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An experimental study of some visually released behaviour patterns in young coho salmon and Kamloops… Stringer, George Everett 1952

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AN EXPERIMENTAL STUDY OF SOME VISUALLY RELEASED BEHAVIOUR PATTERNS IN YOUNG COHO SALMON AND KAMLOOPS TROUT by GEORGE EVERETT STRINGER  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS In the Department of ZOOLOGY  We accept t h i s t h e s i s as conforming to the standard r e q u i r e d from candidates f o r the degree of MASTER OF ARTS.  Members of the Department of Zoology. THE UNIVERSITY OF BRITISH COLUMBIA April, 1952.  ABSTRACT  Coho underyearlings settle toward the bottom when illumination decreases.  The c r i t i c a l Intensity for this  response was found to be approximately 1 foot candle. A study of the nipping phenomenon i n coho and kamloops trout revealed that coho nip more Intensively than trout i n a homotypic group.  However; i n a heterotypic group  of equal numbers, trout nip more r e a d i l y .  In a heterotypic  group coho nip less frequently and show a preference to nip other coho.  By comparison, the nipping Intensity of trout i s  not reduced and they nip either species equally. Factors affecting nipping are size, intensity.  color and l i g h t  In a group of coho or trout, there i s a marked  tendency for the larger members to nip the smaller. orange colors are least effective response.  Red and  i n e l i c i t i n g a nipping  Light intensity changes between H- and 12 foot  candles have no significant effect;  however, below k foot  candles nipping declines r a p i d l y as i l l u m i n a t i o n i s decreased. The s o c i a l releaser for nipping i s movement but size and color are Important components of the releaser. Additional patterns of behavior have been vdescribed for trout, namely, "threatening  11  and f i g h t i n g .  TABLE OF CONTENTS  INTRODUCTION  1  MATERIALS AND METHODS Settling Nipping and T e r r i t o r i a l Defense Light Intensity .. S o c i a l Releaser  . ••  4 5 b 9  RESULTS Settling 11 Nipping and T e r r i t o r i a l Defense ............ 12 Light Intensity 13 S o c i a l Releaser * 14  DISCUSSION Settling Nipping Light Intensity S o c i a l Releaser Behaviour Hierarchy  17 19 25 2o 30  SUMMARY  32  ACKNOWLEDGEMENT S  3^  LITERATURE CITED  35  ii  TABLES  Table I .  Comparison of the nipping i n t e n s i t y of;coho and t r o u t (Chi square = 390, p = /0.001). ...12  Table I I .  Showing the nipping i n t e n s i t y d i s played by t r o u t i n r e l a t i o n to the same and d i f f e r e n t species  15  E f f e c t i v e n e s s of models i n e l i c i t ing a. nipping response when placed i n an aquarium containing 12 t r o u t  l6  Table I I I .  iii FIGURES  Page  Figure  1.  Rheostats (water-cooled) placed i n s e r i e s f o r i n c r e a s i n g or decreasing i l l u m i n a t i o n . A, p o i n t e r l e a d i n g to a c a l i b r a t e d s c a l e ; B, wooden bar f o r operating rheostats simultaneously;- C, rheostat; D, o u t l e t tube f o r c i r c u l a t i n g water; E, e l e c t r i c key. .... 8  Figure  2.  S e t t l i n g of coho when l i g h t i n t e n s i t y decreases. to f o l l o w  11  Figure  j5.  A r i t h m e t i c r e l a t i o n s h i p between l i g h t i n t e n s i t y and nipping phenomenon. to f o l l o w  11  R e l a t i o n s h i p between s i z e of t e r r i t o r y held and s i z e -of f i s h . L, l a r g e ; M, medium; S, s m a l l . ......... to f o l l o w  12  Figure  Figure  Figure  4.  3.  6.  Nipping r e l a t i o n s h i p i n a h e t e r o t y p i c group of 6 coho and 6 t r o u t . T, t r o u t ; C, coho; t o t a l time period of observat i o n s , 19 hours and 43 min. ... to f o l l o w  13  E f f e c t of l i g h t i n t e n s i t y on n i p p i n g (based on 18 hours o b s e r v a t i o n ) . to f o l l o w  13  Increase i n nipping as the l i g h t i n t e n s i t y increases (based on 16 hours o b s e r v a t i o n ) . to f o l l o w  13  r  Figure  7.  Figure  8.  Wooden model showing general features of t r o u t (X . 7 ) . to f o l l o w . 16  Figure  9.  C y l i n d r i c a l wooden model w i t h no d e t a i l (X . 7 ) . .  Figure 1 0 .  Figure 11.  Figure 12. Figure  13.  to f o l l o w  16  A r t i f i c i a l l u r e used to d u p l i c a t e the rhythmical swimming movements of t r o u t (X .7) to f o l l o w  16  Threatening a c t i o n of t r o u t . A, t w i s t e d caudal p o r t i o n of the body; B, mouth open and p e c t o r a l f i n s extended; C, angular p o s i t i o n and t w i s t e d trunk. ... to f o l l o w  28  Trout eating a l e v i n s  28  to f o l l o w  Schematic representation'of the behaviour hierarchy i n trout. ..... to f o l l o w  30  INTRODUCTION  For centuries man has been observing and, to some extent, recording the actions of animals i n t h e i r natural h a b i tat.  For the most part, these observations were not  or a n a l y t i c a l being promoted by a desire to satisfy curiosity.  systematic Innate  With the advance of b i o l o g i c a l knowledge the need  for more co-ordinated information beoame apparent. t h i s requirement animals were, wherever possible,  To meet studied i n a  laboratory; here, observation d i f f i c u l t i e s are minimized and a r i g i d control more readily maintained.  Extrapolation from the  laboratory to the f i e l d has been c r i t i c i s e d .  It i s  questionable,  however, whether a better method has as yet been devised. A number of the behaviour patterns of Juvenile coho salmon (Oncorhynchus kisutch) have been described by Hoar (1951).  In t h i s Investigation the s e t t l i n g ,  nipping and t e r r i -  t o r i a l behaviour of coho has been explored more thoroughly i n r e l a t i o n to l i g h t intensity and the analysis extended to include kamloops trout underyearllngs (Sstlmo g a l r d n e r l i kamloops). P a r t i c u l a r emphasis has been placed on the comparison of v i s u a l l y released behaviour patterns i n the two species. Coho and kamloops trout underyearllngs are excellent material for a study of t h i s type as they are r e a d i l y available  2  and are not v i s i b l y affected by a r t i f i c i a l c o n d i t i o n s .  The  l i f e h i s t o r i e s of these two species d i f f e r markedly a f t e r the i n i t i a l stages.  Coho salmon a d u l t s migrate upstream i n the  f a l l and spawn during November and December. a f t e r spawning.  The a d u l t s d i e  The f r y begin to appear In A p r i l and spend  up to twelve or more months i n f r e s h water.  The majority m i -  grate before the end of t h e i r f i r s t year ( C a r l and Clemens, 1948>).  These f i s h r e t u r n i n t h e i r t h i r d year to complete the  cycle.  In c o n t r a s t , kamloops t r o u t ( r e f e r r e d to i n subsequent  paragraphs as " t r o u t ) spawn i n streams s h o r t l y a f t e r the i c e 8  leaves, u s u a l l y i n May and June. varies i n different l o c a l i t i e s .  The exact spawning time The f r y may remain permanently  i n the stream or enter the lake during the f i r s t year. The f o l l o w i n g d e f i n i t i o n s have been used i n the d e s c r i p t i o n of the behaviour of young coho and t r o u t : (a)  settling  i n which f i s h descend from the upper to the lower l e v e l s of water and become quiescent as the l i g h t i n t e n s i t y i s reduced.  (b)  nipping  " i n which one f i s h makes a guick d a r t i n g movement toward, and b i t e s u s u a l l y close to the base of, another f i s h ' s t a i l .  The a c t i o n does  not Involve any a c t u a l contact between f i s h f o r only the water near the attacked f i s h i s 'bitten'. (Hoar,  The nipped f i s h move© away r a p i d l y . n  1951.)  Slight differences  i n character  of nipping behaviour i n t r o u t w i l l be described later.  3 (c)  defence o f t e r r i t o r y - " i n which a f i s h e s t a b l i s h e s i t s e l f i n a l o c a l i t y and by n i p p i n g keeps other f i s h from t h i s area" (Hoar, :  (d)  behaviour -  a l l the movements o f the i n t a c t animal (Tinbergen,  (e)  1951).  1951).  innate behaviour - behaviour that has been changed by l e a r n i n g (Tinbergen, 1 9 5 1 ) .  (f)  drive -  "the complex o f i n t e r n a l and e x t e r n a l s t a t e s and s t i m u l i leading to a given behaviour'* (Thorpe, 1 9 5 1 ) .  (g)  a p p e t i t i v e behaviour - " t h e v v a r i a b l e i n t r o d u c t o r y phase o f an i n s t i n c t i v e behaviour p a t t e r n o r sequence" (Thorpe, 1 9 5 1 ) .  (h)  instinct -  "an i n h e r i t e d and adapted system o f coordinat i o n w i t h i n the nervous system as a whole, which when a c t i v a t e d f i n d s expression i n behav* i o u r culminating i n a f i x e d a c t i o n p a t t e r n . I t i s organized on a h i e r a r c h i a l b a s i s both on the a f f e r e n t and e f f e r e n t s i d e s " (Thorpe, 1 9 5 1 ) ,  (I)  s o c i a l r e l e a s e r - "any s p e c i f i c feature o r complex o f features of an organism e l i c i t i n g an a c t i v i t y i n another i n d i v i d u a l e i t h e r o f the same o r another species" (Thorpe, 1 9 5 1 ) .  (j)  learning -  "the process which produces adaptive change i n i n d i v i d u a l behaviour as the r e s u l t o f experience" (Thorpe, 1 9 5 1 ) .  4 MATERIALS AND METHODS Settling Coho underyearllngs s e t t l e toward the bottom and become quiescent during the period of darkness (Hoar, 1951). In order to determine the l i g h t i n t e n s i t y at which these f i s h s e t t l e , twelve were placed i n a tank and observed  i n relation  t o changes i n i l l u m i n a t i o n . The observation was metal (90 cm. h i g h , 65  cm.  wide and 50 cm. from back to f r o n t ) with a heavy plate g l a s s f r o n t . I t was marked o f f i n t o three compartments (each 30 high.and numbering 1, 2, and 3 from top to bottom). The  cm.  tank  was placed In a corner so n a t u r a l i l l u m i n a t i o n could f a l l on the surface of the water from windows at the r e a r and on one s i d e . This corner of the room was screened o f f and another  screen  placed h o r i z o n t a l l y at the l e v e l of the top of the tank and a t t a c h ed to the v e r t i c a l one. This arrangement prevented l i g h t from e n t e r i n g the g l a s s f r o n t . An observation chamber was erected and the f i s h observed through a s l i t i n the v e r t i c a l screen. The i n t e r i o r of the tank was coated with p a r a f f i n wax; the bottom was covered with the same m a t e r i a l mixed with f i n e p a r t i c l e s of charcoal to reduce r e f l e c t i o n . This  resulted  i n a gradient of l i g h t i n t e n s i t y . Because of the high r e f l e c t i n g property of wax, counts could be taken at low i n t e n s i t i e s .  A "Photovolt U n i v e r s a l Photometer" (Model 2 0 0 ) was used t o determine the amount of l i g h t s t r i k i n g the water. The p h o t o - e l e c t r i c c e l l was attached to the top of the tank two inches above the water.  D i f f e r e n c e s between t h i s p o i n t and the  surface d £ the water were n e g l i g i b l e .  The l i g h t meter was  operated from the observation chamber and a "pen f l a s h l i g h t " was used t o a i d i n reading the s c a l e . Each group of f i s h was held i n the tank f o r one week and fed i n the morning by t o s s i n g i n food from behind the screen. L i g h t s In the room were not used on days when observations were made. hours. ber  The f i s h were watched f o r period v a r y i n g from 1 to 1 1 / 2 Darkness was always the time l i m i t i n g f a c t o r .  The num-  of f i s h i n compartment 1 and 2 plus the corresponding l i g h t  i n t e n s i t y was recorded a t 5 minute  intervals.  For t h i s experiment the temperature range was 7o&°C9.6°C  ' -;•  Nipping and T e r r i t o r i a l Defense I n a d d i t i o n to s e t t l i n g , coho and t r o u t show a nipping and t e r r i t o r i a l r e a c t i o n .  These behaviour patterns were studied  q u a n t i t a t i v e l y and q u a l i t a t i v e l y .  The e f f e c t of a h e t e r o t y p i c  group of 6 coho and 6 t r o u t was a l s o studied. An aquarium (lcIO cm. long, l c 5 cm. wide and 2 5 cm. deep) was placed i n a darkroom and observations taken from behind a screen. Movements o f the observer were apparently not detected by the f i s h .  The depth of water was 1 0 cm. being  6  r e g u l a t e d by an overflow pipe at one end. the opposite end.  The i n l e t was at  Both i n l e t and o u t l e t were screened  reducing the e f f e c t i v e  l e n g t h to 1^0 cm.  off,  A carbon f i l t e r  ( a d d i t i o n a l d e c h l o r i n a t i n g device) was placed on the end of the aquarium where the water entered.  I l l u m i n a t i o n was from  a 1 2 0 watt l i g h t d i r e c t l y over and f i v e feet above the tank (10.2 foot candles at the s u r f a c e ) .  Twelve f i s h were used i n  each group and were a r b i t r a r i l y c l a s s i f i e d as large cm.), medium (5-5*5 cm.) and small  4-.5 cm.).  (6-6.5  Lengths of  I n d i v i d u a l f i s h were not taken but i n every group four belonged to each s i z e range. IS hours.  The two homotypic groups were recorded f o r  Records were kept of t o t a l number of n i p s ; the r e l a -  t i v e s i z e of f i s h nipping and being nipped; and s i z e of t e r r i t o r y , i f any, h e l d by dominant f i s h .  The h e t e r o t y p i c groups  were observed f o r 1 9 hours and K$ minutes i n order to compare the I n t e r and i n t r a s p e c l f i c r e l a t i o n s h i p .  Temperature range  was 9 ° C . - 1 1 . 7 ° C .  Light Intensity The e f f e c t of l i g h t i n t e n s i t y on n i p p i n g was studied using the same long aquarium and darkroom w i t h a modified l i g h t i n g arrangement.  A s e r i e s of f i v e l i g h t s (60 watts each)  was placed above the aquarium.  Two rheostats were placed i n  the c i r c u i t i n s e r i e s so the I n t e n s i t y could be Increased or  one The r e s i s t a n c e o f r h e o s t a t was 2 0 ohms  decreased as d e s i r e d .  A  and the other *J4 ohms.  The range was from 0 - 1 5 f o o t candles  at the water surface when the l i g h t was passed through f r o s t e d glass plates.  The l a t t e r gave a more even d i s t r i b u t i o n of  illumination. The rheostats were operated simultaneously and c a l i brated by a photometer.  An elecJbrlc key was used t o break the  c i r c u i t (Figure 1 ) . Each group of f i s h was placed i n the aquarium at night and the l i g h t s turned on the f o l l o w i n g morning.  A mini-  mum of 6 hours was given f o r adaptation to the l i g h t i n g . In studying the e f f e c t of decreasing i l l u m i n a t i o n the procedure was as f o l l o w s : (a)  reduce l i g h t s from the maximum ( 1 5 f.c.) to 12  f.c.  (b)  a l l o w 5 minutes f o r adaptation.  (c)  record nipping f o r 1 0 minutes.  (d)  reduce l i g h t s and repeat.  Observations were taken a t 1 2 , g, 6 ,  2.5,1.5, 0.75, 0.25  and 1 2 foot candles r e s p e c t i v e l y . The l a t t e r was a check on the nipping i n t e n s i t y when the i l l u m i n a t i o n was increased.  immediately  ft  The period f o r adaptation was e l i m i n a t e d when d e t e r mining the e f f e c t of i n c r e a s i n g l i g h t and records were kept f o r 1 5 minute i n t e r v a l s .  The l i g h t s were increased from O-ty f . c .  i n increments of 0 . 5 f . c .  I n i t i a l l y i t was Intended to vary  Figure 1.  Rheostats (water-cooled) placed i n s e r i e s f o r i n c r e a s i n g or decreasing i l l u m i n a t i o n . A, p o i n t e r leading to a c a l i b r a t e d s c a l e ; B, wooden bar f o r operating rheostats simultaneously; C, rheostat; D, o u t l e t tube f o r c i r c u l a t i n g water; E, e l e c t r i c key.  9  the r a t e of increase and compare the r e s u l t s ; however, because of the v a r i a b i l i t y between groups and i n the same group a t d i f f e r e n t periods, t h i s procedure was abandoned i n favour o f a simple l i g h t i n c r e a s e — n i p p i n g r e l a t i o n s h i p .  S o c i a l Releaser What i s responsible:.for nipping?  I n an attempt to  answer t h i s question a number o f l i v e f i s h and models were t e s t e d w i t h a group of t r o u t .  The f i s h used were Black Crappie  (Pomoxls nlgro-maculatus LeSueur), G o l d f i s h (Carasslus auratus Linnaeus), S t i c k l e b a c k (Gasterosteus aculeatue Linnaeus), Peamouth chub (Mylochellus caurlnus Richardson),  Goarse-scaled  Sucker (Oatestomus macrochellus G l r a r d ) , P r i c k l y S c u l p l n (Cottus, asper Richardson) and Chum Salmon' a l e v l n s (Oncorhynchus k e t a Walbaum). Models were carved from wood and painted a v a r i e t y of c o l o u r s .  Each was covered w i t h a t h i n coating of p a r a f f i n  wax before u s i n g .  Some were " f i s h l i k e " having the general  c o n f i g u r a t i o n w i t h mouth and caudal f i n ; others were c y l i n d r i c a l having no d e f i n i t e shape (Plate I ) . One end of a f i n e s t e e l wire was passed through the model, the other sealed i n t o a long piece of g l a s s tubing. Models were placed i n the aquarium a t low l i g h t i n t e n s i t i e s . This method could not d u p l i c a t e the rhythmical swimming motion of t r o u t ao a number of a r t i f i c i a l l u r e s were used.  The l a t t e r  10 were p u l l e d through the water. Trout without a d o r s a l , a n a l , or caudal f i n were also tested.  The method was to place 8 small and k large  f i s h i n the tank.  Of the cl small ones, k had one of the above  mentioned f i n s c l i p p e d o f f .  Only the nipping of the four  l a r g e members was recorded. In a d d i t i o n to models and l i v e f i s h , dead t r o u t were used.  Some were mounted on pins and placed i n the tank; others  were suspended on a wire by passing I t through the long a x i s of the body and moved i n the same way as the wooden models.  11  RESULTS  Settling The r e s u l t s of s e t t l i n g observations are shown g r a p h i c a l l y i n Figures 2 and 3. semi-logarithmic r e l a t i o n s h i p .  Figure 2 demonstrates the The c a l c u l a t e d r e g r e s s i o n co-  e f f i c i e n t of the l i n e i s -g,c4 and the 95% confidence -5,15 and -10,93, ("t" t a b l e s ) .  This i s s i g n i f i c a n t at the p=.01  limits  level  Figure 3 i s an a r i t h m e t i c graph and serves to  i l l u s t r a t e the n a t u r a l trend. At high l i g h t i n t e n s i t i e s there i s a tendency f o r f i s h t o i n h a b i t the upper regions of the tank. decreases they g r a d u a l l y s e t t l e . s i t y (Figure 3)  f o r  As l i g h t  The apparent c r i t i c a l i n t e n -  t h i s behaviour i s approximately 1 foot  candle and below t h i s there i s a marked increase i n numbers at o r near the bottom.  From Figure 3  t n e  percent of f i s h i n  the two upper compartments decreases from 59»3# * ° 3^»2# between 0.75 and 0.25 f . c . (mid-points) r e s p e c t i v e l y . There i s a c e r t a i n amount of v a r i a b i l i t y due p r i m a r i l y to t e r r i t o r i a l defense; a f a c t o r that w i l l be d e a l t w i t h l a t e r .  —I  .25  1  .75  1  1 25  1  I.7S  1  2.25  1  2.75  1  3.25  MID POINTS OF LIGHT INTENSITY  Figure 2.  1  3.75  1  4.2S  1  1—  4.75  5 +  (FOOT CANDLES)  S e t t l i n g of coho when l i g h t I n t e n s i t y decreases!.  F i g u r e 3«  A r i t h m e t i c r e l a t i o n s h i p between l i g h t i n t e n s i t y and sett//Tig r • '' :  ;  IE Nipping and T e r r i t o r i a l Defence The r e s u l t s of the q u a n t i t a t i v e n i p p i n g are seen i n Table I . Coho n i p more f r e q u e n t l y than t r o u t inthe r a t i o of 2814:1514. I n both species s i z e i s a f a c t e r i n f l u e n c i n g the f i n a l consummatory a c t of n i p p i n g . A consummatory a c t i s a s p e c i f i c stereotyped set of movements e l i c i t e d by an innate r e l e a s i n g mechanism i n v o l v i n g a simple motor response such as b i t i n g or nipping ( C r a i g , 1918; Tinbergen,  1950).  Table I . Comparison of the n i p p i n g i n t e n s i t y of coho and t r o u t (Chi square - 390, p - /.001). Species  Observation (hours)  Number of Nips  Coho  18  3,814  Trout  18  1,514  Not only do the f i s h n i p but the dominant member or members of a group f r e q u e n t l y d i s p l a y t e r r i t o r i a l behaviour i n that these f i s h w i l l e s t a b l i s h themselves i n an area and* d r i v e other members out by employing nipping and/or chasing t a c t i c s (Hoar, 1951).  The r e l a t i o n s h i p between s i z e of t e r r i t o r y and  s i z e of f i s h can between i n Figure 4. A l a r g e coho held 44.4% on the average while the,, small members held 26.4%. The  50  s 40 « o  C  TROUT  -  M  o  30  u K  20  00  Figure 4.  R e l a t i o n s h i p between s i z e of t e r r i t o r y held and s i z e of f i s h . L, l a r g e ; M, medium; S, small.  CO  1  13 c a l c u l a t e d " t " value i s 2.45 f o r 13 d.f. which, i s s i g n i f i c a n t a t the 0.05 p r o b a b i l i t y l e v e l ("t" t a b l e s ) . For t r o u t the large dominant members held 46.9% and the small t r o u t l 6 . 7 % . The c a l c u l ated " t " value i s 5.18 and f o r 8 d.f. i s s i g n i f i c a n t a t the 0.01 probability level. lAftien a homotypic group i s replaced by a h e t e r o t y p i c one the r e s u l t s are reversed(Figure)5)• "nippers" i n the r a t i o of 1619:601.  Trout are more dominant  I t i s of i n t e r e s t t o note  t h a t the 6 t r o u t i n t h i s group nipped almost as o f t e n as the group of 12. Reducing the r e s u l t s of the h e t e r o t y p i c t o an equivalent time i n t e r v a l , the f i g u r e s are 1514:1475. between the r e s u l t s .  There i s no s i g n i f i c a n c e  Trout show no preference between members  of there species and coho while the l a t t e r n i p t r o u t l e s s f r e q u e n t l y (337:264, Chi square  s  8.867 and p « / 0.01).  I t soon became evident that the nipping a c t i v i t y of coho was depressed by the presence of t r o u t . To t e s t t h i s , t r o u t were removed from group 5 and observations taken f o r a l i k e p e r i o d of time (2 hours).  When t r o u t were present the t o t a l  coho nipping was 19; when the former were removed the t o t a l equalled 64. The Chi square value i s 24.1 which i s h i g h l y significant.  Light Intensity The e f f e c t i v e n e s s of l i g h t as a l i m i t i n g f a c t o r on the nipping response can be seen i n Figures 6 and 7. There i s no general decrease (Figure 6) u n t i l the i n t e n s i t y has been reduced t o 4 f . c . and below t h i s value the d e c l i n e i s r a p i d .  -  •  I  Figure 5*  Nipping r e l a t i o n s h i p i n a h e t e r o t y p i c group of 6 coho and 6 t r o u t . T, t r o u t ; C, coho; t o t a l time p e r i o d of observat i o n s , 19 hours and 45 minutes.  1  "I  12  1  10 LIGHT  Figure  6.  1  1  1  8 INTENSITY  1  1  6 (FOOT  1  4  1  1  2  1  1  r~  0  IZ  CANDLES)  E f f e c t o f l i g h t i n t e n s i t y on n i p p i n g ( b a s e d on 18> h o u r s o b s e r v a t i o n ) .  300  •5 LIGHT  Figure 7.  I  1-5  INTENSITY  2  2-5  (FOOT  3  3-5  4  CANDLES)  Increase i n nipping as the l i g h t i n t e n s i t y increases (based on l 6 hours observations).  14 The dotted l i n e represents the number of nips when the i n t e n s i t y i s immediately increased to 12 f . c .  The l a t t e r i l l u s t r a t e s  q u i t e c o n c l u s i v e l y that the d i m i n i s h i n g l i g h t i n t e n s i t y was responsible f o r the drop i n nipping. Figure 7 d i f f e r s from Figure 6 i n that the l i g h t i s increasing.  Nipping increases slowly at f i r s t and then r a p i d l y .  The point of I n f l e c t i o n f o r the curve i s between 2 and 2.5 f . c ; above t h i s there i s a d e c e l e r a t i o n and a l e v e l l i n g at 4 f . c . In e f f e c t , the two graphs are complementary.  S o c i a l Releaser Table I I and I I I summarize the i n v e s t i g a t i o n of f a c t o r s responsible f o r n i p p i n g .  Neither d o r s a l , caudal or anal  f i n i s the r e l e a s e r since f i s h mutilated i n t h i s way are nipped as f r e q u e n t l y as uninjured ones.  Peamouth chub and small  suckers are nipped r e a d i l y ; however crapples, s t i c k l e b a c k , g o l d f i s h , s c u l p i n s and tadpoles.are not. A l e v l n s were eaten. In general, models were not as e f f e c t i v e as l i v e f i s h but a l l , except the orange-coloured one, e l i c i t e d at l e a s t one response.  Table I I . Showing the nipping i n t e n s i t y d i s p l a y e d by t r o u t i n r e l a t i o n to the same and d i f f e r e n t s p e c i e s . Species  Number  Size (cm.)  Time of observation (hours)  Number of nips  4.5-5  2  12  5-6  2  16  4  4.5-6.5  2  21  Peamouth chub  6  5-6  2  71  Sucker  5  3.5-4.5  , 2  67  G o l d f i s h (gp. 1)  3  7-7.5  2  1  G o l d f i s h (gp. 2)  2  5-5.2  2  •0  3.8-4.S  2  0  C a l i c o bass  5  Stickleback  5 "  P r i c k l y sculpin  G o l d f i s h (gp. 3), Trout without anal  4  4.5-5.5  2  46  Trout without caudal  4  4.5-5.5  2  51  Trout without d o r s a l  4  4.5-5.5  2  3*  2  2  eaten  4.5-5.5  2  163  A l e v l n s (O.gorbuscha) Coho  6  Table I I I .  E f f e c t i v e n e s s o f models ( 4 - 6 cm. i n length) i n e l i c i t i n g a nipping response when placed i n an aquarium containing 12 t r o u t .  Number  Model  Time o f observation (hours)  Number o f nips  Red  1  2  1  Orange  1  2  0  Green  1  2  11  Blue  1  2  14  Brown  1  2  17  Black  1  2  8  Yellow  1  2  1  2  2  2  0  1  2  29  White .;  1  ' Trout on p i n Trout on wire I  was not moved  Plate  Figure  9.  Figure  10.  C y l i n d r i c a l wooden  model  with  no  detail  A r t i f i c i a l l u r e used to d u p l i c a t e the swimming movements o f t r o u t (X .7).  (X  I  .7).  rhythmical  17  DISCUSSION Settling The aquarium was not e n t i r e l y s a t i s f a c t o r y f o r determining the l i g h t i n t e n s i t y at which f i s h w i l l s e t t l e toward the bottom because of t h e i r t e r r i t o r i a l h a b i t s .  In  9 of the 1 7 observations one o f the dominant members s e l e c t e d the lower compartment and drove the others upward as they entered t h i s area.  Figure 3 would i n d i c a t e a c r i t i c a l value  approximately 1 f . c . f o r t h i s response; however, Figure 6 demonstrates a marked decrease i n nipping at t h i s value. Since t e r r i t o r i e s are defended by nipping (Hoar,  1951)»  de-  fense of an area must be l e s s e f f i c i e n t when i l l u m i n a t i o n i s low.  What appears t o be a c r i t i c a l value f o r s e t t l i n g may,  i n a c t u a l i t y , be the r e s u l t of a l o s s of dominance. The c o r r e c t c r i t i c a l i n t e n s i t y f o r s e t t l i n g could be somewhat higher, say 2 o r 3 f . c , A number of observations the l a t t e r t o be the case.  suggested  A l a r g e r tank and a smaller num-  ber of f i s h would reduce s p a t i a l competition and c l a r i f y t h i s point. I t i s w e l l known that l i g h t I s absorbed as i t passes through water.  Because o f t h i s i t would be expected  t h a t , i f there I s a c r i t i c a l stimulus f o r s e t t l i n g , the f i s h  IS  i n the centre compartment would move toward the bottom before those i n the upper.  T o t a l i n g the numbers i n these two  sections  at and below 2 f . c . the f i g u r e s are 3S7:36l (Chi square = O.903S and p s 0 . 5 - 0 . 3 ) .  The t h e o r e t i c a l l i g h t i n t e n s i t y  entering the centre compartment can be c a l c u l a t e d by the formula l / l = e ~ , kl  0  I  0  where I i s the r e s u l t i n g i n t e n s i t y ;  i s the i n i t i a l i n t e n s i t y s t r i k i n g the surface; e i s  k i s the c o e f f i c i e n t ( C l a r k e , 1939).  2.7;  of absorption and 1 the distance i n meters  The absorption c o e f f i c i e n t s  water were used.  using  for d i s t i l l e d  This introduces a c e r t a i n e r r o r but the water  was passed through an a c t i v a t e d carbon d e c h l o r i n a t o r before entering the tank which would remove suspended m a t e r i a l , thereby reducing the e r r o r i n v o l v e d .  The absorption c o e f f i c i e n t s  were  taken from Sverdrup, Johnson and Fleming (1942) and ares (l)  ' u l t r a v i o l e t ( w . l , 0.39 microns) - 0.14S  (ii)  red ( w . l . 0.6 microns)  = 0.21  (iii)  beyond red ( w . l . O.S microns)  = 2.14  When the l i g h t s t r i k i n g the surface i s 1.5 f . c . the u l t r a v i o l e t and red l i g h t entering the centre compartment i s 1.42 and 1.4 f . c . r e s p e c t i v e l y . f . c . enter t h i s area.  For wave lengths O.g microns only 0.75 Wave lengths greater than t h i s are  almost t o t a l l y absorbed i n the f i r s t few centimetres. Although the a c t u a l v i s u a l f i e l d i s ' not known, i t has been e s t a b l i s h e d that f i s h are s e n s i t i v e to the v i o l e t red p o r t i o n of the spectrum (Walls, 1942).  I f the  settling  stimulus i s w i t h i n t h i s range we would not n e c e s s a r i l y expect  19  fewer f i s h i n the centre compartment when d i f f e r e n c e s i n l i g h t I n t e n s i t y are so s m a l l .  Nipping  Coho n i p more f r e q u e n t l y but l e s s than t r o u t .  On the other hand, r e t a l i a t i o n s by the l a t t e r  more common. behaviour  ferociously  In a d d i t i o n , t r o u t show a c h a r a c t e r i s t i c  i n t h a t two members w i l l swim i n a c i r c l e  are  fighting  seemingly  s t r i v i n g f o r a f a v o u r a b l e p o s i t i o n from which to a t t a c k the opponent.  A s s o c i a t e d w i t h f i g h t i n g i s a t h r e a t response  a c t e r i z e d by e x t e n s i o n of f i n s *  char-  e s p e c i a l l y the p e c t o r a l s ; a  t w i s t i n g of the caudal r e g i o n of the trunk toward the opponent; Jerky swimming movements; mouth open; and an a n g u l a r i n space.  These f i g h t i n g and  "threatening™ behaviour  have not been p r e v i o u s l y d e s c r i b e d f o r t r o u t ( F i g u r e The  t h a t r e l e a s e s a maximal r e a c t i o n at one or e l i c i t  a weak response a t another.  s h o l d may  be due  The  time may  vary  temperature  same stimulus have no  effect  Such v a r i a t i o n i n t h r e -  to v a r i a t i o n i n I n t e n s i t y of some e x t e r n a l o r  i n t e r n a l f a c t o r not c o n t r o l l e d i n the experiment  "...  11).  As w i l l be d i s c u s s e d l a t e r , the stimulus i s  present but the response i s not forthcoming.  1951).  patterns  n i p p i n g r a t e i s not constant but w i l l  g r e a t l y i n a one hour p e r i o d even though l i g h t and are u n a l t e r e d .  position  (Tinbergen,  Lorenz ( 1 9 5 0 ) p r e s e n t s a somewhat d i f f e r e n t  the a c t i v i t y i s e x h a u s t i b l e independently  explanation.  from the  general  20  state o f exhaustion  of the organism as a whole ..." ( p . 2 5 2 ) .  "When we suddenly deprive an animal of the object of i t s r e a c t i o n , the a c t i v i t y never breaks  o f f abruptly but n e a r l y  always continues a considerable time i n vacuo.  Doubtless i t  i s a consequence of the same phenomenon that the 'momentum' gained by any a c t i v i t y w i l l carry i t on f o r an appreciable time a f t e r the moment when i t s r e l e a s i n g t h r e s h o l d , r i s i n g cont i n u a l l y throughout the duration of the discharge, has reached the value corresponding to the e x t e r n a l s t i m u l a t i o n at the moment.  impinging  This i s a l s o the reason why an organism that  i s l e f t c o n t i n u a l l y i n the presence of a r e l e a s i n g object does not c o n t i n u a l l y react to i t w i t h a constant i n t e n s i t y , as otherwise would be expected" ( I b i d . , that exhaustion  p,259).  I t seems p l a u s i b l e  of the s p e c i f i c a c t i v i t y , r i s e i n threshold and  a d i v e r t i n g Influence of e x t e r n a l and i n t e r n a l changes are f a c t o r s Responsible f o r v a r i a t i o n i n the nipping r a t e .  I t has  been shown that there i s a d e c l i n e i n frequency of nervous impulses w i t h constant  s t i m u l a t i o n (Adrian and Matthews,  1927).  This d e c l i n e i n discharge may be synonymous w i t h increase i n threshold and account f o r the exhaustion  of a s p e c i f i c a c t i v i t y .  Quiescence f o l l o w s a period o f r e l a t i v e l y nipping.  vigorous  Associated w i t h t h i s i s a d e c l i n e I n threshold value  and a r e p e t i t i o n of events p r o v i d i n g some d i v e r t i n g or i n h i b i t ing  f a c t o r i s not present.  The longer a s t i m u l a t i o n i s withheld  the f i n e r the t r i g g e r r e l e a s i n g i t becomes and may a c t u a l l y reach zero w i t h the r e a c t i o n taking place i n the absence o f a  21 stimulus.  This vacuum e f f e c t i s termed "energy accumulation  a c t i v i t y " (Armstrong, 1942). S t a t i n g the phenomena i n terms of t h i s e x p e r i ment, a "macro" stimulus i s o f t e n necessary to i n i t i a t e n i p ping; however, once s t a r t e d the "nipper" may chase the other the l e n g t h of the tank a number of times or n i p other members i n the v i c i n i t y w i t h Increased v i g o r u n t i l the p o i n t of exhausti o n f o r t h i s s p e c i f i c act i s reached.  O c c a s i o n a l l y t h i s takes  place without any or w i t h a weak v i s u a l stimulus (to the observer) and t h i s i s c a l l e d "energy accumulation a c t i v i t y " . The behaviour of animals tends to f o l l o w s t e r e o typed patterns of movement and once f a m i l i a r w i t h these an observer can p r e d i c t w i t h reasonable accuracy what to expect from the organism (Lorenz, 1950).  An example of t h i s i s the " t h r e a t "  r e a c t i o n and a number of n i p s f o l l o w i n g . made to d i v e r t i n g f a c t o r s . one was the aquarium i t s e l f .  Reference has been  The most important and ever present Should the f i s h come i n contact  w i t h the g l a s s sides or the screen a t e i t h e r end the behaviour breaks o f f at t h i s p o i n t and may not resume f o r many minutes. A r e d u c t i o n of l i g h t and s l i g h t movement of the screen act i n a s i m i l a r manner!  Because of t h i s , i t i s p o s s i b l e to t e l l ,  w i t h i n l i m i t s , where and when nipping w i l l take p l a c e . In a h e t e r o t y p i c group 6 t r o u t nipped as f r e quently as 12 i n a homotypic group.  The more probable explana-  t i o n i s based on the d i f f e r e n t i a l n i p p i n g i n t e n s i t y .  Rarely do  the 6 more dominant members i n a group of 12 n i p l e s s than 9 0  22  percent of the t o t a l and I n some Instances one I n d i v i d u a l may perform 9 5 percent.  I t i s apparent from the conduct of the  trout that they were the dominating species and, since there i s no nipping preference shown by then (Figure 5 ) » "the. r e s u l t s are not g r e a t l y out of l i n e w i t h the others. A d i f f e r e n t i a l n i p p i n g i n t e n s i t y between members of a group i s common i n both species.  Vsing the same argument  as above i t might be concluded that 6 coho would n i p as o f t e n as 12 p r o v i d i n g there i s nothing a c t i n g to r e s t r a i n t h i s a c t i v i t y . But coho n i p coho more than t r o u t and the I n t e n s i t y i s a c c e l e r a t e d by the removal of the l a t t e r .  The presence of one species sup-  p r e s s i n g the a c t i v i t y of another i s not uncommon.  I t has been  demonstrated that g o l d f i s h become more a c t i v e as f a r as t o t a l movement i s concerned when grouped w i t h other f i s h Mlnahan and Shaw,  193&).  (Escobar,  I n other words the presence of the  others modified the behaviour of the g o l d f i s h . Dr. W. S. Hoar (Professor, U n i v e r s i t y of B r i t i s h Columbia) c a r r i e d out p r e l i m i n a r y experiments on the i n t e r a c t i o n of coho and kamloops t r o u t .  H i s r e s u l t s , although not as ex-  tensive as these, i n d i c a t e d the reverse to be t r u e .  Immediately  the question a r i s e s , what i s the e f f e c t of environment, c o n d i t i o n i n g , age, r a c i a l d i f f e r e n c e s ( i f any), e t c . , on the a c t i o n s of f i s h i n t h i s or any other type of behaviour study. v  Knowledge  of f i s h has Increased g r e a t l y i n the l a s t h a l f century but the r e l a t i o n s h i p of the above mentioned f a c t o r s as modifying behav i o u r i s not c l e a r l y understood.  Dr. Hoar's f i s h were " w i l d "  23 f i s h t e s t e d Immediately a f t e r capture. w r i t e r were r e a r e d i n a hatchery a stream.  t r o u t used by  Univer-  months p r i o r to grouping them i n an aquarium,  c o n d i t i o n i n g may  s i b i l i t y may  the  the coho were taken from  Both s p e c i e s were r e t a i n e d s e p a r a t e l y a t the  s i t y f o r two previous  but  The  seem.  have had an e f f e c t , remote as the pos-  I f some or a l l of the p o i n t s mentioned a l t e r  the g e n e r a l behaviour of an organism, much of the present mation, e s p e c i a l l y t h a t concerning a guide u n t i l  but  animal ethology,  infor-  i s , at  i t has been d u p l i c a t e d under a d i f f e r e n t ,  best,  although  comparable set of c o n d i t i o n s . I t i s not known what i s r e s p o n s i b l e i n  determining  whether a f i s h w i l l or w i l l not become, the dominant member and/or show t e r r i t o r i a l defense.  Hoar ( 1 9 5 1 ) nas noted t h a t dominant  members are o f t e n b r i g h t e r i n c o l o u r .  T h i s suggests a hormonal  basis. C o l o u r a t i o n i n regard questionable and  but  the g e n e r a l  trout underyearlings  p l a c i n g them i n a tank. for  to n i p p i n g and dominance i s  s t a t e of h^Lth i s important.  commence n i p p i n g a few hours a f t e r In December, 1 9 5 1 *  10 days without t h i s behaviour being  appeared i n poor c o n d i t i o n . supply was  Coho  I t was  coho were observed  seen.  The  fish  visibly  determined that the water  r e s p o n s i b l e f o r t h i s because o f an excess of c h l o r -  i n a t e d water p a s s i n g  thrbugh the d e o h l o r i n a t l n g u n i t .  As  the  volume of water i n c r e a s e d the e f f i c i e n c y of the l a t t e r decreased. Because of the  s t r e s s p l a c e d on the organism by t o x i c m a t e r i a l s ,  24  p o s s i b l y chloramine, which i s l e t h a l to small t r o u t a t 0.05 p.p.m. (Coventry, S h e l f o r d  and M i l l e r , 1935.)»  A l l f i s h were dead two weeks l a t e r .  nipping  Eventually  an a d d i t i o n a l  carbon f i l t e r was used t o r e c t i f y the s i t u a t i o n . e a r l i e r work was d i s c a r d e d  stopped.  i n order t o e l i m i n a t e  Some o f t h e possible  biased  results. N i p p i n g r e f l e c t s the p h y s i o l o g i c a l c o n d i t i o n o f coho and t r o u t but whether an e m p i r i c a l r e l a t i o n s h i p e x i s t s may be a s c e r t a i n e d  by f u r t h e r study.  Preliminary  by o b s e r v i n g t r o u t i n contaminated water.  t e s t s were made  N i p p i n g d i d n o t occur.  Because of the l i m i t e d number o f o b s e r v a t i o n s , the r e s u l t s can not  be c o n s i d e r e d c o n c l u s i v e .  Coho were not a v a i l a b l e i n a num-  ber  of streams a t t h i s time of y e a r . There I s no "nip" order s i m i l a r to the "peck" order  i n some b i r d s f o r a t one moment "A" w i l l be n i p p i n g "B" but l a t e r the s i t u a t i o n may be r e v e r s e d .  and c h a s i n g  I f "A" i s l a r g e r  than "B" the former w i l l chase and n i p more f r e q u e n t l y * senting  t h i s i n equation form we would have "A" - y ^  lar ily,  l a r g e f i s h w i l l defend l a r g e r t e r r i t o r i e s  Repre-  "B".  (Figure  Simi4 ) and  there i s l e s s p r o b a b i l i t y o f them b e i n g d i s p l a c e d by another member.  Large t r o u t d i s p l a y e d  t e r r i t o r i a l defense on 1 3 o f 1 9 o c c a -  s i o n s ; t h i s was r e c o r d e d twice f o r small  trout.  25 Light Intensity Like s i z e , l i g h t i n t e n s i t y a f f e c t s the general nipping phenomenon below I n t e n s i t i e s of 4 f . c .  From t h i s p o i n t  to 0 f . c . there i s a r a p i d d e c l i n e i n a c t i v i t y ,  There- i s good  evidence to suppose that at 0 f . c . nipping does not.take  place  (Figure 5 ) . No l i t e r a t u r e has been found comparing the s e n s i t i v i t y of the f i s h eye to the same stimulus when the q u a n t i t y of light i s varied.  But i t seems evident that a f i s h can not  as w e l l at 1 f . c . as at 1 0 .  see  A number of workers have intimated  t h i s but a pertinent reference i s not c i t e d .  Walls (1942)  states? " A l l i n a l l , i f a f i s h or whale can d i s t i n g u i s h objects f i f t y feet away at h i s own l e v e l , I t i s a r e d - l e t t e r day f o r him. With i n c r e a s i n g depth or Increased t u r b i d i t y , t h i s distance i s s t i l l f u r t h e r reduced since the absolute amount of l i g h t r e f l e c t e d Into the eye of the animal depends upon the r e l a t i v e amount of s u n l i g h t reaching that depth." ( p p . 3 7 5 - 3 7 6 . ) Rochon-Duvlgneaud and Roule  (1927)  have demonstrated that the  sharpness of v i s i o n i n Salmo and Esox i s considerably reduced below that of man and other t e r r e s t r i a l v e r t e b r a t e s .  The w r i t e r  noted that t r o u t could not detect movements of the observer when i l l u m i n a t i o n was  reduced.  The q u a l i t y of a r t i f i c i a l white l i g h t changes as i t i s reduced and the gradual cessation of nipping may be r e l a t e d to the e l i m i n a t i o n of some component rather than the general r e duction.  At low i n t e n s i t i e s there i s an increased percent  of  26  orange-red p o r t i o n of the spectrum.  A l s o , orange and r e d models  were l e a s t e f f e c t i v e In e l i c i t i n g a response. Takedo  (1951)  Kowamoto and  c a r r i e d out a s e r i e s of experiments on the wave  l e n g t h preference of s i x species:  Oplegnathus f a c l a t u s ,  Monacanthus c l r r h l f e r , Cyblum nlphonlum, Shyraena Japonlca, r  Shyraena nlphobles and A n g u l l l a Japonlca.  A l l species except  A. Japonlca p r e f e r r e d the blue-green wave lengths and avoided red and v i o l e t .  They determined the energies f o r d i f f e r e n t  colours and found v i o l e t and red to be extremely high while blue and green were low. E a r l i e r work by Reeves  (1919)  shows that  g o l d f i s h and horned dace (Semotilus atromaculatus) w i l l go to blue i n preference to red l i g h t but when the " i n t e n s i t y " of red l i g h t i s equivalent t o blue ( f o r human eye) the f i s h f a i l to d i s c r i m i n a t e between them.  Reeves does not i n d i c a t e whether  i n t e n s i t y r e f e r s to:energy or:.a ^photometric reading.  I f energy  i s r e f e r r e d t o the work of Kowamota and Takedo s u b s t a n t i a t e s t h i s ; however, i f a photometric reading o f I n t e n s i t y i s meant, the evidence i s c o n t r a d i c t o r y . An experiment  using coloured f i l t e r s  would help confirm the e f f e c t of wave l e n g t h on n i p p i n g .  S o c i a l Releaser The s o c i a l r e l e a s e r f o r nipping i s movement which must release a s e r i e s of i n t e r n a l processes i n the nervour system, the exact nature of which i s not known (Tinbergen, 19*4-2).  27  This was a r r i v e d at by a process of e l i m i n a t i o n .  When the chub  were nipped the p o s s i b i l i t y of p a r r marks and a s p e c i f i c swimming rhythm was r u l e d out.  S u c k l i n g and Suckling (1950) s t a t e  that the swimming of d i f f e r e n t species cause a d i f f e r e n t e l e c t r i c a l response i n the l a t e r a l l i n e system. removed but the r e s u l t s were negative.  Various f i n s were  When dead trout and  models were used they were nipped only when moved. Crappies, s t i c k l e b a c k , s c u l p i n s , g o l d f i s h and tadpoles do not provide the r e l e a s e r stimulus as o f t e n as chub, suckers and other Salmonolds.  S t i c k l e b a c k and crappies change  s p a t i a l p o s i t i o n by sudden d a r t i n g movements and then remain motionless f o r v a r i a b l e p e r i o d s . When nipped they move away r a p i d l y and are u s u a l l y chased and nipped again.  This i n d i c a t e s ,  as c e r t a i n l y seems to be the case, that the d a r t i n g motion i s s u b - l i m l n a l i n i n t e n s i t y and only e f f e c t i v e when a trout i s s i t u a t e d i n the near p r o x i m i t y and the accumulative e f f e c t of many inadequate s t i m u l i reach the t h r e s h o l d and e v e n t u a l l y produce a response.  Sculpins and tadpoles do not perform d a r t i n g  movements but remain motionless on the bottom changing p o s i t i o n infrequently.  They are nipped only when i n motion.  chub and suckers are nipped e q u a l l y .  Coho, t r o u t ,  These f i s h have a r h y t h -  m i c a l type of movement and do not remain i n one p o s i t i o n f o r long i n t e r v a l s . G o l d f i s h were nipped once i n s i x hours of observ a t i o n even though they are a c t i v e and movements r h y t h m i c a l .  2S  S i z e d i d not make any on l i g h t and  difference.  from the i n f o r m a t i o n  From the p r e v i o u s obtained  c o l o u r a t i o n i s probably r e s p o n s i b l e g o l d f i s h do not  stimulate  discussion  u s i n g models, the  for this.  I t i s not  that  the n i p p i n g response i t s e l f but  rather  the f i n a l consummatory a c t i s i n h i b i t e d . . To c l a r i f y t h i s the behaviour w i l l be o u t l i n e d . the l a t t e r may i t w i l l nip. not  A g o l d f i s h moves near a t r o u t  and  d a r t toward i t showing a l l the i n d i c a t i o n s t h a t At the l a s t moment i t w i l l veer to one  complete the  specific act.  side  and  I t i s suggested t h a t the orange  c o l o u r i s the i n h i b i t i n g element. A l e v l n s are not merely nipped, they are ( F i g u r e 12).  I t has  not been determined whether or not  i n i t i a l a t t a c k i s or i s not However, one  eaten  the  the  same as that i n v o l v i n g n i p p i n g .  p o i n t i s c l e a r l y i l l u s t r a t e d that age  and/or s i z e  of a f i s h i s not important i n d e t e r m i n i n g when i t becomes p i s c i v o r o u s but only the predator-prey  size relationship.  Models were much l e s s e f f e c t i v e t h a n some l i v e f i s h and,  even though the a t t a c k s came as f a r as a c t u a l b i t i n g ,  they were never as i n t e n s e as when l i v e The  specimens were used.  models were moved i n a s t r a i g h t l i n e through the water  t h i s i s a t y p i c a l of the l i v e f i s h . d u p l i c a t e the extent  A l s o , i t was  " t h r e a t " r e a c t i o n shown by  by coho.  The  impossible  t r o u t and  presence of the wire and  Morphological  to  to a l e s s e r  g l a s s rod from  which the models were suspended c e r t a i n l y d e t r a c t e d effectiveness.  and  from t h e i r  f e a t u r e s such as form, i r i d e s c e n c e  of body and pigmentation probably have an a d d i t i v e value  in  Plate I I .  Figure  11,  Threatening a c t i o n of t r o u t . A, t w i s t e d caudal p o r t i o n o f the body; B, mouth open and p e c t o r a l f i n s extended; C, angular p o s i t i o n and t w i s t e d trunk.  Figure  12.  Trout e a t i n g  alevins  29  r e l e a s i n g a response.  P e l k w i j k and Tinbergen  to be true when models  vete  (1937)  found t h i s  used to e l i c i t a response from  stickleback. Movement as an a t t a c k r e l e a s e r i s known to occur i n other f i s h , namely barracuda (Shyraena barracuda) and some sharks (Wright, 194g).  The sharks considered dangerous are the  Brown (Carcharinus galeolamna), Tiger (Galeocerdo a r c t l c u s ) , Hammerhead (Sphyrna s p . ) , and the Great White (Carcharodon s p . ) . Wright spent two and a h a l f years t r a i n i n g the B r i t i s h Sea Reconnaissance Unit i n underwater work o f f the coasts of C a l i f o r n i a , Bahamas, Ceylon and Burma.  During t h i s time the a c t i o n s of  these f i s h were recorded and h i s conclusions are that blood i n the water acts as a stimulus to lower the t h r e s h o l d value of the attack response and causes e x c i t a b i l i t y .  Rapid and/or Jerky  movements are a l s o necessary i n r e l e a s i n g a t t a c k .  The presence  of blood and Jerky o r f r a n t i c movements r e s u l t i n the strongest attack.  Movement i s the a c t u a l r e l e a s e r and w i l l e l i c i t a t t a c k  alone but blood has an accumulative e f f e c t i n hastening and strengthening the response. Trout w i l l n i p tadpoles, which are amphibians, and wooden models which are not even a good approximation of a f i s h . I t seems u n l i k e l y that tadpoles and models have the same r e l e a s i n g value as t r o u t . "The occurrence of such ' e r r o r s or'mistakes' Is one of the most conspicuous c h a r a c t e r i s t i c s o f innate behaviour. I t i s caused by the f a c t that an animal responds ' b l i n d l y ' to only part of the t o t a l environ-^ mental s i t u a t i o n and neglects other p a r t s , although i t s sense organs are p e r f e c t l y able to r e c e i v e them (and probably do receive them),..." (Tinbergen, 1 9 5 1 * 1  p.27).  30  Indeed, such, e r r o r s are not r e s t r i c t e d to f i s h .  The predacepus  water b e e t l e (Dytlecus marginal!s) can be t r a i n e d t o v i s u a l response but the search f o r food can be stimulated by a watery meat e x t r a c t .  The hunting behaviour i s released by chemical  s t i m u l a t i o n (Tinbergen,  1936).  Newly hatched h e r r i n g g u l l  (Larsus a. argentatus Pont) peck a t the beak of the parent when hungry.  Tlie red patch on the b i l l was of great importance as a  s o c i a l r e l e a s e r but the colour of the beak or head had no r e l e a s ing value ^ T i n b e r g e n and Perdeck,  19.50)..  "The animal's sensory  world i s dependent on sign s t i m u l i e s p e c i a l l y when we are d e a l ing w i t h innate behaviour" (Tinbergen,  1951»  p.^2).  Behaviour Hierarchy The h i e r a r c h y of behaviour as shown by Tinbergen (19^2,  19^0% 1 9 5 0 )  i s , to some extent d i s p l a y e d by the t r o u t and  to a l e s s e r extent by coho.  The highest l e v e l of the h i e r a r c h y ,  the d r i v e , has not been determined.  Below the d r i v e l e v e l i s  a p p e t i t i v e behaviour which would c o i n c i d e w i t h the r a p i d d a r t toward another f i s h .  A second l e v e l of a p p e t i t i v e behaviour  would be "threatening" or chasing depending on whether or not the other f l e e s .  F i n a l l y , the motor response of nipping which  i s the lowest l e v e l of the h i e r a r c h y (Figure 1 3 ) . There may be two separate r e l e a s e r s i n v o l v e d i n chasing terminating i n d i f f e r e n t behaviour p a t t e r n s . When an  Figure  13.  Schematic r e p r e s e n t a t i o n hierarchy i n trout.  o f the  behaviour  31  i n t r u d e r enters a defended area i t may be chased and nipped v i g o r o u s l y by the defender, an a c t i v i t y not r e s t r i c t e d to the defended zone.  The. a l t e r n a t i v e i s that the. dominant f i s h swims  toward the i n t r u d e r , d r i v i n g i t out but does not f o l l o w beyond the t e r r i t o r i a l boundary.  No attempt i s made to n i p the " t r e s -  passer" by the f i s h h o l d i n g the t e r r i t o r y . I t i s d i f f i c u l t to J u s t i f y the preference to n i p smaller members on inherent q u a l i t i e s . r o l e played by l e a r n i n g i n t h i s respect? according to Thorpe  (1950),  What, i f any, i s the Insight learning i s ,  the response to simple e x t e r n a l  s t i m u l i based on the perception of r e l a t i o n s and i s nothing more than form perception having i t s counterpart i n a l l the sensory fields.  P o s s i b l y t h i s nipping preference d i s p l a y e d by t r o u t and  coho i s not innate behaviour but i s learned s h o r t l y aft;er the nipping phenomenon f i r s t occurs.  Observations of coho or t r o u t  from hatching to two or three months may c l a r i f y t h i s p o i n t .  32  SUMMARY  1.  Coho underyearllngs s i t y decreases.  s e t t l e to the bottom as the l i g h t i n t e n -  The c r i t i c a l i n t e n s i t y f o r t h i s was  to be approximately 1 foot candle but may  found  be higher i n a,  stream where competition f o r space i n a v e r t i c a l d i r e c t i o n is negligible. ?..  Coho n i p more f r e q u e n t l y than kamloops t r o u t .  However, i n a  h e t e r o t y p i c group of equal numbers t r o u t are dominant and nip e i t h e r species w i t h equal i n t e n s i t y . The presence of trout i n an aquarium decreases the nipping a c t i v i t y of coho. 3.  Nipping i s dependent upon l i g h t and below 4 foot candles decreases r a p i d l y as the l i g h t Is reduced.  4.  L i m i t i n g f a c t o r s on nipping are h e a l t h , s i z e and  colour.  Coho and t r o u t w i l l not n i p i f i n an unfavourable p h y s i o l o g i c a l condition.  There i s a tendency f o r l a r g e r members to  nip the smaller.  Red and orange models and g o l d f i s h were  l e a s t e f f e c t i v e i n e l i c i t i n g a response.  The l a t t e r were  nipped only once i n s i x hours of observation.  I t i s con-  cluded that the p r e r e q u i s i t e f o r nipping i s movement but s i z e and colour are e s s e n t i a l components.  Red and orange  colour and large s i z e have an I n h i b i t i n g e f f e c t .  33  A comparison of the behaviour of coho and t r o u t underyearl i n g s has been made. A d d i t i o n a l patterns are described f o r t r o u t , namely the "threat" and f i g h t i n g behaviour.  34  ACK_TOWLEDG-EMENTS The w r i t e r wishes to thank Dr. W. A. Clemens, Head, Department o f Zoology, U n i v e r s i t y o f B r i t i s h Columbia, f o r permission to work on the problem, generous assistance and valuable c r i t i c i s m .  S p e c i a l thanks goes to Dr. W. S. Hoar,  Professor, Department o f Zoology, f o r s e l e c t i n g the problem, c r i t i c i s m and c o n t i n u a l guidance; and to Dr. J . R. Adams, Professor, Department o f Zoology, f o r suggestion o f a t i t l e . I am indebted to the B r i t i s h Columbia Game Department and e s p e c i a l l y Cultus Lake hatchery o f f i c e r Frank P e l l s f o r supplying the t r o u t . Most o f a l l , the w r i t e r would l i k e to express a p p r e c i a t i o n to h i s w i f e , Evelyn, f o r encouragement and sacri^* f i c e s during u n i v e r s i t y t r a i n i n g .  35  LITERATURE CITED Adrian, E. D. and R Matthews, 1 9 2 7 . A c t i o n of l i g h t on the eye. Jour. P h y s i o l . , 6J, 37S-414. t  Armstrong, E. A., 1942. B i r d D i s p l a y . Cambridge U n i v e r s i t y Press. (Not read but taken from Lorenz, 1 9 5 0 / • C a r l , G. C. and W. A. Clemens, ISkS. The Fresh-water Fishes of B r i t i s h Columbia. King's P r i n t e r , V i c t o r i a , B. C. Clarke, G. L., 1 9 3 9 . The u t i l i z a t i o n of solar energy by aquatic organisms. Problems of Lake B i o l o g y , No.10, 2 7 - 3 ^ . Coventry, F. L., V. E. Shelford and L. F. M i l l e r , 1 9 3 5 * The c o n d i t i o n i n g of chloramine t r e a t e d water supply f o r b i o l o g i c a l purposes. E c o l . , 1 6 , 6 0 - 6 6 . . C r a i g , W,,  1 9 1 3 . A p p e t i t l e s and aversions a s . c o n s t i t u e n t s of Instincts. Biol. Bull., 91-107.  Escobar, R. A., R. P. Mlnahan and R. J . Shaw, 1 9 3 6 . M o t i l i t y f a c t o r s i n mass (physiology: locomotor a c t i v i t y of f i s h e s under conditions of i s o l a t i o n , homotypic grouping, and h e t e r o t y p i c grouping. P h y s i o l . Zool., ]?, 6 6 - 7 8 . Hoar, W. S., 1 9 5 1 . The behaviour of chum, pink and coho salmon i n r e l a t i o n to t h e i r seaward m i g r a t i o n . J o u r . F i s h . Res. Bd. Can., g, 241-263. Kowamoto, N. and M. Takedo, 1 9 5 1 . 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