve stigator C o l o r pattern x Dodger C o l o r pattern x T i m e C o l o r p a t t e r n x Investigator Dodger x T i m e Dodger x I n v e s t i g a t o r T i m e x Investigator Error  14  5  11  13  df 3  .  53  MS  Prob.  1.86  .5 < p < .75 p » .75 .25 < p < .50 .10 < p< . 2 5 .5< p <.75 . 2 5 < p < .50 . 0 2 5 < p< . 0 5 .5 < p < .75 . 0 5 < p < .IX) .10 < p < . 2 5  1  0.00  1  1.33  2  5.25  3  1.00  3  3.22  6  6.53  1  .75  2  7.75  2  4.08  23  2.42  TABLE  V.  M e a n l e n g t h s (cm) o f f i s h c a u g h t on l u r e s f r o m t r o l l i n g e x p e r i m e n t III, L o o n L a k e , B.C., on the b a s i s of c o l o r p a t t e r n of l u r e a n d o n the b a s i s of w h e t h e r o r not a dodger was used. A u g u s t 25 to S e p t e m b e r 1, 1972. Y = m e a n l e n g t h of f i s h caught; n = s a m p l e s i z e ; s = standard deviation.  C o l o r P a t t e r n of L u r e A l l red  n s  All-white  Striped  25.94  23.16  26.48  25.3  18  14  20  15  4.01  5.7  No  Dodger  3.33  5.14  With Dodger  Y  24.20  26.51  n  33  34  s  Checkered  5.43  3.22  20 to these c o n c e r n s i s the absolute quantity of m o t i o n w h i c h a l u r e e x h i b i t s . A l t h o u g h i t may be v e r y difficult to d e v i s e a method for a s s e s s i n g the r e l a t i v e quantities of m o t i o n over the different types of actions, d i s t i n c t i o n s a r e e a s i l y made when the d i f f e r e n c e s a r e l a r g e . The data f r o m e x p e r i m e n t I c o u l d c o n c e i v a b l y be i n t e r p r e t e d w h o l l y on the degree of a c t i o n w h i c h each l u r e e x h i b i t s .  W h i l e the spinner might be s a i d  to exhibit a g r e a t e r amount of a c t i o n than the spoon (due to the speed of the r e v o l v i n g m e m b e r ) , the o v e r a l l path of the l u r e i s i n a s t r a i g h t l i n e without zig-zags or wobbles.  A l s o , because the spinning m e m b e r i s a l w a y s at a  constant angle f r o m the body of the l u r e when a constant speed of t r o l l i s maintained, and because of its h i g h r a t e of r e v o l u t i o n , it tends to l o s e its appearance of m o t i o n and l o o k s m o r e l i k e a s e m i - t r a n s p a r e n t cone s u r r o u n d i n g the body of the l u r e .  Therefore,  at l e a s t to the human eyes, the s p i n n e r l u r e  a p p e a r s to e x h i b i t r e l a t i v e l y l e s s a c t i o n than the spoon.  A s s u m i n g this  appearance to be the same for fish, the f i s h i n g s u c c e s s of the l u r e s i s c o r r e l a t e d w i t h the quantity of a c t i o n .  No attempt has been made to d e t e r m i n e  w h i c h of the q u a l i t a t i v e or quantitative c h a r a c t e r i s t i c s i s the m o r e c r i t i c a l . A n a l y s e s of v a r i a n c e ( A N O V A s ) w e r e done on the lengths of f i s h caught i n t r o l l i n g e x p e r i m e n t I on the b a s i s of both a c t i o n and c o l o r of l u r e , and, stated i n the r e s u l t s section, no d i f f e r e n t i a l s e l e c t i o n showed up.  as  A s a further  check, the n o r m a l i t y of the d i s t r i b u t i o n of lengths was e x a m i n e d using the p r o b a b i l i t y paper method (Sokal and Rohlf, p. 122-123). tails,  E x c e p t for the two  each of w h i c h r e p r e s e n t single i n d i v i d u a l s , the l i n e a r i t y of the g r a p h  i s what one would expect f r o m r a n d o m s a m p l i n g out of a n o r m a l l y d i s t r i b u t e d population, i.e., there was no d i f f e r e n t i a l s e l e c t i o n among the l u r e s . In the g e n e r a l methods for the t r o l l i n g e x p e r i m e n t s it was stated that i t took t h r e e to five minutes to c a t c h a f i s h and r e t u r n the l u r e to i t s f i s h i n g position.  It might be objected,  then, that the number of f i s h r e c o r d e d for  each category does not r e f l e c t the true efficiency of e a c h l u r e s i n c e the t i m e of fishing was shortened by the n u m b e r of f i s h caught t i m e s the amount of t i m e it took to c a t c h a f i s h .  The d a t u m points used i n the a n a l y s i s of v a r i a n c e a r e  21 b i a s e d in favor of the poorer l u r e s . have suggested,  T h i s bias i s probably not as strong as I  since line checks were not p e r f o r m e d on those l i n e s that had  just r e c e n t l y been out of the water.  N e v e r t h e l e s s , to check against the worst  possible case of biasing, each datum point was r e - c a l c u l a t e d for a shorter fishing p e r i o d -- the total p e r i o d minus five minutes times the number of f i s h c a u g h t — a n d an analysis of v a r i a n c e was significant change was  done on these t r a n s f o r m e d values.  observed for any category of effect.  It was  No  a s s u m e d that  these c o r r e c t i o n s would have a s i m i l a r effect on the data f r o m t r o l l i n g e x p e r i ments II and III, so no further analyses were made. The distribution of f i s h between the morning and evening fishing p e r i o d s of experiment II was highly unlikely on the b a s i s of chance alone (p = .007),  and  so the data probably r e f l e c t a different set of c i r c u m s t a n c e s f r o m that of experiment I.  It is not known what caused this uneven distribution. The c o l o r x investigator interaction effect of experiment III is difficult  to explain except on the b a s i s that an improbable event o c c u r r e d .  A set  procedure was laid out and followed in a l l aspects of fishing by a l l i n v e s t i g a t o r s . N o r m a l l y this type of interaction effect would occur i f one f i s h e r m a n always used a p a r t i c u l a r l u r e when fishing was  good, while another f i s h e r m a n chose  a different one; or if one f i s h e r m a n tended to be m o r e skilful than another in the use of a p a r t i c u l a r lure; but, as the order of lure testing was l a i d out in advance, the f o r m e r p o s s i b i l i t y was r u l e d out, and the e x p e r i m e n t a l design was  s p e c i f i c a l l y chosen to l i m i t the latter.  Under the conditions of the e x p e r i -  ment, the only way this effect could have been manifested was  if, for instance,  one of the f i s h e r m e n had p a r t i c u l a r difficulties with a dodger fouling the line and took an e x c e s s i v e amount of time c o r r e c t i n g this p r o b l e m . only the color x investigator effect was  However,  significant, and the assistants were  d i r e c t e d to r e p o r t any occasions when, for one r e a s o n or another, a given line was not fishing as long as the others (for a time greater than 20 minutes), so that a suitable c o r r e c t i o n could be made.  T h i s o c c u r r e d only two or three  t i m e s during the course of a l l three of the experiments.  22  A l t h o u g h I have not come a c r o s s any study on s e l e c t i o n by d o d g e r s p e r se, L a r k i n (1949) mentions that a l l of the gang t r o l l s used on K o o t e n a y L a k e selected for s m a l l e r f i s h .  T h e r e i s a s i m i l a r i t y between a l u r e p r e c e d e d  by a dodger and the hooked e n d - p i e c e of a gang t r o l l p r e c e d e d by n o n - h o o k e d flashers.  The fact that the s i l v e r dodger used i n this e x p e r i m e n t was a c t u a l l y  a f l a s h e r f r o m a D a v i s gang t r o l l lends further c r e d i b i l i t y to the c o m p a r i s o n . F r o m this point of v i e w m y r e s u l t s d i s a g r e e w i t h those of L a r k i n . the c o m p a r i s o n i s , perhaps,  not as c l o s e as it might be.  First,  However, it i s most  c o m m o n for the p a r t s of a gang t r o l l to be r a t h e r c l o s e l y matched i n s i z e , shape,  and m a t e r i a l .  U s u a l l y the hooked e n d - p i e c e i s made of a shiny m e t a l l i c  m a t e r i a l l i k e the non-hooked f l a s h e r s p r e c e d i n g i t .  In my e x p e r i m e n t the l u r e s  w e r e a l l c o n s i d e r a b l y s m a l l e r than the dodger, had a different shape (except for the spinner), and had a coat of paint, w h i l e the dodgers w e r e of shiny metallic material.  Furthermore,  the coat of paint i t s e l f r e s u l t e d i n a  different type of r e f l e c t e d l i g h t f r o m the dodgers and the l u r e s .  W h i l e gang  t r o l l s m i g h t have up to six m e m b e r s j o i n e d together, my a r r a n g e m e n t had only two.  P e r h a p s these differences are enough to e x p l a i n the d i s a g r e e m e n t  between the two s t u d i e s . It i s i n t e r e s t i n g to note the p r o g r e s s i v e change i n the sex r a t i o s throughout the t r o l l i n g e x p e r i m e n t s .  F r o m an even 50:50 r a t i o i n J u l y i t  changed to 2?:lo" i n the e a r l y part of A u g u s t arid 3$: Id* i n the l a t t e r p a r t .  These  r a t i o s m o s t l i k e l y r e f l e c t changes i n the a v a i l a b i l i t y of the f i s h and do not point to differences i n the s e l e c t i v i t y of the groups of l u r e s used i n each e x p e r i m e n t . To be s p e c i f i c , four c o l o r s of f l a t f i s h l u r e s w e r e used i n both e x p e r i m e n t s I and II; and for each e x p e r i m e n t , the sex r a t i o s of the f l a t f i s h c a t c h m i r r o r e d that of the o v e r a l l c a t c h f r o m that e x p e r i m e n t .  T h e r e f o r e , the noted d i f f e r e n c e s  between e x p e r i m e n t I and e x p e r i m e n t II, at least, i n different groups of l u r e s .  a r e not a r e s u l t of s e l e c t i o n  F u r t h e r m o r e , t h e r e was no d i f f e r e n t i a l s e l e c t i o n  among l u r e s w i t h i n an e x p e r i m e n t , thus g i v i n g further evidence against l u r e s e l e c t i v i t y being an explanation for the sex r a t i o s . One p o s s i b l e factor l e a d i n g to the i n c r e a s i n g p r o p o r t i o n of f e m a l e s i n the c a t c h as the s u m m e r p r o g r e s s e s has been suggested by A . Tautz of the  23 B r i t i s h C o l u m b i a F i s h and W i l d l i f e B r a n c h ( p e r s o n a l c o m m u n i c a t i o n ) .  It  a p p e a r s that some of the age 2+ m a l e s i n the lake w i l l r e a c h a s i z e sufficient for t h e m to spawn just before the t i m e of the spawning run, and they w i l l thus j o i n the older f i s h i n the m i g r a t i o n out of the l a k e . r e a c h this c r i t i c a l s i z e .  The p r e c o c i o u s m a l e s ,  None of the 2+ f e m a l e s in going t h r o u g h the r i g o r s  of spawning and i n l e a v i n g the r i c h feeding a r e a s of the lake, do not g r o w as fast as t h e i r female s i b l i n g s that stayed behind. have enjoyed a l o n g e r g r o w i n g season, f i s h e r y (around 20 c m ) .  L a t e r on, the f e m a l e s ,  which  r e a c h a s i z e sufficient to enter the  T h i s i n c r e m e n t t h r o w s off the r a t i o of the t h r e e - y e a r  old and older f i s h i n favor of m o r e f e m a l e s as the season  progresses.  The f i s h i n g s u c c e s s of the f l a t f i s h i s notable i n that it c o n t r a s t s s t a r k l y w i t h that for L a r k i n ' s w o r k on K a m l o o p s trout in P a u l and Kootenay L a k e s (1949).  In P a u l L a k e , except for the month of M a y , f l a t f i s h had a c o n s i s t e n t l y  l o w e r c a t c h per unit effort than a group of m i s c e l l a n e o u s t r o l l s .  In K o o t e n a y  Lake,  However,  out of twelve c a t e g o r i e s of l u r e , f l a t f i s h r a n k e d p o o r e s t .  there s e e m s to be a m a r k e d difference i n the s u c c e s s of l u r e s on v a r i o u s l a k e s . On P a u l L a k e the f l y was the poorest of t h r e e types of l u r e i n five out of s i x months, w h i l e on Kootenay L a k e i t was the second best of twelve c a t e g o r i e s over the season. L a r k i n also notes a tendency for l u r e s w h i c h have a h i g h c a t c h a b i l i t y to select for s m a l l f i s h .  T h i s holds for both l a k e s ; but for K o o t e n a y L a k e  plugs, f l a t f i s h , and l a r g e spoons are used i n the s p r i n g and f a l l for what i s e s s e n t i a l l y a separate f i s h e r y (i.e., l a r g e f i s h over 1-1/4 l b ) .  F l y fishing,  gang t r o l l s , w o b b l e r s and s p i n n e r s a r e used i n m i d - s u m m e r and a r e h i g h l y s e l e c t i v e of s m a l l e r f i s h , f i r s t group.  thus m a k i n g t h e m not s t r i c t l y c o m p a r a b l e to the  In L o o n L a k e the f l a t f i s h caught the s m a l l e s t f i s h on the  average,  and spoons caught the l a r g e s t ; but the differences w e r e not s i g n i f i c a n t . A l t h o u g h i n none of the t r o l l i n g e x p e r i m e n t s was c o l o r a s i g n i f i c a n t effect,  i n a l l three the s o l i d r e d l u r e caught the most f i s h - - t i e d w i t h y e l l o w  i n e x p e r i m e n t II.  24 P A R T II.  A.  FEEDING EXPERIMENTS  Introduction  It was r e a s o n e d that i f trout s t r u c k at l u r e s because they m i s t o o k t h e m for food, then perhaps m o r e could be l e a r n e d of t h e i r p r e f e r e n c e for different c o l o r s of l u r e s by feeding t h e m s i m u l t a n e o u s l y different c o l o r s of food, o b s e r v i n g t h e i r o r d e r of s e l e c t i o n .  and  If four c o l o r s of food w e r e p r e s e n t e d at a  t i m e , ' t h e f i r s t and second c o l o r s chosen would i n d i c a t e m o s t c l e a r l y a p r e ference,  as a s e l e c t i o n would be made among four or t h r e e a l t e r n a t i v e s ,  respectively.  The t h i r d and f o u r t h c h o i c e s would i n v o l v e fewer a l t e r n a t i v e s ,  and it i s l i k e l y they could be s e l e c t e d on a m o r e r a n d o m b a s i s as the " l e f t overs".  T h e r e f o r e , the m o s t p o w e r f u l a n a l y t i c a l test would be one that  a s s i g n e d v a l u e s to the f i r s t and second c h o i c e s only, and i g n o r e d the t h i r d and fourth c h o i c e s . In the two feeding e x p e r i m e n t s d e s c r i b e d here, t h i s s o r t of t e s t was performed.  In feeding e x p e r i m e n t I food of four d i s c r e t e c o l o r s was p r e s e n t e d  to i n d i v i d u a l r a i n b o w trout i n tanks of v a r i o u s c o l o r s and i n feeding e x p e r i m e n t II food of two c o l o r s as w e l l as food of a single c o l o r was p r e s e n t e d to see i f b i - c o l o r e d food would be p r e f e r r e d ; and, i f so, to see i f t h e r e was a p a r t i c u l a r second c o l o r that elevated the p r e f e r e n c e l e v e l m o r e than o t h e r s .  B.  General Methods  T r o u t eggs dyed r e d , yellow, g r e e n and blue w e r e fed to r a i n b o w trout i n two e x p e r i m e n t s between M a y 22 and A u g u s t 3, 1973.  Feedings were  g e n e r a l l y done e v e r y second day between the h o u r s of 2:00 p . m . and 5:30 p . m . ( P a c i f i c D a y l i g h t Saving T i m e ) i n a l a b o r a t o r y at the U n i v e r s i t y of B r i t i s h Columbia. The f i s h used i n the e x p e r i m e n t w e r e j u v e n i l e r a i n b o w trout f r o m the  25 b r o o d stock of the B r i t i s h C o l u m b i a F i s h and W i l d l i f e B r a n c h h a t c h e r y at Abbotsford,  British Columbia.  When they w e r e brought to the U n i v e r s i t y  (October, 1972), they w e r e m a i n t a i n e d i n i n d o o r tanks on a 1 2 - h r light,  12-hr  d a r k photoperiod until the e x p e r i m e n t s w e r e f i n i s h e d , a n d fed d r i e d f i s h food. A t the t i m e when the e x p e r i m e n t s w e r e r u n the mean s i z e of the f i s h was 18.7 c m , w i t h 68 per cent of t h e i r lengths l y i n g i n the range of 16.7 to 20.6 c m . E x p e r i m e n t s w e r e done i n b i p a r t i t e tanks (see F i g u r e 2) w i t h i n s i d e d i m e n s i o n s of 117 c m length by 61 c m w i d t h by 74.5 c m depth.  The l e n g t h of  the test c h a m b e r was 90 c m and that of the p r e p a r a t i o n c h a m b e r was 26 c m , w i t h a s l i d i n g d i v i d e r of about 1 c m t h i c k n e s s between the two, adding up to a t o t a l length of 117 c m . of the tank.  T h i s d i v i d e r was painted the same c o l o r as the r e s t  On the floor of each test c h a m b e r , 8 to 10 c m off the bottom, was  a w i r e m e s h g r i l l (square mesh) w i t h 11 m m h o l e s f o r m e d by w i r e of d i a m e t e r 1.5 m m .  T h i s m e s h s i z e was chosen.to a l l o w food to s i n k beneath the g r i l l  w h e r e the f i s h c o u l d not r e a c h it after a feeding t r i a l . Sheets of b l a c k p l a s t i c supported by an angle i r o n f r a m e w o r k s u r r o u n d e d the tank and kept out ambient l i g h t .  A s m a l l peephole was cut i n the side w a l l  for o b s e r v a t i o n without d i s t u r b i n g the f i s h .  A c r o s s the top of the f r a m e w o r k  was a flat wooden roof to w h i c h was attached a S y l v a n i a L i f e l i n e c o o l white fluorescent fixture.  The i n s i d e of both the p l a s t i c sheeting and the roof w e r e  painted the same c o l o r as the tank. 4 r e d , yellow, g r e e n or b l u e .  E a c h of the four tanks w e r e painted e i t h e r  These p a r t i c u l a r paints w e r e c h o s e n on the  b a s i s of t h e i r having a high p u r i t y of c o l o r and a h i g h s a t u r a t i o n . The water depth i n the tank was kept at 70 c m +_ 2 c m by a f l o w - t h r o u g h s y s t e m p r o v i d i n g 2.7 l / m i n + 0 . 6 1 / m i n of f r e s h d e - i o n i z e d w a t e r .  The  t e m p e r a t u r e of the water r e m a i n e d w i t h i n the range of 9 - 1 2 ° C throughout  " C o l o r Y o u r W o r l d " h i g h - g l o s s m a r i n e e n a m e l polyurethane: 1. B r i g h t R e d , 2. B r i g h t B l u e , 3. Sun Y e l l o w ; C i l u x M a r i n e E n a m e l #6210 T r o p i c G r e e n .  Feeding hole  Rolled up front flap  Fluorescent lamp  Peephole Sliding divider  Outlet pipe  Wire mesh grill  F i g u r e 2.  Cutaway v i e w of e x p e r i m e n t a l tank used i n feeding e x p e r i m e n t s I and II at the U n i v e r s i t y of B . C . , M a y 22 to June 6, 1973; and J u l y 23 to A u g u s t 3, 1973.  27 feeding e x p e r i m e n t I, and w i t h i n 12 - 1 3 . 5 ° C throughout feeding e x p e r i m e n t II. The water was a e r a t e d w i t h a b u b b l e r w h i c h was t u r n e d off 20 m i n u t e s before an e x p e r i m e n t and r e m a i n e d off throughout the e x p e r i m e n t . In feeding e x p e r i m e n t I the f l u o r e s c e n t l a m p s w e r e used w i t h f u l l l i n e voltage (120 volts) i n each of the four test t a n k s . v a l u e s of i l l u m i n a t i o n ,  T h i s gave the f o l l o w i n g  m e a s u r e d w i t h an underwater photometer ( G M m o d e l  1 5 - M - 0 2 / 1 ) equipped w i t h a W e s t o n c e l l , for the b o t t o m c e n t e r of each tank: r e d tank, 4 5 lux; y e l l o w tank, lux.  130 lux; g r e e n tank,  53 lux; and blue tank,  44  In the second e x p e r i m e n t it was p o s s i b l e to adjust the l i n e voltage to  give a light r e a d i n g of 72 l u x + 10 l u x for each tank at a depth of 32 c m beneath the s u r f a c e .  T h i s depth r e p r e s e n t s a p p r o x i m a t e l y the halfway m a r k i n the  water c o l u m n and i s about the depth w h e r e the f i s h would be u s i n g v e r t i c a l l y r e f l e c t e d l i g h t to see the eggs. T r o u t eggs f r o m the S u m m e r l a n d T r o u t H a t c h e r y of the B r i t i s h C o l u m b i a F i s h and W i l d l i f e B r a n c h w e r e used as e x p e r i m e n t a l food.  The f r o z e n eggs  w e r e allowed to thaw i n a cup of w a t e r and left to soak for two d a y s .  They  w e r e then d i v i d e d among four c o l o r s of dye bath c o n s i s t i n g of 1 p a r t by weight of f a b r i c dye  to about 200 p a r t s w a t e r .  They w e r e left i n the dye for 48 h o u r s ,  and shaken gently about e v e r y 12 h o u r s to ensure even d i s t r i b u t i o n of the dye over the c o m p l e t e surface of the eggs.  The exact c o n c e n t r a t i o n of the dye  solution was not c r i t i c a l , and m e a s u r e m e n t s w e r e u s u a l l y made by eye.  (The  eggs r e a c h e d a s i m i l a r shade of c o l o r i n g throughout a wide range of c o n c e n t r a tions of dye.)  They w e r e r e m o v e d f r o m the dye bath and r i n s e d i n c o l d f r e s h  water for at l e a s t 30 minutes b e f o r e being used i n an e x p e r i m e n t .  D y e d eggs  could be s t o r e d i n f r e s h water i n a r e f r i g e r a t o r for two to three days without l o s i n g an a p p r e c i a b l e amount of c o l o r . A t l e a s t 48 h o u r s before an e x p e r i m e n t , four f i s h were s e l e c t e d at r a n d o m f r o m a stock of about 70 i n the holding tanks (except that an effort was  T i n t e x F a b r i c D y e s : #50 E n s i g n R e d , #5 B r i l l i a n t Y e l l o w , #49 C r e m e de Menthe; R i t C o n c e n t r a t e d T i n t and Dye, #27 E v e n i n g B l u e .  28 made to get f i s h of at l e a s t 17.5 c m length), and one was p l a c e d i n e a c h of four e x p e r i m e n t a l tanks.  C.  Feeding Experiment I  1. Methods  The f i r s t feeding e x p e r i m e n t was conducted between M a y 22 and June 6, 1973, i n a l a b o r a t o r y at the U n i v e r s i t y of B r i t i s h C o l u m b i a .  The e x p e r i m e n t a l  food was p r e p a r e d by taking one egg f r o m e a c h c o l o r of dye b a t c h and f o r m i n g a group of four on a wet 8 i n c h by 8 i n c h p l e x i g l a s s plate.  In this manner 25 to  30 groups of four d i f f e r e n t - c o l o r e d eggs w e r e p l a c e d on the plate (enough for 20 s e r v i n g s plus a few e x t r a s ) .  A group of four eggs was s l i d off the p l e x i g l a s s  through the hole i n the top of the r o o f using a s t a i n l e s s s t e e l s p a t u l a . constituted one " s e r v i n g " .  The eggs f e l l through the a i r to the w a t e r  This surface;  t h e r e they w e r e v u l n e r a b l e to the trout u n t i l they d r i f t e d t h r o u g h the w i r e m e s h on the b o t t o m of the tank.  A feeding u s u a l l y c o n s i s t e d of twenty s e r v i n g s ,  each  of w h i c h followed the p r e v i o u s one by about t h i r t y seconds. The c o l o r s of the f i r s t and second eggs eaten w e r e r e c o r d e d , p r o v i d i n g the f i s h ate t h e m before any one of the four eggs d r i f t e d through the w i r e m e s h grill.  If an egg d i d drift t h r o u g h the g r i l l f i r s t , then the r e s u l t s f r o m that  s e r v i n g w e r e r e j e c t e d as a l l c o l o r s of egg d i d not have an equal chance (length of time) to be eaten. If the f i r s t two eggs w e r e eaten s i m u l t a n e o u s l y , they w e r e both s a i d to be f i r s t c h o i c e s (and s c o r e d as such), and a second c h o i c e was not r e c o r d e d for that s e r v i n g .  T h i s o c c a s i o n a l l y happened,  and it r e s u l t e d i n the t o t a l  s c o r e for some s e r v i n g s being s l i g h t l y higher than for o t h e r s . continued until twenty sets of r e a d i n g s had been taken.  Servings were  Often 21 s e r v i n g s w e r e  r e q u i r e d to get twenty sets of r e a d i n g s , but the n u m b e r of e x t r a s e r v i n g s s e l d o m went over two, and n e v e r over f o u r .  The o r d e r in w h i c h the f i s h i n  29  the four tanks were fed was r a n d o m i z e d for each d a y ' s feeding. A s c o r e of two was g i v e n e a c h time a c o l o r of egg was c h o s e n f i r s t and a s c o r e of one was a s s i g n e d to a second c h o i c e .  T h e r e f o r e , for a g i v e n  feeding a t o t a l s c o r e of 40 i n one c o l o r n o r m a l l y i n d i c a t e d 100 per cent s e l e c tion, i.e., that c o l o r was chosen f i r s t out of the four for e a c h s e r v i n g i n that feeding.  The s c o r e for e a c h c o l o r was d i v i d e d by 40, c o n v e r t e d to a per cent,  and then t r a n s f o r m e d u s i n g the a r c s i n t r a n s f o r m a t i o n .  E a c h t r a n s f o r m a n t so  attained r e p r e s e n t e d one data point for the a n a l y s i s of v a r i a n c e .  The l e v e l of  s i g n i f i c a n c e was set a t a = .05. A second r e p l i c a t e was done before the f i s h w e r e t r a n s f e r r e d f r o m one tank to the next.  T r a n s f e r then o c c u r r e d w i t h i n 24 h o u r s of i t s c o m p l e t i o n .  The f i s h a l w a y s had at l e a s t 24 h o u r s to a c c l i m a t i z e to a tank before the next e x p e r i m e n t a l feeding.  The o r d e r i n w h i c h the f i s h w e r e m o v e d f r o m tank to  tank was f r o m g r e e n to y e l l o w to r e d to blue to g r e e n . A f t e r a feeding was f i n i s h e d the d i v i d e r between the test c h a m b e r and the p r e p a r a t i o n c h a m b e r was r a i s e d and the f i s h was " e n c o u r a g e d " into the preparation chamber.  The d i v i d e r was then dropped and the m e t a l g r i l l c o u l d  be r e m o v e d f r o m the test c h a m b e r , thus a l l o w i n g the e x c e s s food to be c l e a n e d out without p h y s i c a l l y d i s t u r b i n g the f i s h .  A s soon as the cleanup was c o m -  pleted, the g r i l l was r e p l a c e d , the d i v i d e r r a i s e d , and the f i s h was " e n c o u r a g e d " back to the test c h a m b e r .  2. R e s u l t s  R e d - c o l o r e d food was the o v e r a l l f a v o r i t e , w i t h an average s e l e c t i o n i n t e n s i t y 50 per cent of the highest p o s s i b l e (if r e d was chosen f i r s t each t i m e ) .  30 T h i s was f o l l o w e d by blue, y e l l o w , and g r e e n w i t h s e l e c t i o n i n t e n s i t i e s 43 per cent, 39 per cent and 36 per cent r e s p e c t i v e l y of the highest p o s s i b l e . The effect of food c o l o r was s i g n i f i c a n t at the .001 l e v e l of p r o b a b i l i t y (see Table VI).  A l t h o u g h the c o l o r of the tank i s s t a t i s t i c a l l y i m p o r t a n t i n m o d i f y i n g the choice of c o l o r s of food, no c l e a r p a t t e r n e m e r g e s (see T a b l e VII and F i g u r e 3).  The g r e a t e s t range i n i n t e r a c t i o n effects o c c u r r e d i n the r e d tank,  but the o r d e r of s e l e c t i o n of food was not i n a g r e e m e n t w i t h that for the o v e r all experiment. The o r d e r of s e l e c t i o n of v a r i o u s c o l o r s of food i s a l s o dependent upon w h i c h f i s h i s doing the s e l e c t i n g (see Table VIII and F i g u r e 4).  A l l of the f i s h  have the highest s e l e c t i o n i n t e n s i t y for r e d , but f a i l to c o n c u r on the o r d e r for the other c o l o r s . Further,  a f i s h ' s o r d e r of s e l e c t i o n changes depending on the c o l o r of  the tank i n w h i c h it i s h e l d . F o r t h r e e of the f i s h this m o d i f i c a t i o n was of sufficient strength so as to effect a r e v e r s a l i n s e l e c t i o n o r d e r between t a n k s , i . e . , a c o l o r that was the f a v o r i t e i n one tank was the l e a s t p r e f e r r e d i n a d i f f e r e n t - c o l o r e d tank.  S e l e c t i o n i n t e n s i t y is a m e a s u r e of the degree to w h i c h a f i s h s e l e c t s and eats a p a r t i c u l a r i t e m of food when it has a c h o i c e of s e v e r a l . It may r e f l e c t a h i e r a r c h y of p r e f e r e n c e s w h i c h the f i s h has t o w a r d the food i t e m s , or it may r e s u l t f r o m a different set of f a c t o r s , such as the v i s i b i l i t y of an i t e m against a g i v e n background, thus g i v i n g no i n d i c a t i o n w h a t s o e v e r as to the f i s h ' s l i k e s and d i s l i k e s . The t e r m "per cent s e l e c t i o n i n t e n s i t y " r e f e r s to the s c o r e for a c o l o r d i v i d e d by the total p o s s i b l e s c o r e for a feeding (40), e x p r e s s e d as a per cent; " s e l e c t i o n i n t e n s i t y " , by itself, r e f e r s to the a r c s i n t r a n s f o r m a n t of the per cent s e l e c t i o n i n t e n s i t y . The t e r m s " p r e f e r e n c e " , "preference i n t e n s i t y " , and "per cent p r e f e r e n c e i n t e n s i t y " w i l l be used i n place of the above when the situation seems to indicate that the f i s h i s showing r e s p o n s e s based on a s p e c t r u m of l i k e s and d i s l i k e s .  TABLE  VI.  S e l e c t i o n i n t e n s i t i e s of c o l o r s of food i n v a r i o u s c o l o r s of t a n k . e x p e r i m e n t I, U n i v e r s i t y o f B.C., M a y 22 to J u n e 6, 1973. f r o m the a n a l y s i s of t h i s d a t a .  Feeding  ANOVA  table  T h e u p p e r n u m b e r i s the s e l e c t i o n i n t e n -  s i t y f r o m the f i r s t r e p l i c a t e . T h e l o w e r n u m b e r i s the s e l e c t i o n i n t e n s i t y f r o m the s e c o n d r e p l i c a t e . feeding  Red  C o l o r of T a n k Fish 1  Fish 2  The highest possible  selection intensity for a  (if that c o l o r i s c h o s e n f i r s t e v e r y t i m e ) i s 90. C o l o r of F o o d Green  Yellow  Blue  28.3  37.8  36.3  50 .8  50.7  39.2  31.6  31 .6  Yellow  46.4 46.4  30 40.7  24.7 24.7  47 .9 3 9 .2  Green  43.6 45.0  33.2 26.6  37.8 34.8  4 5 .0  Blue  37.8 55.2  36.3 36.3  47.9 26.6  30 .0 33 .2  Red  30.0  28.3  49.3  24.7  31.6  40.7  4 5 .0 52 .2  Red  Yellow  26.6  26.6  26.6  24 .7 28 .3  37.8  43.6  20.7  37.8  34.8  46 .4 37 .8  Blue  60.0 58.4  26.6 24.7  39.2 30.0  24 .7 36 .3  Red  39.2 30.0  30.0 22.8  40.7  42.1  47.9  50.8  45.0  33.2  36.3  37.8  52.2  33.2  28.3  36.3  45.0  42.1  28.3  39.2  37.8  40.7  40.7  34.8  47.9 40.7  24.7  33.2  46.4  37.8  31.6  45.0  42.1  43.6 42.1  37.8  43.6  28.3  30.0 39.2  49.3 52.2  33.2 39.2  18.4 28.3  47.9 33.2  36.3  47.9 46.4  24.7 22.8  40.7  47.9 47.9 65.3  36.3  34.8  33.2  •31.6  26.6  28.3  1459.6 45.613  1127.7 3 5.241  Yellow  Green  Blue  Fish 4  43.6  43.6  Green  Fish 3  55.2 74.1  37 .8  Red  Yellow  Green  Blue  EY Y  Source Food color  .  '•  df .  3  1041.0 32.531  MS  Probability  1020  p«.001  Tank color x Food color  . 9  302  p«.001  Indiv. d i f f . x F o o d c o l o r  9  101  .01<p<.025  Indiv. d i f f . x Tank c o l o r x F o o d c o l o r  27  89.5  Error  64  41.5  .005<p<.01  34.8  1230.6 38.456  4858.9 37.960  32  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n e f f e c t s f o r c o l o r s o f f o o d i n v a r i o u s c o l o r s o f tank. F e e d i n g E x p e r i m e n t I, U n i v e r s i t y of B.C., M a y 22 t o J u n e 6, 1973. C o r r e c t i o n f o r f o o d c o l o r e f f e c t s w a s m a d e by s u b t r a c t i n g t h e c o r r e c t i o n f a c t o r f o r the c o l u m n ( c o l o r of food) i n T a b l e V I I A f r o m e a c h s e l e c t i o n i n t e n s i t y i n that c o l u m n . C o r r e c t e d v a l u e s a r e g i v e n i n T a b l e V I I B . I n t e r a c t i o n e f f e c t s a r e c a l c u l a t e d b y s u b t r a c t i n g t h e c o r r e c t e d s e l e c t i o n i n t e n s i t i e s of T a b l e V I I B f r o m the o v e r a l l m e a n s e l e c t i o n i n t e n s i t y f o r the e x p e r i m e n t (37.956) I n t e r a c t i o n e f f e c t s a r e a m e a s u r e of the e f f e c t of the c o l o r of t a n k o n the s e l e c t i o n i n t e n s i t y of the c o l o r of f o o d . ^ C o r r e c t i o n factor: Number in parentheses r e p r e s e n t s the m e a n s e l e c t i o n i n t e n s i t y f o r a c o l o r o f f o o d m i n u s the o v e r a l l m e a n s e l e c t i o n i n t e n s i t y f o r f e e d i n g e x p e r i m e n t I (37.956).  A.  U n c o r r e c t e d for F o o d C o l o r  Effect  (+7.6)*  Food (-2.7)  Color  Red  Yellow  (-5.4) Green  34.4 35.0  39.1 26.7  Green  36.1 52.6 42.1  39.8  30.6  36.9 39.6  Blue  51.6  31.8  33.7  34.6  182.4  141.0  130.1  153.8  Tank  Color  Red Yellow  (0.4) Blue 42.7  607.3 Y  C o r r e c t e d for F o o d Color  Effects  Red Yellow  28.5 4 5.0  37.1  44.5 32.1  42.2  37.7  Green  34.5 44.0  42.5  36.0  34.5  39.1  39.1 34.1  152.0  151.8  151.7  151.8  Blue  =  36.4  607.3  Interaction Effects +4.24  SlYl 21.10  - .26  +6.54 -5.86  -1.56  14.72  +4.54  -1.96  +1.14  11.10  +6.04  -3.46  +1.14  -3.86  14.50  EY  +0.16  -0.04  26.00  -0.04 9.12  -0.14  ZIYI  15.50  10.80  Red  - .86  Yellow  -9.46 +7.04  Green  -3.46  Blue  6l.62|  33 A.  U n c o r r e c t e d f o r E f f e c t of F o o d C o l o r  55  50 MEAN 45 SELECTION 4CH INTENSITY  35H  3(H  25 Red  Yellow COLOR  B.  OF  Green  Blue  TANK  C o r r e c t e d for E f f e c t of F o o d C o l o r 55T  50 MEAN 45H SELECTION 40INTENSITY 35  30  25  —i—  Yellow  Red  COLOR F i g u r e 3.  OF  Green  Blue  TANK  G r a p h of m e a n s e l e c t i o n i n t e n s i t i e s of c o l o r s of food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B . C . , M a y 22 to June 6, 1973. ^> a* r e d food; ao blue food. food; B• -a g r e e n food;  yellow  34  TABLE  A.  VIII.  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects f o r c o l o r s of food a m o n g different f i s h . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B . C . , M a y 22 to J u n e 6, 1973. ^ N u m b e r s in p a r e n t h e s e s a r e c o r r e c t i o n f a c t o r s (see T a b l e VII for explanation of c a l c u l a t i o n s ) .  U n c o r r e c t e d for F o o d C o l o r E f f e c t  Fish Number 1  2 3 4  (+7.65)* Red  Food (-2.72) Yellow  Color (-5.43) Green  (+.49) Blue  44.2 48.0 42.2 48.1  35.0 32.8 33.1 40.0  33.0 33.5 35.9 27.7  39.4 36.9 41.6 35.9  182.5  140.9  130.1  153.8  607.3 Y  B.  = 37.956  C o r r e c t e d for F o o d C o l o r E f f e c t 1 2 3 4  Interaction  36.6 40.4 34.6 40.5  37.7 35.5 35.8 42.7  38.4 38.9 41.3 33.1  38.9 36.4 41.1 35.4  152.1  151.7  151.7  151.8  + .94 -1.56 +3.14 -2.56  Effects  1 2 3 4  -1.36 +2.44 -3.36 +2.54  - .26 -2.46 -2.16 +4.74  + .44 + .94 +3.34 -4.86  EY  + .26  + .12  .14  9.70  9.62  9.58  EfY|  -  .04 8.20  607.3  Uncorrected  for Effect  of F o o d  Color  45 MEAN 40 SELECTION 35H INTENSITY  30H  25  20 Fish 1  B.  1—  Fish 3  Fish 2  C o r r e c t e d f o r E f f e c t of F o o d  Fish 4  Color  45n MEAN  40 SELECTION 35H INTENSITY 30H  25 20 Fish 1  F i g u r e 4.  Fish 2  G r a p h of m e a n s e l e c t i o n different fish. May  Feeding  22 t o J u n e 6,  food; D  Fish 3  Fish 4  intensities ofc o l o r s offood  among  e x p e r i m e n t I, U n i v e r s i t y o f B.C.,  1 973. n  B g r e e n food;  & r e d food;o  :  &  blue  a yellow food.  36 3. D i s c u s s i o n  It would s e e m r e a s o n a b l e that the effect of different c o l o r s of tank on the o r d e r of s e l e c t i o n of food would be r e l a t e d to the degree of s i m i l a r i t y between the c o l o r of food and the c o l o r of tank. this assumption:  Two hypotheses e m e r g e  from  (1) that food i n a s i m i l a r - c o l o r ed tank would be l e s s v i s i b l e  than food i n a c o n t r a s t i n g - c o l o r e d tank,  so that a r e s u l t a n t d e c r e a s e i n the  s e l e c t i o n i n t e n s i t y f r o m that expected on the b a s i s of c o l o r of food alone would be manifest; and (2) that the s e l e c t i o n i n t e n s i t i e s of c o n t r a s t i n g - c o l o r e d foods would be augmented in r e l a t i o n to t h e i r " s p e c t r a l d i s t a n c e " f r o m the c o l o r of tank i n w h i c h they are being fed. effect,  The f i r s t of these we w i l l c a l l the " c a m o u f l a g e "  and the second, the " c o m p l e m e n t " effect.  (One i s r e a l l y the o b v e r s e  of the other.) F r o m Table VII A it can be seen that the s e l e c t i o n i n t e n s i t i e s for the camouflage c e l l s (along the d i a g o n a l f r o m the top left to the b o t t o m right) are l o w w i t h r e s p e c t to those for the same c o l o r of food i n the other t a n k s . v a l u e s for r e d , g r e e n and blue are 21 per cent,  6 per cent,  and 10 per cent  l o w e r than the m e a n v a l u e s for t h e i r r e s p e c t i v e c o l o r s of food. difference for the y e l l o w tank.)  The  ( T h e r e i s no  It i s p o s s i b l e , however, to l o o k at this effect  separated out f r o m the effect of the c o l o r of food. s e l e c t i o n i n t e n s i t i e s would be i n t h i s i n s t a n c e .  T a b l e V I I B shows what the  The a c t u a l i n t e r a c t i o n effects,  w h i c h s t o w the effect of the c o l o r of tank on the s e l e c t i o n i n t e n s i t y of the c o l o r s of food, are g i v e n i n Table VII C .  E x c e p t for the r e d c o l o r , this effect  was quite weak, and a s u m of s q u a r e s test on the camouflage v e r s u s the n o n camouflage means of Table VII B f a i l e d to show a s i g n i f i c a n t different at cv=.0 5. A g a i n , f r o m Table VII B , it i s p o s s i b l e to d i v i d e the means s u c h that one group (the " c o m p l e m e n t " group) r e p r e s e n t s c o m b i n a t i o n s of c o l o r s that are s p e c t r a l l y distant f r o m each other (red w i t h green, r e d w i t h blue, and y e l l o w w i t h blue), and the other group  r e p r e s e n t s a l l the other c o m b i n a t i o n s .  A l t h o u g h the average i n t e r a c t i o n effect for the c o m p l e m e n t a r y g r o u p i s p o s i t i v e ( +1.39),  and the average i n t e r a c t i o n effect for the n o n - c o m p l e m e n t a r y group  37 i s negative (-0.84),  a s u m of squares test on the c o r r e c t e d s e l e c t i o n i n t e n s i t i e s  f a i l s to show a s i g n i f i c a n t difference (CY = .05). T h e r e f o r e , neither the camouflage effect nor the r e l a t e d complementaryc o l o r effect a r e sufficient by t h e m s e l v e s to e x p l a i n the s i g n i f i c a n c e of the tank c o l o r x food c o l o r i n t e r a c t i o n .  Whatever the p r o c e s s i s that i s p r i m a r i l y  r e s p o n s i b l e for this i n t e r a c t i o n , i t s mode of o p e r a t i o n i s not s y m m e t r i c a l , as the i n t e r a c t i o n effect for a c o l o r of food i n another c o l o r of tank (except for c o l o r c o m b i n a t i o n s i n v o l v i n g blue) is of opposite s i g n f r o m that when the c o l o r s are r e v e r s e d . One other thing to notice i s the fact that the i n t e r a c t i o n effects strongest when a r e d c o l o r i s i n v o l v e d .  are  When the absolute v a l u e s of the  i n t e r a c t i o n effects are s u m m e d a c r o s s the r o w s , the g r e a t e s t t o t a l o c c u r s for the r e d tank, and s i m i l a r l y , when the i n t e r a c t i o n effects are s u m m e d down the c o l u m n s .  It could be objected that these are not orthogonal c o m p a r i s o n s ,  and that the l a r g e value for the r e d food i n the r e d tank boosts the t o t a l s for both the r o w and the c o l u m n .  H o w e v e r , even i f we let that value be equal to  the mean of the other c e l l s i n the r o w (and s i m i l a r l y for the c o l u m n ) , the totals for i n t e r a c t i o n s i n v o l v i n g r e d are s t i l l seen to be the h i g h e s t . The mean square of s e l e c t i o n i n t e n s i t i e s among the tanks was about t h r e e t i m e s as g r e a t as that among the f i s h . t i v e values for interaction p action  T h i s i s r e f l e c t e d i n the r e s p e c -  p for the two i n t e r a c t i o n s (for the tank c o l o r x food c o l o r .001, w h i l e for the i n d i v i d u a l d i f f e r e n c e s x food c o l o r i n t e r -  .01 < p < .0 25).  T h e r e f o r e , i n m a k i n g quantitative m e a s u r e m e n t s  of food s e l e c t i o n based on food c o l o r , it i s m o r e c r i t i c a l to s t a n d a r d i z e the b a c k g r o u n d c o l o r than it i s to get u n i f o r m i t y i n test subjects. The l e s s e r i m p o r t a n c e of i n d i v i d u a l differences i n d e t e r m i n i n g o r d e r of s e l e c t i o n shows up in the f o r m of a good c o n s i s t e n c y of s e l e c t i o n o r d e r between r e p l i c a t e s , , both for the f i s h as a whole, and for i n d i v i d u a l f i s h (see Table IXA).  The o r d e r for both r e p l i c a t e s was red, blue, y e l l o w and g r e e n  when the f i s h are taken as a g r o u p .  L o o k i n g at s e l e c t i o n o r d e r s of i n d i v i d u a l  38  TABLE  IX.  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n e f f e c t s f o r c o l o r s of food among different fish, f o r each r e p l i c a t e . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of B.C., M a y 22 to J u n e 6, 1973. T h e a v e r a g e s i z e of i n t e r a c t i o n e f f e c t i s e q u a l to the s u m of the a b s o l u t e v a l u e s of the i n t e r a c t i o n e f f e c t s i n a r o w o r c o l u m n d i v i d e d b y 8.  Uncorrected for Food Color  Effect C o l o r of F o o d  F i s h Number  Replicate  Red  1  1 2  39.0 49.3  1  45.8  2  50.2  35.5 30.2  1 2  44.3 40.2  32.5  34.6 37.1  41.7  1  43.9 52.2  40.2  28.9 26.5  38.0  39.8  364.9  281.8  260.2  307.6  2  3  4  2 EY  Corrected for Food 1  3  4  Interaction  Green  Blue  34.3  36.7  35.7  29.4  41.6 37.2  34.0  35.2  33.0  38.6  33.6  41.4  33.9  Color Effect 1 2  2  Yellow  31.4  37.1  42.1  41.1  41.7  38.4  34.8  36.8  1  38.1  38.2  39.4  34.7  2  42.6  32.9  38.4  38.2  1  36.6  35.2  40.0 .  2  32.5  36.4  42.6  40.9 41.2  1  36.2  43.0  34.4  37.4  2  44.6  42.6  31.9  33.4  EY  303.7 .  303.8  304.6  303.7  Effects  Average  s i z e of  interaction 1  .2  3  4  1  -6.58  - .91  4.14  3.16  2  3.71  .46  -3.11  -1.21  1  .14  -3.26  4.59  .29 -5.06  1.42  2  .49  .19  1.93  1  -1.34  -2.74  2.09  2  -5.44  -1.61  4.59  2.92 3.26  3.00  1  -1.71 6.64  5.02 4.59  -3.61 -6.04  - .51 -4.58  4.09  3.77  2.58  3.19  2.39  2 A v e r a g e s i z e of interaction  e f f e c t ' |Y|  2.91  effect,  39  f i s h it i s seen that the r a n k for a g i v e n c o l o r of food i s n e v e r m o r e than one different f r o m that i n the o v e r a l l o r d e r .  O n l y two f i s h (fish #1 r e p l i c a t e 1 and  f i s h #3 r e p l i c a t e 2) had two of these r e v e r s a l s of a c o l o r w i t h its n e a r e s t neighbor; a l l the others had either one r e v e r s a l or none.  Also,  comparing  the s e l e c t i o n o r d e r for an i n d i v i d u a l f i s h between r e p l i c a t e s , it i s seen that, again, the g r e a t e s t shift i n r a n k i s one p l a c e .  O n l y f i s h n u m b e r 4 was c o n -  sistent between r e p l i c a t e s , and this i s the f i s h that had the g r e a t e s t a v e r a g e s i z e of i n t e r a c t i o n effect (see Table I X C ) .  A l l told, there i s the g r e a t e s t  agreement on the p l a c e of r e d i n the o r d e r of s e l e c t i o n , i t being c h o s e n f i r s t six t i m e s out of eight. The average s i z e of i n t e r a c t i o n effect for e a c h f i s h i s a m e a s u r e of the amount that each f i s h deviated f r o m the average s e l e c t i o n o r d e r of the g r o u p . C o m p a r i n g this amount of d e v i a t i o n among the fish, f i s h #4 had t w i c e as m u c h d e v i a t i o n o v e r a l l as f i s h #2, and about 50 p e r cent m o r e than e i t h e r f i s h #1 or f i s h #3.  It c a n a l s o be seen by e x a m i n i n g the c o l u m n s u m s that the c o l u m n for  r e d food had the l a r g e s t t o t a l .  T h i s means that, even though the f i s h w e r e  m o s t a g r e e d on the place of r e d i n the s e l e c t i o n o r d e r , range of " a t t r a c t i v e n e s s " of any c o l o r .  it had the g r e a t e s t  G r e e n came second, and y e l l o w and  blue t i e d for t h i r d p l a c e . The i n t e r a c t i o n between the c o l o r of food, c o l o r of tank, and i n d i v i d a u l f i s h means that i n d i v i d u a l f i s h make different changes i n t h e i r o r d e r of s e l e c t i o n when tested i n one c o l o r of tank and then another.  A s i m p l e way of  "getting at" this effect is to r a n k the c o l o r s of food for e a c h feeding 1, 2, 3, and 4, a c c o r d i n g to their s e l e c t i o n i n t e n s i t y v a l u e .  The s u m of the d i f f e r e n c e s  i n rank o r d e r between r e p l i c a t e s for a p a r t i c u l a r f i s h w i l l give a m e a s u r e of the i n c o n s i s t e n c y of that f i s h i n its choice of food c o l o r s (see Table X ) . H o w e v e r , this i s a m e a s u r e of i n c o n s i s t e n c y w i t h i n a c o l o r of tank.  T o get a  m e a s u r e of i n c o n s i s t e n c y among tanks, the v a r i a n c e (S ) of the mean r a n k for s  the two r e p l i c a t e s can be found for each c o l o r of food.  The average of these  four values w i l l be a m e a s u r e of the i n c o n s i s t e n c y of food c h o i c e of an i n d i v i d u a l f i s h among the four c o l o r s of tank.  F r o m Table X it i s seen that f i s h #4  I S  the  TABLE  X.  Variability in selection order between replicates and between tanks. Feeding experiment I, University of B.C., May 22 to June 6. 1973. Numbers represent order of selection of food (selection rank) in first and second replicates. S = variance of mean selection rank. See text for explanation. *D : difference 2  1 and 2). Color of Tank  Red  Red  4  1 3 2(2)  i  3 2 1(2.5)  4 4 0(4)  1 3 2(2)  4 4 0(4)  2 3 1(2.5)  2 1 1(1.5)  3 2 1(2.5)  1 4 3(2.5)  4 3 1(3.5)  (.750)  (.500)  (.750)  . 4 3 1(3.5) 2 3 1(2.5)  1 2 1(1.5)  2 1 1(1.5)  3 3 0(3)  4 2 2(3)  2 2 0(2)  4 4 0(4)  1 2 1(1.5)  3 4 1(3.5)  2 3 1(2.5)  4 2 2(3)  (.563)  (1.083)  (.75)  I  1(1.5) S = (.396) 2  Red  3 4 1(3.5) 1 1 0(1)  Yellow  Green  Blue  3 1 2(2) 1 1 0(1) S = (1.396) 2  Red  3 3 0(3)  4 4 0(4)  2 1 1(1.5)  1 2 1(1.5)  Yellow  1 1 0(1)  4 3 1(3.5)  3 4 1(3.5)  2 2 0(2)  Green  1 3 2(2)  2 1_ 1(1.5)  4 1 3(2.5)  3 4 1(3.5)  1 2 1(1.5) S2 = (.729)  4 3 1(3.5)  3 4 1(3.5)  I  (1.229)  (.917)  (.896)  2 1 1(1.5) 1 J_ 0(1) 3 1_ 2(2)  1 2 1(1.5)  3 4 1(3.5)  4 3 1(3.5)  3 2 1(2.5) 1 2 1(1.5)  4 4 0(4) 4 4 0(4)  2 3 1(2.5) 2 3 1(2.5)  1 1 0(1)  2 2 0(2)  3 4 1(3.5)  4 3 1(3.5)  (.229)  (.083)  (.333)  Blue  Fish <?4  Blue  3 3 0(3)  1 1 0(1) 2  Blue  Food Green  2 2 0(2)  1(1.5) Green  of  I  *3(2.5) + 2  Yellow  Color Yellow  Red  Yellow  Green Blue  S2 = (.22'))  E*D =17 r  S = .599 2  £ D =14 r  S = .948 2  t D =15 • r  2  1(1.5) S  2  = .943  t D =12 r  S  2  = .219  41  m o s t consistent both w i t h i n a g i v e n c o l o r of tank and between c o l o r s of tank. The value of the i n t e r - t a n k i n c o n s i s t e n c y m e a s u r e m e n t when the r a n k s a r e a s s i g n e d at r a n d o m among the four c o l o r s of food is S  2  = .625.  Therefore,  two of the f i s h w e r e m o r e consistent i n t h e i r c h o i c e s than would be expected if they w e r e made on a r a n d o m b a s i s , w h i l e two of the f i s h w e r e m a r k e d l y l e s s consistent. Table X I shows the i n t e r a c t i o n effects for the second o r d e r i n t e r a c t i o n (food c o l o r x tank c o l o r x i n d i v i d u a l d i f f e r e n c e s ) .  A m o n g the v a r i o u s c o l o r s  of food the greatest, i n t e r a c t i o n effects o c c u r for r e d ( | Y | = 4.38).  There is  the g r e a t e s t difference among f i s h i n t h e i r change of p r e f e r e n c e for r e d food upon being t r a n s f e r r e d f r o m tank to tank. as the m o r e n e u t r a l an o r g a n i s m ' s  T h i s i s , perhaps,  to be expected,  " f e e l i n g s " are t o w a r d an object,  e n v i r o n m e n t a l f a c t o r s w i l l affect those f e e l i n g s , and v i c e v e r s a .  the l e s s  Taken in  conjunction w i t h the wide range of a t t r a c t i v e n e s s of r e d to i n d i v i d u a l fish,  this  explains why the s e c o n d - o r d e r i n t e r a c t i o n effects are g r e a t e s t for the r e d c o l o r of food.  H o w e v e r , the t - t e s t f a i l s to show a s i g n i f i c a n t d i f f e r e n c e  between the i n t e r a c t i o n effects for the r e d food and the mean value for those of the other three c o l o r s . In a feeding e x p e r i m e n t s u c h as this, w h e r e the f i s h go f r o m h a v i n g an empty gut to an a l m o s t full one, any p r e f e r e n c e shown for a g i v e n c o l o r might o c c u r only when the f i s h has a l m o s t r e a c h e d a state of satiation; so that s e l e c t i o n for c o l o r i s l i m i t e d to the t i m e of " d w i n d l i n g appetite".  If one w e r e  doing a f o r c e d - f e e d i n g p r o g r a m on a group of fish, it would be i n t e r e s t i n g to know what c o l o r was l a s t "given u p " as it c o u l d be used for " d e s s e r t " after a feeding of n o r m a l - c o l o r e d food.  T h i s c o u l d be an i m p o r t a n t factor if it was  difficult or c o s t l y to dye food that p a r t i c u l a r c o l o r . W i t h the intent of i n v e s t i g a t i n g t h i s p o s s i b i l i t y , the data f r o m the e x p e r i m e n t were d i v i d e d into two p a r t s :  See B r o w n l e e , K . A . , 1965.  r e s u l t s of s e r v i n g s 1 - 10, and  TABLE  XI.  I n t e r a c t i o n effects for s e c o n d - o r d e r i n t e r a c t i o n (food c o l o r x tank c o l o r x i n d i v i d u a l d i f f e r e n c e s ) - - a v e r a g e f o r two r e p l i c a t e s . F e e d i n g e x p e r i m e n t I, U n i v e r s i t y of. B . C . , . ..May.22 .to June 6, 1973.  C o l o r of Tank  Red  Color Yellow  F i s h #1  Red Yellow Green Blue  +4.88 -5.02 +3.58 -3.88  F i s h #2  Red Yellow Green Blue  F i s h #3  F i s h #4  Food Green  Blue  +4.48 + .52 -9.52 +4.78  -5.48 -2.62 +5.38 +3.02  -2.38 +5.48 + .92 -3.98  SIYI = 65.92  -11.08 +9.42 -3.82 +5.08  -1.88 +2.48 +3.48 -3.68  +5.08 -1.22 -3.68 - .12  +7.52 -9.08 +4.12 -2.08  SlYl = 73.82  Red Yellow Green Blue  +1.98 - .88 +2.68 -4.02  -5.72 + .28 +3.88 +1.62  +1.98 +2.08 + .68 -4.72  + .68 -3.22 -5.68 +7.92  SlYl = 48.02  Red Yellow Green Blue  +4.32 -4.58 -2.52 +2.38  +3.82 -3.62 +2.72 -2.58  -1.08 +1.32 -1.88 +1.78  -5.48 +5.98 + .78 -1.32  SlYl = 46.16  Z|Y|  70.12  55.06  42.12  66.62  4.38  3.44  2.63  4.16  A v e r a g e size of i n t e r a c t i o n effect, IYI  of  43 r e s u l t s of s e r v i n g s 11 - 20.  A n a n a l y s i s of v a r i a n c e s i m i l a r to the o r i g i n a l  one was c a r r i e d out, except w i t h a f o u r t h m a i n effect:  whether the data w e r e  f r o m the f i r s t half or the second h a l f of the feeding. T h e r e were no s i g n i f i c a n t effects due to the data b e i n g f r o m the f i r s t or second half of the feeding (a-.0 5). factor w e r e s i g n i f i c a n t .  None of the i n t e r a c t i o n s i n v o l v i n g this  The only noteworthy difference between the two  A N O V A s was that the i n d i v i d u a l differences x c o l o r of food i n t e r a c t i o n was significant at the .00 5 l e v e l of p r o b a b i l i t y r a t h e r than j u s t at the .025 l e v e l .  D.  F e e d i n g E x p e r i m e n t II 1. M e t h o d s T r o u t w e r e fed b i c o l o r e d food i n the p r e v i o u s l y d e s c r i b e d tanks between  J u l y 23 and A u g u s t 3, 1973.  F o u r f i s h w e r e c h o s e n at r a n d o m f r o m a holding  tank and one was p l a c e d i n each of the four e x p e r i m e n t a l t a n k s .  A l l tests for  a g i v e n tank w e r e done w i t h this f i s h . E x p e r i m e n t a l food was p r e p a r e d as f o l l o w s :  a hot s o l u t i o n of one p a r t  gelatine to ten p a r t s water was p o u r e d into a flat pan to a depth of 3 - 4 m m . The pan was p l a c e d i n a r e f r i g e r a t o r ,  a l l o w i n g the gelatine to h a r d e n for two  d a y s . It was then r e m o v e d , and r e c t a n g u l a r h o l e s w e r e s l i c e d i n the gelatine just l a r g e enough to a c c o m m o d a t e two eggs side by side (see F i g u r e 5). F o r any g i v e n feeding one of the four c o l o r s of egg - - r e d ,  yellow,  g r e e n or blue - - was chosen to be the "tag" c o l o r , i . e . , t h i s c o l o r of egg was i n c l u d e d as the "tag" and was one m e m b e r of each p a i r ' o f eggs that w e r e put into a hole i n the g e l a t i n e . g r e e n or b l u e .  The other egg was one of the c o l o r s r e d ,  yellow,  F o r e x a m p l e , for a g i v e n feeding, i f y e l l o w was c h o s e n as  the tag c o l o r , the f o l l o w i n g p a i r s of eggs would be f o r m e d :  y e l l o w w i t h red,  y e l l o w w i t h y e l l o w , y e l l o w w i t h green, y e l l o w w i t h blue (designated Y R , Y Y , Y G and Y B , r e s p e c t i v e l y ) .  loo)  too]  oo  foo]  (ool  foo]  |oo|  too]  l£Oj  lool  tool  [750] fool loo] loo] looj fool  tool  foo]  m m m  tM |oo|  t^oj  m  lOOl  foo]  too]  too]  m m fool m loo] \m  fool  tool  foo]  foo]  [oo]  too]  too]  too]  loo]  tool  too)  too]  too]  too]  foo]  tM  tool  Ho]  loo]  |oo(  m  loo]  tool  looj  too]  foo] 160]  lool  fool  fool  too]  t22l  loo|  fool  lool  Eg  F i g u r e 5.  loo]  \oo\  I22) tool  fool  m m m  00  m m m  fool  t£o]  m  too] tool  m  P r e p a r a t i o n of food for feeding e x p e r i m e n t I I - a r r a n g e m e n t of eggs i n the gelatine; plan v i e w . F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 22 to A u g u s t 3, 1973.  45 A s l i g h t l y l e s s c o n c e n t r a t e d s o l u t i o n of gelatine was made up, a l l o w e d to cool to r o o m t e m p e r a t u r e ,  and then p o u r e d into the pan to f i l l i n a l l the  gaps and p r o v i d e a thin l a y e r c o m p l e t e l y c o v e r i n g the tops of the eggs.  The  pan was r e t u r n e d to the r e f r i g e r a t o r and the f r e s h gelatine was a l l o w e d to h a r d e n for two d a y s . I m m e d i a t e l y before a feeding r e c t a n g u l a r b l o c k s j u s t l a r g e enough (about .5 c m x .7 c m x 1.0 cm) to i n c l u d e a p a i r of eggs and enough gelatine to support t h e m w e r e cut out and the b l o c k s were p l a c e d i n a j a r of c o l d w a t e r . T h i s a l l o w e d t h e m to be e a s i l y managed without the gelatine d i s s o l v i n g . One b l o c k of each of the four c o l o r c o m b i n a t i o n s was taken f r o m i t s j a r to f o r m a group near the edge of a wet p l e x i g l a s s plate.  E n o u g h groups  w e r e f o r m e d to p r o v i d e a complete feeding for one f i s h , plus some e x t r a s .  A  group of four b l o c k s was fed to a f i s h i n a s i m i l a r manner as i n e x p e r i m e n t I by s l i d i n g the b l o c k s through the hole i n the roof.  The f i s h had t i m e to s t r i k e  at the b l o c k s w h i l e they drifted down f r o m the surface to the g r i l l i n the b o t t o m of the tank.  The gelatine binding the eggs together was i n v i s i b l e to the human  eye when the b l o c k s were i n the w a t e r . U s u a l l y a f i s h s t r u c k at and s w a l l o w e d both eggs i n a b l o c k at once; only o c c a s i o n a l l y d i d it eat f i r s t one egg and then the o t h e r .  If this d i d  happen, the r e s u l t s for that s e r v i n g w e r e deleted u n l e s s the f i s h ate the second egg before s t r i k i n g at another b l o c k .  None of the f i s h c o u l d take the intended  twenty s e r v i n g s , so each was fed as many s e r v i n g s as it would take.  Feeding  was stopped when the f i s h r e p e a t e d l y s t r u c k at no m o r e than one b l o c k or when it r e g u r g i t a t e d p a r t s of p r e v i o u s l y eaten eggs.  One feeding w i t h each  c o l o r of tag was done i n a l l four t a n k s . The o r d e r i n w h i c h the b l o c k s w e r e eaten was r e c o r d e d , the c o l o r of food being designated by the non-tag egg.  A value of 2 was g i v e n for a f i r s t  c h o i c e and a value of 1 for second c h o i c e .  These w e r e then t o t a l l e d and d i v i d e d  by 2n (n=the number of s e r v i n g s that a f i s h would take), and c o n v e r t e d to a  46  p e r cent.  The per cent was i n t u r n c o n v e r t e d u s i n g the a r c s i n t r a n s f o r m a t i o n  and an a n a l y s i s of v a r i a n c e was done on the  transformants.  2. R e s u l t s  R e d food was the f a v o r i t e , f o l l o w e d by yellow, green,  and blue food  w i t h s e l e c t i o n i n t e n s i t i e s 49 per cent, 43 p e r cent, 42 per cent and 34 p e r cent r e s p e c t i v e l y of the m a x i m u m p o s s i b l e , i . e . , if that c o l o r of food w e r e chosen f i r s t e v e r y t i m e (see Table X I I ) .  R e d , yellow, and g r e e n food a r e i n  the same o r d e r w i t h r e s p e c t to e a c h other as i n feeding e x p e r i m e n t I, but blue s l i p p e d f r o m second to fourth p l a c e .  The i n t e r a c t i o n between the tag egg and  the food egg (the effect of having b i - c o l o r e d food) was s i g n i f i c a n t at the .001 probability level.  In g e n e r a l , having a tag w i t h a c o l o r w i d e l y s e p a r a t e d i n  the s p e c t r u m f r o m that of the food enhanced the s e l e c t i o n for that c o l o r of food. The effect of feeding the t r o u t i n different c o l o r s of tank was a l m o s t s t a t i s t i c a l l y significant, but it i s not evident just what t h i s effect c o n s i s t e d of.  It  does not s e e m to be c e n t e r e d a r o u n d either the c o m p l e m e n t a r y c o l o r effect or the camouflage effect.  A s the s e c o n d - o r d e r i n t e r a c t i o n was used as the  e r r o r t e r m i n the a n a l y s i s of v a r i a n c e , nothing c a n be s a i d about the effect of feeding c o l o r s of food w i t h c o l o r s of tag i n different c o l o r e d t a n k s .  3. . D i s c u s s i o n The strong tag c o l o r x food c o l o r i n t e r a c t i o n effects a r e manifest as the effect of c o m p l e m e n t a r y c o l o r s and the effect of d i v e r s i t y of c o l o r (Table XIII), both of w h i c h are shown to be s i g n i f i c a n t w i t h the t - t e s t (a-.05).  The effect of  d i v e r s i t y of c o l o r i s analogous to the camouflage e f f e c t o f the tank c o l o r x food c o l o r i n t e r a c t i o n s of e x p e r i m e n t s I and II except that a s i m i l a r c o l o r e d tag egg cannot r e a l l y be thought of as c a m o u f l a g i n g the food egg. that the two eggs " l a c k d i v e r s i t y of c o l o r " .  Instead,  it i s s a i d  In c o n t r a s t to the c o l o r of tank x  c o l o r of food effect of e x p e r i m e n t I, the s u m of the absolute v a l u e s of the i n t e r a c t i o n effects was least for the r e d c o l o r of food and for the r e d c o l o r of tag.  T h i s means that t h e r e was the s m a l l e s t difference i n s e l e c t i o n i n t e n s i t i e s  47  TABLE  XII.  Red Tank  Yellow Tank  G r e e n Tank  Blue T a n k  ANOVA  S e l e c t i o n i n t e n s i t i e s of b i - c o l o r e d food in v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973. A N O V A table f r o m the a n a l y s i s of the data. The highest p o s s i b l e s e l e c t i o n i n t e n s i t y for a feeding (if that c o l o r is c h o s e n f i r s t e v e r y time) is 90.  Tag Color  Red  Color Yellow  Red Yellow Green Blue  36.9 18.4 49.6 33.2  15.4 0.0 54.7 63.4  45.0 90.0 35.2 26.6  49.0 45.0 0.0 33.2  138.1  133.5  196.8  127.2  39.2 54.9 60.0 48.4  45.0 24.3 56.8 62.0  26.6 45.0 22.8 32.0  42.1 32.6 0.0 0.0  20 2.5  188.1  126.4  74.7  37.8 42.1 60.0 39.2  48.6 22.8 45.0 47.9  41.4 50.8 16.7 26.6  37.8 42.1 24.1 39.2  179.1  164.3  135.5  143.2  35.2 43.2 55.7 52.2  24.1 30.0 34.3 47.4  48.3 41.4 31.5 20.7  45.0 37.8 34.3 32.7  186.3  135.8  141.9  149.8  Red Yellow Green Blue  Red Yellow Green Blue  Red Yellow Green Blue  of  Food Green  Blue  EY  =  706.0  621.7  600.6  494.9  Y  =  44.125  38.856  37.537  30.931  TABLE Source  df  MS  Probability  Food Color Tank color x F o o d color Tag color x F o o d color Error  3 9 9 27  472 295 936 153  .025 < p < .05 .05 < p < .10 p « .001  2423.2  48 TABLE  XIII.  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects f o r c o l o r s of food w i t h v a r i o u s c o l o r s of t a g . F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973. N u m b e r s i n p a r e n t h e s e s i n T a b l e X I I I B a r e c o r r e c t i o n f a c t o r s , , as e x p l a i n e d in T a b l e V I I . . B e c a u s e the s e l e c t i o n i n t e n s i t i e s of feeding e x p e r i m e n t II w e r e b a s e d on feedings having different n u m b e r s of s e r v i n g s , a g r e a t e r amount of r a n d o m e r r o r was i n t r o d u c e d when c a l c u l a t i n g the a r c s i n of the p e r c e n t s e l e c t i o n intensity than o c c u r r e d i n s i m i l a r c a l c u l a t i o n s f o r f e e d i n g e x p e r i m e n t I. T h e v a l u e s i n T a b l e XIIIB have b e e n c o r r e c t e d for t h i s r a n d o m e r r o r as w e l l as for the food c o l o r effect; so they a r e not e q u a l to the v a l u e s i n T a b l e XIIIA m i n u s the c o r r e c t i o n f a c t o r .  Uncorrected for Food C o l o r Effect  Tag Color Red Yellow Green Blue  Red  Food Color Green Yellow  Blue  37.28 39.65 56.32 43.25  33.28 19.28 47.70 55.18  40.32 56.80 26.55 26.48  43.48 39.38 14.60 26.28  176.50  155.44  150.15  123.74  C o r r e c t e d for F o o d C o l o r E f f e c t  Tag Color  Red (+6.26)  . Food Color Green Yellow (-.33) (+1.0)  Red Yellow Green Blue  30.29 32.48 51.63 37.06  31.55 17.37 48.27 54.25  39.92 56.22 28.45 26.88  49.68 45.40 23.10 33.28  151.46  151.44  151.47  151.46  Blue (-6.93)  Interaction Effects  Tag Color  Red  Red Yellow Green Blue  - 7.57 - 5.38 +13.77 .80  EY  +  S|Y|  Food Color Yellow Green  Blue  - 6.31 -20.49 +10.41 +16.39  + 2.06 +18.36 - 9.41 -10.98  +11.82 + 7.54 -14.76 - 4.58  +  +  .02  0.00  27.52  53.60  .03  40.81  27.76 51.77 48.35 32.75  .02 38.70  160.63  due to being fed w i t h different c o l o r s of tag for the r e d - c o l o r e d food.  The  r e d egg p l a y e d the g r e a t e s t r o l e i n setting the o v e r a l l p r e f e r e n c e for the " p a c k e t " of food. or down.  The other egg m o d i f i e d this l e v e l of p r e f e r e n c e a l i t t l e up  On the other hand, the p r e f e r e n c e l e v e l f o r the y e l l o w food was  h i g h l y influenced by the c o l o r of the other egg i n the packet.  T h e r e was Little  difference i n the sums of the absolute values of the i n t e r a c t i o n effects for the g r e e n eggs and the blue eggs, both of t h e m l y i n g i n a p o s i t i o n i n t e r m e d i a t e to those for the y e l l o w eggs and r e d eggs.  These sums of absolute v a l u e s of  i n t e r a c t i o n effects are r e a l l y a m e a s u r e of the dominance of one c o l o r over others i n setting the o v e r a l l p r e f e r e n c e l e v e l for a packet of food; the Lower the sum, the g r e a t e r i s the d o m i n a n c e of that food c o l o r i n setting the l e v e l of p r e f e r e n c e .  (The i n t e r a c t i o n effects a r e not m e a s u r e s r e l a t i v e to the  s t r e n g t h of the food c o l o r , but a r e absolute m e a s u r e s of the amount that the tag c o l o r adds or s u b t r a c t s f r o m the p r e f e r e n c e l e v e l of the v a r i o u s c o l o r s of food.) It i s perhaps s i g n i f i c a n t that the i n t e r a c t i o n effect for R R (the r e d c o l o r e d tag w i t h the r e d - c o l o r e d food) i s the m o s t negative of any i n i t s c o l u m n or r o w .  E v i d e n t l y , the effect of g i v i n g a double dose of r e d i s not as " f a v o r a b l e  as m a k i n g one egg r e d and the other egg another c o l o r - - any other c o l o r . A g a i n , d i v e r s i t y of c o l o r i s shown to be i m p o r t a n t i n e l e v a t i n g the s e l e c t i o n intensity. The effect of the c o l o r of tank on the s e l e c t i o n of v a r i o u s c o l o r s of food i s not e a s i l y i d e n t i f i e d .  A l t h o u g h a c a m o u f l a g i n g effect c o u l d be i n t e r p r e t e d  for the r e d and g r e e n tanks, the effect of s i m i l a r c o l o r e d food i n the y e l l o w and blue tanks was to i n c r e a s e t h e i r s e l e c t i o n i n t e n s i t i e s to the m a x i m u m . The effect of having the tank c o l o r and the food c o l o r w i d e l y s e p a r a t e d in the s p e c t r u m was to s l i g h t l y d e c r e a s e the s e l e c t i o n i n t e n s i t y r a t h e r than to i n c r e a s e it  (see T a b l e X V ) .  L o o k i n g at the data (Table X I V ) , it i s difficult to see any-  thing but a r a n d o m d i s t r i b u t i o n of effects. these r e s u l t s since  P e r h a p s that i s how we should v i e w  p was between .0 5 and .10.  1  50  TABLE  XIV.  M e a n s e l e c t i o n i n t e n s i t i e s and i n t e r a c t i o n effects f o r c o l o r s of food i n v a r i o u s c o l o r s of tank. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973. Numbers i n parentheses in T a b l e X I V B a r e c o r r e c t i o n f a c t o r s , as e x p l a i n e d i n T a b l e V I I . T h e v a l u e s i n T a b l e X I V B have b e e n c o r r e c t e d f o r the r a n d o m e r r o r i n t r o d u c e d i n c a l c u l a t i n g the s e l e c t i o n i n t e n s i t i e s , as e x p l a i n e d i n T a b l e XIII.  U n c o r r e c t e d for F o o d C o l o r  Tank Color Red Yellow Green Blue  Effect  Red  Food Yellow  Color Green  Blue  34.52 50.62 44.78 46.58  33.38 47.02 41.08 33.95  49.20 31.60 33.88 35.48  31.80 18.68 35.80 37.45  176.50  155.43  150.16  123.73  605.82 Y = 37.86  C o r r e c t e d for F o o d C o l o r  Tank Color  Red Yellow Green Blue  Effect  Red (+6.26)  Food Yellow (+0.99)  28.90 45.24 37.50 39.82 151.46  Color (-0-32)  Blue (-6.93)  33.03 46.91 39.07 32.46  50.16 32.80 33.18 35.30  39.37 26.49 41.71 43.88  151.45  151.46  151.45  Green  Interaction Effects  Tank Color  Red  Red Yellow Green Blue  - 8.96 + 7.38 .36 + 1.96  EY E|Y|  +  .02 18.66  Green  Blue  ELIL  4.83 9.05 1.21 5.40  +12.30 - 5.06 - 4.68 - 2.56  + 1.51 -11.37 + 3.85 + 6.02  27.60 32.86 10.10 15.94  .03  0.00  20.49  24.60  Yellow  +  +  .01 22.75  86.50  TABLE XV.  Effect of wide s p e c t r a l s e p a r a t i o n of food c o l o r and tank c o l o r on food c o l o r x tank c o l o r i n t e r a c t i o n effects of feeding e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973. 1  Note: Wide s p e c t r a l s e p a r a t i o n is defined as c o m b i n a t i o n s w h e r e one of the c o l o r s i s r e d and the other i s g r e e n or blue (RG, R B , GR, B R ) or the c o m b i n a t i o n of y e l l o w and blue ( Y B or B Y ) . T h e s e c o l o r s w i l l be r e f e r r e d to as " c o m p l e m e n t a r y " , although they may not be t r u e p s y c h o p h y s i c a l c o m p l e m e n t s . A l l other c o m b i n a tions are s i m p l y designated " n o n - c o m p l e m e n t a r y " .  Complementary Colors  Non-Complementary Colors  Combination  I n t e r a c t i o n Effect  Combination  GR BR BY RG RB YB  .36 + 1.96 - 5.40 +12.30 + 1.51 -11.37  RR YR RY YY GY YG GG BG GB BB  EY  -  Y  1.36 .23  I n t e r a c t i o n Effect + + + + +  8.96 7.38 4.83 9.05 1.21 5.06 4.68 2.56 3.85 6.02  + 1.42 +  .14  52 Why should t h e r e have been s u c h a strong effect of tank c o l o r i n e x p e r i m e n t I and supposedly none i n e x p e r i m e n t II?  The most obvious  r e a s o n i s that i n e x p e r i m e n t II the effect of feeding a g i v e n c o l o r of egg i n a g i v e n c o l o r of tank was g r e a t l y d i l u t e d since this c o m b i n a t i o n was p r e s e n t e d w i t h four different c o l o r s of tag egg.  F o r each packet of food t h e r e w o u l d  a c t u a l l y be two i n t e r a c t i o n s between tank c o l o r and c o l o r of egg: that between the tank c o l o r and food egg, and the one between the tank c o l o r and tag egg. F u r t h e r m o r e , i n e x p e r i m e n t I each f i s h was fed t w i c e in e a c h c o l o r of tank, m a k i n g a t o t a l of eight r e p l i c a t e s over w h i c h a tank c o l o r i n t e r a c t i o n effect c o u l d make i t s e l f evident.  In e x p e r i m e n t II one f i s h was fed i n e a c h  tank for each c o l o r of tag, m a k i n g a total of only four r e p l i c a t e s over w h i c h to p i c k out the tank c o l o r i n t e r a c t i o n effect.  A l s o , the f o r m e r e x p e r i m e n t a l  d e s i g n makes it p o s s i b l e to separate out the effects of i n d i v i d u a l d i f f e r e n c e s among the f i s h f r o m the effects of the .color of tank.  In e x p e r i m e n t II it i s  quite p o s s i b l e that the i n t e r a c t i o n effect i n v o l v i n g i n d i v i d u a l d i f f e r e n c e s c o u l d w o r k against that i n v o l v i n g tank c o l o r , and thus l e s s e n the i m p o r t a n c e of the latter. A l t h o u g h i t was not p o s s i b l e to evaluate the c o m b i n e d effect of tank c o l o r and tag c o l o r on the s e l e c t i o n of food (because this s e c o n d - o r d e r i n t e r a c t i o n was used as the. e r r o r t e r m in the A N O V A ) ,  it i s p o s s i b l e to c a t e g o r i z e  e a c h o b s e r v a t i o n on the b a s i s of the d i v e r s i t y of c o l o r shown among food c o l o r , tank c o l o r , and tag c o l o r .  Thus, for 24 of the o b s e r v a t i o n s the food c o l o r i s  different f r o m both the tank c o l o r and the tag c o l o r ; for 36 o b s e r v a t i o n s t h e r e are two c o l o r s s i m i l a r ; and for four o b s e r v a t i o n s a l l three c o l o r s are the s a m e . H a v i n g d i v i d e d the data up i n this manner (see Table X V I ) ,  one can see that  both the coefficient of v a r i a n c e ( C V ) and the m e a n s e l e c t i o n i n t e n s i t y (Y) i n c r e a s e w i t h d i v e r s i t y of c o l o r .  53 T A B L E XVI.  S e l e c t i o n i n t e n s i t i e s f r o m feeding e x p e r i m e n t II grouped a c c o r d i n g to s i m i l a r i t y of c o l o r s of tank, tag egg, and food egg. F e e d i n g e x p e r i m e n t II, U n i v e r s i t y of B . C . , J u l y 23 to A u g u s t 3, 1973. C V = coefficient of v a r i a n c e . See text for e x p l a n a t i o n .  No C o l o r s S i m i l a r 54.7 63.4 90.0 26.6 45.0 0.0 60.0 48.4 26.6 32.0 42.1 0.0 42.1 39.2 48.6 47.9 37.8 42.1 43.2 55.7 24.1 34.3 48.3 41.4  EY n Y CV  993.5 24 41.4 45.34%  Two C o l o r s S i m i l a r 18.4 49.6 33.2 15.4 45.0 49.0 0.0 35.2 33.2 45.0 56.8 62.0 54.9 45.0 32.6 39.2 22.8 0.0 41.4 50.8 26.6 60.0 45.0 24.1 37.8 22.8 39.2 45.0 37.8 34.3 52.2 47.4 20.7 35.2 30.0 31.5 1319.1 36 36.6 40.47%  Three Colors. Similar  36.9 24.3 16.7 32.7  110.6 4 27.65 32.49%  54 INCIDENTAL OBSERVATIONS  A.  Effect of B a c k g r o u n d C o l o r on A c t i v i t y L e v e l of T r o u t In the c o u r s e of c a r r y i n g out the feeding e x p e r i m e n t s two i n c i d e n t a l  o b s e r v a t i o n s w e r e made w h i c h c o u l d suggest a d i r e c t i o n for further  study.  P r e l i m i n a r y tests on these ideas are d e s c r i b e d b e l o w . _ A t c e r t a i n t i m e s (e.g., when the stock tank was being c l e a n e d or r e p a i r e d ) , the stock of trout was d i s t r i b u t e d among four s m a l l tanks that w e r e painted the same c o l o r s (red, yellow, g r e e n and blue) as the e x p e r i m e n t a l tanks.  D u r i n g many c a s u a l o b s e r v a t i o n s , I n o t i c e d that the f i s h i n the y e l l o w  tank s e e m e d to be m u c h m o r e a c t i v e than those i n the r e d , g r e e n or blue tanks. In an attempt to v e r i f y this o b s e r v a t i o n , the f o l l o w i n g e x p e r i m e n t was c a r r i e d out. 1. M e t h o d s S i x f i s h c h o s e n at r a n d o m f r o m the stock w e r e p l a c e d i n e a c h of the four e x p e r i m e n t a l tanks:  r e d , yellow, g r e e n and blue. A n 8 m i l l i m e t e r s u p e r - 8  m o v i e c a m e r a was p l a c e d face down on the r o o f of the tank so that the lens " l o o k e d " through the hole through w h i c h the f i s h had p r e v i o u s l y been fed.  The  f i e l d of v i s i o n i n c l u d e d about f i v e - s i x t h s of the length of the tank and a l l of the width.  B r i g h t n e s s of i l l u m i n a t i o n was set to the same v a l u e s as i n feeding  e x p e r i m e n t II (7 2 l u x at the 32 c m depth). The f i s h w e r e fed on the day of t r a n s f e r and g i v e n 24 h o u r s to settle. They were then f i l m e d in 1 5 - s e c o n d " s h o t s " i n each of the four tanks. o r d e r of f i l m i n g was r a n d o m i z e d for each set of four shots.  The  A t least thirty  minutes was left between sets of shots so that the a c t i v i t y l e v e l of the f i s h d u r i n g one shot would not be a " l e f t o v e r " f r o m the p r e v i o u s set of shots.  Five  sets of shootings were done on J u l y 19. after w h i c h the f i s h had to be r e m o v e d f r o m these tanks.  L a t e r , on A u g u s t 6, another s i x f i s h c h o s e n at r a n d o m f r o m  the stock were put into each of the tanks and left for 24 h o u r s .  The f i l m i n g  55 p r o c e d u r e was r e p e a t e d  t h r e e sets of shots w e r e t a k e n - - and then the f i s h  w e r e t r a n s f e r r e d f r o m one tank to the other as f o l l o w s : to r e d to blue.  blue to g r e e n to y e l l o w  They w e r e left for another 24 h o u r s and then two sets of shots'  w e r e taken. A m e a s u r e m e n t of a c t i v i t y l e v e l was obtained i n the f o l l o w i n g manner for e a c h r o l l of f i l m . a wall.  The p r o j e c t o r was set up and the f i l m was shown against  A line of b l a c k t h r e a d was h e l d on the w a l l w i t h pins so that it b i s e c t e d  d i a g o n a l l y the p r o j e c t e d p i c t u r e .  The n u m b e r of t i m e s any f i s h s w a m " a c r o s s "  the line was t o t a l l e d for e a c h 1 5 - s e c o n d shot.  A s some of the shots w e r e  s l i g h t l y longer than 15 seconds, e a c h total was adjusted to an exact t i m e of twenty seconds by m u l t i p l y i n g the t o t a l by twenty d i v i d e d by the d u r a t i o n of the shot i n seconds ( m e a s u r e d w i t h a stop-watch). A l t o g e t h e r , ten shots w e r e taken i n e a c h c o l o r of tank w i t h t h r e e different groups of fish, and so the data w e r e b l o c k e d as shown i n T a b l e X V I I , and a n a l y z e d w i t h a t w o - w a y A N O V A (a = .0 5).  2. R e s u l t s The c o l o r of tank had a m a r k e d effect on the a c t i v i t y . l e v e l of the f i s h . The f i s h w e r e most active i n the y e l l o w tank and l e a s t a c t i v e i n the g r e e n tank, w i t h i n t e r m e d i a t e l e v e l s for the r e d and blue tanks.  A s it was o r i g i n a l l y  postulated that t h e r e would be a higher a c t i v i t y l e v e l i n the y e l l o w tank,  an  a p r i o r i test of the y e l l o w t r e a t m e n t m e a n v e r s u s "the o t h e r s " showed a significant difference ato = .0 5. ,  A n a p o s t e r i o r i test of the g r e e n t r e a t m e n t  mean v e r s u s the r e d and blue means c o m b i n e d was a l s o s i g n i f i c a n t at the .0 5 l e v e l of p r o b a b i l i t y .  N e i t h e r group d i f f e r e n c e s nor the i n t e r a c t i o n between the  groups and the c o l o r s of tank were s t a t i s t i c a l l y s i g n i f i c a n t .  3. D i s c u s s i o n T h i s e x p e r i m e n t d e m o n s t r a t e s that a y e l l o w b a c k g r o u n d c a u s e s an  56  T A B L E XVII.  M e a s u r e s of a c t i v i t y l e v e l s of f i s h i n d i f f e r e n t c o l o r e d h a b i t a t s . A N O V A table f r o m , the a n a l y s i s of t h i s d a t a . E a c h value r e p r e s e n t s a m e a s u r e of the a c t i v i t y l e v e l of a g r o u p of six f i s h in a p a r t i c u l a r c o l o r of tank, and is a p p r o x i m a t e l y e q u a l to the n u m b e r of t i m e s any f i s h c r o s s e d f r o m one side of the tank to the other i n a 20 s e c o n d interval. D a t a a r e d i v i d e d into t h r e e g r o u p s of f i l m i n g s ("shootings") u s i n g different f i s h for e a c h g r o u p .  Color G r o u p Nunber 1  ANOVA  TABLE  of  Tank  Red  Yellow  Green  Blue  10.13 16T2 5 6.52 4.94 11.76  19.23 8.86 9.26 11.39 13.92  2.53 5.41 9.00 0.00 10.53  6.90 13.33 12.00 8.86 6.49  49.60  62.66  27.47  47.58  8.54 12.82 12.35  8.97 11.11 23.08  8.86 7.41 9.76  13.41 6.33 10.53  33.71  43.16  26.03  30.27  16.25 13.16  15.00 10.13  10.13 1.33  13.75 17.50  29.41  25.13  11.46  31.25  97.25  112.72  130.95  64.96  109.10  417.73  Source  df  MS  Probability  C o l o r of tanks Groups G r o u p s x C o l o r of T a n k s Error  3 2 6 28  79 26 11 17.25  x < .001 .10 < x < .25 x >.7 5  EY  187.31  133.17  57  i n c r e a s e i n the l e v e l of a c t i v i t y over that for r e d or blue, while a g r e e n background causes a d e c r e a s e .  If the average speed of s w i m m i n g r e f l e c t s the  average m e t a b o l i c rate of the fish, then i t i s p o s s i b l e that f i s h r a i s e d i n a y e l l o w tank a r e using up m o r e energy in maintenance and c h a n n e l l i n g l e s s into g r o w t h .  The r e s u l t s of the e x p e r i m e n t s e e m to support the t r a d i t i o n a l  h a t c h e r y p o l i c y of painting f i s h ponds and tanks a g r e e n - b l u e (turquoise) c o l o r . H o w e v e r , B u r r o w s (1969), i n h i s study of the influence of f i n g e r l i n g q u a l i t y on the s u r v i v a l of adult s a l m o n , as w e l l as noting that s i z e of f i s h at t i m e of r e l e a s e had a positive effect on the s u r v i v a l of adults, found that those f i s h that had been e x e r c i s e d d u r i n g t h e i r r e a r i n g had a h i g h e r rate of r e t u r n of adults to the h a t c h e r y than f i s h that had not been e x e r c i s e d .  He therefore sug-  gested using ponds i n w h i c h a h i g h v e l o c i t y of water c o u l d be m a i n t a i n e d . Whether or not an adequate e x e r c i s e l e v e l could be m a i n t a i n e d t h r o u g h adjusting the b a c k g r o u n d c o l o r of the tank i s , p e r h a p s , w o r t h i n v e s t i g a t i n g .  B.  A d a p t a t i o n of S k i n of T r o u t to B a c k g r o u n d C o l o r The second thing n o t i c e d was the high degree to w h i c h the t r o u t w e r e  able to adapt the c o l o r of t h e i r s k i n to that of the tank c o l o r .  T h i s adaptation  c o n s i s t e d not only i n a change of the lightness or d a r k n e s s of the s k i n , but i n a c o n v i n c i n g matching of the b a c k g r o u n d hue.  It was planned to leave s e v e r a l  f i s h i n each c o l o r of tank for two days, then photograph t h e m and a n a l y z e the t r a n s p a r e n c i e s a c c o r d i n g to a s p e c t r o p h o t o m e t r i c technique.  T h i s I s t a r t e d to o  do, but before a n a l y z i n g the photographs,  I became aware of a b a s i c flaw  this technique w h i c h r e n d e r e d any further a n a l y s i s of no v a l u e .  in  Therefore,  what I have to r e p o r t w i l l be r a t h e r subjective.  A l t h o u g h the photograph of the f i s h ' s s k i n might appear to the h u m a n eye to a c c u r a t e l y p o r t r a y the s k i n c o l o r , i n r e a l i t y only three p r i m a r y hues are c o m i n g f r o m it; what i s " s e e n " is a r e s u l t of the c a p a c i t y of the b r a i n to " b l e n d " those hues to f o r m a p e r c e p t i o n of a hue different f r o m any one of i t s c o m p o n e n t s . Of c o u r s e , a s p e c t r o p h o t o m e t e r would r e g i s t e r only the v a r y i n g amounts of these three p r i m a r y hues. W i t h perfect exposure one might be able to c a l c u l a t e the dominant wavelengths  58  L o o k i n g at a f i s h f r o m the side, I have somewhat a r b i t r a r i l y d i v i d e d the surface into three a r e a s , A , B , and C (see F i g u r e 6).  The a r e a that is  most g r e a t l y affected by the c o l o r of tank i s p r o b a b l y the d o r s a l s t r i p ( A r e a A).  T h i s i s where the g r e a t e s t range of hue and b r i g h t n e s s i s found, the  r e g i o n of s k i n that p r o v i d e s the c l o s e s t m a t c h to the hue and b r i g h t n e s s of the tank.  F o r the s i z e of f i s h that I was using, the w i d t h of the d o r s a l s t r i p was  2 - 3 c m (1.0 - 1.5 c m on either side of the d o r s a l fin), and it r a n f r o m the tip of the snout to the peduncle r e g i o n . A r e a B c o n s i s t s of the r e s t of the d o r s a l half of the f i s h to the l a t e r a l l i n e , and i s u s u a l l y a zone of fading f r o m the deep c o l o r of the d o r s a l s t r i p to the w h i t i s h c o l o r of the b e l l y r e g i o n .  S o m e t i m e s the l a t e r a l l i n e showed a  c o l o r d i f f e r i n g f r o m that of the s u r r o u n d i n g skin, and i f so, this i s noted i n Table X V I I I .  The r e m a i n d e r of the side is c a l l e d a r e a C, and it i s the l i g h t e s t  part of the f i s h . The t e r m s used to d e s c r i b e c o l o r s of s k i n and s i z e of spots i n T a b l e X V I I I are subjective and good only for c o m p a r a t i v e p u r p o s e s .  No m e a s u r e -  ments w e r e taken; however, c o m p a r i s o n s between f i s h f r o m different tanks w e r e checked w i t h the a i d of the c o l o r s l i d e s . On June 12, 1973, a l l of the f i s h i n the stock tank were cold-branded on the d o r s a l s t r i p near the d o r s a l f i n on the left side of the body.  (A b l a c k  footnote 8 continued of l i g h t r e f l e c t e d f r o m the f i s h ' s s k i n if: ( 1 ) the f i l m a c c u r a t e l y r e p r o d u c e d the c o l o r of the s k i n ; and (2) one knew a f o r m u l a for c a l c u l a t i n g the " p s y c h o l o g i c a l " hue r e s u l t i n g f r o m the blending of the f i l m ' s p r i m a r y c o l o r s . M y p i c t u r e s tended to be r a t h e r underexposed, and I had no way of a s c e r t a i n i n g the s e n s i t i v i t y of the f i l m dyes to c o r r e c t for u n d e r e x p o s u r e . In short, I was not "set up" for the c o m p l e x i t y and s o p h i s t i c a t i o n of technique r e q u i r e d for such an e x p e r i m e n t .  F i g u r e 6.  R e g i o n s of s k i n for s k i n c o l o r o b s e r v a t i o n s . Incidental o b s e r v a t i o n s , (See text for explanation.)  TABLE  XVIII.  of f i s h f r o m  d i f f e r e n t c o l o r e d tanks.  D e s c r i p t i o n  C o l o r of Tank  Red  D e s c r i p t i o n of s k i n c o l o r  Region A  of  Incidental observations.  Skin  Region B  Region  C  D a r k n e s s of s k i n : m e d i u m  R e g i o n of f a d i n g c o l o r to l a t e r a l  S i l v e r - w h i t e with a faint g r e e n i s h  Hue;  line.  tinge.  brown-green  L a t e r a l line i s a p i n k i s h  color. L a r g e b l a c k spots a r e c o n s p i c u o u s .  L a r g e b l a c k spots.  B l a c k s p o t s s m a l l e r , but e x t e n d i n g to m i d - v e n t r a l l i n e .  Yellow  D a r k n e s s of s k i n : l i g h t  R e g i o n of f a d i n g g o l d c o l o r to l a t e r a l  S i l v e r - w h i t e with perhaps a slight  Hue:  line.  y e l l o w i s h tinge.  greenish gold  Lateral line has a pinkish  color. B l a c k spots h a v e a l m o s t f a d e d out  O n l y the s l i g h t e s t v e s t i g e of b l a c k  by l a t e r a l l i n e .  s p o t s b e n e a t h the l a t e r a l l i n e .  R e g i o n of f a d i n g g r e e n c o l o r to l a t e r a l line.  B e l l y r e t a i n s s l i g h t b l u i s h - g r e e n tint on white s k i n .  L a r g e b l a c k spots p a r t l y camouf l a g e d by d a r k g r e e n b a c k g r o u n d .  B l a c k spots d e c r e a s i n g i n size.  B l a c k s p o t s continue to d e c r e a s e i n s i z e and f r e q u e n c y to h a l f w a y b e t w e e n l a t e r a l l i n e and m i d - v e n t r a l r e g i o n w h e r e they s t o p - - b o t t o m h a l f of b e l l y without s p o t s .  D a r k n e s s of s k i n :  very  R e g i o n of f a d i n g g r e e n - b l u e  Hue:  deep  S m a l l black spots.  Green  D a r k n e s s of s k i n : Hue:  Blue  dark dark  green  dark green-blue  L a r g e b l a c k s p o t s d i f f i c u l t to p i c k out a g a i n s t d a r k g r e e n - b l u e ground.  back-  color  B e l l y r e t a i n s s l i g h t g r e e n - b l u e tint on  to l a t e r a l l i n e .  white  B l a c k spots d e c r e a s i n g i n size.  B l a c k s p o t s c o n t i n u e to d e c r e a s e i n  skin.  s i z e a n d f r e q u e n c y to h a l f - w a y  between  l a t e r a l l i n e and m i d - v e n t r a l r e g i o n , w h e r e they s t o p - - b o t t o m without s p o t s .  h a l f of b e l l y  61 b r a n d m a r k develops 2 to 3 days after b r a n d i n g ) .  Two months l a t e r some of  the b r a n d s had s t a r t e d to fade out, and those on f i s h f r o m the blue and g r e e n tanks w e r e e s p e c i a l l y d i f f i c u l t to r e a d .  Some of the b r a n d s w e r e a c t u a l l y  i l l e g i b l e and c o u l d not be r e a d even on c l o s e i n s p e c t i o n .  H o w e v e r , upon  t r a n s f e r r i n g the f i s h to the y e l l o w tank (and to a l e s s e r extent the r e d tank), the b r a n d s could again be read, although they w e r e not as d a r k as i n i t i a l l y . T h i s I was able to do for about another month, when a l l of the b r a n d s w e r e faded, even those on f i s h kept i n y e l l o w tanks.  DISCUSSION  A.  Background Literature  1. C o l o r v i s i o n i n f i s h . E a r l y i n v e s t i g a t o r s r e l i e d on s e c o n d a r y r e s p o n s e s to test for c o l o r v i s i o n of f i s h .  G r a b e r (1884, 1885 ) and H e s s (1910, 1911, 1913, 1914 ) ob9  9  s e r v e d what s e c t i o n of tank a f i s h would s w i m to when v a r i o u s p a r t s of the tank w e r e i l l u m i n a t e d w i t h l i g h t of different w a v e l e n g t h s . White (1919) and H i n e l i n e (1927) t r a i n e d mudminnows, and B r o w n (1937) t r a i n e d b a s s to make a p o s i t i v e a s s o c i a t i o n of food w i t h a p a r t i c u l a r c o l o r and a negative a s s o c i a t i o n w i t h other c o l o r s .  They then tested the f i s h ' s a b i l i t y to d i s c r i m i n a t e between the  c o l o r s i n the c o m p l e t e absence of the c o n d i t i o n i n g s t i m u l i by o b s e r v i n g whether a p o s i t i v e ( s w i m m i n g towards) or negative ( s w i m m i n g away from) r e s p o n s e was e l i c i t e d upon p r e s e n t a t i o n of each c o l o r .  The f o r m e r type of  e x p e r i m e n t has been c a l l e d by W a r n e r (1931) the " p r e f e r e n c e method", and the l a t t e r ,  the " l e a r n i n g m e t h o d " .  Both types of e x p e r i m e n t have been  plagued by inadequate attempts to c o n t r o l for i n t e n s i t y d i f f e r e n c e s between test s t i m u l i that are supposed to d i f f e r - i n wavelength-only.  Quoted in B r o w n , 1937.  A t t e m p t s to  62 equate the l u m i n o s i t y of the s o u r c e s by p h o t o m e t r i c m e a s u r e m e n t are i r r e l e vant as the s e n s i t i v i t y c u r v e for the spectrophotometer the c u r v e of r e t i n a l s e n s i t i v i t y for the f i s h .  i s not l i k e l y to m a t c h  W h e r e these e x p e r i m e n t s have  had a m e a s u r e of s u c c e s s i s when they t e s t e d w i t h a wide range of hue i n t e n s i t i e s and then f o l l o w e d up w i t h d i s c r i m i n a t i o n tests between the c o l o r s and a s e r i e s of g r e y s of v a r y i n g i n t e n s i t i e s . A t h i r d l i n e of evidence i n v o l v e s m o d i f i c a t i o n s of s k i n p i g m e n t a t i o n of c e r t a i n fishes upon being exposed to different b a c k g r o u n d c o l o r s .  The s t r i k i n g  a b i l i t y of flounders to m i m i c the shade,  c o l o r and p a t t e r n of t h e i r b a c k g r o u n d  has been d e m o n s t r a t e d by M a s t (1 916).  He p r e s e n t s a n u m b e r of c o l o r photo-  graphs w h i c h attest to his d e s c r i p t i o n s of c o l o r changes i n the f i s h . That c o l o r change was m e d i a t e d t h r o u g h the eyes, effect of l i g h t on the c h r o m a t o p h o r e s ,  and not as a d i r e c t  was shown i n two w a y s .  e x p e r i m e n t s one or both eyes w e r e e x c i s e d .  In c e r t a i n  If only one eye was r e m o v e d ,  there would r e s u l t a t e m p o r a r y i n t e r f e r e n c e w i t h the adaptive p r o c e s s e s i n the skin; i f both eyes w e r e r e m o v e d , a permanent c e s s a t i o n of these p r o c e s s e s occurred,  such that changes in b a c k g r o u n d had no apparent effect on the appear-  ance of the s k i n .  In other e x p e r i m e n t s the f i s h was found r e s t i n g ,  or was  p l a c e d at the d i v i d i n g l i n e i n a tank painted half b l a c k and half w h i t e .  It was  found to take w h i c h e v e r shade the head (eyes) of the f i s h was r e s t i n g o v e r . If the f i s h was p l a c e d lengthwise so that one eye was on e i t h e r side of the d i v i d i n g l i n e , it adapted to an i n t e r m e d i a t e shade.  S i m i l a r r e s u l t s w e r e obtained when  the hue was v a r i e d . Once it was c e r t a i n that these r e s p o n s e s w e r e m e d i a t e d t h r o u g h the eye, they p r o v e d to be good evidence for the existence of c o l o r v i s i o n because,  if  the f i s h was able to p e r c e i v e differences in hue only as differences in b r i g h t ness, there was no explanation as to how it was able to m a t c h the hue of its s k i n to that of the e n v i r o n m e n t . A s the e a r l y e x p e r i m e n t e r s r e f i n e d t h e i r techniques they c o n t r o l l e d the  63 b r i g h t n e s s factor m o r e effectively,  and soon evidence was mounting for c o l o r  v i s i o n i n a number of s p e c i e s of f i s h .  A t the same t i m e , m o r e d i r e c t e v i d e n c e  was being sought by f o c u s s i n g on the r e t i n a . that the r e t i n a had two types of r e c e p t o r c e l l s :  It had been known for a long t i m e r o d s and c o n e s .  In 1802,  T h o m a s Young had suggested that c o l o r v i s i o n depended upon the p r e s e n c e of at l e a s t three r e c e p t o r substances,  e a c h m a x i m a l l y s e n s i t i v e to different  r e g i o n s of the s p e c t r u m . A n d i n 1866 M a x S c h u l t z e had stated that the cone i s the r e c e p t o r for photopic v i s i o n while the r o d i s the r e c e p t o r for scotopic v i s i o n ; and f u r t h e r m o r e ,  that the cone alone i s r e s p o n s i b l e for c o l o r v i s i o n ,  since i n d i m light c o l o r s are not v i s i b l e - - e v e r y t h i n g i s seen i n shades of grey.  But for a long time h i s t o p h y s i o l o g i c a l techniques w e r e not capable of  an e x a m i n a t i o n of the pigments f r o m i n d i v i d u a l cones, nor a d e t e r m i n a t i o n of t h e i r nervous a c t i v i t y . In the late 1950s and e a r l y 1960s the technique of m i c r o spectrophoto m e t r y a l l o w e d v a r i o u s w o r k e r s to d e t e r m i n e the a b s o r p t i o n s p e c t r a of the pigments i n i n d i v i d u a l cone c e l l s .  M a r k s (1965) d e t e r m i n e d the s p e c t r a l  s e n s i t i v i t y c u r v e s for 113 g o l d f i s h cones; eighteen had t h e i r w a v e l e n g t h of m a x i m u m a b s o r p t i o n near 450 my, 66 near 530 my, 24 near 630 my, 2 near 570 mp., and 3 near 480 m|ji.  The two n e a r 570 my w e r e not f r o m s p e c t r a of  s i n g l e cones, but f r o m the c o m p o s i t e s p e c t r a of touching t w i n cones; the three near 480 my w e r e p r o b a b l y the r e s u l t of a g r e a t e r tendency for v a r i a t i o n i n wavelength m a x i m u m (X max) i n the blue due to m o r e p r o m i n e n t photoproducts, or because m i s a l i g n m e n t c a u s e d m o r e c h r o m a t i c m o t i o n of the b e a m i n the blue.  T a k i n g this into c o n s i d e r a t i o n , these data i n d i c a t e there are j u s t three  types of cones i n the g o l d f i s h r e t i n a w i t h \ max near 450 my, 530 my, and 630 m y . B a k e r and R u s h t o n (1965b) have used the method of r e t i n a l d e n s i t o m e t r y to d e t e r m i n e the a c t i o n s p e c t r a for the r e d cone pigment (erythrolabe) of the n o r m a l human eye, and have c o m p a r e d it to that found for the r e d - s e n s i t i v e pigment i n the deuteranopic eye.  T h e i r method c o n s i s t e d of b l e a c h i n g the r e d  64  pigment w i t h deep r e d l i g h t and m e a s u r i n g the r e s u l t a n t change i n t r a n s m i s s i v i t y at the r e d end of the s p e c t r u m .  The m e a s u r e m e n t was made by shining a t h i n  p e n c i l of l i g h t through the center of the p u p i l to the fovea of the r e t i n a ,  where  i t p a s s e d t h r o u g h the pigmented l a y e r s , r e f l e c t e d f r o m the c h o r o i d and t r a v e l l e d along a s l i g h t l y different path back through the pupil to a p h o t o s e n s i t i v e c e l l , which measured its intensity.  T h i s i n t e n s i t y was c o m p a r e d to that c o m i n g  f r o m a v e r y deep r e d standard l i g h t (700 mjj.) s i m i l a r l y r e f l e c t e d t h r o u g h the retinal layers.  The dominant w a v e l e n g t h of this l a t t e r l i g h t was c h o s e n so that  a l l r e t i n a l pigments would be t r a n s p a r e n t to i t .  By i n s e r t i n g an o p t i c a l wedge  into the path of the light, i n t e n s i t i e s f r o m the test and c o n t r o l b e a m s c o u l d be b a l a n c e d , and the distance the wedge was i n s e r t e d would give a m e a s u r e of the change i n t r a n s m i s s i v i t y at the w a v e l e n g t h of the test l i g h t .  The w a v e l e n g t h of  the test light was v a r i e d to d e t e r m i n e the a c t i o n s p e c t r u m for that p i g m e n t . Unfortunately, the d e n s i t o m e t r i c method r e q u i r e s a c c u r a t e a l i g n m e n t of the beams of l i g h t being shone on the r e t i n a .  T h i s was attained for h u m a n sub-  j e c t s by use of a dental i m p r e s s i o n and b r o w r e s t , and by r e q u e s t i n g t h e m to fixate on a given spot.  F o r this r e a s o n r e t i n a l d e n s i t o m e t r y has l i t t l e p o t e n t i a l  for m e a s u r i n g photopigments of s p e c i e s other than man, but it has s u p p l i e d an opportunity to check the a c c u r a c y of other techniques w h i c h are m o r e a p p r o p r i a t e . The e l e c t r o r e t i n o g r a p h i c methods developed by S v a e t i c h i n and c o l l e a g u e s (Svaetichin and M a c N i c h o l , on e x c i s e d r e t i n a e .  1958) do not have these d r a w b a c k s , and can be used  B y i n s e r t i n g a m i c r o e l e c t r o d e into the r e t i n a ( f r o m b r e a m  or perch) to the a p p r o x i m a t e depth of the cone inner segments,  they w e r e able  to r e c o r d what they thought was the r e s t i n g potential of the cones  (about - 4 0 m v ) .  T h i s was later found to be one of the s o - c a l l e d "S p o t e n t i a l s " f r o m a deeper l a y e r . When light was shone onto the r e t i n a a change i n potential o c c u r r e d w h i c h l a s t e d throughout the t i m e when the light was on.  A c t u a l l y two separate  effects c o u l d be i s o l a t e d depending upon the depth at w h i c h the e l e c t r o d e s were placed.  The f i r s t effect,  c a l l e d the " l u m i n o s i t y r e s p o n s e " was o b s e r v e d when  the e l e c t r o d e was p o s i t i o n e d near the l a y e r of giant h o r i z o n t a l c e l l s .  It c o n -  65 s i s t e d of an i n c r e a s e d negative potential, r e g a r d l e s s of the wavelength of the stimulating light.  The " c h r o m a t i c i t y r e s p o n s e " i s perhaps the m o r e i n t e r e s t i n g  of the two w i t h r e s p e c t to c o l o r v i s i o n t h e o r y .  When the e l e c t r o d e was l o c a t e d  twenty to t h i r t y m i c r o n s deeper w i t h i n the inner n u c l e a r and p l e x i f o r m Layer a r e s p o n s e o c c u r r e d c h a r a c t e r i z e d by having two m a x i m a of opposite p o l a r i t y . These m a x i m a w e r e found either i n the y e l l o w and blue r e g i o n s of the s p e c t r u m or i n the r e d and g r e e n r e g i o n s .  B e t w e e n the m a x i m a there was a n e u t r a l  point where i l l u m i n a t i o n by l i g h t of that p a r t i c u l a r w a v e l e n g t h c a u s e d no i n c r e a s e or d e c r e a s e i n the p o t e n t i a l .  G e n e r a l l y the c h r o m a t i c i t y r e s p o n s e s  w e r e negative for those wavelengths s h o r t e r than the n e u t r a l point and p o s i t i v e for those wavelengths l o n g e r .  F u r t h e r , by c o m p a r i n g r i s e t i m e s and l a t e n c i e s  for the generated potentials f r o m short wavelength s t i m u l a t i o n v e r s u s long wavelength s t i m u l a t i o n it was found that the c h r o m a t i c i t y r e s p o n s e had two components g i v i n g potentials of opposite s i g n w h i c h w e r e somehow s u b t r a c t e d f r o m each other. When the e l c t r o d e was p o s i t i o n e d s t i l l deeper i n the g a n g l i o n l a y e r (site of the a c t u a l n e u r a l t r a n s m i s s i o n s to the b r a i n ) another dependent r e s p o n s e was r e c o r d e d .  frequency-  If the s t i m u l a t i o n l i g h t was of s h o r t wave-  length the g a n g l i o n c e l l s produced a b u r s t of i m p u l s e s when the l i g h t was t u r n e d on.  If the s t i m u l a t i n g l i g h t was of long wavelength, there was a  s u p p r e s s i o n of a c t i v i t y d u r i n g i l l u m i n a t i o n and a b u r s t of i m p u l s e s when the light was turned off.  It s e e m e d that the g a n g l i a r e c e i v e d connections f r o m  groups of r e c e p t o r s having s e n s i t i v i t i e s i n a number of r e g i o n s of the s p e c t r u m . B u t what i s known of the e l e c t r i c a l a c t i v i t y of the r e c e p t o r s  themselves?  T o m i t a e_t al_., (1 967) d e s c r i b e a technique w h e r e b y a m i c r o e l e c t r o d e i s ;  s l o w l y advanced through the r e t i n a l l a y e r s of a c a r p until a negative p o t e n t i a l is detected.  If the e l e c t r o d e is w i t h i n the r e c e p t o r l a y e r and no a r e a effect is  apparent the s p e c t r a l r e s p o n s e c u r v e s a r e then obtained and these a r e a s s u m e d to come f r o m a single cone.  Once these m e a s u r e m e n t s have been taken,  the  m i c r o e l e c t r o d e i s further advanced into the r e t i n a u n t i l an S - p o t e n t i a l is recorded.  T h i s is taken as further evidence that what was in fact m e a s u r e d  66 was the r e c e p t o r p o t e n t i a l . F r o m the a n a l y s i s of 142 c a r p r e c o r d s they found t h r e e groups of cones: 74 per cent had their peak r e s p o n s e i n the r e d (6ll+_23 my), 10 per cent peaked i n the g r e e n (529 +_14 my), and 16 per cent peaked i n the blue (462 + 15 my).  It  i s not known whether the r e s p e c t i v e percentages r e f l e c t e d the a c t u a l population d i s t r i b u t i o n for the three types of cone or whether they w e r e an a r t i f a c t of the sampling procedure. K o b a y a s h i and A l i (1971) used a s i m i l a r e l e c t r o r e t i n o g r a p h i c technique to m e a s u r e the photopic s p e c t r a l s e n s i t i v i t y for b r o o k trout ( S a l v e l i n i s f o n t i n a l i s ) a c l o s e r e l a t i v e of r a i n b o w t r o u t . measurement,  They d i d not i s o l a t e i n d i v i d u a l cones for  but r e c o r d e d the s u m m a t e d r e s p o n s e of the r e t i n a to wavelengths  between 400 and 700 m y .  N e v e r t h e l e s s , the s p e c t r a l s e n s i t i v i t y c u r v e showed  t h r e e d i s t i n c t m a x i m a c o r r e s p o n d i n g to the wavelengths of m a x i m u m a b s o r p t i o n for each of the t h r e e types of c o n e s .  These m a x i m a o c c u r r e d at 425 my,  545 my, and 595 mj,.  2. T r a n s m i s s i v i t y of light i n w a t e r . The eyes of many f i s h a r e capable of c o l o r d i s c r i m i n a t i o n , but are t h e r e c o l o r s to d i s c r i m i n a t e where the f i s h l i v e ?  One of the arguments H e s s  used against c o l o r v i s i o n i n f i s h was that m o n o c h r o m a t i c light, e s p e c i a l l y of the longer wavelengths, penetrates water to s u c h a s h a l l o w depth that c o l o r v i s i o n would be of l i t t l e value to fish,  should they p o s s e s s i t .  He p e r f o r m e d an  e x p e r i m e n t where he l o w e r e d different c o l o r e d p a p e r s p r o t e c t e d in c e l l u l o i d into the water,  and o b s e r v e d t h e m f r o m the s u r f a c e .  none of the c o l o r s c o u l d be r e c o g n i z e d .  A t a depth of 5.6 m e t e r s  W a r n e r poses the c r i t i c a l question as -  to whether this d i s a p p e a r a n c e of c o l o r s was c a u s e d by the depth of water through w h i c h the l i g h t p a s s e d or the quantity of w a t e r .  Of c o u r s e ,  Hess  should have o b s e r v e d the papers w i t h his eye s u b m e r g e d to the l e v e l of the  67 Cousteau and D u m a s (1953, p. 255) d e s c r i b e a study w h e r e they phot o graphed v a r i o u s c o l o r e d plates at depths to 120 feet.  The p i c t u r e s show that  at forty feet the r e d plate appeared v i r t u a l l y b l a c k , and by 120 feet y e l l o w had begun "to t u r n " to g r e e n .  Behan, _et al_. (1972) take i s s u e w i t h C o u s t e a u ' s }  r e s u l t s , c l a i m i n g that photographic f i l m does not r e p r o d u c e what the human eye i s capable of d i s c e r n i n g .  They sent six t e a m s of two d i v e r s down to  t h i r t y , s i x t y and ninety feet i n the ocean w i t h d i a g n o s t i c c o l o r b l i n d n e s s plates (for testing r e d - g r e e n and y e l l o w - b l u e c o l o r b l i n d n e s s ) .  T h e r e they  w e r e to attempt to identify the n u m b e r s w r i t t e n on the plates, thus t e s t i n g t h e i r a b i l i t y to see c o l o r s at these depths.  A c h i - s q u a r e test on the o b s e r v e d  r e s u l t s v e r s u s those expected on the b a s i s of no l o s s of c o l o r for each of the t h r e e depths showed a p r o b a b i l i t y for the o b s e r v e d d e v i a t i o n s of > 0.6. H o w e v e r , neither  of these studies c o m p l e t e l y c l e a r s up the m a t t e r .  C o u s t e a u d i d not attempt to put any of his o b s e r v a t i o n s into quantitative t e r m s , and he d i d not m e n t i o n any difference i n s e n s i t i v i t y between the eyes of the photographer and the f i l m w h i c h he was u s i n g .  On the other hand, B e h a n  f a i l e d to state what effect the n a r r o w i n g and shifting of bandwidth of light w i t h depth has on the r e f l e c t i v i t y of the test plate c o l o r s . sun,  In " w h i t e " l i g h t f r o m the  the v a r i o u s p a r t s of the test plates (the n u m e r a l v e r s u s the background)  may r e f l e c t to the eye equal i n t e n s i t i e s of light, but i n the g r e e n - b l u e l i g h t of deep water the r e f l e c t i v i t i e s may be quite different.  Hence, a c o l o r - b l i n d  subject could c o n c e i v a b l y d i s c r i m i n a t e the n u m e r a l on a c o l o r - b l i n d n e s s test plate by b r i g h t n e s s c o n t r a s t at great depth when he would be unable to do so at the s u r f a c e . H o w e v e r , B e h a n d e s c r i b e s a further test w h i c h suggests the r e s u l t s of his study-do i n d i c a t e a true c o l o r p e r c e p t i o n r a t h e r than b r i g h t n e s s p e r c e p t i o n . P i c t u r e s of the c o l o r b l i n d n e s s plates were taken w i t h an u n d e r w a t e r c a m e r a i n the a i r , at a depth of three feet i n a s w i m m i n g pool, and i n the ocean at fifty feet.  Under a l l the conditions of v i e w i n g the photographer was able to see both  the c o l o r s and n u m e r a l s on a l l of the p l a t e s .  The p i c t u r e s taken i n the a i r  68  r e p r o d u c e d a l l of the c o l o r s and f i g u r e s on the p l a t e s .  H o w e v e r , those taken  i n the pool and ocean f a i l e d to r e c o r d a l l of the f i g u r e s that the photographer c o u l d see on the p l a t e s . F r o m c a s u a l questionning of S C U B A - d i v i n g f r i e n d s , I have found g e n e r a l agreement that a f u l l range of c o l o r s can be d i s c r i m i n a t e d at fifty to s i x t y feet.  3.. R e l e v a n c e to t r o l l i n g and feeding e x p e r i m e n t s .  The consensus of the l i t e r a t u r e i s c l e a r - - f i s h have c o l o r v i s i o n . A l i (1961) states that, " T e l e o s t s as a group, w i t h the p o s s i b l e e x c e p t i o n of deep sea f o r m s w i t h pure r o d r e t i n a e , a r e b e l i e v e d to be able to p e r c e i v e colors."  (See a l s o W a l l s ,  1963, p. 488).  He found that cones of the A t l a n t i c  s a l m o n (Salmo s a l a r ) w e r e s t a r t i n g to light adapt i n white l i g h t of i n t e n s i t y 10  foot candles (ft-c).  A s s u m i n g the same amount of u n i f o r m i t y w i t h r e s p e c t  to c o l o r v i s i o n t h r e s h o l d i n the S a l m o genus as t h e r e i s i n the O n c o r h y n c h u s genus ( A l i , 1959). we can expect the cones of S a l m o g a i r d n e r i to b e g i n l i g h t -2 adaptation at no g r e a t e r than 10  ft-c illumination.  T h i s is a l m o s t the same  i n t e n s i t y of light r e q u i r e d for human c o l o r v i s i o n - - .003 ft-c ( G e l d a r d , 1972). In light of B e h a n ' s w o r k (1972), this v i r t u a l l y e n s u r e s that the f i s h w e r e seeing p h o t o p i c a l l y at a l l t i m e s d u r i n g the t r o l l i n g and feeding e x p e r i m e n t s . A rough check on the depths at w h i c h the l u r e s w e r e r u n n i n g i n d i c a t e d a m a x i m u m depth of fifteen feet for t r o l l i n g e x p e r i m e n t s I and II, and no g r e a t e r than fifty feet for t r o l l i n g e x p e r i m e n t III.  In the tanks where the feeding  e x p e r i m e n t s w e r e done the g r e a t e s t decay i n light l e v e l w i t h depth o c c u r r e d in the blue tank, and even here the d a r k e s t part of the tank m e a s u r e d 38 lux (at 3.5 f t - c ) .  B.  T h i s i s m o r e than enough l i g h t to i n i t i a t e cone v i s i o n .  I n t e r p r e t a t i o n of R e s u l t s The s i g n i f i c a n c e of c o l o r i n the feeding e x p e r i m e n t s i s attested to e l s e -  69 where i n the l i t e r a t u r e .  G i n e t z and L a r k i n (1973) d e s c r i b e a feeding e x p e r i -  ment in w h i c h they fed seven c o l o r s of dyed eggs to five r a i n b o w t r o u t i n 7.3 meter long troughs painted a pale g r e e n i s h - b l u e .  T h i r t y - f i v e eggs of e a c h of  two c o l o r s were p l a c e d i n the i n l e t of the trough, and those that w e r e not eaten as they p a s s e d down the t r o u g h w e r e c o l l e c t e d i n a t r a p at the outlet and counted. F o u r r e p l i c a t e s w e r e done (one t r o u g h per day) for each p o s s i b l e c o m b i n a t i o n of two c o l o r s of egg.  The average number of eggs eaten per t r i a l over the  e n t i r e e x p e r i m e n t w e r e as follows (a = .0 5): 26.78; orange,  blue, 29.54; r e d , 27.0 5; b l a c k ,  23.84; b r o w n , 23.46; yellow, 22.54; and green, 20.36.  In a second e x p e r i m e n t G i n e t z and L a r k i n matched the b a c k g r o u n d c o l o r of the tank w i t h one of the two c o l o r s of eggs p r e s e n t e d to the f i s h .  T h i s was  done for a l l p o s s i b l e c o m b i n a t i o n s of r e d , yellow, blue and b l a c k only.  This  t i m e the r e d c a m e out ahead of the blue w i t h the f o l l o w i n g a v e r a g e n u m b e r s of eggs eaten per t r i a l :  r e d , 21.94; y e l l o w , 21.66; blue, 20.38; and b l a c k , 15.69.  A l t h o u g h p r e f e r e n c e was m e a s u r e d i n a different manner i n G i n e t z ' s e x p e r i m e n t s than i n mine (total n u m b e r of eggs eaten r a t h e r than o r d e r of selection), the o r d e r of p r e f e r e n c e for r e d , y e l l o w and g r e e n eggs i n r e l a t i o n to each other, i n h i s f i r s t e x p e r i m e n t i s the same as i n my feeding e x p e r i m e n t s I and II.  Since, among four e x p e r i m e n t s , the r a n k of blue i n the p r e f e r e n c e  h i e r a r c h y a s s u m e d f i r s t , second, t h i r d and fourth p o s i t i o n s , it must be c o n c l u d e d that the l e v e l of p r e f e r e n c e for blue i s highly v a r i a b l e , perhaps g r e a t l y dependent upon the conditions under w h i c h it i s being p r e s e n t e d to the f i s h . A unique r e a c t i o n of f i s h to r e d has been mentioned by other a u t h o r s . In h i s r e v i e w of the c o l o r v i s i o n l i t e r a t u r e , W a r n e r (1931) c i t e s a study where f i s h r e a c t e d n e g a t i v e l y and v i o l e n t l y when p l a c e d i n a r e g i o n of a tank i l l u m i n a t e d with red light.  He also c i t e s another study where f i s h gathered in a r e g i o n of  r e d i l l u m i n a t i o n i n p r e f e r e n c e to d a r k n e s s .  B r o w n (1937) found that b a s s w e r e  able to d i s t i n g u i s h shades of r e d f r o m a s e r i e s of shades of g r e y w i t h a g r e a t e r a c c u r a c y than for other c o l o r s .  They w e r e a l s o p a r t i c u l a r l y r a p i d i n  l e a r n i n g to a s s o c i a t e a r e w a r d or punishment w i t h r e d .  Wolf and W a l e s (19 53)  70 " f e d " painted c o r k s to r a i n b o w t r o u t and b r o o k trout.  "When green, blue,  yellow, brown, b l a c k or white c o r k s w e r e t o s s e d onto the surface of the ponds, the trout d e m o n s t r a t e d a n e a r l y u n i f o r m l a c k of i n t e r e s t .  On the other hand,  when a r e d c o r k was t h r o w n among those of other c o l o r s , the f i s h l i t e r a l l y " b o i l e d " around it, s t r i k i n g it so v i g o r o u s l y that it would be k n o c k e d out of the water and soon d r i v e n to s h o r e . "  It is apparent that, whether the r e a c t i o n  t o w a r d it i s p o s i t i v e or negative, the attention paid to the c o l o r r e d by f i s h i s very high. If r a i n b o w trout show such a definite h i e r a r c h y of c o l o r p r e f e r e n c e s  as  i n d i c a t e d i n the feeding e x p e r i m e n t s , the obvious question i s why these p r e f e r e n c e s w e r e not evident i n the t r o l l i n g e x p e r i m e n t s .  A number of f a c t o r s  may help e x p l a i n t h i s . First,  it i s p o s s i b l e that the f i s h "shift t h e i r a t t e n t i o n " f r o m one set of  cues to another i n a manner s i m i l a r to that p r o p o s e d by D a w k i n s (1969).  While  they may at one t i m e be attending to the c o l o r s of objects, they may at another t i m e attend to t h e i r shape or p o s i t i o n .  It i s p a r t of D a w k i n s ' t h e s i s that only  one s y s t e m of cues can be attended to at a t i m e .  W i t h this i n m i n d , one may  c o n s i d e r the r e s u l t s of e x p e r i m e n t s p e r f o r m e d by H o r i o i n 1 9 3 8 . ^ H o r i o was i n t e r e s t e d i n the r e l a t i v e strength of f o r m and c o l o r s t i m u l i to f i s h .  To this purpose he t r a i n e d c a r p p o s i t i v e to a r e d d i s c and negative to  a blue one.  They w e r e able to l e a r n this a s s o c i a t i o n m o r e e a s i l y than a s i m i l a r  a s s o c i a t i o n using a white t r i a n g l e (positive) and a white square (negative).  He  then found a p a i r of c o l o r s as d i f f i c u l t to t e l l a p a r t as the white t r i a n g l e and white square: blue and v i o l e t .  " T r a i n e d p o s i t i v e to a v i o l e t d i s c v e r s u s a blue  one and to a white t r i a n g l e v e r s u s a white square, then offered a v i o l e t square v e r s u s a blue t r i a n g l e , the f i s h went to the p o s i t i v e c o l o r r a t h e r than to the positive f o r m . "  (from Walls,  Described in Walls,  1963.  1963).  C o l o r thus seems to be m o r e i m p o r t a n t  71 for c a r p than f o r m r e g a r d i n g i t s attention v a l u e . F o r trout this may be r e v e r s e d .  E v e n if not, i t i s l i k e l y that the  actions e x h i b i t e d by the l u r e s c o m m a n d e d a g r e a t e r amount of attention than the static shapes used by H o r i o .  If so, the f i s h i n the t r o l l i n g e x p e r i m e n t may  have been p r i m a r i l y attending to the actions of the l u r e s to the n e g l e c t of t h e i r colors.  Since i n the feeding e x p e r i m e n t s the " a c t i o n s " of the eggs d r i f t i n g  down through the water c o l u m n w e r e at l e a s t s i m i l a r , the f i s h may have shifted t h e i r attention to the s y s t e m of c o l o r cues, and made t h e i r c h o i c e s on that b a s i s . T h i s is p o s s i b l y why c o l o r was s i g n i f i c a n t i n the one e x p e r i m e n t and not i n the other. F u r t h e r , the tighter c o n t r o l of extraneous f a c t o r s p o s s i b l e w i t h a l a b o r a t o r y e x p e r i m e n t over a f i e l d study p r o b a b l y p l a y e d a r o l e i n i l l u m i n a t i n g what may be a weaker effect.  A l s o , the t w o - p r o n g e d effect of u s i n g a d o m e s t i c  stock of trout i n a l a b o r a t o r y e x p e r i m e n t , w h i l e u s i n g w i l d t r o u t i n a f i e l d study, may have been r e s p o n s i b l e for some of the d i f f e r e n c e s i n r e s u l t s (for example, t h e i r p r e v i o u s feeding h i s t o r i e s were different). The i m p l i c a t i o n s of the r e s u l t s f r o m the t r o l l i n g and feeding e x p e r i ments w i t h r e s p e c t to the d e s i g n of an effective l u r e p r o b a b l y only apply to r a i n b o w trout, and may even apply only to the stocks of f i s h studied.  It was  found that:  1.  A m o n g t r o l l i n g l u r e s of a p p r o x i m a t e l y equal s i z e , the a c t i o n of the l u r e was found to be m o r e i m p o r t a n t than the c o l o r i n d e t e r m i n i n g i t s a t t r a c t i v e n e s s to r a i n b o w trout, as m e a s u r e d by the n u m b e r of s t r i k e s made on a p a r t i c u l a r l u r e .  It is not known whether the c r i t i c a l a s p e c t s  of the a c t i o n are quantitative or q u a l i t a t i v e ; both appear to c o r r e l a t e w i t h the m e a s u r e d a t t r a c t i v e n e s s of the l u r e s . 2.  A l t h o u g h the c o l o r of l u r e 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 i n the t r o l l i n g experiments,  r e d l u r e s caught the g r e a t e s t number of f i s h in a l l t h r e e  experiments.  The c o l o r p a t t e r n was found not to cause s i g n i f i c a n t  differences. No s e l e c t i o n for s i z e or sex of f i s h o c c u r r e d on the b a s i s of e i t h e r c o l o r or a c t i o n of l u r e . L u r e s t r o l l e d w i t h dodgers s e l e c t e d for l a r g e r f i s h than those t r o l l e d without d o d g e r s .  T h e r e was no difference i n the  sex r a t i o s of f i s h caught by l u r e s t r o l l e d w i t h d o d g e r s f r o m those t r o l l e d without d o d g e r s . The t i m e of day of f i s h i n g was found to be significant i n one e x p e r i m e n t and not significant i n the two o t h e r s .  The r e a s o n for this d i f f e r e n c e i s  not known. C o l o r of food was found to play a significant r o l e i n the o r d e r of s e l e c t i o n of dyed trout eggs fed to r a i n b o w t r o u t .  The h i g h e s t p r e f e r e n c e  was for r e d followed by y e l l o w , then g r e e n .  The p r e f e r e n c e for blue  eggs was v a r i a b l e ; it was p r o b a b l y m o r e dependent on the c o n d i t i o n s of feeding than the p r e f e r e n c e s for the other c o l o r s . A l t h o u g h a l l the f i s h p r e f e r r e d r e d eggs to other c o l o r s of eggs,  the  g r e a t e s t range of p r e f e r e n c e i n t e n s i t y among the f i s h was found for r e d eggs.  The p r e f e r e n c e s e x h i b i t e d by the f i s h w e r e not dependent on t h e i r  l e v e l of hunger, as i n d i c a t e d by the amount of food i n t h e i r s t o m a c h s . Both the c o l o r of b a c k g r o u n d and the c o l o r of the tag affect the o r d e r of s e l e c t i o n of dyed trout eggs.  egg w e r e found to  D i v e r s i t y of c o l o r  between the tag egg and the food egg i n c r e a s e d the p r e f e r e n c e i n t e n s i t y for a packet of food.  It i s not c e r t a i n how the effect of b a c k g r o u n d  c o l o r e x e r t s its influence, but there is evidence that the p r e f e r e n c e intensity i s higher if one, and e s p e c i a l l y i f both, the tag egg and the food egg c o n t r a s t w i t h the c o l o r of b a c k g r o u n d . T h e r e w e r e significant differences among the f i s h i n t h e i r o r d e r of s e l e c t i o n of different c o l o r e d food.  These d i f f e r e n c e s w e r e not as  73 i m p o r t a n t as those c a u s e d by changing the b a c k g r o u n d c o l o r of the tank. I n d i v i d u a l f i s h modify t h e i r o r d e r of s e l e c t i o n of c o l o r e d food i n different ways i n different c o l o r e d t a n k s .  T h i s study has made only a start on the c o m p l e x q u e s t i o n of what makes a good l u r e .  The a c t i o n of the l u r e was found to be of p r i m e i m p o r t a n c e .  t r o l l i n g e x p e r i m e n t s , i n light of the r e s u l t s of the feeding e x p e r i m e n t s ,  The  indi-  cate the i m p o r t a n c e of c o l o r , at l e a s t to the extent that r e d i s h i g h l y p r e f e r r e d . Only when s i m i l a r e x p e r i m e n t s ar e done on other populations of r a i n b o w t r o u t and on other s p e c i e s of f i s h can we b e g i n to a s s e s s the u n i v e r s a l i t y of these generalizations. P r o p e r l y designed e x p e r i m e n t s are m o r e l i k e l y to y i e l d r e l e v a n t resuLts than a r e a n a l y s e s of c r e e l c e n s u s d a t a .  T h i s i s e s p e c i a l l y so if the e x p e r i m e n t s  a r e d e s i g n e d to elucidate the qualities' of a good l u r e r a t h e r than act as p i l o t studies for management p r o p o s a l s .  W i t h the great w e a l t h of f a c t o r s that can  affect the r e l a t i v e s u c c e s s of a l u r e , utmost c a r e must be taken to s t a n d a r d i z e techniques and to c o n t r o l , as best one can, v a r i a b l e s other than the test variable.  H o w e v e r , knowledge gained f r o m this type of e x p e r i m e n t i s c e r t a i n  to benefit both the f i s h e r i e s manager and the f i s h e r m a n by m a k i n g p o s s i b l e f i n e r c o n t r o l on the efficiency and s e l e c t i v i t y of t r o l l i n g gear, w h i c h , i n the long run, should r e s u l t i n higher sustained y i e l d s .  74 REFERENCES CITED  A l i , M.A. 1959. The o c u l a r s t r u c t u r e , r e t i n o m o t o r and p h o t o b e h a v i o ^ a l responses of j u v e n i l e P a c i f i c salmon. Can. J . of Z o o l . , 37:965-996. A l i , M.A. 1961. H i s t o p h y s i o l o g i c a l s t u d i e s on the j u v e n i l e A t l a n t i c salmon (Salmo s a l a r ) r e t i n a . I I . Responses to l i g h t i n t e n s i t i e s , wavelengths, temperature and c o n t i n u o u s l i g h t and dark. Can. J . Z o o l . , 39:511-526. Baker, H.D., and W.A.H. Rushton. 1965. The r e d - s e n s i t i v e pigment i n normal cones. J . P h y s i o l . 176:56-72. Behan-, F.L., R.A. underwater.  Behan, and H.W. Wendhausen. Human F a c t o r s , 1 4 ( l ) : 4 1 - 4 4 .  1972.  Color  perception  Beukema, J . J . 1970. A c q u i r e d hook-avoidance i n the p i k e Esox l u c i u s L. f i s h e d w i t h a r t i f i c i a l and n a t u r a l b a i t s . J . F i s h . B i o l . , 2_: 155-160. Boerema, L'.K. 1956. Some experiments on f a c t o r s i n f l u e n c i n g mesh s e l e c t i o n i n trawls. J . Cons, i n t . E x p l o r . Mer., 21:175-191. Borowik, J . 1930. On what does the c a t c h of u n d e r s i z e d f i s h depend? J . Cons, i n t . E x p l o r . Mer., 5(2):195-215. Boydstun, L.B. 1972 P l u g s ( l u r e s ) i n the management of the C a l i f o r n i a t r o l l salmon f i s h e r y . P a c i f i c Marine F i s h e r i e s Commission, B u l l e t i n 8:5-13. Brown, Frank A. ( J r . ) 1937. Responses of the large-mouth b l a c k bass t o colors. I l l i n o i s Nat. H i s t . Surv. B u l l . , 21:33-55. Brownlee, K.A. 1965. E n g i n e e r i n g . New  S t a t i s t i c a l Theory and Methodology York, John W i l e y & Sons, 590 pp.  i n S c i e n c e and  Burrows, Roger E. 1969. The i n f l u e n c e of f i n g e r l i n g q u a l i t y on a d u l t salmon s u r v i v a l s . T r a n s . Amer. F i s h . S o c , 98 (4) : 777-784. Cousteau, J.Y.,and and Row.  F. Dumas.  1953.  The S i l e n t World.  New  York, Harper  Davis, F.M. 1929. P r e l i m i n a r y note on e x p e r i m e n t a l t r a w l i n g w i t h cod-end meshes of d i f f e r e n t s i z e s . J . Cons, i n t . E x p l o r . Mer., 4^(3): 287-299. Dawkins, R. 1969. 134-141.  The a t t e n t i o n t h r e s h o l d model.  Anim. Behav., 17:  Emig, John W. 1971. C a l i f o r n i a i n l a n d a n g l i n g s u r v e y f o r 1969, w i t h c o r r e c t i o n s f o r the 1964 survey. C a l i f . F i s h & Game, 57(2):99-106. E s p i n o s a , F.A. ( J r . ) , and James E. Deacon. 1971. Comparative a n g l e r s u c c e s s a t Lake Mead (Arizona-Nevada). P r o g r . F i s h - C u l t . , 3 3 ( 3 ) : 170-174. ~  75 G e l d a r d , F.A. 1972. and Sons, x i + 5 8 4  The Human S e n s e s , pp.  G i n e t z , R.M., a n d P.A. L a r k i n . 1973. r a i n b o w t r o u t (Salmo g a i r d n e r i ) . 229-234.  2nd  e d . New  York, John Wiley  by  Choice of c o l o r s of food items J . F i s h . R e s . Bd. C a n . , 3 0 ( 2 ) :  G r a b e r , V. 1884. G r u n d l i n i e n z u r E r f o r s c h u n g des H e l l i g k e i t s - und Farbensinnes der T i e r e . P r a g , T e m p s k y , 322 p. ( c i t e d f r o m W a r n e r ,  1931).  . 1885. Ueber d i e H e l l i g k e i t s - und F a r b e n e m p f i n d l i c h k e i t e i n i g e r Meertiere. S i t z - Ber. Akad. Wiss. Wien., math-naturw. K l . , A b t . I., £1:129-150. ( c i t e d from Warner, 1931).  n H e s s , C. 1910. Uber den a n g e b l i c h e n Nachweis v o n F a r b e n s i n n b e i F i s c h e n . A r c h i v f u r d i e gesammte P h y s i o l o g i e , 1 3 4 ( 1 , 2 ) : 1 - 1 4 . Aug. 15. ( c i t e d from Brown, 1937). . 1911. E x p e r i m e n t e l l e Untersuchungen zur v e r g l e i c h e n d e n P h y s i o l o g i e des G e s i c h t s s i n n e s . A r c h i v f u r d i e gesammte P h y s i o l o g i e , 142 (9,10,11,12):405-46. ( c i t e d from Brown, 1937). . 1913. U n t e r s u c h u n g e n z i i r F r a g e n a c h dem Vorkommen v o n F a r b e n s i n n bei Fischen. Zoologische Jahrbucher; Abteilung f u r allgemeine Z o o l o g i e und P h y s i o l o g i e d e r T i e r e , .31(4):629-46. ( c i t e d from Brown, 1937). . 1914. Untersuchungen z u r P h y s i o l o g i e des G e s i c h t s s i n n e s d e r Fische. Z e i t s c h r i f t f u r B i o l o g i e , 63[45 n.s.]:245-274. (cited from Brown, 1937). H i n e l i n e , G e r t r u d e M. ( W h i t e ) . 1 9 2 7 . J . Exp. Z o o l . , 4 7 ( l ) : 8 5 - 9 4 .  Color v i s i o n  i n t h e mudminnow.  H o r i o , G. 1938. D i e F a r b - u n d F o r m d r e s s u r an K a r p f e n . J a p . J o u r . S c i . , P a r t I I I ( B i o p h y s i c s ) , 4:395-402.  Med.  J e s t e r , D.B. 1973. V a r i a t i o n s i n c a t c h a b i l i t y of f i s h e s w i t h c o l o r gillnets. T r a n s Amer. F i s h . S o c , 1 0 2 ( 1 ) : 1 0 9 - 1 1 5 .  of  K o b a y a s h i , H., a n d M.A. A l i . 1971. E l e c t r o r e t i n o g r a p h i c d e t e r m i n a t i o n of s p e c t r a l s e n s i t i v i t y i n a l b i n o and p i g m e n t e d b r o o k t r o u t ( S a l v e l i n u s fontinalis, Mitchill). Can. J . o f P h y s i o l o g y a n d P h a r m a c o l o g y , 49(12):1030-1037. Larkin, P.A. 1949. R e p o r t on r e l a t i v e e f f i c i e n c i e s o f v a r i o u s t y p e s o f f i s h i n g gear w i t h s p e c i a l r e f e r e n c e to Kamloops t r o u t . Report to t h e 1949 P r o v i n c i a l [ B r i t i s h C o l u m b i a ] Game C o m m i s s i o n . M c C r a c k e n , F.D. 19 63. S e l e c t i o n b y c o d e n d m e s h e s a n d h o o k s on c o d , h a d d o c k , f l a t f i s h a n d r e d f i s h , pp. 1 3 1 - 1 5 5 . I n : The S e l e c t i v i t y o f F i s h i n g Gear. S p e c i a l p u b l . No. 5; b e i n g v o l u m e 2 o f P r o c e e d i n g s o f J o i n t ICNAF/ICES/FA0 S p e c i a l S c i e n t i f i c M e e t i n g , L i s b o n , 1957.  76  Marks, W.B. 1965. V i s u a l pigments of single g o l d f i s h cones. 178:14-32.  J . Physiol.,  Mast, Samuel 0. 1916. Changes i n shade, color, and pattern i n f i s h e s , and their bearing on the problems of adaption and behavior, with especial reference to the flounders Paralichthys and Ancyclopsetta. B u l l . Bur. Fish. (U.S.), 34:175-238. P i t r e , K.R. 1970. Summary of "shaker" investigations i n the west coast of Vancouver Island t r o l l fishery i n 1968 and 1969. Dept. of F i s h , and For., Pac. Reg. Tech. Rept., 1970-71, 10 pp. Pycha, R.L. 1962. The r e l a t i v e e f f i c i e n c y of nylon and cotton g i l l n e t s for taking lake trout i n Lake Superior. J . Fish. Res. Bd. Can., 19(6):1085-1094. Ricker, W.E. 1958. Handbook of computations for b i o l o g i c a l s t a t i s t i c s of f i s h populations. B u l l . Fish. Res. Bd. Canada, No. 119. 300 pp. Shetter, D.S., and G.R. Alexander. 1965. Results of angling under s p e c i a l and normal trout f i s h i n g regulations i n a Michigan trout stream. Trans. Amer. Fish. S o c , 94 (3) : 219-226. Sokal, R., and F. Rohlf. 776 pp.  1969. Biometry.  San Francisco, W.H. Freeman,  Svaetichin, Gunnar, and E.F. MacNichol, J r . 1958. Retinal mechanisms for chromatic and achromatic v i s i o n . Ann. N.Y. Acad. S c i . , 74:385-404. Tomita, T., A. Kaneko, M. Murakami, and E.L. Pautler. 1967. Spectral response curves of single cones i n the carp. V i s . Res., _7:519-531. Walls, G.L. 1963. The Vertebrate Eye and i t s Adaptive Radiation. York, Hafner Publishing Co., v i i + 785 pp. Warner, Lucien H. 1931. The problem of color v i s i o n i n f i s h e s . Rev. B i o l , 6(3):329-348.  New Quart.  White, Gertrude M. 1919. Association and color discrimination i n mudminnows and sticklebacks. J . Exp. Zool., 27(4):443-498. Wolf, H., and J . H. Wales. 1953 (4):234-236.  1953. Color perception i n trout.  Copeia,  Zupanovic, S. 1963. Experiments on the f i s h i n g effectiveness of trawls using wire cable b r i d l e and wire cable b r i d l e with manila, pp. 222-225. In: The S e l e c t i v i t y of Fishing Gear. Special publ. No. 5; being volume 2 of Proceedings of Joint ICNAF/ICES/FAO Special S c i e n t i f i c Meeting, Lisbon, 1957.  

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