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A comparative study of the behaviour of two sympatric species of freshwater sculpins, Cottus asper Richardson… Fenwick, Julie M. 1968

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A COMPARATIVE STUDY OF THE BEHAVIOUR _ :  OF TWO SYMPATRIC SPECIES OF FRESHWATER SCULPINS, Cottus asner Richardson AND Cottus a l e u t i c u s G i l b e r t , IN RELATION TO THEIR DIFFERENCES IN MICROHABITAT .  by J u l i e M. Fenwick  B.Sc.,  McGill  U n i v e r s i t y , 1966  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in  the  Department of  Zoology  We accept t h i s t h e s i s as conforming to required  standard  THE UNIVERSITY O F BRITISH COLUMBIA December,  1968  the  In p r e s e n t i n g an  this  thesis  advanced degree at  the  Library  I further for  shall  the  his  of  this  agree that  written  of  be  available  Dec,  g r a n t e d by  gain  ZOOLOGY  19.  1968  for  for extensive  permission.  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  British  the  It i s understood  for financial  Department of  Date  University  permission  representatives. thesis  f u l f i l m e n t of  make i t f r e e l y  s c h o l a r l y p u r p o s e s may  by  in p a r t i a l  Columbia  shall  requirements  Columbia,  Head o f my  be  I agree  r e f e r e n c e and copying of  that  not  the  that  Study.  this  thesis  Department  c o p y i n g or  for  or  publication  allowed without  my  ABSTRACT  The behaviour o f two sympatric s p e c i e s of s c u l p i n s , asper and C o t t u s a l e u t i c u s , tats,  Cottus  which occupy d i f f e r e n t m i c r o h a b i -  was s t u d i e d by the comparative method.  The aim of  the  study was to determine some of the important b e h a v i o u r a l adaptations  to the d i f f e r e n c e s  i n their microhabitats.  C. asper occurs i n areas of slov; c u r r e n t and f i n e strate  sub-  and G. a l e u t i c u s i n areas of f a s t c u r r e n t and coarse  sub-  strate. The p o s t u r e ,  o r i e n t a t i o n to the c u r r e n t , and locomotary  and f e e d i n g behaviour of the s p e c i e s were examined i n the l a b o r a t o r y under d i f f e r e n t  c o n d i t i o n s of c u r r e n t and  C. asper responds to a c u r r e n t by l y i n g f l a t strate.  C. a l e u t i c u s  on a g r a v e l s u b s t r a t e , toral  also exhibits raises  substrate. on the  sub-  t h i s posture on sand, but  the body, by spreading the  pec-  fins. C. a l e u t i c u s  adopts a p a r a l l e l o r i e n t a t i o n to the c u r r e n t  more f r e q u e n t l y than a broadside o r i e n t a t i o n , "prefers" the broadside p o s i t i o n .  but C . asper  However, both s p e c i e s assume  the broadside p o s i t i o n more f r e q u e n t l y on sand than on g r a v e l , and the p a r a l l e l o r i e n t a t i o n more f r e q u e n t l y on g r a v e l than on sand. C. asper i s  a much poorer swimmer than C . a l e u t i c u s ,  pecially i n a current.  i s much more a c t i v e  than  C. asper at a l l times of day and under a l l c o n d i t i o n s of  cur-  rent  tested.  C. a l e u t i c u s  es-  ii  C. asper i s a l u r k i n g predator and takes food from the surface of the s u b s t r a t e .  C. a l e u t i c u s i s  a more a c t i v e  and feeds by swimming'to the water s u r f a c e , the s u b s t r a t e  feeder,  b y . t a k i n g food from  surface and by f o r a g i n g i n the c r e v i c e s of  the  gravel. From l a b o r a t o r y o b s e r v a t i o n s i t relies  on s i g h t i n food d e t e c t i o n  appears that C .  to a greater  aleuticus  extent than does  C. a s p e r . The f i n d i n g s of t h i s  study were compared with f i e l d  obser-  v a t i o n s and with p r e v i o u s s t u d i e s of other c o t t i d s p e c i e s . was concluded from t h i s that C . a l e u t i c u s  1  posture,  It  orientation  to the c u r r e n t , and locomotory and feeding behaviour are a r e flection  of a more a c t i v e way of l i f e  s p e c i a l problems of l i f e ever,  is  dwelling,  and are r e l a t e d to  i n a strong current.  C . asper,  the how-  t y p i c a l , both i n behaviour and morphology, of bottomsedentary  fish,  of r e c l u s i v e  habits.  iii  ACKNOWLEDGMENT  The N.R.  author wishes to express her s i n c e r e g r a t i t u d e to D r .  Liley  f o r h i s f i n a n c i a l a s s i s t a n c e and advice throughout  the course of t h i s study and f o r h i s help i n the p r e p a r a t i o n of t h i s manuscript. I would a l s o l i k e to thank D r . D. McPhail and D r . G . G . E . Scudder f o r t h e i r h e l p f u l s u g g e s t i o n s . To a l l my f e l l o w graduate students, B.H. mens,  i n p a r t i c u l a r Mr.  Seghers and Mr. D . L . Kramer, who helped to c o l l e c t my s i n c e r e  speci-  thanks.  Thanks are a l s o due to Mrs. Caren Jones f o r t y p i n g the manuscript and to Mr. Eugene McCulloch f o r h i s help i n cons t r u c t i n g apparatus. Finally,  s p e c i a l thanks are due to my husband, J i m , f o r  h i s help and encouragement  throughout the course of t h i s  study.  Iv  TABLE OF CONTENTS Page ABSTRACT.  i  . . .  ACKNOWLEDGMENTS  .  .  .  TABLE OF CONTENTS  iv vi  LIST OF TABLES. LIST OF FIGURES .  INTRODUCTION.  iii  . •  viii  .  .  . 1 5  MATERIALS AND METHODS D e s c r i p t i o n of Species  . 5  • .  . 5  C o l l e c t i n g and H o l d i n g C o n d i t i o n s . Flow Tank . . . . . . . . . . . .  . . . . .  . . . . . 9  Times of O b s e r v a t i o n s RESULTS O r i e n t a t i o n With Respect to the Current .  7  .  .  . . . .  .  .11  .  .11  A.  Observation.  11  B.  Method  .11  C.  Results  .12 20  Stance A.  Observation  .20  B.  Method  .23  C.  Results.  .  • •: • . 2 3 26-  Movement i n Response to Current A.  Observation  B.  Method .  C.  Results  .26 27 .' .  .  . .29  V  Feeding Behaviour A.  Observation.  B.  Method  C.  Results.  DISCUSSION.  .  .32  . . . . . . . . . .  .32  . . . . . . .  .34  .  '  . . . . . .  .  .  . .38  .  .38  D i s c u s s i o n of R e s u l t s General D i s c u s s i o n  .36  ." .  .  .41 47  SUMMARY  BIBLIOGRAPHY.  .49  .  .52  APPENDIX. to Laboratory C o n d i t i o n s .  . . . . .  .52  A.  Adaptability  B.  Influence on Numbers on Behaviour  :52  C.  Response to U n f a m i l i a r S t i m u l i  .54  D.  Cryptic Colouration.  ". .  .55  vi  LIST OF TABLES Page I  The frequency with which C . asper and C . aleuticus  faced " i n t o , " "away" from and  "broadside" to the c u r r e n t on a sand substrate, II  .13  a t four c u r r e n t speeds  The frequency with which C . asper and C . aleuticus  faced " i n t o , " "away" from and  "broadside" to the c u r r e n t on a g r a v e l substrate, III  . .14  at four c u r r e n t speeds  The frequency w i t h which C . asioer and C . aleuticus  faced i n three d i r e c t i o n s at  four c u r r e n t speeds on a sand s u b s t r a t e IV  .  faced i n three d i r e c t i o n s at  four c u r r e n t s speeds on a g r a v e l s u b s t r a t e  faced i n three d i r e c t i o n s at .  . . . . .18  four c u r r e n t speeds on a g r a v e l substrate  19  four c u r r e n t speeds on a sand s u b s t r a t e The frequency v/ith which C . asper and C . aleuticus  VII  faced i n three d i r e c t i o n s at  Postures assumed by C . asper on sand and gravel substrates  under two c o n d i t i o n s of  current VIII  16  The frequency v/ith which C . asper and C . aleuticus  VI  . . . .15  The frequency with which C . asper and C . aleuticus  V  .  .24  Postures assumed .by C_. a l e u t i c u s and g r a v e l s u b s t r a t e s of c u r r e n t  on sand  under two c o n d i t i o n s „  25  vii Page IX  T o t a l number of i n c h e s moved by C . asper a n c  * C». a l e u t i c u s i n f i f t e e n minutes at  four c u r r e n t speeds „ . X  .  .  .  30  . .  Mean number of i n c h e s moved by C . asper and C . a l e u t i c u s i n f i f t e e n minutes at four c u r r e n t speeds  . . . . . .  XI  A b i l i t y to d e t e c t food by chemical senses .  XII  Summary of r e s u l t s of s u b s t r a t e / c u r r e n t  . .  .31 . .37  v e l o c i t y choice experiments (G. T a y l o r , 1 9 6 6 )  XIII  E c o l o g i c a l data on the areas of the  4 2  Little  Campbell R i v e r from which C . asper and C . a l e u t i c u s were c o l l e c t e d .  43  viii  LIST OF FIGURES Page 1  The flow tank and c u r r e n t producing apparatus used i n l o c o m o t i o n , o r i e n t a t i o n , and posture experiments  ...8  2  Four p o s t u r e s of C . asper and C . a l e u t i c u s . . .  3  The methods used to swim i n a c u r r e n t .  k  The Y trough used f o r food d e t e c t i o n experiments  .  . . . . . . . .  . .22 .28  .35  1  INTRODUCTION  This thesis i s  concerned with a comparative study of  behaviour o f two c l o s e l y family Cottidae.  r e l a t e d s p e c i e s of freshwater  Cottus asper and Cottus a l e u t i c u s  the  sculpins,  are known  to d i f f e r i n t h e i r m i c r o h a b i t a t s v/ith r e s p e c t to the nature of the s u b s t r a t e present  and the c u r r e n t v e l o c i t y  (Taylor, 1966).  The  study was a comparison of the behaviour of these s p e c i e s  under d i f f e r e n t  c o n d i t i o n s of c u r r e n t and s u b s t r a t e  which are the important b e h a v i o u r a l a d a p t a t i o n s  to  determine  to these  dif-  ferences i n m i c r o h a b i t a t . One of the d i s t i n g u i s h i n g f e a t u r e s of the family C o t t i d a e is  the absence of a swimbladder.  this,  As would be expected from  the group as a whole i s b e n t h i c .  rubble (Bailey,  1 9 5 2 ) , g r a v e l (Simon and Brown, 1943)j and mud  and sand ( T a y l o r , 1 9 6 6 ) .  They are found i n p o o l s ( T a y l o r ,  1 9 6 6 ) , i n slow streams (Smyley, et a l . , 1 9 5 1 ) ,  and r i f f l e s  commonly c o l l e c t e d  1 9 5 7 ) , and i n t o r r e n t s  (Bailey,  i n association  type and a c e r t a i n c u r r e n t  Each s p e c i e s  and that a given c u r r e n t  types (Zarbock, 1 9 5 D »  association  with  B a i l e y (1952) found  t h a t although C. b a i r d i a p p a r e n t l y chose i t s type,  substrate  1952) that the p r i n c i p a l  only apparently s e l e c t e d owing to i t s  the b a s i s of s u b s t r a t e  is  at l e a s t i n the spawning sea-  the nature of the s u b s t r a t e ,  c e r t a i n substrate  (Carl  velocity.  f a c t o r governing h a b i t a t c h o i c e ,  speed i s  1952).  with a s p e c i f i c  I t has been suggested ( B a i l e y ,  son, i s  C o t t i d s occur over  spawning s i t e s on  most of the n e s t s were found i n  2  areas where the s u r f a c e v e l o c i t y was q u i t e h i g h . water movements i n s i d e the nest i t s e l f  However,  were r a t h e r g e n t l e .  Another common feature of the freshwater s c u l p i n s i s they u s u a l l y occur i n groups of two or more s p e c i e s ,  that  each one  of which i s more frequent i n some p a r t s of the r i v e r or stream than i n o t h e r s ,  a c c o r d i n g to the d i s t r i b u t i o n o f c u r r e n t speed  and s u b s t r a t e type (Straskaba et a l . , 1 9 6 6 ; B a i l e y , 1 9 5 2 ; Smyley, 1 9 5 7 ; T a y l o r , 1 9 6 6 ) .  C o a s t a l B r i t i s h Columbia i s com-  p a r a t i v e l y "Impoverished," i n that o n l y two s p e c i e s , prickly sculpin, sculpin,  C o t t u s asper R i c h a r d s o n ,  Cottus a l e u t i c u s G i l b e r t ,  the  and the A l e u t i a n  are p r e s e n t .  This area  t h e r e f o r e p r e s e n t s a somewhat s i m p l i f i e d s i t u a t i o n , amenable to study. S c u l p i n s a l l over the n o r t h e r n hemisphere appear to have rather similar diets,  c h i e f l y c o n s i s t i n g of bottom d w e l l i n g i n -  v e r t e b r a t e s (Smyley, 1 9 5 7 ; Bond, 196ft; N o r t h c o t e , 1 9 5 f t ) .  They  eat organisms w i t h i n c e r t a i n s i z e ranges that depend on the mouth s i z e  of the s c u l p i n .  The s i z e  d i f f e r s not o n l y between s p e c i e s , of  a single  of food taken t h e r e f o r e  but a l s o d u r i n g the  lifetime  individual.  C o t t u s asper and C o t t u s a l e u t i c u s are sympatric i n the L i t t l e Campbell R i v e r of southwest tion studies  (Taylor,  microhabitats, finely of  Collec-  1 9 6 6 ) i n d i c a t e t h a t they d i f f e r i n t h e i r  C . asper i n h a b i t i n g areas of slov/ c u r r e n t and  textured substrate,  swift  B r i t i s h Columbia.  and C . a l e u t i c u s o c c u r r i n g i n areas  c u r r e n t and coarse s u b s t r a t e .  o v e r l a p to some extent,  These m i c r o h a b i t a t s  and where C . asper i s  scarce or absent,  3  C. a l e u t i c u s may occupy C . asper type h a b i t a t s . Laboratory studies species exercise  (Taylor,  1966)  i n d i c a t e that these  some degree of s e l e c t i v i t y i n t h e i r e n v i r o n -  ment w i t h r e g a r d to s u b s t r a t e type and c u r r e n t v e l o c i t y .  In  the l a b o r a t o r y C . asper and C . a l e u t i c u s tend to choose c u r r e n t and s u b s t r a t e c o n d i t i o n s that resemble those o c c u r r i n g i n t h e i r natural habitat.  However T a y l o r d i d not examine the a n i m a l s '  behaviour once the choice-was made to determine i f the  species'  behaviour d i f f e r e d i n a way that could be c o r r e l a t e d with the s u b s t r a t e and c u r r e n t type that they had chosen. I t seems l i k e l y that these d i f f e r e n c e s i n m i c r o h a b i t a t would be r e f l e c t e d i n the everyday behaviour of the s c u l p i n s . Consequently C . asper and C . a l e u t i c u s were observed i n l a b o r a t o r y s i t u a t i o n s i n which c u r r e n t speed and s u b s t r a t e type were varied. noted,  T h e i r behaviour i n these v a r i o u s circumstances was and experiments were then conducted to examine  further  any d i f f e r e n c e s which these o b s e r v a t i o n s had i n d i c a t e d . The f e e d i n g behaviour of C . asper and C . a l e u t i c u s was a l s o s t u d i e d , as i t  appeared to be r e l a t e d to the  differences  i n the behaviour of the two s p e c i e s i n c u r r e n t c o n d i t i o n s . The present study was, i n a sense, a departure from " c l a s s i c a l " v e r t e b r a t e ethology,  i n that the behaviour considered  was not a form of s o c i a l behaviour, but the means used by the i n d i v i d u a l to meet the problems of food g e t t i n g and locomot i o n that the environment p r e s e n t s  daily.  Throughout t h i s study the comparative method was chosen as the most f r u i t f u l  means of d i s c o v e r i n g the s i g n i f i c a n c e of  b e h a v i o u r a l d i f f e r e n c e s as e c o l o g i c a l a d a p t a t i o n s (Lack, 1965).  5  MATERIALS AND METHODS  D e s c r i p t i o n of  Species  C . asper and C . a l e u t i c u s (see  are r a t h e r s i m i l a r i n appearance  C a r l et a l . , 1 9 5 9 , f o r complete d e s c r i p t i o n ) .  However,  they do d i f f e r m o r p h o l o g i c a l l y i n s e v e r a l r e s p e c t s t h a t have a b e a r i n g on t h e i r behaviour i n d i f f e r e n t  current and  substrate  conditions. C . asper i s 1 5 0 mm.  the l a r g e r s p e c i e s ,  a t t a i n i n g a l e n g t h of up to  A few i n d i v i d u a l s may be up to twice t h i s s i z e .  aleuticus,  r a r e l y exceeds 1 0 0 mm i n l e n g t h .  however,  has a very l a r g e ,  broad head and mouth r e l a t i v e  C.  C . asper  to body s i z e ,  but C . a l e u t i c u s has a mouth and head more i n p r o p o r t i o n to rest  of i t s body.  compressed,  C . a s p e r ' s body i s  somewhat  the  dorso-ventrally  and the width of the body decreases markedly from  head to t a i l .  C . a l e u t i c u s i s more c y l i n d r i c a l i n shape and  has a l e s s pronounced t a p e r i n g from the a n t e r i o r to the  pos-  t e r i o r of the body.  C o l l e c t i n g and H o l d i n g C o n d i t i o n s C. asper and C  t |  a l e u t i c u s were c o l l e c t e d  Campbell R i v e r i n a seine net  from the L i t t l e  ( 2 , 4 m x 1 . 6 m x 3 mm mesh)  equipped with aluminum p o l e s and heavy weights. l e a d s were used as these e f f e c t i v e l y and d i s t u r b e d the s c u l p i n s . t i o n a r y while the s u b s t r a t e downstream towards the n e t .  R o l l e r type  s t i r r e d up the  substrate  At times the seine was held  sta-  was d i s t u r b e d by someone s p l a s h i n g However, best result's were u s u a l l y  6  obtained by t a k i n g s h o r t , middle of the  deep d r i v e s i n deep p o o l s ,  streambed towards the shore,  sweeps upstream i n shallower water.  from the  or by making l o n g  Large C . a l e u t i c u s were  sometimes c o l l e c t e d by j a b b i n g the aluminum p o l e s under the overhanging banks i n r i f f l e areas and suddenly l i f t i n g the  net  with a scooping motion. The f i s h ' w e r e 8")  h e l d i n four outdoor troughs (7'2"  w i t h r u n n i n g d e c h l o r i n a t e d water and a i r hoses.  x 16" x Some  fish  were a l s o h e l d i n a small unheated hut, i n two plywood tanks (40" x 12" x 1 8 £ " ) and i n one metal tank (8« x 1 0 £ " x 8v") r u n n i n g d e c h l o r i n a t e d water and a i r hoses. were each equipped w i t h three p l e x i g l a s s and were used to observe  The plywood tanks  windows on one  the general behaviour of the  These tanks had g r a v e l s u b s t r a t e s  of v a r y i n g depths.  v e l a t the deep .water end of the tank was 2 3/4" depth of the s u b s t r a t e  with  side,  fish. The g r a -  thick,  and the  g r a d u a l l y i n c r e a s e d u n t i l a t the  shallow  water end the g r a v e l was 10?"  to 11 3/4"  thick.  were held a t v a r i o u s times i n bare troughs,  Both s p e c i e s  over g r a v e l ,  or  over sand. The indoor tanks were provided with "hides" i n the form of halved c l a y f l o w e r p o t s .  The outdoor tanks were p a r t i a l l y  covered to g i v e the f i s h a r e f u g e . The temperatures i n these tanks f l u c t u a t e d month of February to l 6 ° C i n J u l y . tolerant  C . a l e u t i c u s i s not  of h i g h temperatures as C . asner,  c o l l e c t e d i n areas w i t h a seasonal than 1 5 ° C ( T a y l o r , 1966).  from 0 ° C i n  and i s  as  u s u a l l y not  h i g h temperature of  Consequently,  the  most of the C.  greater  7  a l e u t i c u s were kept i n the i n d o o r troughs as the summer temperat u r e i n the hut c o u l d be kept lower than outdoors. were exposed to the n a t u r a l seasonal The c o t t i d s were fed thawed,  and d a i l y l i g h t  variations.  concentrated b r i n e s h r i m p .  The d i e t was v a r i e d w i t h s m a l l f i s h , and small g o l d f i s h .  A l l fish  such as guppies,  Feeding times were unscheduled,  gouramis and a t  i r r e g u l a r i n t e r v a l s they r e c e i v e d no food f o r a day or two. T h i s was done not only to prevent the f i s h from developing a conditioned a c t i v i t y c y c l e , the c o t t i d s  but a l s o because i t was found t h a t  ate more i f they were d e p r i v e d of food one or two  days i n every v/eek. A l l tanks were t r e a t e d r e g u l a r l y w i t h one or two drops of a 1% s o l u t i o n of malachite green,  as a f u n g i c i d e .  Flow Tank For s e v e r a l experiments i t was necessary r e n t s of s e v e r a l d i f f e r e n t (8  1  20-1-" x  x  ( F i g . 1) tition  consisted  (6'2"  a plexiglas other  (8  of  1  x  speeds.  to produce c u r -  A flow tank was c o n s t r u c t e d  plywood and £ » p l e x i g l a s .  T h i s tank  of two channels separated by a plywood p a r x Hi").  One channel (5*8"  x 9l" x H i " )  w a l l through which the f i s h were observed,  x 9i"" x H i " )  had  and the  was f o r the r e c i r c u l a t i o n of water.  ends of the viewing channel were screened and a t times the  The fish  were r e s t r a i n e d i n the middle p o r t i o n of the channel i n a wire fence ( 2 3 " x  9 i " x 151").  A small submersible pump ( L i t t l e Giant model 1,115 was p l a c e d i n the r e c i r c u l a t i o n channel to provide a  volts)  constant  8  F i g u r e 1.  The flow tank and c u r r e n t producing apparatus used i n locomotion, o r i e n t a t i o n , and posture experiments.  s peedt rol overflow  0/  pipe  water  t a p ~~~~~^=S drill plexi glas  window  drive impeller  shaft  blade  9  slow c u r r e n t of l e s s than 6 cm/sec.  T h i s was c u r r e n t 1,  equi-  v a l e n t to T a y l o r ' s (1966) "noncurrent." Other c u r r e n t c o n d i t i o n s were produced by a 5" i m p e l l e r blade mounted i n the water behind the screen a t one end of viewing c h a n n e l .  T h i s was connected by a rubber i n s u l a t e d  d r i v e s h a f t to a heavy duty i n d u s t r i a l d r i l l suspended outside speedtrol  the  the tank.  The d r i l l  (Rockwell  r")  758R;  speed was r e g u l a t e d by a  (Model SC1000; C . C . I n d u s t r i e s  Inc., Philadelphia,  With t h i s apparatus surface v e l o c i t i e s of 1 3 , 2 0 , and 25  Pa.).  cm/sec were obtained ( c u r r e n t s 2 , 3 and L\.).  Various quantities  of a 1% s o l u t i o n of methylene blue were p l a c e d i n t h i s to study the p a t t e r n of the c u r r e n t .  The c u r r e n t appeared to be  r a t h e r uniform from the water surface to the surface of substrate,  system  the  except i n the area immediately i n f r o n t of the i m -  p e l l e r b l a d e , where there was much t u r b u l e n c e .  Times of Observations The f i s h used i n t h i s study were held e i t h e r i n outdoor troughs or i n a small hut which was p a n e l l e d i n f i b r e g l a s which admitted d i f f u s e  natural l i g h t .  They were t h e r e f o r e  served under n a t u r a l d a y l i g h t c o n d i t i o n s .  It  apparent t h a t both species-were more a c t i v e than at o t h e r s . active  sheets ob-  soon became  at some times of day  Both C . asper and C . a l e u t i c u s  were r a t h e r  u n t i l approximately 11 am, a f t e r which a c t i v i t y was main-  t a i n e d at a lower l e v e l very l i t t l e  u n t i l about 1 pm, and there was then  a c t i v i t y u n t i l e a r l y evening,  about dusk.-  asper were l e s s a c t i v e a t a l l times of day than the C .  The C .  10  aleuticus,  and they remained m o t i o n l e s s  "hides" throughout most of the  under t h e i r  afternoon.  I t was suggested t h a t perhaps t h i s low l e v e l a c t i v i t y i n C . asper was compensated activity.  Experiments were t h e r e f o r e  t u s designed by Byrne ( 1 9 6 8 ) ,  flowerpot  of daytime  f o r by a higher conducted,  to see i f  u s i n g appara-  the a c t i v i t y  of the two s p e c i e s d i f f e r e d r a d i c a l l y i n shape.  nighttime  cycles  The locomotary ^  a c t i v i t y of four f i s h of each s p e c i e s was recorded a u t o m a t i c a l l y . Recordings were made c o n t i n u o u s l y o f C . asper f o r ten days and °f  C« a l e u t i c u s  f o r twenty-one days.  I t was d i s c o v e r e d that i n both s p e c i e s there was a  slightly  higher l e v e l of a c t i v i t y d u r i n g most of the n i g h t than d u r i n g the day, and a b r i e f  burst of a c t i v i t y s h o r t l y a f t e r dusk.  s p e c i e s were more a c t i v e i n the e a r l y morning than i n the  Both late  afternoon. I t was t h e r e f o r e  decided that experiments  should be con-  ducted i n the e a r l y morning to ensure that' the f i s h would be observed at a time when they were normally a c t i v e l i g h t conditions  suitable  for  observation.  and under  11  RESULTS  O r i e n t a t i o n With Respect to the Current A.  Observation When C . asper and C. a l e u t i c u s were observed a t r e s t under  current conditions,  it  was noted that they a l i g n e d  i n a r a t h e r s p e c i f i c manner with r e s p e c t flow of the c u r r e n t .  themselves  to the d i r e c t i o n of  On a l l but a very few o c c a s i o n s ,  they  could be c l a s s i f i e d as e i t h e r p a r a l l e l to or broadside to d i r e c t i o n of flow.  Further,  it  appeared that the two s p e c i e s  d i f f e r e d i n t h e i r preference f o r one of these The o r i e n t a t i o n responses with r e s p e c t so c o n s i s t e n t  that i t  the  positions.  to the c u r r e n t were  was thought that they must be of c o n s i -  derable importance to the a n i m a l s .  Experiments were  therefore  conducted to determine the d i f f e r e n c e s i n the f r e q u e n c i e s of p o s i t i o n s adopted by the tv/o s p e c i e s .  the  I f one can demonstrate  d i f f e r e n c e s i n the response of two sympatric s p e c i e s to  changes  i n c e r t a i n environmental parameters one may then speculate on the s i g n i f i c a n c e  B.  of these d i f f e r e n c e s as e c o l o g i c a l  adaptations.  Method To f i n d the " p r e f e r r e d " d i r e c t i o n of o r i e n t a t i o n with r e -  spect  to the c u r r e n t , that i s ,  the one most f r e q u e n t l y assumed,  ten f i s h of one s p e c i e s v/ere p l a c e d i n a bottomless wire cage i n the middle p o r t i o n of the flow tank, where a c u r r e n t of uniform v e l o c i t y could be m a i n t a i n e d . to a c u r r e n t of constant  They were then exposed  speed for f i f t e e n  minutes.  At the end  12  o f t h i s t i m e t h e number o f f i s h f a c i n g " i n t o , " "away" from and "broadside"  t o t h e c u r r e n t source was r e c o r d e d .  Three subse-  quent r e c o r d i n g s were made a t i n t e r v a l s o f f i v e minutes.. Each group o f t e n f i s h was t e s t e d a t f o u r c u r r e n t speeds; l e s s t h a n 6 cm/sec ( " n o n c u r r e n t " ) ,  and 1 3 ,  2 0 , and 25 cm/sec.  F o r t y f i s h o f each s p e c i e s were t e s t e d on a g r a v e l s u b s t r a t e , and t h i r t y o f each s p e c i e s on sand.  C.  Results I n a n a l y s i n g these d a t a , i t was thought b e s t t o c o n s i d e r  the p a r a l l e l a l i g n m e n t as two c a t e g o r i e s , " i n t o " and "away," a s t h e r e would be a c o n s i d e r a b l e d i f f e r e n c e i n t h e p a t t e r n o f c u r r e n t f l o w around a n i m a l s i n these  positions.  The d a t a o b t a i n e d on sand and g r a v e l s u b s t r a t e s were t e s t e by two a n a l y s e s o f v a r i a n c e  ( T a b l e s I and I I ) . I n b o t h c a s e s  the o n l y one of t h e c o n d i t i o n s t h a t showed a s i g n i f i c a n t f e r e n c e a t p<0.01 was t h e d i r e c t i o n actions species x d i r e c t i o n  f a c e d ( D ) . The i n t e r -  (S x D) and d i r e c t i o n  (D x C) were a l s o s i g n i f i c a n t a t p < 0 . 0 1 . the second o r d e r i n t e r a c t i o n  dif-  x current  I n n e i t h e r case was  species x d i r e c t i o n  x current  significant. The means were compared by the Student-Newman-Keul t e s t . As can be seen from T a b l e s I I I and I V , C. a l e u t i c u s assumed t h e p a r a l l e l a l i g n m e n t more f r e q u e n t l y t h a n t h e b r o a d s i d e , C. a s p e r d i d the r e v e r s e . s i g n i f i c a n t preference tion.  while  At no time d i d G. a l e u t i c u s show a  f o r the "broadside"  over t h e " i n t o "  posi  13  TABLE I The frequency with which C . asper and C . a l e u t i c u s faced " i n t o , " "away" from and "broadside" to the c u r r e n t on a sand s u b s t r a t e , a t four c u r r e n t speeds.  SOURCE Species  SS (S)  Direction  (D)  Current (C)  0.0 1157.25 0.0 382.58  S x D  df  MS  __—  1 2  F  578.625  186.89*  3 2  191.29  61.786*  S x C  0.0  3  D x C  53.91  6  8.985  2.902*  S x D x C  36.89  6  6.148  1.986  817.37  264  3.096  Error  2448.0  Total  ^significant  at p<0.01.  287  14  TABLE I I The frequency with which C. asper and C . a l e u t i c u s faced " i n t o , " "away" from and "broadside" to the c u r r e n t on a g r a v e l s u b s t r a t e , at four c u r r e n t speeds.  SOURCE Species  SS (S)  Direction  (D)  Current (C)  0.0 265.85 0.0  MS  F  1  __ _  2  132.925  65.513*  118.975  58.637*  3  S x D  237.95  2  S x C  0.0  3  D x C  57.80  6  9.633  4.748*  S x D x C  15.33  6  2.556  1.259  ,  Error  730.4  360  2.029  Total  1307.33  383  -—  *signifleant  at p<0.01.  15  TABLE I I I The frequency with which C . asper and C . a l e u t i c u s faced i n three d i r e c t i o n s at four c u r r e n t speeds on a sand s u b s t r a t e . Data are arranged to compare " i n t o , " "away" and "broadside" o r i e n t a t i o n s at each of four c u r r e n t speeds. Tabulated v a l u e s are means obt a i n e d from 3 0 f i s h of each s p e c i e s , observed 10 at a time,  C.  asper  Current  Into  Away  1  2.75  1.0  6.25  2  1.17  0.83  8.0  3  1.25  1.0  7.75  4  1.0  0.75  8.. 25  Current  Into  Away  1  3.67  2.58  3.75  2  4.0  1.58  4.42  3  3.83  1.08  5.08  4  4.5  0.83  4.67  C.  Broadside  aleuticus Broadside  Means j o i n e d by dotted l i n e s are s i g n i f i c a n t l y p < 0 . 0 5 by the Student-Newman-Keul t e s t .  different  at  16  TABLE IV The frequency with which C . asper and C . a l e u t i c u s faced i n three d i r e c t i o n s at four c u r r e n t speeds on a gravel substrate. Data are arranged to compare " i n t o , " "away" and "broadside" o r i e n t a t i o n s at each of four c u r r e n t speeds. Tabulated values are means obtained from 40 f i s h of each s p e c i e s , observed 10 at a t i m e .  C.  asper  Current  Into  Away  1  2.25  2.75  5.0  2  2.69  1.81  5.5  3  2.38  1.56  6.06  4  1.31  2.88  5.81  Current  Into  Away  1  3.75  3.13  3.13  2  4.o  3.25  2.75  3  3.56  2.63  3.81  4  3.13  2.94  3.94  C.  Broadside  aleuticus Broadside  Means j o i n e d by dotted l i n e s are s i g n i f i c a n t l y p < 0 . 0 5 by the Student-Newman-Keul t e s t . .  different  at  17  C. asper behaved i n much the same manner on sand as on gravel,  except t h a t the preference  f o r the "broadside'" p o s i t i o n  was more pronounced on sand. C. a l e u t i c u s ,  however,  showed c o n s i d e r a b l e d i f f e r e n c e s  t h i s behaviour on g r a v e l and on sand.  On a g r a v e l  in  substrate  no one p o s i t i o n was p r e f e r r e d at e i t h e r c u r r e n t 1 or c u r r e n t 4. At c u r r e n t 2 there was a s i g n i f i c a n t l y mals t h a t assumed the "into" p o s i t i o n .  g r e a t e r number of  ani-  At c u r r e n t 3 "broad-  side" was more frequent than "away," but not more than " i n t o . " On a sand s u b s t r a t e  C. aleuticus  showed no preference  at  cur-  r e n t 1, but a t the other three c u r r e n t speeds "broadside" and and "into" were both more frequent than "away," although no significant  difference  could be found between "into" and "broad-  side." The "away" category does not appear to f o l l o w an describable pattern. than i n C . a s p e r , ference  I t was much more frequent i n C .  r e f l e c t i n g C. a l e u t i c u s '  f o r the p a r a l l e l alignment.  easily aleuticus  o v e r a l l greater pre-  At no time,  however,  more frequent than the "into" p o s i t i o n i n C . a l e u t i c u s .  was  it  C.  asper adopted the "away" p o s i t i o n more f r e q u e n t l y than the  "into"  a t h i g h c u r r e n t speeds on g r a v e l . As can be seen from Tables V and V I , c u r r e n t speeds had very l i t t l e  e f f e c t on the frequency with which C .  assumed any p o s i t i o n .  No s i g n i f i c a n t  differences  aleuticus were d e t e c -  t a b l e by the Student-Newman-Keul t e s t . C. a s p e r ,  however,  d i d respond to changing c u r r e n t speed  with a change i n p o s i t i o n .  On a g r a v e l s u b s t r a t e  the  frequency  18  TABLE V The frequency with which C . asper and C. a l e u t i c u s faced i n three d i r e c t i o n s ~ a t four c u r r e n t speeds on a sand s u b s t r a t e . Data are arranged to show the e f f e c t of four c u r r e n t speeds on a s i n g l e o r i e n t a tion. Tabulated v a l u e s are means obtained from 30 f i s h of each s p e c i e s , observed 10 at a time.  C.  asper  >  1  2  Into  2.75  1.17  1.25  1.0  Away  1.0  0.83  1.0  0.75  Broadside  6.25  8.0  7.75  8.25  1  2  3  4  Into  3.67  4. o  3.83  4.5  Away  2.58  1.58  1.08  0.83  Broadside  3.75  4.42  5.08  4.67  Current  3  4  Direction  C.  aleuticus  Current Direction  Means j o i n e d by dotted l i n e s are s i g n i f i c a n t l y p < 0 . 0 5 by the Student-Newman-Keul t e s t .  different  at  19  TABLE VT The frequency with which C . asper and C . a l e u t i c u s faced i n three d i r e c t i o n s a t ' f o u r c u r r e n t speeds on a gravel substrate. Data are arranged to show the e f f e c t of four c u r r e n t speeds on a s i n g l e o r i e n t a tion. Tabulated values are means obtained from 40 f i s h of each s p e c i e s , observed 10 at a time.  C.  asper  Current  1  2  3  4  Direction Into  2.25  2.69  2.38  1.31  Away  2.75  1.81  1.56  2.88  Broadside  5.0 .  5.5  6.06  5.81  2  3  4  C.  aleuticus  Current  1  Direction Into  3.75  4.0  3.56  3.13  Away  3.13  3.25  2.63  2.94.  Broadside  3.13  2.75  3.81  3.94  Means j o i n e d by dotted l i n e s are s i g n i f i c a n t l y p < 0 . 0 5 by the Student-Newman-Keul t e s t .  different  at  20  of  the " i n t o " category decreased at the h i g h e s t c u r r e n t speed  used, (ft),  and t h i s was s i g n i f i c a n t l y d i f f e r e n t  quency at c u r r e n t 2. first  from the  fre-  The frequency of the "away" category  d e c l i n e d and then i n c r e a s e d with c u r r e n t speed,  at  signifi-  c a n t l y d i f f e r e n t means being obtained between c u r r e n t s 1 and 3> and c u r r e n t s 3 and  ft.  The "broadside" category remained at  about the same frequency at a l l c u r r e n t speeds. On a sand s u b s t r a t e different. category, ficant.  the behaviour of C . asper was  There was a d e c r e a s i n g frequency of the the d i f f e r e n c e s  somewhat  "into"  between c u r r e n t s 2 and 3 b e i n g  signi-  The "away" category remained about the same; r a t h e r  was the "broadside" frequency which changed. of a s i g n i f i c a n t l y  T h i s category  it was  lower frequency at c u r r e n t 1, than a t any  of the other three c u r r e n t speeds.  Stanc e A.  Observation E a r l y i n the course of t h i s study i t was n o t i c e d that C .  asper and C . a l e u t i c u s  had s e v e r a l  c h a r a c t e r i s t i c postures  regard to the p o s i t i o n of head arid body and the degree of tension  of the  frequencies species.  fins.  ex-  in  the  v/ith which these "stances" were assumed by the  two  Further,  it  There appeared to be a d i f f e r e n c e  with  appeared to be p o s s i b l e  given c o n d i t i o n of s u b s t r a t e  to c o r r e l a t e a  and c u r r e n t w i t h a stance f o r each  species. The most common posture assumed by C . asper when at r e s t a sand s u b s t r a t e  was to l i e  with the b e l l y pressed  flat  on  against  21  the sand, the head h o r i z o n t a l , the d o r s a l f i n s tended and the p e c t o r a l , C. a l e u t i c u s gravel substrate fins,  ex-  folded.  a l s o assumed t h i s posture on sand, but on a they-, more f r e q u e n t l y extended  the p e c t o r a l  thus l i f t i n g the body out of the hollows between the  stones.  Under many c o n d i t i o n s of c u r r e n t and s u b s t r a t e C .  aleuticus 2),  p e l v i c and caudal f i n s  somewhat  assumed the "head down" or "head up" p o s i t i o n s  i n which the body was i n c l i n e d a t an angle to the  (Fig.  substrate.  The "head up" p o s i t i o n was about as frequent as the h o r i z o n t a l , but the "head down" was u s u a l l y only observed when the animal was f o r a g i n g f o r food among the r o c k s , of extreme  or i f i t  was i n an area  turbulence.  The d o r s a l f i n s  of C . a l e u t i c u s were most o f t e n  extended,  although under some c o n d i t i o n s the f o l d e d posture was of equal frequency. When C . asper were placed on a g r a v e l s u b s t r a t e tained t h e i r c h a r a c t e r i s t i c posture,  they r e -  so that they l a y between -  the s t o n e s . It  seemed l i k e l y t h a t the stances assumed by the  s p e c i e s would make a c o n s i d e r a b l e d i f f e r e n c e to the c u r r e n t .  to t h e i r  exposure  Experiments were t h e r e f o r e conducted to  termine d i f f e r e n c e s between the s p e c i e s .  i n the f r e q u e n c i e s  of the v a r i o u s  By comparing the stances of the  i n a v a r i e t y of c o n d i t i o n s of c u r r e n t and s u b s t r a t e , speculate  two  on the f u n c t i o n of these  postures.  de-  postures animals one could  22  F i g u r e 2.  Four postures  of C . asper and C .  a)  head up  b)  head dovm  c)  pectoral fins  expanded  d)  pectoral fins  folded  aleuticus  23  B.  Method To determine the stance most commonly assumed i n any given  c o n d i t i o n of s u b s t r a t e and c u r r e n t , f i v e  f i s h of one s p e c i e s  were p l a c e d together i n the flow tank and exposed to one of two current conditions,  "noncurrent" ( l e s s than 6 cm/sec)  r e n t " ( g r e a t e r than 10 c m / s e c ) .  and " c u r -  The f i s h were a c t u a l l y observed  a t three d i f f e r e n t c u r r e n t speeds, but s i n c e there was no detectable  d i f f e r e n c e among these c a t e g o r i e s  as one.  Consequently there are three times as many r e c o r d i n g s  f o r " c u r r e n t " as " n o n c u r r e n t . "  they were considered  The p o s i t i o n of the head and  body, and the degree of expansion of the d o r s a l and p e c t o r a l f i n s were n o t e d .  The p e c t o r a l f i n s were not c o n s i d e r e d to be  "expanded" i f they were merely fanned out f l a t a g a i n s t the substrate,  but only i f they.were h e l d at an angle to the  substrate  ( F i g . 2). A t o t a l of /+73 r e c o r d i n g s were made, f i f t e e n s p e c i e s b e i n g observed on sand, and f i f t e e n  f i s h of each  on g r a v e l .  Recor-  d i n g s were made f o r approximately f i v e minutes at a time.  C.  Results The counts obtained were grouped a c c o r d i n g to  e.g.,  " p e c t o r a l folded" ( p . f o l . )  alternatives,  and " p e c t o r a l extended"  (p.ex.).  2 A s e r i e s of X  t e s t s were then performed on the groups (Tables  VII and V I I I ) . C. asper assumed the f o l d e d p o s i t i o n of the p e c t o r a l under a l l c o n d i t i o n s t e s t e d ,  fins  the most marked preference b e i n g  shown w i t h g r a v e l and c u r r e n t (Table V I I ) .  The h o r i z o n t a l  2ft  TABLE VII Postures assumed by C. asper on sand and g r a v e l s t r a t e s under tv/o c o n d i t i o n s of c u r r e n t . 1  Sand Current Pectoral  sub-  Gravel  Noncurrent  . Current  Noncurrent  Fins  Extended  lft  3  5  0  Folded ,  33  13  57  15  ft3.6  15.0  X  7.68  6.25  p.fol.  p.fol,  p.fol.  p.fol,  Extended  37  10  55  15  Folded  10  6  7  0  15.5  l.o*  2  Preferred Dorsal F i n  Preferred  d. ex.  37.16  15.0  d. ex.  d. ex..  Head Horizontal  ftl  lft  53  lft  Head Up  5  2  9  1  Head Dov/n  1  0  0  0  Preferred  ^6  cm/sec and  *not s i g n i f i c a n t  82.99  21.5  77.85  2ft. ft  hor.  hor.  hor.  hor.  >10  cm/sec.  at  p<0.05.  25  TABLE V I I I P o s t u r e s assumed by C . a l e u t i c u s on sand and s u b s t r a t e s under two c o n d i t i o n s of c u r r e n t .  gravel  1  Gravel  Sand Current Pectoral  Noncurrent  Current  Noncurrent  Fins  Extended  26  3  95  80  Folded  45  17  62  5  5.08  9.8  p.fol.  Extended  6.93  66.18  p.fol,  p . ex.  p. ex.  59  17  70  59  Folded  12  3  87  26  X  31.11  9.8  d . ex.  d . ex.  Horizontal  58  13  77  39  Head Up  12  7  75  ^2  1  0  5  4  Preferred Dorsal  Fins  2  Preferred  1.84*  12.81 d. ex.  Head  Head Down X  2  Preferred  <6 cm/sec and  >10  61.79  12.70  64.3  hor.  hor.  hor./h.u.  cm/sec.  *not s i g n i f i c a n t at p < 0 . 0 5 .  31.51 h.u./hor.  26  (hor.)  p o s i t i o n of the body.was s i m i l a r l y g r e a t l y p r e f e r r e d ,  the preference b e i n g more marked i n c u r r e n t s i t u a t i o n s . extended posture of the d o r s a l f i n s than the d o r s a l f o l d e d p o s i t i o n preference  was s i g n i f i c a n t  The  ( d . e x . ) was more frequent  (d.fol.)  at a l l times and t h i s  except under sand and noncurrent  conditions. C. aleuticus  showed a much g r e a t e r v a r i a b i l i t y of  w i t h changing c o n d i t i o n s . d i s t i n c t preference substrate.  L i k e C . asper,  C. aleuticus  stance showed' a  f o r the p e c t o r a l f o l d e d posture on a sand  However, when placed on g r a v e l C . a l e u t i c u s much  p r e f e r r e d the p e c t o r a l extended p o s t u r e . marked under noncurrent C. aleuticus  T h i s was  especially  conditions.  assumed the d o r s a l extended posture with a-<  g r e a t e r frequency than the d o r s a l f o l d e d i n three out of cases.  The exception was a s m a l l n o n s i g n i f i c a n t  four  preference  for  the d o r s a l f o l d e d p o s i t i o n v/ith g r a v e l and c u r r e n t . C. a l e u t i c u s  favoured the h o r i z o n t a l p o s i t i o n on sand,  but  on g r a v e l the "head up" ( h . u . ) p o s i t i o n occurred w i t h equal frequency. Thus the two s p e c i e s behaved i n a very s i m i l a r manner on a sand s u b s t r a t e , gravel  but d i f f e r e d markedly i n t h e i r response  substrate.  Movement i n Response A.  to a  to Current  Observation I t was observed that C . asper had great d i f f i c u l t y i n moving  around i n the tank i n a . c u r r e n t of any magnitude,  and that  even  i n noncurrent c o n d i t i o n s theyx_did not move about as much as C. aleuticus. C. a l e u t i c u s i s a much b e t t e r  swimmer than C . a s p e r .  attempting to move up or downstream i n the presence rent, it  C . a l e u t i c u s kept close, to the s u b s t r a t e ,  was g r a v e l ,  3a).  and moved i n a s e r i e s of s h o r t ,  Using t h i s method,  of a c u r -  particularly i f rapid leaps ( F i g .  they had a remarkable a b i l i t y to main-  t a i n t h e i r p o s i t i o n i n areas of extreme upstream a g a i n s t  When  turbulence and to move  a c u r r e n t capable of d i s p l a c i n g the  gravel.  C. asper attempted to move up or downstream by swimming up at an angle  (Fig. 3 b ) .  to the s u b s t r a t e  They were r a r e l y able  to make any advances upstream i n any but the slowest c u r r e n t s , and t h e i r p r o g r e s s downstream was c o n s i d e r a b l y hastened by the current.  At times they appeared to be caught up by the c u r r e n t  and swept h e l p l e s s l y tank f a r t h e s t  a l o n g u n t i l they reached the end of  from the c u r r e n t source..  the  They were then a b l e  to  r i g h t themselves by t w i s t i n g t h e i r bodies u n t i l they were p a r a llel  to the s u b s t r a t e  and to sink to the bottom of the  tank.  Experiments were c a r r i e d out to d e t e c t a q u a n t i t a t i v e ference  i n the amount of movement up or downstream by the  s p e c i e s under v a r i o u s c u r r e n t  B.  diftwo  conditions.  Method To t e s t the amount of movement of the s p e c i e s ,  a bottomless  wire cage was p l a c e d i n the middle p o r t i o n of the flow where a c u r r e n t of constant w a l l of the tank,  speed could be maintained.  above the p l e x i g l a s  tank, The s i d e  window, was marked o f f  in  28  F i g u r e 3»  The methods used to swim i n a c u r r e n t a)  C. a l e u t i c u s  b)  C . asper  ^ d i r e c t i o n f  l o w  of  29  i n c h e s a l o n g the l e n g t h of the wire fence,  so that the  fish's  p o s i t i o n c o u l d be determined at a glance through the window (Fig.  1).  The p o s t e r i o r margin of the f i r s t d o r s a l f i n was.  taken as a p o s i t i o n marker, to e l i m i n a t e in  and i t s  f i s h was i n t r o d u c e d at the midpoint of the  p o s i t i o n was recorded every three minutes f o r  minutes while i t  cage,  fifteen  was exposed to a c u r r e n t of constant  At the end of t h i s time the  speed.  f i s h was removed and an i n d i v i d u a l  the other s p e c i e s and approximately the same s i z e was s i m i -  l a r l y tested.  These f i s h were then d i s c a r d e d and another  was t e s t e d at the same c u r r e n t  conditions  ten under "noncurrent"  ( l e s s than 6 cm/sec) and t h i r t y a t three  c u r r e n t speeds ( 1 3 , 2 0 and 23  pair  speed.  A t o t a l of f o r t y f i s h were t e s t e d ,  different  cm/sec).  T h i s experiment was conducted on a g r a v e l  C.  of changes  the d i r e c t i o n faced without any movement up or down stream. A single  of  the e f f e c t  substrate.  Results The data from t h i s experiment v/ere t e s t e d by an a n a l y s i s  v a r i a n c e (Table I X ) . a t p<0.05  (F = 3 7 . 2 3 ) .  The s p e c i e s d i f f e r e n c e  aleuticus  significant  C u r r e n t s (C) and the s p e c i e s x c u r r e n t s  i n t e r a c t i o n (S x C) v/ere not The  (S) v/as  of  significant.  s p e c i e s means v/ere compared by T u k e y ' s w (Table X ) .  C.  showed a g r e a t e r amount of movement than C . asper  under a l l c u r r e n t  conditions.  The only s i g n i f i c a n t  change i n amount of movement with, i n -  creased c u r r e n t speed was a decrease i n movement by C .  aleuticus  30  TABLE IX T o t a l number of i n c h e s moved by C . asper and C. a l e u t i c u s i n f i f t e e n minutes at four c u r r e n t speeds.  SOURCE  SS  Species  70.33  1  70.33  Current  1.77  3  0.59  0.31  S x C  4. 2  3  1.4  0.74  Error  60.48  32  Total  136.78  39  * s i g n i f i c a n t at p<0.05.  df  . MS  .  1.89  F 37.23*  31  TABLE X Mean number of i n c h e s moved by C . asper and C . a l e u t i c u s i n f i f t e e n minutes at four current"" speeds. Comparison of s p e c i e s means. Tukey's w = 2 . 3 6 0 9 .  CURRENT Means f o r : C . asper  0.1  0.2  0.1  0.8  C. a l e u t i c u s  6.8  5.5  7.8  4.8  Difference between the s p e c i e s means  5.7*  5.3*  7.7*  4.0*  1  •significantly  different  at p<0.05.  .  s i g n i f i c a n t l y d i f f e r e n t at p<0.05, when comparing w i t h i n a s i n g l e s p e c i e s at d i f f e r e n t c u r r e n t speeds.  32  betv/een c u r r e n t s 3 and k (Table X ) . nonsignificant  There i s a d e f i n i t e  i n c r e a s e i n movement by C . a l e u t i c u s  but  between  c u r r e n t s 2 and 3 .  Feeding Behaviour A.  Observation The s u p e r i o r swimming a b i l i t y and g r e a t e r " a l e r t n e s s "  C. aleuticus i s reflected  i n the species* f e e d i n g behaviour.  The most common method i n both s p e c i e s i s  to make s h o r t ,  h o r i z o n t a l d a r t s a c r o s s the bottom of the tank to s e i z e t h a t i s l y i n g on the surface of the s u b s t r a t e above i t .  or f l o a t i n g  T h i s behaviour i s  d i r e c t e d towards i n e d i b l e o b j e c t s , asper r e l i e d almost e x c l u s i v e l y The l a r g e s t  i n their hides, refuge,  food just  Such " d a r t s and grabs" have been r e p o r t e d i n another  c o t t i d s p e c i e s by Smyley (1957).  ting.  of  sometimes  which are then spat out.  C.  on t h i s technique o f food get-  i n d i v i d u a l s , which spent most of the  daytime  made b r i e f s o r t i e s f o r food not f a r from the  and q u i c k l y r e t u r n e d to i t .  T h i s method v/as used  small food items such, as b r i n e s h r i m p , and a l s o f o r small  for fish.  A method that was very r a r e l y observed i n C . asper but quite often i n C. aleuticus-was to get  swimming to the water  food that v/as d r i f t i n g down.  At times the  surface  fish's  would be almost p e r p e n d i c u l a r to the water s u r f a c e ,  v/hile  body the  p e c t o r a l f i n s were used i n a fanning motion, and the body undulated. and i t  This a c t i v i t y usually lasted  l e s s than t h i r t y seconds  v/as most commonly used when e a t i n g b r i n e s h r i m p .  C. a l e u t i c u s  would q u i t e  f r e q u e n t l y move over the g r a v e l ,  33  p u t t i n g the head down i n the c r e v i c e s up food that had s e t t l e d t h e r e .  i n the s u b s t r a t e  to  pick  T h i s f o r a g i n g behaviour was  used mainly i n o b t a i n i n g b r i n e s h r i m p , although o c c a s i o n a l l y guppy that was  a  small enough to s e t t l e between the stones was  eaten i n t h i s way. C. a l e u t i c u s  ate r e a d i l y whenever  food was a v a i l a b l e ,  d u r i n g the times of day i n which t h e i r general l e v e l v i t y was somewhat reduced. as i t  was presented,  of the  C. a l e u t i c u s i n obtaining i t s  ate  acti-  food as soon  and d u r i n g t h e i r r e l a t i v e l y i n a c t i v e  i o d they would u s u a l l y eat the entrance  C. asper l e s s often  of  only i f  even  the food was deposited  perat  hide.  seemed to r e l y on s i g h t to a c e r t a i n extent ; food.  I  The dropper by which the brineshrimp  were i n t r o d u c e d to the tank had only to appear above the water surface lar,  to set  o f f a b u r s t of a c t i v i t y i n the  fish;  in particu-  swimming to the water surface beneath the dropper. C. asper were observed to r o l l  the food w i t h t h e i r eyes as i t  t h e i r eyes up and to  d r i f t e d to the bottom of  follow the  tank. The r o l e of the chemical senses i n o b t a i n i n g food was more difficult  to determine.  I n d i v i d u a l s of both s p e c i e s were ob-  served to t u r n around and swim towards food that had been i n troduced out of l i n e tank.  away i n a  But whether t h i s was a response to chemical s t i m u l i ,  to the a c t i v i t y of  of t h e i r s i g h t some d i s t a n c e  of other f i s h i n the tank,  the experimenter,  or a chance  could not be determined.  sight  or  3ft  B.  Method P r e l i m i n a r y t e s t s were conducted In an attempt  to  ascer-  t a i n the r o l e t h a t the chemical senses played i n d e t e c t i n g presence of food.  the  The t e s t s were conducted i n a Y shaped maze  (29" x 5 i " x 6 i " ) (Fig.  ft).  The stem of the Y was p a r t i t i o n e d  o f f w i t h a p i e c e of b l a c k p l e x i g l a s ' ( 4 " x 6 " x 1 / 1 0 " ) which could be r a i s e d or lowered on a s t r i n g by the The maze was completely  enclosed  experimenter.  by b l a c k p o l y e t h y l e n e  cur-  t a i n s with narrow s l i t s through which the f i s h could be observed. A continuous small ( l / l 6 " ) on a s h e l f  flow of d e c h l o r i n a t e d water was provided by  plastic  hoses d r a i n i n g from two 5 g a l l o n  behind the e n c l o s u r e .  tanks  These hoses fed i n t o the  two  arms of the Y and a siphon d r a i n e d o f f the excess water at  the  stem of the Y. by  Water flow through the tubes was  controlled  stopcocks. A s i n g l e f i s h that had been food d e p r i v e d for about a week  was placed i n the  stem of the Y behind the p l e x i g l a s  i n the evening and l e f t  undisturbed o v e r n i g h t .  The  barrier following  morning approximately 5 ™l of thawed brineshrimp was i n t r o d u c e d i n t o one arm of the Y.  The b a r r i e r was then r a i s e d and the  f i s h ' s movements recorded f o r 3 0 minutes. F i v e f i s h of each s p e c i e s were t e s t e d i n t h i s way. The d i r e c t i o n and r a t e of d i f f u s i o n of f l u i d s i n t h i s maze were studied by observing the p a t t e r n of d i f f u s i o n of v a r i o u s amounts of a 1% s o l u t i o n of methylene the f i r s t  blue.  It  was found  that  t r a c e s of the dye were d e t e c t a b l e by the human eye  35  F i g u r e 4.  The Y trough used f o r food experiments.  detection  — plastic  hose  black  polyethylene  curtains  stopcock  -90  plexiglas  barrier-  si  H P  overflow  pipe  36  at the stem of the Y a maximum of f i v e minutes a f t e r the dye had been i n t r o d u c e d to the arms of the Y. the d i f f u s i o n of the h e a v i e s t manner was f i f t e e n  C.  The maximum time f o r  c o n c e n t r a t i o n of the dye i n  this  minutes.  Results The r e s u l t s of t h i s experiment can o n l y serve as an i n d i c a -  t i o n of the d i r e c t i o n that  future experiments should take,  as  the number of f i s h t e s t e d v/as l i m i t e d by the time a v a i l a b l e f o r this  study. Four out of f i v e C. a l e u t i c u s made " i n c o r r e c t " f i r s t  choices  (Table X I ) .  Only three C. asper made a c h o i c e ,  three chose c o r r e c t l y .  but a l l  T h i s may be e x p l a i n e d i n p a r t by c e r t a i n  d i f f e r e n c e s i n the behaviour of these s p e c i e s .  When C. asper.  are d i s t u r b e d they most o f t e n r e a c t by: l y i n g very s t i l l some time a f t e r the s t i m u l u s i s removed.  for  C. a l e u t i c u s u s u a l l y  swim q u i c k l y away from the source of the d i s t u r b a n c e (Appendix C).  As a r e s u l t ,  v/hen the b a r r i e r was r a i s e d , the C. asper  stayed i n the stem of the Y f o r as l o n g as 27 minutes before making t h e i r f i r s t choice C. a l e u t i c u s ,  Four out of f i v e of  however, v/hen d i s t u r b e d by the b a r r i e r l e f t  stem of the Y i n the f i r s t raised.  (Table X I ) .  the the  t h i r t y seconds a f t e r the b a r r i e r was  The three f i s h that swam i n t o the i n c o r r e c t arm moved  to the c o r r e c t a f t e r 6 to 6 . 5 minutes had e l a p s e d .  37  TABLE XI A b i l i t y to d e t e c t food by chemical ness of f i r s t c h o i c e .  Time of F i r s t Choice (Minutes)  senses,  Correctness of F i r s t Choice  Correct-  Time of F i r s t C o r r e c t Choice (Minutes)  C.•asper  1  11.5  correct  11.5  k  27.0  correct  27.0  5  19.5  correct  19.5  2 3  C.  aleuticus  1  0.5  incorrect  6.0  2  0.5  incorrect  6.5  3  0.5  correct  0.5  k  0.5  incorrect  6.5  5  20.0  incorrect  23.0  38  DISCUSSION  D i s c u s s i o n of  Results  Since C . a l e u t i c u s  on a sand substrate  posture  (pectoral, f i n s folded,  zontal)  that v/as common i n C . asper i t i s probable that  position i s  a response  dorsal fins  adopted a f l a t - l y i n g extended,  body h o r i -  to C. a s p e r ' s usual s u b s t r a t e .  i s indeed a r e a c t i o n to a sand s u b s t r a t e  this That  this  i s i n d i c a t e d by the  f a c t that both s p e c i e s e x h i b i t e d t h i s posture on sand i n c u r r e n t and "noncurrent" c o n d i t i o n s . gobio,  Smyley ( 1 9 5 7 ) r e p o r t e d that C .  which i n h a b i t s areas of slov/ to moderate c u r r e n t , and  which e x h i b i t s many b e h a v i o u r a l t r a i t s s i m i l a r to those of C . asper,  has a marked "preference"  f o r keeping the body i n  contact  w i t h some s u r f a c e . The preference  on the p a r t of C . a l e u t i c u s  s i o n of the p e c t o r a l f i n s on a g r a v e l s u b s t r a t e i n c o n d i t i o n s of "noncurrent" than c u r r e n t .  f o r the  exten-  v/as more marked  I t may be that  this  p o s i t i o n exposes the animal to a c e r t a i n amount of c u r r e n t , t h a t the stance has a f u n c t i o n that i s  sufficiently  "important"  to ensure t h a t t h i s posture w i l l be r e t a i n e d i n s w i f t though at a reduced frequency. posture might be that i t  The s i g n i f i c a n c e  stone as i t  forages  water,  of t h i s  among the r o c k s .  drift-  ease from stone to  I t would a l s o allow  f i s h to m a i n t a i n a more v i l ^ g a n t watch on i t s  the  surroundings.  In areas of extreme turbulence and c u r r e n t of g r e a t e r 2 5 cm/sec C . a l e u t i c u s  al-  raised  permits the animal to catch food  i n g i n the water or to move with greater  but  put the head down i n t o the c u r r e n t .  than  39  However t h i s posture was uncommon i n a r e g u l a r , even c u r r e n t except when i t  was used f o r h u n t i n g f o r food.  I t might  the animal to maintain p o s i t i o n i n areas of great The f u n c t i o n a l s i g n i f i c a n c e  enable  turbulence.  of the alignment with r e s p e c t  to the c u r r e n t i s a matter f o r s p e c u l a t i o n ,  but i t does appear  to be r e l a t e d to the postures that the s p e c i e s assume.  Animals  which l i v e i n a s t r o n g c u r r e n t have s p e c i a l problems which they can meet i n a v a r i e t y of ways.  Animals with s t r e a m l i n e d body  shapes that o f f e r a minimum of r e s i s t a n c e against  the c u r r e n t .  Those with f l a t t e n e d  c l i n g i n g h a b i t s minimize the e f f e c t against  the s u b s t r a t e .  take s h e l t e r  body shapes and  of the c u r r e n t by p r e s s i n g  And s t i l l o t h e r s escape a l t o g e t h e r and  under r o c k s or i n mats of a q u a t i c  (Needham e t . a l . ,  1935).  I t could be that  c u r r e n t and s p r e a d i n g the pectoral- f i n s resist  to the water can swim  the c u r r e n t more e f f e c t i v e l y .  vegetation  f a c i n g p a r a l l e l to  the  enables C. a l e u t i c u s  to  However, C . asper p r e -  sumably o b t a i n s an even g r e a t e r degree of s e c u r i t y by l y i n g -down between the  stones of a g r a v e l s u b s t r a t e .  The advantages  a l e u t i c u s remaining on the surface of the stones must  to C .  outweigh  the i n c r e a s e d exposure to the c u r r e n t . The " i n t o " p o s i t i o n appears to have a s p e c i a l f o r C. a l e u t i c u s .  Since C . a l e u t i c u s  f l o a t i n g i n the water,  significance  feeds p a r t l y on organisms  the "into" p o s i t i o n would enable them to  d e t e c t food f l o a t i n g downstream and to i n t e r c e p t i t more efficiently. it  I f the f i s h faces away from the oncoming c u r r e n t  has to swim downstream a f t e r  current i t  the f o o d .  can dart up to i n t e r c e p t i t .  If i t  faces i n t o  the  Such quick d a r t s and  40  l e a p s are more c h a r a c t e r i s t i c of these s p e c i e s than prolonged swimming. The f a c t  that both s p e c i e s assumed the broadside  position  more f r e q u e n t l y on sand than on g r a v e l suggests that t h i s t i o n i s an a d a p t a t i o n to a sand environment. u n l i k e l y that i t r e n t since i t  posi-  I t would seem  has a f u n c t i o n as a means of a v o i d i n g the  p l a c e s more of the f i s h ' s  body d i r e c t l y i n  path of the c u r r e n t than any other p o s i t i o n .  cur-  the  However, C . asper  employed t h i s p o s i t i o n more f r e q u e n t l y i n c u r r e n t than noncurrent,  on sand.  Since C . asper i s  i n a c u r r e n t , the s i g n i f i c a n c e it  a poor swimmer,  especially  of t h i s p o s i t i o n might be  that  enables the animal to move most of the time a t an angle  the d i r e c t i o n of flow,  so that i t i s l e s s e a s i l y  to  d i s p l a c e d by  the c u r r e n t . In the l i g h t of t h e i r feeding behaviour observed i n laboratory i t  the  i s l i k e l y that C . a l e u t i c u s depends oh v i s i o n  a g r e a t e r extent than C . asper does.  to  C . asper probably depend  mostly on t h e i r chemical senses to d e t e c t food and only use t h e i r v i s i o n to l o c a t e to s e i z e i t .  food more p r e c i s e l y  as they d a r t forward  The ease and frequency with v/hich C.  take f l o a t i n g food i n d i c a t e  aleuticus  that they depend on v i s i o n to some  degree. That a t l e a s t some s p e c i e s of c o t t i d s r e l y on v i s i o n  to  some extent i s i n d i c a t e d by Smyley (1957) and P h i l l i p s and Claire tively,  (1966), who s t u d i e d C . gobio and C . perplexus  respec-  and who found that these s p e c i e s p r e f e r r e d moving food.  C. a s p e r ' s r e l u c t a n c e  to feed d u r i n g the day i s probably  41  r e l a t e d to i t s  i n h i b i t i o n against  l e a v i n g the hide d u r i n g t h i s  Smyley ( 1 9 5 7 ) noted that C . gobio ate very c l o s e  period.  the hide and seldom emerged to hunt food, The d i f f e r e n c e  except at  to  night.  i n swimming a b i l i t y between these s p e c i e s  i s probably a l s o r e l a t e d to t h e i r feeding behaviour, as C . asper appears to be a l u r k i n g p r e d a t o r , at l e a s t i n the whereas C. a l e u t i c u s i s an a c t i v e  General  daytime,  forager and h u n t e r .  Discussion  T a y l o r ( 1 9 6 6 ) attempted to determine the extent to which C . asper and C . a l e u t i c u s  s e l e c t the c u r r e n t and s u b s t r a t e  types  with which they are a s s o c i a t e d  i n the L i t t l e Campbell R i v e r .  presented i n d i v i d u a l s of three  s i z e groups ( l e s s than 4 0 mm, 40  to 85 mm and 8 5 to 90 mm) v/ith a choice of f i n e (gravel)  substrate.  He a l s o presented  choices simultaneously.  Table X I I .  All  His r e s u l t s  and c u r r e n t and subare summarized on  Comparing t h i s v/ith the c u r r e n t and s u b s t r a t e  d i t i o n s at the c o l l e c t i o n C. a l e u t i c u s  (sand) or coarse  c u r r e n t ( 4 5 cm/sec) and  "noncurrent" ( l e s s than 7 cm/sec) c h o i c e s , strate  He  s i t e s (Table X I I I ) , one can see  behaved as one would expect from f i e l d  conthat  observations.  s i z e groups s e l e c t e d c u r r e n t and g r a v e l over noncurrent and  sand.  No s i g n i f i c a n t  choice of the l a r g e s t  difference  v/as detected i n the  gravel/sand  s i z e group but t h i s a c c o r d s v/ith t h e i r  occurrence i n the pool h a b i t a t .  S i m i l a r l y , the l a c k of p r e f e r -  ence with r e g a r d to c u r r e n t i n the C . a l e u t i c u s  f r y corresponds  with t h e i r c o l l e c t i o n i n areas of slow c u r r e n t . The r e s u l t s  of the C . asper t e s t s are l e s s c o n v i n c i n g i n  42  TABLE XII Summary of r e s u l t s of s u b s t r a t e / c u r r e n t v e l o c i t y experiments (G. T a y l o r , 1 9 6 6 ) .  choice  C o n d i t i o n S e l e c t e d '/Then Presented With:  Size Group  gravel/sand  noncurrent/ current  s a n d / g r a v e l and noncurrent/ current  < 4 0 mm (Fry) C.  asper  gravel  no preference  no preference  C.  aleuticus  gravel  no preference  current/gravel  no preference  noncurrent  no preference  gravel  current  c urrent/gravel  40 to 85 mm C.  asner  C. a l e u t i c u s  85 to 90 mm C.  asper  no preference  no preference  no preference  C.  aleuticus  no preference  current  current/gravel  43  TABLE XIII E c o l o g i c a l data on the areas of the L i t t l e Campbell R i v e r from which C . asper and C , a l e u t i c u s were collected.  Pools  Riffles  silt, mud, oyster shell  sand, silt, mud  sand, fine gravel  coarse and fine gravel  0-30  0-45  C.  C.  Estuary Most Common Substrate  Current* cm/sec Species Collected  Middle R i v e r  Lower River  asper  C. a l e u t i c u s Fry « 4 0 mm)  •measured by T a y l o r  (1966).  asper  <7.5 C . asper mm  >100  C. a l e u ticus >50 mm  0-90 C. aleuticus  4A  t h a t a s u r p r i s i n g l a c k of a preference by two s i z e groups.  f o r noncurrent i s  T h i s may have been due to T a y l o r ' s e x p e r i -  mental method, v/hich i n v o l v e d checking the f i s h ' s intervals,  shown.'  r a t h e r than continuous o b s e r v a t i o n .  t h a t many C. asper never l e f t  position  at  He r e p o r t e d  the s t a r t i n g p o i n t where the  cur-  r e n t was r a t h e r low. Taylor did f i n d ,  however,  that the g r e a t e s t divergence  choice between C. asper and C. a l e u t i c u s  occurred i n the  group t h a t was most s h a r p l y segregated i n n a t u r e . laboratory findings,  when compared with h i s f i e l d  in  size  Taylor's observations,  i n d i c a t e that the l a b o r a t o r y c o n d i t i o n s corresponded to the n a tural habitat.  T h i s enables one to assume that behaviour ob-  served i n these c o n d i t i o n s i s response  to i t s  a real  feature  of the  animal's  environment.  The f i n d i n g s of t h i s study agree on the whole with T a y l o r ' s . C. asper tends to avoid c u r r e n t on a g r a v e l s u b s t r a t e down among the  stones,  and to minimize the e f f e c t  on sand by keeping the body pressed C. a l e u t i c u s ,  however,  a c t u a l l y exposes i t  flat  against  by l y i n g  of c u r r e n t the  substrate.  adopts a posture and an o r i e n t a t i o n  that  to the e f f e c t s of the c u r r e n t , on a g r a v e l  substrate. That the s p e c i e s are d i f f e r e n t i a l l y adapted to t h e i r m i c r o h a b i t a t s i n some way i s f i n d i n g s of t h i s adaptations  apparent from T a y l o r ' s r e s u l t s .  The  study i n d i c a t e what some of the b e h a v i o u r a l  are.  The morphology of C . asper and C . a l e u t i c u s the d i f f e r e n c e s  i n their habitats.  Among r e l a t e d  also  reflects  s p e c i e s of  45 f i s h that d i f f e r i n t h e i r swimming h a b i t s i t i s a general r u l e that  the more a c t i v e  form has a s l e n d e r e r caudal peduncle and a  more s t r e a m l i n e d shape than i t s al.,  1962).  sedentary r e l a t i v e s  Dorso-ventral depression i s  d w e l l i n g stream f i s h and i t  associated  ( L a g l e r et/ with bottom  presumably a i d s them i n keeping i n  p o s i t i o n i n a s t r o n g c u r r e n t ( L a g l e r et a l . , 1 9 6 2 ) .  C . asper  is  thus t y p i c a l of the trend i n sedentary bottom d w e l l e r s and C . aleuticus i s representative /  of more a c t i v e  C . asper and C . a l e u t i c u s  f i s h which i n h a b i t swift  fish.  l a c k swim b l a d d e r s , as do many  streams  (Lagler  et a l . , 1 9 6 2 ) .  Al-  though the absence of a swim bladder i s no drawback to a sedent a r y bottom d w e l l e r , tage to a more a c t i v e hydrostatic  i t might at f i r s t species.  organs enable  appear to be a d i s a d v a n -  Swim b l a d d e r s which f u n c t i o n  as  f i s h to expend a minimum amount of  energy i n m a i n t a i n i n g p o s i t i o n  ( L a g l e r et a l . , 1 9 6 2 ) .  However,  i n a s t r o n g c u r r e n t to be of equal d e n s i t y with the water r e quires greater, et  al.,  not l e s s ,  energy to maintain p o s i t i o n  1962).  The mouth s i z e of c o t t i d s i s determines 1954).  (Lagler  of the f i r s t  the s i z e of the food that they eat  Of the two s p e c i e s c o n s i d e r e d here,  a l s o has the l a r g e r mouth r e l a t i v e t o r y they feed almost substrate  exclusively  importance,  the l a r g e r C . asper In the  on organisms r e s t i n g i n Northcote  (1954)  that C. asper of g r e a t e r than 5 0 mm mainly eat aquatic l a r v a e such as P l e c o p t e r a , Ephemoptera, T r i c h o p t e r a , (chironomids),  it  (Northcote,  to body s i z e .  or f l o a t i n g j u s t above i t .  as  laborathe  reported insect  and D i p t e r a  which l i v e among weeds and stones'"or burrow i n  46  sand or mud (Macan and Worthington, 1 9 5 1 ) . l a r g e r p l a n k t o n i c forms,  S c u l p i n f r y eat  such as C l a d o c e r a .and Copepoda (North-  c o t e , 1 9 5 4 ) , -which, l i k e a l l p l a n k t o n i c s p e c i e s , small animals (Macan and. Worthington, 1 9 5 1 ) . mouthed s c u l p i n s , ploit  the  such as C . a l e u t i c u s ,  are r a t h e r  Active,  small  could continue  to  ex-  the p l a n k t e n as an a d d i t i o n a l food source when a d u l t s .  T h i s would r e q u i r e a s u p e r i o r swimming a b i l i t y and a g r e a t e r dependence on v i s i o n than the bottom f e e d i n g h a b i t .  I f the  i n h a b i t s a r e a s of strong c u r r e n t i t must adopt modes of haviour t h a t enable i t ter.  permitting i t  itself  o r i e n t s p a r a l l e l to the d i r e c t i o n of  above the r o c k s on spread p e c t o r a l  to survey i t ' s  surroundings and to launch  q u i c k l y upwards to c a t c h f l o a t i n g C. asper i s  a poor swimmer.  c i e n c y as a r e s u l t  of  to the s u b s t r a t e  tive,  affi-  however,  These i n c l u d e a gain i n mimetic (Appendix D), and i n the  (Lagler et a l . , 1962),;  C . asper i s  spending most of the b r i g h t e s t  l o g s or stones or i n mats of  itself  Such a l o s s of swimming  such s e c r e t i v e h a b i t s as the use of stones or other  as s h e l t e r  fins,  food.  of d o r s o - v e n t r a l depression i s ,  o f f s e t by c e r t a i n advantages. resemblance  be-  to o b t a i n t h i s k i n d of food i n f a s t wa-  Thus C . a l e u t i c u s  flow and l i f t s  fish  efficiency objects  extremely  secre-  hours of the day under  vegetation.  SUMMARY  T h i s study i s an examination of the behaviour of two r e l a t e d sympatric s p e c i e s which occupy d i f f e r e n t  microhabitats  to determine which are some of the important b e h a v i o u r a l adaptations  to these d i f f e r e n c e s  C. asper i s  collected  textured substrate.  i n environment.  i n areas o f slow c u r r e n t and  C . a l e u t i c u s i s most f r e q u e n t l y found i n  areas of moderate to f a s t c u r r e n t and coarse When exposed  substrate.  to a c u r r e n t i n the l a b o r a t o r y C . asper  p r e s s e s the body a g a i n s t  the s u b s t r a t e  and l i e s at r i g h t angles  to the c u r r e n t , thus a v o i d i n g the c u r r e n t , or at l e a s t mizing i t s  mini-  effects.  In a c u r r e n t C . a l e u t i c u s  faces p a r a l l e l to the  of flow and on a g r a v e l s u b s t r a t e r a i s e s s i o n of the p e c t o r a l f i n s . may be that i t food.  finely  direction  the body by the  One of the f u n c t i o n s of t h i s  enables the animal to s i g h t  on and c a t c h  expanposture floating  The spread p e c t o r a l f i n s might a l s o enable the animal  to r e s i s t  the c u r r e n t .  In both s p e c i e s stance and o r i e n t a t i o n to the c u r r e n t seem to be i n p a r t a response C. asper and C . a l e u t i c u s  to the nature of the. s u b s t r a t e .  Both  adopt a t y p i c a l l y C . asper posture and  o r i e n t a t i o n on sand with a greater frequency than on g r a v e l , and C. a l e u t i c u s  type behaviour i s more frequent i n both s p e c i e s on  g r a v e l than on sand.  However, C . asper s t i l l assumes the broad-  s i d e p o s i t i o n on g r a v e l with an equal or g r e a t e r frequency than the p a r a l l e l , and C_. a l e u t i c u s  still  shows a p r e f e r e n c e ,  48  although a reduced one,  f o r the p a r a l l e l alignment on sand.  Both s p e c i e s appear to employ v i s i o n and the senses i n o b t a i n i n g food, but to d i f f e r e n t  chemical  extents.  C. a l e u -  t i c u s appears to employ v i s i o n more than C. asper does. ever,  How-  C. asper would r e q u i r e some a i d from v i s i o n to s i g h t  the food before d a r t i n g forward to s e i z e C. a l e u t i c u s  relies  shown by t h i s  it.  on v i s i o n to l o c a t e  feeds on f l o a t i n g organisms.  on  However, the  its  food when  it  f o r a g i n g behaviour  s p e c i e s suggests t h a t they a l s o use the chemical  senses i n h u n t i n g , although perhaps t h e i r a b i l i t y to d e t e c t food i n t h i s manner operates over a much s h o r t e r d i s t a n c e  than  i n C. a s p e r . C. asper i s a very poor swimmer compared to C. a l e u t i c u s and moves around much l e s s i n both current and noncurrent c o n d i tions. its  T h i s corresponds with C. a s p e r s r e l u c t a n c e to leave  hide d u r i n g the  1  daytime.  49  BIBLIOGRAPHY  B a i l e y , Jack E . 1952C L i f e h i s t o r y and ecology of the s c u l p i n Cottus b a i r d i / p u n c t u l a t u s - i n southwestern Montana. Copeia  1952 ( 4 ) : 2 4 3 - 2 5 5 . Bond, C . E . / 1 9 6 3 / D i s t r i b u t i o n and ecology of freshwater s c u l p l n s ' ^ g e n u s C o t t u s , i n Oregon. P h . D . t h e s i s . Univers i t y of~MichiganT 186 p. Byrne, John E . 1 9 6 8 . The e f f e c t s of photoperiod and temperature on the d a i l y p a t t e r n of locomotion a c t i v i t y i n j u v e n i l e sockeye salmon (Oncorhynchus nerka, Walbaum). P h . D . thesis. U n i v e r s i t y of B r i t i s h Columbia. 120 p . Carl,  G. C l i f f o r d , W.A. Clemens and C C . L i n d s a y / 1959. The freshwater f i s h e s of B r i t i s h Columbia, B r i t i s h Columbia p r o v i n c i a l museum Handbook no. 5* 189 p.  D a i b e r , F r a n k l i n C. 1956. A comparative a n a l y s i s feeding h a b i t s of tv/o benthic stream f i s h e s .  of the winter Copeia 1956  ( 3 ) : 141-151. D a v i s , Gerald E . and C h a r l e s E . Warren. 1965. Trophic r e l a t i o n s of a s c u l p i n i n l a b o r a t o r y stream communities. J. of W i l d l i f e Management 29 ( 4 ) : 8 4 6 - 8 7 1 . Dineen, Clarence F . 1951A comparative study of the food hab i t s of Cottus b a i r d i i and a s s o c i a t e d s p e c i e s of s a l monidae. Am. Midland N a t u r a l i s t 4 6 : 640-645. Dobzhansky, T h . 1956. What i s a l i s t 90: 337-347.  an adaptive  trait?  Am. Natur-  Greenbank, John. 1957. A g g r e g a t i o n a l behaviour i n a f r e s h water s c u l p i n . Copeia 1957 ( 2 ) : 157. Hartley, P . H . T . 1948. Food and f e e d i n g r e l a t i o n s h i p s i n a community of freshwater f i s h e s . J . Animal E c o l . 1 7 : 1 - 1 4 . Heard, W i l l i a m R. 1965. L i m n e t i c c o t t i d l a r v a e and t h e i r u t i l i z a t i o n as food by j u v e n i l e sockeye salmon. Trans. Am. F i s h e r i e s . Soc. 9 4 : 191-193. Hinde, R . A . 1959* Behaviour and s p e c i a t i o n i n b i r d s and lower vertebrates. B i o l . Rev. 3 4 : 8 5 - 1 2 8 . K r e s j a , Richard Joseph. 1965. The s y s t e m a t i c s of the p r i c k l y s c u l p i n Cottus asper:- an i n v e s t i g a t i o n of g e n e t i c and nongenetic v a r i a t i o n w i t h i n a p o l y t y p i c s p e c i e s . P h . D . thesis. U n i v e r s i t y of B r i t i s h Columbia. 183 p.  50  Lack, D a v i d . 1965. 34: 223-231.  Evolutionary ecology.  J . Animal E c o l .  L a g l e r ^ K a r l F . , John E . BaTd'acM and Robert R. M i l l e r . ,s\ / I c t h y o l o g y . John Wiley' and Sons, I n c . , New York.  1962. 545 p .  L i l e y , N.R. 1966. E t h o l o g i c a l i s o l a t i n g mechanisms i n four sympatric s p e c i e s of p o e c i l i i d f i s h e s . Behaviour Supplement X I I I . 197 p . Macan, T . T . and E . B . Worthington. 1951. Rivers. C o l l i n s . London. 272 p.  L i f e i n Lakes and  Mason, Herbert L . and Jean H.'Lagenh'eim. 1961. Natural select i o n as an e c o l o g i c a l concept. Ecology 4 2 (1): 158-165. Mayr, E r n s t . 1947. Ecological factors i n speciation. t i o n 1 ( 3 ) : 263-288.  Evolu-  McLarney, W i l l i a m 0 . 1 9 6 4 . The coast range s c u l p i n Cottus aleuticus: S t r u c t u r e of a p o p u l a t i o n and p r e d a t i o n on eggs of the p i n k salmon, Oncorhynchus gorbuscha. M.S. t h e s i s . U n i v e r s i t y of M i c h i g a n . 83 p. M i l l e r , Alden H. 1942. H a b i t a t s e l e c t i o n among higher v e r t e b r a t e s and i t s r e l a t i o n to i n t r a s p e c i f i c v a r i a t i o n . Am. N a t u r a l i s t 7 6 : 25-35. M o r r i s , Desmond. 1954. Reproductive behaviour of the r i v e r Bullhead (Cottus gobioj with s p e c i a l r e f e r e n c e to fanning activity. Behaviour 7 (1): 1-32. Needham, James G . , Jay R. Traver and Y i n - C h i Hsu. 1935. b i o l o g y of M a y f l i e s . Comstock P u b l i s h i n g Co. I n c . , Ithaca, N.Y.  The  Northcote, Thomas G. 1954. Observations on the comparative ecology of two s p e c i e s of f i s h , Cottus asper and C o t t u s rhotheus, i n B r i t i s h Columbia. Copeia 1954 (1): 25-28. , and G . F . Hartman. 1959. A case of "schooling" behaviour i n the p r i c k l y s c u l p i n C o t t u s asper R i c h a r d s o n . Copeia  1959 (2): 156-158.  O r i a n s , Gordon H. 1 9 6 2 . N a t u r a l s e l e c t i o n and theory. Am. N a t u r a l i s t 9 6 : 257-263.  ecological  P h i l l i p s , Robert W. and E r r o l W. C l a i r e . 1966. Intragravel movement of the r e t i c u l a t e s c u l p i n , Cottus perplexus, and i t s p o t e n t i a l as a predator on salmonid embryos. Trans. Am. F i s h e r i e s Soc. 95 (2): 210-212.  51  Roe,  Anne and George Gaylord Simpson ( e d s . ) . 1958. Behaviour and e v o l u t i o n . Yale U n i v e r s i t y P r e s s . New Haven, Conn. 555 P.  S i e g e l , Sidney. 1 9 5 6 . Nonparametric s t a t i s t i c s . Book Co. I n c . T o r o n t o . 3 1 2 p.  McGraw-Hill  Simon, James R. and Robert C . Brown. 1 9 4 3 . O b s e r v a t i o n s on the spawning of the s c u l p i n Cottus semiscaber. Copeia 1943 ( 1 ) : 4 1 - 4 2 . Smyley, W . J . P . 1 9 5 7 . The l i f e h i s t o r y of the Bullhead or M i l l e r ' s thumb (Cottus gobio L . ) . P r o c . Z o o l . Soc. London. 128 ( 2 ) : 4 3 1 - 4 5 3 . S t e e l , Robert G . D . and James H. T o r r i e . I960. P r i n c i p l e s and procedures of s t a t i s t i c s . McGraw-Hill Book Co. I n c . Toronto. 4 8 1 p. Straskaba, M i l a r , J i r i C h i a r , S t a n i s l a v Frank and V a c l a v Hruska. 1 9 6 6 . C o n t r i b u t i o n to the problem of food compet i t i o n among the s c u l p i n , minnow and brown t r o u t . J. Animal E c o l . 3 5 : 3 0 3 - 3 1 1 . T a y l o r , Gerald D. 1 9 6 6 . D i s t r i b u t i o n and h a b i t a t response of the coastrange s c u l p i n (Cottus a l e u t i c u s ) and p r i c k l y s c u l p i n (Cottus asper) i n the L i t t l e Campbell R i v e r , B r i t i s h Columbia. M.Sc. t h e s i s . U n i v e r s i t y of B r i t i s h Columbia. 89 p. Tax,  Sol ( e d . ) . i960. E v o l u t i o n a f t e r Darwin. v e r s i t y of Chicago P r e s s . 629 p .  Vol. I.  Thorpe, W.H. 1945* The e v o l u t i o n a r y s i g n i f i c a n c e selection. J . Animal E c o l . 14 ( 2 ) : 6 7 - 7 0 .  of  Uni-  habitat  Zarbock, W i l l i a m M. 1 9 5 1 . L i f e h i s t o r y of the Utah s c u l p i n , Cottus b a i r d i semiscaber (Cope), i n Logan R i v e r , Utah. T r a n s . Am. F i s h e r i e s Soc. 8 l ' : 2 4 9 - 2 5 9 .  52  APPENDIX  In the course of t h i s  study,  many hours v/ere spent simply  o b s e r v i n g the f i s h i n a v a r i e t y o f s i t u a t i o n s ,  i n an attempt  form a general i m p r e s s i o n of t h e i r b e h a v i o u r .  Many i n c i d e n t s  were observed which were not f u r t h e r examined by but which have c o n s i d e r a b l e b e a r i n g on t h i s Appendix,  therefore,  is  of these o b s e r v a t i o n s ,  A.  A d a p t a b i l i t y to L a b o r a t o r y C o n d i t i o n s  This  appeared toadapt more q u i c k l y to the  t o r y c o n d i t i o n s than C . a s p e r . sooner a f t e r  study.  which make up the background f o r much of  research.  C» a l e u t i c u s  experiments,  an o u t l i n e of some of the more p e r t i n e n t  this  "  f i s h from the f i e l d to eat,  it  labora-  C . a l e u t i c u s began to eat much  they were brought i n t o the l a b o r a t o r y .  In i n d u c i n g  was noted that the smaller  v i d u a l s of both s p e c i e s were the f i r s t  to take the  food.  p l a c i n g i n d i v i d u a l s from a group of f i s h that were e a t i n g i n a group that were not e a t i n g , second group to  to  it  was p o s s i b l e  indiBy well  to induce  the  eat.  I n d i v i d u a l s of both s p e c i e s were kept a l i v e and i n apparent good h e a l t h f o r over a y e a r , i n d i c a t i n g that they were w e l l adapted to l a b o r a t o r y c o n d i t i o n s .  B.  Influence  on Numbers on Behaviour  In keeping these f i s h and i n o b s e r v i n g t h e i r behaviour, numbers o f i n d i v i d u a l s kept i n a s i n g l e  tank seemed to be of  the  53  some importance.  Both s p e c i e s e x h i b i t e d very l i t t l e  behaviour among themselves,  aggressive  except v/hen extremely crowded.  though c o t t i d s are t e r r i t o r i a l i n the b r e e d i n g season  Al-  (Morris,  1954; Smyley, 1 9 5 7 ) and the l a r g e r specimens ( g r e a t e r than 80 mm) were u s u a l l y c o l l e c t e d only a few at a t i m e , appear to be any n e c e s s i t y aquaria.  In f a c t ,  there d i d not  to separate the f i s h i n i n d i v i d u a l  i t v/as found that whenever the f i s h were  i s o l a t e d i n t h i s manner they stopped e a t i n g and soon d i e d .  This  i s not to say t h a t the deaths were a t t r i b u t a b l e to s t a r v a t i o n , as i n most cases the dead f i s h v/ere of normal  weight.  V/hen ten to t h i r t y f i s h were kept t o g e t h e r , would a s s o c i a t e  under a s i n g l e  flowerpot.  many i n d i v i d u a l s  T h i s was p a r t i c u l a r l y  marked i n C . a s p e r , which spent so much of t h e i r time i n these refuges. One male C . a l e u t i c u s i n breeding c o n d i t i o n e s t a b l i s h e d a 1  t e r r i t o r y i n one flowerpot i n a tank v/ith about f i f t e e n fish,  but very l i t t l e  response  other  to h i s d i s p l a y s was noted i n the  other i n d i v i d u a l s . Some a g g r e s s i v e  behaviour was seen i n connection with f e e d -  i n g when the animals were very crowded. noticeable i n C. aleuticus, m a r i l y fed with i t s  which i n these c o n d i t i o n s  p e c t o r a l , c a u d a l , and d o r s a l f i n s ,  sometimes i t s ' operculum spread. aggressive  T h i s was p a r t i c u l a r l y  and  T h i s i s very s i m i l a r to  behaviour noted by M o r r i s ( 1 9 5 5 ) i n C . g o b i o .  mally these " d i s p l a y s " d i d not r e s u l t i n any o v e r t activity,  custo-  although a few i n c i d e n t s were noted.  the Nor-  aggressive  The most common  a c t i v i t y of t h i s nature was p e c t o r a l f i n b i t i n g , although there  54  was a l s o some c h a s i n g and n i p p i n g . were a l s o noted i n C . asper,  D i s p l a y s of t h i s  but l e s s f r e q u e n t l y ,  nature  and overt  a g g r e s s i v e behaviour was very r a r e . Cases of aggregation behaviour have been r e p o r t e d i n field  f o r both C . a l e u t i c u s  (Northcote and Hartman,  C.  the  (Greenbank, 1 9 5 7 ) and C . asper  1959).  Response to U n f a m i l i a r S t i m u l i On many d i f f e r e n t  they were presented  occasions  these f i s h were observed when  with u n f a m i l i a r o b j e c t s or s t i m u l i .  times t h i s was done d e l i b e r a t e l y ,  at others i t  Some-  occurred as a  r e s u l t of an experiment that was p r i m a r i l y designed  f o r some  other purpose. V/hen the s t i m u l u s was an u n f a m i l i a r v a r i a n t of one which was common i n the n a t u r a l environment, shrimp,  the  such as f r o z e n b r i n e -  f i s h d i d not behave i n an-."excited" manner.  might i g n o r e the u n f a m i l i a r o b j e c t then approach s l o w l y ,  They  f o r minutes or even days;  and f i n a l l y e x h i b i t e d no a v o i d a n c e ' b e -  haviour when another such o b j e c t v/as i n t r o d u c e d . S t i m u l i which the human observer might expect to be ghtening were r e a c t e d to i n a v a r i e t y of ways. such as a styrofoam shape, deep water, eyerolling.  fri-  An o b j e c t ,  dragged over the surface i n r a t h e r  e l i c i t e d very l i t t l e  response  other than upward  However, i f a handnet was dragged a l o n g the  o f the tank both s p e c i e s became very " e x c i t e d , " q u i c k l y away from the d i s t u r b e d are of the L i g h t s of even very low i n t e n s i t y  bottom  swimming  substrate.  shone on a darkened tank,  55  and t a p p i n g on the side of the tank, ferent  elicited  behaviour i n the two s p e c i e s .  somewhat d i f -  The animal would  either  "freeze" i n p o s i t i o n and remain immobile,  or i t would swim  q u i c k l y away,  The former r e a c t i o n  often  to the nearest h i d e .  was most common i n C . asper,  D.  the l a t t e r i n C .  aleuticus.  Cryptic Colouration Both C . asper and C . a l e u t i c u s  alter  have a remarkable a b i l i t y  the shade and p a t t e r n of t h e i r c o l o u r a t i o n to s u i t  background.  T h i s makes them very d i f f i c u l t  to see,  t  their  when they  are observed from above. On a uniform, p a l e coloured background, such as  grayish  sand, 0. asper became u n i f o r m l y pale gray, and t h e i r f i n s nearly transparent.  are  On a more v a r i e d background, such as gray  and b l a c k g r a v e l and/or brown sand with weeds, they are marbled v/ith f i v e  or s i x pronounced dark v e r t i c a l saddles under the  dorsal fins.  The b e l l y i s l i g h t  In C . a l e u t i c u s ,  colouration i s  the i n d i v i d u a l a n i m a l . white,  coloured. f a i r l y characteristic  Most i n d i v i d u a l s are speckled  of  gray and  with three b l a c k saddle marks and b l a c k b a r s on d o r s a l ,  p e c t o r a l and caudal f i n s . brown and white, or b l a c k s a d d l e s . strate, when the  A few f i s h ,  however,  are  speckled  producing a sandy c o l o u r , with v e r y dark brown In a l l i n d i v i d u a l s on a h i g h l y v a r i a b l e sub-  such as g r a v e l ,  the  saddles are. prominent,  f i s h i s p l a c e d on a uniform background.  but they fad  

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