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Effect of a parasitic nematode, Truttaedacnitis truttae on growth and swimming ability of rainbow trout Russell, L. Robert 1977

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EFFECT OF A PARASITIC NEMATODE, TRUTTAEDACNITIS GROWTH AND SWIMMING ABILITIES  TRUTTAE ON  OF RAINBOW TROUT  by L. ROBERT RUSSELL B.Sc,  University of B r i t i s h  Columbia  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  i n the Department of Zoology  We a c c e p t t h i s t h e s i s as conforming to t h e r e q u i r e d s t a n d a r d  THE UNIVERSITY OF BRITISH COLUMBIA May, 1977  (O  L. Robert Russell, 1977  In  presenting  this  thesis  an a d v a n c e d d e g r e e a t the L i b r a r y I  further  for  agree  scholarly  by h i s of  shall  this  written  the U n i v e r s i t y  make  it  freely  that permission  for  It  financial  British  2075 Wesbrook Place Vancouver, Canada V6T 1W5  of  Columbia,  British for  gain shall  Columbia  the  requirements  reference copying of  I agree and this  that  not  copying or  for that  study. thesis  by t h e Head o f my D e p a r t m e n t  is understood  Depa r t m e n t of  of  for extensive  permission.  The U n i v e r s i t y  fulfilment  available  p u r p o s e s may be g r a n t e d  representatives. thesis  in p a r t i a l  or  publication  be a l l o w e d w i t h o u t my  ii  ABSTRACT  Growth e f f i c i e n c i e s and swimming a b i l i t i e s o f f i n g e r l i n g and l!g y e a r o l d rainbow t r o u t Truttaedacnitis  i n f e c t e d w i t h t h e nematode  t r u t t a e a r e examined.  i n the laboratory  different rations of trout  increasing rates,  similar  chow ( 1 % , 2%, 3%, o r 4% o f wet body weight  S l i g h t l y d e c r e a s i n g growth r a t e s were c o r r e l a t e d  numbers o f nematode p a r a s i t e s .  Differences  with  between growth  amounts o f food consumed and growth e f f i c i e n c i e s o f i n f e c t e d and  speed, f i x e d v e l o c i t y and b u r s t swimming a b i l i t i e s  more c l o s e l y r e l a t e d  significant.  and time t o f a t i g u e  to f i s h  s i z e and r a t i o n s  trout.  swimming simi-  Maximum  a t c r u i s i n g speeds were f i s h were f e d than t o  numbers o f worms w i t h which f i s h were i n f e c t e d . s u r v i v a l of large natural  Critical  v e l o c i t y stamina t e s t s r e v e a l e d  i n both c o n t r o l and i n f e c t e d  swimming speeds a t t a i n e d  trout  infected  each o f f o u r e x p e r i m e n t a l groups f e d  n o n - i n f e c t e d f i s h were n o t s t a t i s t i c a l l y  lar  t r o u t and t r o u t  w i t h 5, 10, 20, 40, o r 80 worms e x h i b i t e d  growth c h a r a c t e r i s t i c s w i t h i n  fed per day).  Control  parasite  Importance t o rainbow  i n f e c t i o n s w i t h T. n r u t t a e i s d i s c u s s e d .  TABLE OF CONTENTS TITLE PAGE ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES ACKNOWLEDGEMENTS INTRODUCTION Source o f P a r a s i t i c  Infection  Source o f E x p e r i m e n t a l H o s t s MATERIALS AND  METHODS  1.  I n f e c t i o n Techniques  2.  Growth Experiment  3.  Stamina  Experiments  ANALYSIS OF DATA RESULTS 1.  Growth Experiment i. ii. iii.  Growth Rate v s . P a r a s i t e Numbers Food Consumed v s . P a r a s i t e Numbers Growth E f f i c i e n c y v s . P a r a s i t e Numbers  i v . Growth Rate v s . R a t i o n v. Food Consumed v s . R a t i o n vi. vii. 2.  Growth E f f i c i e n c y v s . R a t i o n Growth E f f i c i e n c y v s . Growth Rate  Stamina i. ii. iii.  Experiments  Body Morphology  and C o n d i t i o n F a c t o r  C r i t i c a l Velocity  Tests  Fixed V e l o c i t y  Tests  i v . Burst V e l o c i t y  Tests  T a b l e o f Contents  (cont'd)  iv Page  DISCUSSION  33  1.  Growth Experiments  3$  2.  Stamina Experiments  j^f  Conclusions  59  LITERATURE CITED APPENDIX  62 ^£7  I  V  LIST OF TABLES Page TABLE  I.  Variables tested  In growth experiment  1.0  i  TABLE  TABLE  TABLE  II.  III.  IV.  a. Dry weight d e t e r m i n a t i o n s f o r c o n t r o l and i n f e c t e d rainbow t r o u t f e d 1%, 2%,' 3% o r 4% r a t i o n s / d a y . ,  20  b. Dry weight d e t e r m i n a t i o n o f t r o u t chow used t o feed e x p e r i m e n t a l f i s h  20  F. v a l u e s (Model I ANOVA where F[4/24 0.05] = 2.8) f o r d i f f e r e n c e i n body morphology measurements between c o n t r o l and i n f e c t e d f i n g e r l i n g rainbow t r o u t maintained on 1%, 2%, o r 4% r a t i o n s Mean c o n d i t i o n f a c t o r s o f f i n g e r l i n g and lh y r o l d rainbow t r o u t p r i o r t o stamina experiments  31  y  TABLE  TABLE  V.  VI.  Gross and net growth e f f i c i e n c y o f f i n g e r l i n g rainbow t r o u t A c t i v e and s t a n d a r d m e t a b o l i c r a t e s and scope f o r a c t i v i t y o f f i n g e r l i n g and lh y r o l d rainbow t r o u t  32 44  58  vi LIST OF FIGURES Page FIGURE 1.  FIGURE 2.  FIGURE 3.  FIGURE 4.  FIGURE 5.  FIGURE 6.  FIGURE 7.  FIGURE 8.  FIGURE 9.  FIGURE 10.  FIGURE 11.  FIGURE 12.  FIGURE 13.  FIGURE 14.  Growth rate, o f i n f e c t e d and c o n t r o l f i n g e r l i n g and 1% y r o l d rainbow t r o u t m a i n t a i n e d on f o u r d i f f e r e n t food r a t i o n s  18  Growth r a t e o f f i n g e r l i n g and lh y r o l d rainbow t r o u t i n r e l a t i o n t o number o f p a r a s i t e s w i t h which they were i n f e c t e d  21  Food consumption o f f i n g e r l i n g and 1% y r o l d rainbow t r o u t i n r e l a t i o n t o number o f p a r a s i t e s w i t h which they were i n f e c t e d Growth e f f i c i e n c y o f f i n g e r l i n g and 1% y r o l d rainbow t r o u t i n r e l a t i o n t o number o f p a r a s i t e s w i t h which they were i n f e c t e d Growth r a t e o f f i n g e r l i n g and lh y r o l d r a i n bow t r o u t / i n r e l a t i o n t o r a t i o n s f e d  22  23 25  Food consumption o f f i n g e r l i n g and 1% y r o l d rainbow t r o u t i n r e l a t i o n to r a t i o n s f e d  26  Growth e f f i c i e n c y o f f i n g e r l i n g and 1% y r o l d rainbow t r o u t i n r e l a t i o n t o r a t i o n s f e d  28  Growth e f f i c i e n c y o f f i n g e r l i n g and lh y r o l d rainbow t r o u t i n r e l a t i o n t o growth r a t e  29  Length o f f i n g e r l i n g and 1%. y r o l d rainbow trout i n r e l a t i o n to c r i t i c a l v e l o c i t i e s attained Time taken by f i n g e r l i n g rainbow t r o u t ( f e d 2% r a t i o n s ) t o f a t i g u e i n f i x e d v e l o c i t y tests Time f i n g e r l i n g rainbow t r o u t ( f e d 1%, 2%, or 4% r a t i o n s ) m a i n t a i n e d b u r s t swimming activity G e o m e t r i c a l d e t e r m i n a t i o n o f optimum and maintenance r a t i o n s f o r f i n g e r l i n g rainbow trout Growth r a t e o f f i n g e r l i n g and 1% y r o l d rainbow t r o u t i n r e l a t i o n to f i s h weight C r i t i c a l v e l o c i t i e s a t t a i n e d by f i n g e r l i n g and lh y r o l d rainbow t r o u t i n r e l a t i o n t o , f i s h weight and l e n g t h  33  35  37  42 46  50  L i s t of Figures (cont'd)  vii Page  FIGURE 15.  FIGURE 16.  Composite swimming curve r e l a t i n g steady and burst swimming a b i l i t i e s of f i n g e r l i n g r a i n bow trout Temperature-weight responses for active and standard metabolic rates of f i n g e r l i n g and 1% yr o l d rainbow trout  55  57  LIST OF APPENDICES  APPENDIX  I.  Equations f o r regression l i n e s a p p e a r i n g i n F i g u r e s 2, 3, and 4  APPENDIX  II.  Equations f o r regression appearing i n Figure 8  lines  APPENDIX  III.  Equations f o r regression a p p e a r i n g i n F i g u r e 11  lines  APPENDIX  IV.  Mean l e n g t h s , weights and c r i t i c a l v e l o c i t i e s o f f i s h used i n stamina experiments  ix  ACKNOWLEDGEMENTS  I w i s h t o express  my g r a t i t u d e t o Dr. J.R. Adams, my s u p e r v i s o r ,  f o r many v a l u a b l e s u g g e s t i o n s  and i d e a s d u r i n g the study and f o r h i s  a s s i s t a n c e i n p r e p a r a t i o n o f t h e manuscript.  Dr. D.R. Jones  provided  e s s e n t i a l i n f o r m a t i o n r e g a r d i n g performance o f stamina experiments and a s s i s t e d i n e d i t i n g the write-up. and Mary Jackson  D r s . T.H. C a r e f o o t , J.D. M c P h a i l  read the manuscript  and made many v a l u a b l e  suggestions.  T e c h n i c a l a s s i s t a n c e was p r o v i d e d by Mr. F. Smith and Mr. B. Land. Many s u g g e s t i o n s and i d e a s were made by Mr. J . D ' S i l v a , Mr. M. Kennedy and  Dr. H. Ching.  Mrs. P. Waldron k i n d l y a s s i s t e d by t y p i n g t h e f i n a l  manuscript. Finally, understanding  I w i s h t o thank my w i f e , M a r i l y n , f o r h e r i n s p i r a t i o n , and a s s i s t a n c e i n p r e p a r a t i o n o f t h e m a n u s c r i p t .  1  INTRODUCTION  Rainbow t r o u t are North America.  As  among the most important  such the  d i s e a s e s and  become i n f e c t e d have been the 1970).  Truttaedacnitis  t h a t a t t a c h e s to the trout out  (Hiscox and  the  parasites  and  and  epithelium  w i t h which these  of c o n s i d e r a b l e r e s e a r c h  i n t e s t i n a l epithelium  Brocksen, 1973).  C a l i f o r n i a ( H i s c o x and  trout inhabit  lakes  (Smedley, 1933;  Brocksen, 1973).  p r o b a b l y reduce the  absorbtive capacity  of  The  the  through-  columnar  pyloric  ( R u s s e l l , unpublished data).  nematode p a r a s i t e s  have been found i n a s i n g l e mature rainbow t r o u t  a l observation).  Truttaedacnitis  trimental fluence tish  e f f e c t s on  the  therefore  the p h y s i o l o g y o f i t s h o s t and  and  parasite's  caeca c o n s i d e r a b l y  t r u t t a e may  As many as  rainbow  Bangham  attachment a c t i v i t i e s cause s e v e r e denudation of the and  parasite  o f the p y l o r i c caeca of  Infected  fish  (Snieszko,  t r u t t a e fl,ane 1916^is a s p i r u r i d nematode  c e n t r a l i n t e r i o r o f B r i t i s h Columbia  Adams, 1954) feeding  subject  gamefish c u l t i v a t e d i n  360  o f these, (person-  have numerous  thus may  de-  directly in-  s u r v i v a l o r r e p r o d u c t i v e c a p a b i l i t i e s of rainbow t r o u t i n B r i -  Columbia. A f i s h ' s growth r a t e and  food and  avoid  (Brown, 1957;  its ability  p r e d a t o r s ) are Brett,  1964).  two  investigating  parasites  the  and  parasites  y i e l d u s e f u l i n f o r m a t i o n about  measurable e f f e c t s o f t h i s h o s t - p a r a s i t e  gastro-intestinal parasites  growth c h a r a c t e r i s t i c s  i n f e c t e d with p o t e n t i a l l y harmful  t r u t t a e should therefore  Numerous s t u d i e s  capture  e s s e n t i a l components o f i t s s u r v i v a l  D e t e r m i n a t i o n of  swimming e f f i c i e n c i e s of t r o u t such as T\  to swim ( n e c e s s a r y to  the  association. growth of animals i n f e c t e d w i t h  have attempted to determine the  e f f e c t the w e l l - b e i n g o f t h e i r h o s t s .  e x t e n t to which  S t u d i e s of common i n f e c t i o n s  i n domestic animals w i t h i n t e s t i n a l nematodes i n c l u d e t h a t o f S p i n d l e r (1947) who  found marked growth i n h i b i t i o n i n p i g s d u r i n g the m i g r a t i o n  of l a r v a l Ascaris lumbricoides.  W h i t l o c k (1949) observed i n i t i a l  rapid  growth f o l l o w e d by reduced growth i n lambs i n f e c t e d w i t h T r i c h o s t r o n g y l u s axei.  S i m i l a r l y , reduced food i n t a k e and growth e f f i c i e n c y a r e known to  o c c u r i n sheep as a r e s u l t of i n f e c t i o n s w i t h Haemonchus c o n t o r t u s , T r i c h o s t r o n g y l u s c o l u b r i f o r m i s , C o o p e r i a c u r t i c e i , Nematodirus  spathiger,  Oesophagostomum columbianum and Bunostomum t r i g o n o c e p h a l u m by  (Spedding et  al.,  1957,  1958;  Soulsby,  Gordon, 1950,  1958;  Andrews, 1938;  Shumard e t a l . ,  and  1965).  E f f e c t s o f p a r a s i t e s on the growth c h a r a c t e r i s t i c s o f f i s h have been examined l e s s f r e q u e n t l y . larvae  I n f e c t i o n o f the upper i n t e s t i n e w i t h tapeworm  ( P r o t e o c e p h a l u s sp.) was  found by Hubbs (1927) t o cause  i n growth and an i n t e r r u p t i o n i n development i n the c y p r i n i d P l a t y g o b i s g r a c i l i s .  retardation  o f melanophores and  Similarly, Miller  (1945)  f i n rays  demonstrated  a reduced growth r a t e i n c o r e g o n i d f i s h e s h a r b o u r i n g m u s c l e - e n c y s t e d  plero-  c e r c o i d s o f T r i a e n o p h o r u s c r a s s u s and r e t e n t i o n o f l a r v a l c h a r a c t e r s and l o s s o f weight  in  Echinorhynchus  truttae  (Wisniewsky,  rainbow  t r o u t has been a t t r i b u t e d t o the presence o f :  ( S t e i n s t r a s s e r , 1936);  1932), and T_. nodulosus  i n f e c t e d w i t h 5 to 10 Eubothrium  Cyathocephalus t r u n c a t u s  (Novikova, 1934).  s a l v e l i n i were 5 mm  than n o n - i n f e c t e d smolts o f the same age  Sockeye  salmon smol :s  s h o r t e r and 1 g l i g h t e r  (Smith and M a r g o l i s , 1970).  Con-  v e r s e l y , K l e i n e^t a l . (1969) observed no e f f e c t o f s u b s t a n t i a l numbers of Crepidostomum f a r i o n i s on the l e n g t h , weight o r c o n d i t i o n f a c t o r of i n f e c t e d rainbow  trout.  3 Few  investigations  parasites  o f t h e e f f e c t s on growth o f g u t - i n h a b i t i n g  o f f i s h have been undertaken.  nematode  R e i c h e n b a c h - K l i n k e and E l k a n  (1965)  noted t h a t young salmonids i n f e c t e d w i t h C a p i l l a r i a sp. were emaciated and reluctant  to feed.  teristics,  H i s c o x and Brocksen  over a ten-day p e r i o d ,  a q u a r i a on v a r i o u s r a t i o n s . bers of Truttaedacnitis ciently  than  (1973), s t u d i e d  the growth c h a r a c -  o f rainbow t r o u t m a i n t a i n e d i n i n d i v i d u a l  They suggest that  f i s h h a r b o u r i n g moderate num-  t r u t t a e grow more s l o w l y and u t i l i z e  food l e s s  controls.  D e t e r m i n a t i o n o f t h e components d e f i n i n g f i s h e s has been d i s c u s s e d e x t e n s i v e l y  swimming a b i l i t y  by B a i n b r i d g e  F r y and Cox (1970), Webb (1971a, b , 1975) and B r e t t  i n salmonid  (1960), B r e t t and G l a s s  (1964),  (1973).  t o t h e importance o f swimming t o t h e s u r v i v a l o f f i s h i t i s s u r p r i s i n g measurement o f s t a m i n a h a s n o t been i n c o r p o r a t e d parasite  relationships.  i n t o more s t u d i e s  t r o u t and salmon i n f e c t e d  of host-  ( i n t h e body musculature) w i t h l a r g e numbers o f swimming speeds and  f a s t e r i n endurance swimming t e s t s than c o n t r o l s .  Sockeye salmon  tapeworm burdens o f up t o 5% o f t h e wet body weight o f the  f i s h swam o n l y 2/3 as f a r as n o n - i n f e c t e d smolts K l e i n ej: 'al.  that  ( B r e t t , 1964) t o show t h a t  trematode m e t a c e r c a r i a e a t t a i n lower maximum s u s t a i n e d  smolts c a r r y i n g  Owing  Fox (1965) and B u t l e r and Millemann (1971) used  c r i t i c a l v e l o c i t y and f i x e d v e l o c i t y swimming t e s t s  fatigue  effi-  (1969), on t h e o t h e r hand, c o u l d  (Smith and M a r g o l i s , 1970).  f i n d no e f f e c t on stamina o f  rainbow t r o u t h a r b o u r i n g l a r g e numbers o f i n t e s t i n a l f l u k e s  (Crepidostomum  farionis). S i n c e growth s t u d i e s of h o s t - p a r a s i t e  r e v e a l much i n f o r m a t i o n about.harmful consequences  associations  and s i n c e  i n v e s t i g a t i o n o f swimming  abilities  of p a r a s i t i z e d f i s h may y i e l d v a l u a b l e d a t a on s u r v i v a l p o t e n t i a l o f i n f e c t e d fish,  i t i s my i n t e n t i o n  to examine the e f f e c t s o f the p a r a s i t i c nematode,  4  Truttaedacnitis  t r u t t a e , on the growth c h a r a c t e r i s t i c s and swimming  a b i l i t i e s o f rainbow t r o u t . to the s u c c e s s f u l  Documentation o f any e f f e c t s  s u r v i v a l o f rainbow t r o u t may  detrimental  provide useful  informa-  t i o n f o r f i s h e r i e s b i o l o g i s t s concerned w i t h the i n c i d e n c e of p a r a s i t i c i n f e c t i o n i n B r i t i s h Columbia's gamefish p o p u l a t i o n s .  Source of P a r a s i t i c Infection Naturally infected rainbow trout were collected i n July 1976 by e l e c t r o f i s h i n g from Loon Inlet Creek located at the north-east end of Loon Lake, about 40 miles north-east of Cache Creek, B.C.  Mature  fish  were transported to the University of B.C. i n a 450 l i t r e stocking tank and maintained i n a 2000 l i t r e holding tank under natural daylight conditions i n c i r c u l a t i n g water at 11°C.  Upon dissection these f i s h were found  to harbour between 13 and 360 adult and immature nematode parasites, Truttaedacnitis truttae.  Source of Experimental Hosts Two hundred and s i x t y disease-free 8-month o l d "domestic stock" r a i n bow trout f i n g e r l i n g s , averaging 12 cm i n length, were obtained from the P r o v i n c i a l Fish Hatchery at Abbotsfcrd, B.C. i n July 1976.  Ten f i s h selec-  ted at random were examined for the presence of parasites and none were found.  The remaining f i s h were divided into 4 groups of 60 f i s h each and  maintained i n c i r c u l a t i n g water aquaria at 11°C for 1 week p r i o r to a r t i f i c i a l parasitic infection.  MATERIALS AND METHODS 1.  Infection Techniques Adult Truttaedacnitis truttae were dissected from the upper i n t e s t i n e  and p y l o r i c caeca of freshly k i l l e d Loon Lake rainbow trout with scissors and fine pointed forcepe.  A sample of 60 worms (30 male and 30 female) w a s  taken for species determination and measurement.  Worms for this purpose w o r e  fixed i n warm (20°C) 10% formaldehyde, preserved i n 10% glycerine i n 70% ethanol, stained with 0.0025% Cotton Blue i n Lactophenol and examined with  6  a L e i t z compound  microscope.  Worms to be used f o r i n f e c t i o n purposes were placed with eye droppers into a 5% solution of NaHCO^ i n Alsever's saline solution at 10°C (Hiscox and Brocksen, 1973) and stored f o r not more than 3 hours i n buffered Alsever's solution (pH 6.1) at 10°C u n t i l used to i n f e c t hatchery-reared  fingerlings.  Preliminary i n f e c t i o n t r i a l s showed that longer storage periods reduced T_. truttae attachment success. Hatchery-reared  rainbow trout were l i g h t l y anaethesetized i n a  1/10,0.00 solution of MS 222 (Sandoz) , blotted dry on moist toweling, measured to the nearest millimeter and weighed to the nearest 0.1 g on a Sartorius Model 2116 electrobalance.  Counted l o t s of adult nematodes were drawn into  a 1 cc syringe (B-D Plastipak #5623) along with 0.2 to 0.4 ml Alsever's solution.  The worms were introduced into the test f i s h stomachs using a 5 cm  length of polyethylene tubing 1.19 mm i n inside diameter  (Intra-Medic For-  mulation PHF, Clay Adams and Co.) f i t t e d to the syringe with a Luer-Lok adaptor following the per os method of Hiscox and Brocksen  (1973).  Slightly  greater numbers of worms were injected than those desired i n the f i n a l i n f e c t i o n to allow f o r d i f f e r e n t i a l attachment success of the worms (Hiscox and Brocksen, 1973).  Thus, where a 10 worm i n f e c t i o n was desired 12 worms  were introduced. In order to check attachment progress and i n f e c t i o n success two f i s h were k i l l e d at 1/2, 1, 2, 4, 8, and 24 hours post i n f e c t i o n .  Their p y l o r i c  caeca were examined for the presence of _T. truttae. Worms were found loose i n the stomach and p y l o r i c caeca up to 8 hours post i n f e c t i o n but most were firmly attached to the caecal mucosa a f t e r 24 hours.  Infection success aver-  aged about 80% (80% of the injected worms attached to the caeca).  This i s  7 c o n s i s t e n t w i t h t h e f i n d i n g s o f H i s c o x and Brocksen  (1973).  U s i n g the per-os method d e s c r i b e d above f i n g e r l i n g f i s h were i n f e c t e d w i t h 5, 10, o r 20 worms each. t r o l s were s h a m - i n f e c t e d , those used  Three groups o f c o n t r o l f i s h were used.  s u b j e c t e d o n l y to h a n d l i n g procedures  f o r i n f e c t e d f i s h o r n o t handled  Following i n f e c t i o n a l l experimental f i n g e r l i n g t a g ; (3 mm c l e a r p l a s t i c to  s i m i l a r to  at a l l .  f i s h were tagged w i t h a numbered  d i s c sewn through  the s k i n j u s t  t h e d o r s a l f i n ) t h e numbers c o r r e s p o n d i n g t o the l e v e l o f i n d u c e d  tion. ing  Most c o n t r o l s and sham c o n t r o l s were a l s o tagged,  anterior infec-  the number 0 denot-  a sham c o n t r o l and t a g s w i t h o u t numbers d e n o t i n g c o n t r o l s .  the c o n t r o l s were n o t tagged  Con-  One t h i r d o f  so t h a t the e f f e c t o f the t a g on c o n t r o l s c o u l d  be e s t i m a t e d i n terms o f r e l a t i v e growth and stamina. In old  a d d i t i o n t o the f i n g e r l i n g s mentioned above a group o f s i x t y 1-1/2 y r  h a t c h e r y - r e a r e d ranbow t r o u t were a l s o i n f e c t e d  (10, 20, 40 o r 80 worms  i n j e c t e d p e r f i s h ) and tagged a c c o r d i n g t o the number o f worms i n j e c t e d . a l l o w e d a comparison o f growth and stamina between young and maturing  This  trout  l i v i n g w i t h a v a r i e t y o f worm burdens. Numbers o f T T . t r u t t a e i n t r o d u c e d were i n t e n d e d t o approximate n a t u r a l worm burdens i n s o f a r as numbers removed from f i e l d - c o l l e c t e ' d t r o u t were cerned. fish.  The e x c e p t i o n was the 20 worm i n f e c t i o n a d m i n i s t e r e d t o f i n g e r l i n g T h i s worm l o a d was chosen to r e p r e s e n t the maximum a f i n g e r l i n g coulc:  support owing t o t h e s m a l l s i z e o f i t s p y l o r i c 2.  con-  Growth  caeca.  Experiment  Two hundred and f o r t y t i o n procedures  f i n g e r l i n g s s u b j e c t e d t o the h a n d l i n g and i n f e c -  o u t l i n e d above were d i v i d e d i n t o f o u r groups o f s i x t y  each and m a i n t a i n e d  i n 4 identical circulating  (approx.  fish  1 l e n g t h / s e c . ) water  8" tanks each w i t h a volume o f 55 1. all  tanks but f l u c t u a t e d  Water temperatures  from 11.5°  n a t u r a l d a y l i g h t - d a r k n e s s regime was  were the same i n  to 10°C d u r i n g the experiment. m a i n t a i n e d throughout  A  the study w i t h  an i l l u m i n a t i o n d u r i n g the day o f 77 l u x a t the s u r f a c e o f the water p r o v i d e d by f l o r e s c e n t l i g h t s suspended D i s t u r b a n c e of the f i s h was with translucent  2.3 m above the tanks.  kept to a minimum by c o v e r i n g the tanks  f i b e r g l a s s c o v e r s which were removed o n l y d u r i n g f e e d i n g .  Each tank o f f i s h c o n t a i n e d 10 f i s h  i n f e c t e d w i t h 5 worms each,  10  w i t h 10 worms, 10 w i t h 20 worms p l u s 30 c o n t r o l s o f which t e n were tagged sham-infected f i s h , group  o f f i s h was  of wet Co.,  m a i n t a i n e d on a r a t i o n e d d i e t o f e i t h e r 1%,  body weight  Utah).  t e n were tagged c o n t r o l s and t e n were not tagged.  per day o f Growers Crumbles #3 t r o u t chow  D u r i n g the 10 week experiment,  weekly f o r each r a t i o n group  2%,  Each  3% o r  4%  (Moore-Clark  food a l l o t m e n t s were a d j u s t e d  a c c o r d i n g to weight  gained by the f i s h .  Fish  were f e d as many times d a i l y as they r e q u i r e d to consume t h e i r r a t i o n w i t h out w a s t i n g any  food.  F i s h were weighed and measured e v e r y seven  days  u s i n g the a n a e s t h e t i c b l o t - d r y i n g t e c h n i q u e d e s c r i b e d f o r the i n i t i a l i n fection. at  Two  c o n t r o l s and two  the end o f the f i r s t ,  weight still  fifth  i n f e c t e d f i s h were removed from each and  t e n t h weeks o f the experiment  tank  f o r dry  d e t e r m i n a t i o n and to i n s u r e t h a t the i n f e c t i o n w i t h T. t r u t t a e  was  present. One-and-one-half-year-old  experiment. circulating regimes  Two  groups  rainbow were a l s o i n c l u d e d i n a growth  o f 30 f i s h each were m a i n t a i n e d i n 1 3 0 ' l i t r e  (about 1 l e n g t h / s e c ) water tanks under temperature  identical  to those under which the f i n g e r l i n g  and  light  t r o u t were k e p t .  9  These  f i s h , m a i n t a i n e d on 1% and 3% d i e t regimes, were f e d as many times  d a i l y as they r e q u i r e d to consume t h e i r r a t i o n o f C l a r k s 3/32 i n c h trout p e l l e t s .  Each group o f 30 f i s h  comprised s i x groups o f f i v e  fish  each: 10, 20, 40 and 80 worm i n f e c t i o n s p l u s two groups o f c o n t r o l s ; f i v e o f which were s h a m - i n f e c t e d , and f i v e which were h a n d l e d b u t n o t infected.  A l l o f t h e s e f i s h were tagged a c c o r d i n g t o t h e numbers o f  worms w i t h which  they had been i n f e c t e d .  These  f i s h were weighed  on an  Ohaus Model 700 T r i p l e Beam Balance and measured every seven days over a ten  week p e r i o d u s i n g the a n a e s t h e t i c b l o t - d r y i n g t e c h n i q u e d e s c r i b e d  previously. For  Food a l l o t m e n t s were a d j u s t e d a c c o r d i n g t o weight g a i n e d .  d r y weight d e t e r m i n a t i o n s f i s h and t r o u t p e l l e t s were  weighed wet on a model DL T2-1 T o r s i o n B a l a n c e , d r i e d  first  to constant  weight f o r 48 hours a t 100°C i n a Despatch d r y i n g oven and reweighed on the  T o r s i o n b a l a n c e t o the n e a r e s t O.Olg. T a b l e I shows the v a r i a b l e s t e s t e d i n the growth  3.  Stamina  experiment.  Experiments  F o l l o w i n g c o m p l e t i o n o f the growth  experiment, stamina experiments  were undertaken i n o r d e r t o see whether swimming a b i l i t y was a f f e c t e d as a r e s u l t o f p a r a s i t i c  infection.  P r i o r t o swimming t e s t s , measurements o f body morphology  including  l e n g t h , weight, depth, b r e a d t h and volume were taken from a l l f i s h in for  the growth experiments d e s c r i b e d above.  used  S t a e t l e r d i v i d e r s were used  l e n g t h , w i d t h and depth measurements w h i l e volume was measured by  immersing Dimensions  the f i s h i n a known volume o f water  i n a graduated  cylinder.  o f p a r a s i t i z e d v e r s u s c o n t r o l f i s h were compared u s i n g a  Model I A n a l y s i s o f V a r i a n c e to ensure t h a t an a l t e r a t i o n i n body  shape  10  TABLE I VARIABLES TESTED IN GROWTH EXPERIMENTS Age of Fish  8 months  Infection Level  Ration on which Fish were Maintained (% wet body weight per day) and Number of Fish used at each Infection Level — — —_ __. 2%  Control(tagged)  1% 10  10  3% 10  Control(no tag)  « •  11  • 1  i t  It  Sham Control  n  Inf. ( 5 worms)  • t  i i  1t  I n f . ( 1 0 worms)  •t  11  11  I n f . ( 2 0 worms)  11  11  1%  \\ years  Control(tagged) Sham Control I n f . ( 1 0 worms) I n f . ( 2 0 worms) I n f . ( 4 0 worms) I n f . ( 8 0 worms)  5  3% 5  10  II  11  due t o p a r a s i t i c i n f e c t i o n had n o t o c c u r r e d which would performance  ( B a i n b r i d g e 1960, 1962; B e l l and Terhune,  alter  swimming  1970, B r e t t 1964,  1965; B r e t t and G l a s s 1973; F r y and Cox 1970; Webb 1971 a,b,1975). The c l o s e d c i r c u i t  stamina chamber used i n a l l swimming p e r f o r m -  ance t e s t s c o n s i s t e d o f a 12.7 cm ID p l e x i g l a s s  tube 86 cm i n l e n g t h  through which r e f r i g e r a t e d water was r e c i r c u l a t e d by a v a r i a b l e pump.  speed  Flow r a t e s i n the chamber had been c a l i b r a t e d p r e v i o u s l y by  Jones e_t a l . (1974) w i t h a m o d i f i e d Aqua-Log flowmeter and were r e l a t e d to pump rpm.  Three 0.3 cm mesh g r i d s a t the head o f the chamber i n -  t r o d u c e d m i c r o t u r b u l e n c e i n the swimming tube c r e a t i n g a f l a t  velocity  p r o f i l e and a l l o w i n g a maximum f l o w r a t e o f 100 cm/sec (Jones e t a l . , 1974).  An e l e c t r i c g r i d  (5 v o l t s ; B r e t t , 1964) a t the t a i l  end o f the  stamina chamber i n d u c e d f i s h t o swim t o e x h a u s t i o n o r t o a t t a i n b u r s t v e l o c i t i e s i n experiments d e s c r i b e d below. the system c o n t i n u o u s l y  F r e s h water was added to  (10 1/min) and p0£ i n t h e flow chamber was  monitored u s i n g an oxygen e l e c t r o d e  (Radiometer module PHA 930) t o  ensure an adequate  to the f i s h .  s u p p l y o f oxygen  A l l experiments were  performed a t 10°C, t h e same as t h a t i n the c i r c u l a t i n g water t a n k s , i.  C r i t i c a l Velocity  Tests  As a b a s e l i n e f o r f u r t h e r stamina experiments c r i t i c a l  velocities  (maximum s u s t a i n e d swimming speeds) o f c o n t r o l and i n f e c t e d f i s h were determined i n the f o l l o w i n g manner. fish  (12-15  cm  Four c o n t r o l o r f o u r  parasitized  long) were i n t r o d u c e d i n t o the stamina chamber w i t h  the water speed a d j u s t e d chamber o v e r n i g h t  to lOcm/sec  ( B r e t t , 1964).  and a l l o w e d to e q u i l i b r a t e i n the  B l a c k p l a s t i c was wrapped around the  head end o f the tube t o g i v e the f i s h a r e f e r e n c e p o i n t  and t o p r e v e n t  12  v i s u a l disturbance. The following morning the v e l o c i t y i n the chamber was increased i n increments every 20 minutes (Jones, 1971) u n t i l the f i s h fatigued and were  exhausted against the e l e c t r i c  grid.  Speed  increments were adjusted so that c r i t i c a l v e l o c i t i e s of a l l the f i s h (removed one at a time as they fatigued) were attained i n s i x increments (Jones et al_. , 1974) .  Fatigued f i s h were measured and the  number of worms with which they were infected was recorded. C r i t i c a l v e l o c i t i e s were determined f o r f i n g e r l i n g s on 1%, 2% and 4% rations and f o r 1% year old rainbow on the 1% diet (one f i s h tested i n the chamber at a time).  Eight controls and eight f i s h i n -  fected with the largest numbers of parasites were tested f o r each diet and age group. Since most f i s h swam f o r less than 20 minutes at t h e i r f i n a l speed increment, c r i t i c a l v e l o c i t y was determined by i n t e r p o l a t i o n as described by Brett (1964) and l a t e r formulated by  Jones et al.(1974).  C V . = Vp + [ (Vf - Vp ) x | | ] where  Vp = penultimate water v e l o c i t y (cm/sec) Vf = f i n a l water v e l o c i t y (cm/sec) tF = time to fatigue at Vf (sec) t l = time between v e l o c i t y increments  ii.  Fixed V e l o c i t y Tests  Once the maximum sustained swimming speeds had been computed, fatigue tests were conducted i n which f i s h were made to swim at 90% of their c r i t i c a l v e l o c i t y u n t i l exhausted.  Test procedures were  modifications of those described by Brett (1967) and Jones et al_. (1974) ,  13  Four f i n g e r l i n g s (2 c o n t r o l , 2 i n f e c t e d ) were allowed to e q u i l i b r a t e overnight The  i n the stamina chamber at a water v e l o c i t y of 10 cm/sec.  f o l l o w i n g day flow r a t e s were i n c r e a s e d  each l a s t i n g 3 m i n u t e s , u n t i l v e l o c i t y ) was reached.  i n 4 equal i n c r e m e n t s ,  the t e s t v e l o c i t y (90% o f the c r i t i c a l  The t e s t v e l o c i t y was m a i n t a i n e d f o r 600  minutes o r u n t i l a l l the f i s h had been exhausted.  F i s h were removed  as they f a t i g u e d , t h e i r l e n g t h s were measured, t h e i r p a r a s i t e  load  r e c o r d e d , and the t i m e - t o - e x h a u s t i o n n o t e d . A comparison o f f a t i g u e times o f c o n t r o l and i n f e c t e d f i s h  was  made (12 c o n t r o l and 12 i n f e c t e d f i n g e r l i n g s on 2% r a t i o n s o n l y were tested)  i n order  ability  as a r e s u l t o f p a r a s i t i c i n f e c t i o n ,  iii.  Burst  For Fairchild  to a s c e r t a i n any d i f f e r e n c e s i n s u s t a i n e d  Swimming  swimming  Tests  these t e s t s the stamina chamber was m o d i f i e d FPT 100 p h o t o t r a n s i s t o r s  by p l a c i n g 3  25 o r 30 cm from the e l e c t r i c  grid.  S i n g l e f i s h were a l l o w e d to e q u i l i b r a t e i n the chamber f o r % hour p r i o r to each b u r s t  swimming t e s t .  ances by a l l o w i n g  F i s h were s h i e l d e d  them to r e s t i n an area b l a c k e d  immediately ahead o f the d e a c t i v a t e d (resting i t s t a i l against  and  grid.  i t into burst  disturb-  out w i t h p l a s t i c  In a burst  the g r i d ) was s u b j e c t e d  f o r 20 m i l l i s e c o n d s which f r i g h t e n e d tube.  from o u t s i d e  film  t e s t , the f i s h  to a 100 v o l t  shock  swimming a l o n g the  As i t passed through the l i g h t beam between the p h o t o t r a n s i s t o r s  the l i g h t  a Tektronix  s o u r c e (American O p t i c a l I l l u m i n a t o r //735C) a t r a c e on  Type 564B s t o r a g e  o s c i l l o s c o p e ( t r i g g e r e d v i a a Grass S6C  s t i m u l a t o r ) was i n t e r r u p t e d which r e g i s t e r e d the time o f the b u r s t . Oscilloscope  t r a c e s were photographed w i t h a P o l a r o i d CR-9 Land Camera  14 using Type 107 f i l m and time elapsed during burst swimming was computed from measurement of trace lengths taken from the photographs. Distance the f i s h t r a v e l l e d m u l t i p l i e d by the time elapsed gave the burst v e l o c i t i e s attained. A l l control and infected f i n g e r l i n g trout at a l l r a t i o n levels were tested four times each on two occasions i n order that maximum swimming speeds of p a r a s i t i z e d and control f i s h could be compared.  15  ANALYSIS OF DATA Growth Experiment Mean growth r a t e s ,  amounts o f food consumed, and growth e f f i c -  i e n c i e s o f f i s h a t each l e v e l o f i n f e c t i o n ( c o n t r o l , sham  control,  n o - t a g c o n t r o l , 5 worms, 10 worms, 20 worms, 40 worms, o r 80 worms p e r fish) within  a p a r t i c u l a r r a t i o n group and age c a t e g o r y were compared  using covariance  analysis.  R e g r e s s i o n l i n e s were drawn r e l a t i n g the f o l l o w i n g experimental trout  components o f  growth:  Growth Rate v s Number o f P a r a s i t e s  w i t h which F i s h were  Food Consumption vs Number o f P a r a s i t e s  w i t h which F i s h were  Growth E f f i c i e n c y vs Number o f P a r a s i t e s Food Consumed vs R a t i o n  Infected  w i t h which F i s h were  Infected Infected  ( f i n g e r l i n g trout)  Growth E f f i c i e n c y v s Growth Rate Significance  of regressions  v a r i a n c e ) and r e l a t e d fected  and the r a t i o n s  e f f i c i e n t s representing for  each r e g r e s s i o n  Swimming  t o numbers o f p a r a s i t e s  Regression co-  i n f e c t e d and n o n - i n f e c t e d t r o u t were determined  and compared u s i n g a t t e s t .  Experiments and v e l o c i t y  t r o u t ) , time t o f a t i g u e  l i n e a r regressions trout  ( c r i t i c a l v e l o c i t y t e s t s , lh y r .  and v e l o c i t y ( f i x e d v e l o c i t y t e s t s ) and  time m a i n t a i n e d and v e l o c i t y ( b u r s t  control  w i t h which f i s h were i n -  on which f i s h were m a i n t a i n e d .  Data r e l a t i n g l e n g t h old  o b t a i n e d was compared ( a n a l y s i s o f c o -  representing  v e l o c i t y t e s t s ) were d e s c r i b e d  swimming a b i l i t i e s  fed various rations of trout  g r e s s i o n s o b t a i n e d was t e s t e d by a n a l y s i s  chow.  by  o f p a r a s i t i z e d and Significance  of covariance.  of r e -  Differences  16  between regression  c o e f f i c i e n t s of infected and non-infected f i s h  on each r a t i o n were compared using a t t e s t . Length vs v e l o c i t y data derived  from c r i t i c a l v e l o c i t y measure-  ments of f i n g e r l i n g trout were not suitable f o r regression Maximum sustained  analysis.  swimming speeds of control and infected f i n g e r -  l i n g s tested were therefore  compared using a t test.  o  17 RESULTS 1.  Growth Experiment No s i g n i f i c a n t differences  (p = 0.05) between growth rates of  control and infected f i n g e r l i n g trout were observed during the ten week period of the study (Fig 1 a-d) although control f i s h grew slightly  faster than infected f i s h at each ration l e v e l .  Among para-  s i t i z e d f i s h , those harbouring more worms grew more slowly than those infected with fewer worms.  Fish maintained on 1% wet body weight per  day rations grew to about 1/3 the size of f i s h fed 3% rations.  No  difference i n growth was observed between f i s h kept on 3% and 4% rations. Growth rates of control and infected f i s h were s i m i l a r also i n the groups of \\ year old rainbow maintained on 1% and 3% rations (Fig l e , f ) .  As a group, infected f i s h grew s l i g h t l y  faster than  controls on 1% rations whereas on 3% rations controls had a s l i g h t l y greater rate of growth than trout infected with T. truttae. no s i g n i f i c a n t difference t i z e d and unparasitized  However,  (p=0.05) i n growth between groups of p a r a s i -  f i s h was observed.  Trout maintained on 3%  rations grew about three times as fast as those fed 1% rations. 'Comparison of growth curves of 8 month and \\ year old f i s h (Fig 1) revealed  a lower over a l l increase  ten week period for lh year o l d trout.  i n body weight during the  These data confirm the findings  of Brown (1957) and Brett and Shelbourn (1975) i n which larger f i s h maintained on d i e t s of the same proportion  as smaller f i s h grew at a  slower rate. To analyse more completely the data on r e l a t i v e growth of control  17a  Figure 1.  Growth rate of infected and control f i n g e r l i n g and 1-ir year old rainbow trout maintained on four d i f f e r e n t food rations* represent + 2 S.E.  V e r t i c a l bars  IS R O  w T 200 R * 160 E .  %  INC. WET WT  2% t MO  120  80  8 MO  1%  i  40  4 /o 8 MO  3% 8 MO  160 M0 G R 0 120  w  140  120  H  0  ioo H  A  1 °/o INC. WET WT.  PCON  H  80-  6 0  :INF  80  .  60  40  40  20  20H 1  2  4 TIME  INFECTION  6  8  1  (WEEKS)  10 TIME ( W E E K S )  KEY  C CONTROL NT NO T A G C O N T R O L S SHAM CONTROL  2  5 10 20  5 W O R M INFECTION 10 20  " "  "  /  1 i YR,  19  and  i n f e c t e d f i s h on  determined from the  d i f f e r e n t r a t i o n s , growth e f f i c i e n c i e s (K) were growth r a t e s  (Aw)  ( R A t) of e x p e r i m e n t a l f i s h u s i n g and  Dickie  using  the  food consumption  formula derived  by  rates  Paloheimo  (1966a,b) where log  Growth and  and  K = log  (Aw/RAt)  consumption were e x p r e s s e d as mg/g  dry weight of  c o n v e r s i o n f a c t o r s from dry weight d e t e r m i n a t i o n s o f  mental f i s h and  t r o u t chow (Table  fish/day experi-  II).  Growth r a t e s , consumption r a t e s , and  growth e f f i c i e n c i e s were  then compared w i t h numbers o f p a r a s i t e s w i t h which f i s h were i n f e c t e d and  r a t i o n s which f i s h were f e d .  efficiency  and  growth r a t e was  The  r e l a t i o n s h i p between growth  then determined i n o r d e r t h a t  a comparison  of r e s u l t s o f t h i s growth study w i t h p r e v i o u s growth experiments  could  be made, i,  i i ,i i i .  Growth Rate, Food Consumption, and  vs Numbers of P a r a s i t e s Growth r a t e s s i t e load  and  w i t h which F i s h were  Growth E f f i c i e n c y  Infected  amounts of food consumed were compared w i t h p a r a -  (Fig.2a,b; Fig.3a,b).  No  significant correlations  (p=0.05)  were found f o r e i t h e r f i n g e r l i n g o r 1% y r o l d t r o u t m a i n t a i n e d on ration. no  These r e s u l t s suggested t h a t  apparent e f f e c t on  the  test No  the  the nematode i n f e c t i o n s used  r a t e of growth or amount of food consumed  had by  fish. significant correlations  (p=0.05) between growth e f f i c i e n c y  and  number of p a r a s i t e s w i t h which f i s h were i n f e c t e d were o b t a i n e d  any  r a t i o n l e v e l w i t h e i t h e r f i n g e r l i n g or 1% y r o l d f i s h  This  any  indicated  t h a t T.  t r u t t a e had  no  at  (Fig.4a,b).  demonstrable e f f e c t on  the  20  TABLE II a.  DRY V/EIGHT DETERMINATIONS FOR CONTROL AND INFECTED TROUT FED \% 2%. 3%. OR k% RATIONS/DAY t  Diet  \%  3%  2%  h  o/  0  I n f e c t i o n Level  Inf.  Con. I n f . Con. I n f . Con. I n f . Con.  % Wet Weight  22.a  23.0  28.9  27.2  28,9  24.8.  25-5  26.3  (mean of 5 determinations)  D.  DRY WEIGHT DETERMINATION OF TROUT CHOW USED TO FEED EXPERIMENTAL FISH  Trout Chow % Wet Weight (mean o f 5 determinations)  96.31  20a  F i g u r e 2.  Growth r a t e  o f f i n g e r l i n g and  year o l d rainbow  t r o u t i n r e l a t i o n to number o f p a r a s i t e s which they were  infected.  with  21a  Figure 3.  Food consumption of f i n g e r l i n g and  year o l d  rainbow trout i n r e l a t i o n to number of parasites with which they were i n f e c t e d .  22 160*  N U M B E R OF P A R A S I T E S RATION GROUP  • O  \*y 3°/g o  22a  Figure if. Growth e f f i c i e n c y of f i n g e r l i n g and 1£ year old rainbow trout i n r e l a t i o n to number of parasites with which they were i n f e c t e d .  23  24 c o n v e r s i o n e f f i c i e n c y o f rainbow t r o u t under the  conditions  of  these  growth experiments. Equations f o r regression  l i n e s a p p e a r i n g i n F i g u r e s 2,3  and  4  are p r e s e n t e d i n Appendix I . iv.  Growth Rate vs  Growth r a t e s rations  (7.5-  maximum 4%,  Ration  of f i n g e r l i n g t r o u t  12 mg/g  increased  r a p i d l y from 1%  dry wt/day), whereas from 2%  increases  rations  up  i n growth r a t e were l e s s pronounced  Growth r a t e curves were s i m i l a r f o r b o t h i n f e c t e d and  to  to  2%  the  (Fig.5a).  non-infected  fish. The  histogram representing  shows a two rations  to t h r e e - f o l d  growth of 1% y r o l d t r o u t  increase  compared w i t h those f i s h  i n growth r a t e  fed 1%  r a t i o n l e v e l s were not  incorporated  space l i m i t a t i o n s , the  gradual decline  rate with increasing Differences were not ration  fed  3%  Since 2%  and  4%  i n t o these experiments owing to  between growth r a t e s  statistically  i n the  increase  i n growth  of c o n t r o l and  infected  s i g n i f i c a n t (p=0.05) at e i t h e r the  1%  not  seen.  fish or  3%  level.  Correlations  Ration  between food consumed and  f i s h were s i g n i f i c a n t (p=0,01) and (Fig.6a).  control  for f i s h  r a t i o n o b s e r v e d f o r f i n g e r l i n g t r o u t was  v. Food Consumed vs  gression  rations.  (Fig.5b)  There was  no  rations  experimental  p o s i t i v e for f i n g e r l i n g trout  significant difference  c o e f f i c i e n t s f o r the  fed  l i n e s representing  (p=0.05) between r e parasitized  and  fish.  Food consumed by  1%  yr old  f i s h i n r e l a t i o n to r a t i o n s  fed i s  24a  Figure 5.  Growth rate of f i n g e r l i n g and  year old  rainbow trout i n r e l a t i o n to rations (1%,  2%,  3%,  fed per day). ± 2  S.E.  or 4% of wet  weight of  fed fish  V e r t i c a l bars represent  25a  Figure 6.  Food consumption of f i n g e r l i n g and 1-jr year o l d rainbow trout i n r e l a t i o n to rations  fed (1%,  2%, 3%, or k% of wet weight of f i s h fed per day).  V e r t i c a l bars represent + 2 S.E.  27  shown i n F i g . 6b. e q u a l amounts o f  I n f e c t e d and trout  food  the  amount o f  vi.  Growth E f f i c i e n c y vs  food was  ration  levels  of  3%  4%  and  and  approximately  Ration  (K=0.185) and  f i n g e r l i n g s were g r e a t e s t  decreased by  about 1/3  at r a t i o n  E f f i c i e n c y curves were s i m i l a r  for  growth e f f i c i e n c y vs  r a t i o n was  o n l y two  i n r e l a t i o n to e f f i c i e n c i e s of infected  trout  r a t i o n l e v e l ( t t e s t ; p=  r e p r e s e n t e d by  a histogram  Significant positive  fish  and  b).  correlations  No  ent  rations  utilize  each  (p=0.01) between growth  In a d d i t i o n ,  lh  and  infected  year  age  s t a t i s t i c a l l y significant differences  f i s h were observed.  level.  rations.  growth e f f i c i e n c i e s at  f o r b o t h f i n g e r l i n g and  i n g growth r a t e s imply i n c r e a s i n g ration  rations  Growth Rate  r e g r e s s i o n c o e f f i c i e n t s of the  infected  (Fig.7b).  3%  growth r a t e were o b t a i n e d f o r both c o n t r o l  ( F i g . 8 a and  tween the  1%  levels,  0.05).  at a l l r a t i o n l e v e l s and  classes  f i s h m a i n t a i n e d on  showed s i m i l a r  Growth E f f i c i e n c y vs  e f f i c i e n c y and  levels  control  ration  Growth e f f i c i e n c i e s decreased o n l y s l i g h t l y f o r f i s h f e d  vii.  at  fish.  S i n c e 1% y r o l d f i s h were m a i n t a i n e d on  C o n t r o l and  proportion  fed.  (Fig.7a).  parasitized  ate  consumed i n d i r e c t  Growth e f f i c i e n c i e s of 8 month o l d 2%  trout  chow at each r a t i o n l e v e l .  These d a t a suggest t h a t to  non-infected  lines representing  These r e s u l t s  indicate  control  that  growth e f f i c i e n c i e s at a  f i s h m a i n t a i n e d on  t h e i r food more e f f i c i e n t l y f o r a g i v e n r a t e  increas-  fixed  comparison o f r e g r e s s i o n l i n e s f o r  i n F i g u r e 8 suggests that  be-  lower  differrations  of growth than  do  2J7a  Figure 7.  Growth e f f i c i e n c y of f i n g e r l i n g and 1-J year o l d rainbow trout i n r e l a t i o n to rations  fed (1%,  3%, or k% of wet weight of f i s h fed per day)» V e r t i c a l bars represent + 2 S.E.  2%,  28a  Figure 8.  Growth e f f i c i e n c y of f i n g e r l i n g and l£ year o l d rainbow trout i n r e l a t i o n Percentage  to growth rate.  figures represent d i f f e r e n t groups  of experimental f i s h fed d i f f e r e n t rations of trout chow  Z%  t  f i s h fed per day).  3%, or 4% o f wet weight of  29  CON  030  8 mo  © INF RATION GROUP  8  10  12  GROWTH  14  16  R A T E  18  9  RATE  22  C  O  N  2  24  (Mg/^DRY WT/DAY )  ~r G R O W T H  20  / /o A INF A CON  O  i 10  ( Mg/gORY W T / D A Y  RATION  Vo •»/• o ©INF B I N F  GROUP  OCON O C O N  12 )  B INF °CON, * S o • INF V CON  30 fish  fed l a r g e r  rations.  Equations d e s c r i b i n g  these r e g r e s s i o n  l i n e s are p r e s e n t e d  in  Appendix I I . 2,  Stamina Experiments i.  Body Morphology and No  and  C o n d i t i o n F a c t o r s of E x p e r i m e n t a l  significant difference  infected  tained.  (p=0.05) i n body shape between  f i n g e r l i n g s m a i n t a i n e d on  (Table I I I ) .  were s i m i l a r w i t h i n 1% y e a r age  influence  categories  (Table IV).  of d i f f e r e n c e s  These f i n d i n g s  (fingerling) allowed  undertaken w i t h o u t c o n s i d e r a t i o n  i n body morphology or c o n d i t i o n  non-infected  C r i t i c a l Velocity  perimental f i s h  c a t e g o r y and  Data r e p r e s e n t i n g  was  f i n g e r l i n g trout  r e s t r i c t e d s i z e range of f i s h  therefore  unsuitable  appeared to tested  for regression  f i n g e r l i n g s i n each r a t i o n group. 0.05)  No  i n maximum s u s t a i n e d  statistically  by  ex-  tested be  i n each r a t i o n  analysis.  were used to compare c r i t i c a l v e l o c i t i e s o f c o n t r o l and  ences (p=  factor  Tests  are p l o t t e d i n r e l a t i o n to l e n g t h s of f i s h  to the  of  trout.  C r i t i c a l v e l o c i t i e s (measured i n L e n g t h s / s e c ) a t t a i n e d  clumped due  control  W  each r a t i o n group i n both 8 month  between i n f e c t e d and  (Fig.9a-d).  ob-  (cm)  swimming performance t e s t s to be  ii.  r a t i o n s was  W = weight(g) L = length  the  2% or 4%  control  formula 100  and  1%,  C o n d i t i o n f a c t o r s of p a r a s i t i z e d and  f i s h , , computed u s i n g the  where  Fish  T  tests  infected  significant differ-  swimming speeds of i n f e c t e d  and  TABLE I I T  F  VALUES (MODEL I ANOVA WHERE F ( !j  DIFFERENCES  0.005)=2.8)  IN BODY MORPHOLOGY MEASUREMENTS  CONTROL AND I N F E C T E D FINGERLING  RAINBOW  BETWEEN  TROUT  MAINTAINED ON 1 % . 2 % . OR k% RATIONS  Diet  V/L  L/B  n  0.33  1.15  1.14  Z%  0.87  0.8  2.3  1.5  k%  1.29  0.85  0.58  0.67  0.81  W/L  V= V o l u m e (cc) L= L e n g t h (cm) B= B r e a d t h D= D e p t h  (cm)  (cm)  W= W e i g h t ( g )  FOR  TABLE IV MEAN CONDITION FACTORS OF FINGERLING AND \$ YEAR OLD RAINBOW TROUT PRIOR TO STAMINA EXPERIMENTS Age yr  Ration  1% 11 t t  11 11 1t  y/o •i 11 • i 11  8  mo  1 0/ /o 1I I  11 11  11 1 1  8 ao  2I %t 1 f 11 1 t 11  8  mo 11 11 •»  8  mo  k% 11  11  • i 11 11  I n f e c t i o n Level  Condition Factor  n  1.25 1.20 1.31 1.31 1.29 1.28 1.45 1.28 1.45 1.44 1.46 1.4? 1.14  5 5 4 5  8 0 worms  10 20  »« «•  40 " Sham Control Control 8 0 worms  10 20 40  •• «' •'  Sham Control Control 5 worms  10 20  1  '• '  1.71  1.20 1.16 1.18 1.18 1 .22 1.24  No Tag Control Sham. Control Control 5 worms  10 20  •• ••  1.31  1.25 1.29  No Tag Control Sham Control Control 5 worms  1.26  10 •» 20 '  1.36 1.29 1.26 1.23 1.29  10 20  1.33 1.36 1.35  1  No Tag Control Sham Control Control 5 worms  . •« »'  No Tag Control Sham Control Control  1.25  '  1.28  1.27  1.35  4  5 5 5 5 5 5 5 8 7 8 10 6  8  6  8 7 10 8 7 8 7 6  8 7 7 8 7 6 7 8 8  32a  Figure 9 .  Length of f i n g e r l i n g and 1-£ year o l d rainbow trout i n r e l a t i o n to c r i t i c a l v e l o c i t i e s which they attained.  Percentage figures  represent d i f f e r e n t groups of experimental f i s h fed d i f f e r e n t rations of trout chow (1%,  2%, or k% of wet weight of f i s h fed per  day) .  34 non-infected f i n g e r l i n g trout were found. Regression analysis of data representing swimming performances of 1% y r old f i s h fed 1% rations revealed s i g n i f i c a n t (p=0.01) negative correlations between length and c r i t i c a l c e l o c i t y Differences between regression c o e f f i c i e n t s of infected  (Fig.9d).  and non-  infected trout were not s t a t i s t i c a l l y s i g n i f i c a n t . These data suggest that i n f i s h populations of uniform size (fingerlings on 1% rations, 12- 15 cm; fingerlings on 2% rations, 14- 16.5 cm; f i n g e r l i n g s on 4% rations, 15- 19 cm) c r i t i c a l v e l o c i t i e s which trout may a t t a i n may resemble a random d i s t r i b u t i o n .  In  populations where there i s considerable range i n size (lh yr o l d f i s h fed 1% rations, size range 22.5- 31.5 cm) larger f i s h a t t a i n r e l a t i v e l y lower c r i t i c a l v e l o c i t i e s than smaller f i s h . iii.  Fixed Velocity Tests  A s i g n i f i c a n t negative correlation fatigue  (p=0.05) between time to  and v e l o c i t y was found f o r f i n g e r l i n g f i s h on 2% rations swum  at 90% of t h e i r mean c r i t i c a l v e l o c i t y (49.76 cm/sec) when the time i n t e r v a l 20 seconds to 200 minutes was plotted  (Fig.10).  Brett (1964)  demonstrated a sustained swimming capacity i n f i s h which maintained imposed fatigue v e l o c i t i e s f o r longer than 200 minutes. when times to fatigue  Similarly,  from 200 to 600 minutes vs v e l o c i t y were plotted  for f i n g e r l i n g s on 2% rations  (Fig.10) no s i g n i f i c a n t c o r r e l a t i o n was  obtained (p=0.05) i n d i c a t i n g continuous performance by the f i s h swimming after 200 minutes.  No s i g n i f i c a n t difference  still  (p=0.05)  between regression c o e f f i c i e n t s of infected and control f i s h was found. i v . Burst Velocity Tests S i g n i f i c a n t negative correlations  between time maintained and  34a  Figure 1 0 . Time taken by f i n g e r l i n g rainbow trout (fed 2% rations) to fatigue i n fixed v e l o c i t y t e s t s . Regressions representing f i s h are compared.  control and i n f e c t e d  0.1-  0.05-J  0  VEL0C5IY(L/SEC.)  36  burst  v e l o c i t y were o b t a i n e d f o r a l l f i n g e r l i n g r a t i o n groups  (Fig.11).  Control  f i s h on 1% r a t i o n s , i n f e c t e d and c o n t r o l f i s h on  3% r a t i o n s and i n f e c t e d f i s h on 4% r a t i o n s were r e p r e s e n t e d by c o r r e l a t i o n s s i g n i f i c a n t a t the p=0.01 l e v e l . and  f i s h on 1% r a t i o n s  c o n t r o l f i s h on 4% r a t i o n s showed c o r r e l a t i o n s between time main-  tained  and b u r s t  cant d i f f e r e n c e and  Infected  v e l o c i t y s i g n i f i c a n t a t the p=0.05 l e v e l . (p=0.05) between r e g r e s s i o n  No  signifi-  c o e f f i c i e n t s of infected  c o n t r o l t r o u t was found. These r e s u l t s suggest t h a t  f o r which they can be m a i n t a i n e d Equations f o r regression sented i n Appendix I I I .  as b u r s t  v e l o c i t i e s increase  the time  decreases.  l i n e s appearing i n Figure  11 a r e p r e -  36a  Figure 11.  Time f i n g e r l i n g rainbow trout (fed 1%, 2%, or W/o rations) maintained burst swimming a c t i v i t y . Regressions representing control and i n f e c t e d f i s h are compared.  VELOCITY (L SEC.)  33 DISCUSSION  The two  growth c h a r a c t e r i s t i c s and  swimming a b i l i t i e s  components of t h e i r p h y s i o l o g y e s s e n t i a l to s u r v i v a l .  purpose of t h i s i n v e s t i g a t i o n to determine the t r u t t a e , a p a r a s i t i c nematode, on The  following  discussion  consumption and velocities,  l a t i o n to the ature.  e f f e c t of  examines growth parameters  growth e f f i c i e n c i e s ) and  I t was  trout.  (growth r a t e s ,  burst  food  (critical  v e l o c i t i e s of  four d i f f e r e n t r a t i o n s i n r e -  i n t e r p r e t a t i o n s of o t h e r experiments r e p o r t e d s u g g e s t i o n s f o r f u r t h e r study of the  Salmo g a i r d n e r i h o s t - p a r a s i t e  the  Truttaedacnitis  stamina measurements  c o n t r o l t r o u t m a i n t a i n e d on  In a d d i t i o n ,  are  these components i n rainbow  time to f a t i g u e at f i x e d v e l o c i t i e s and  p a r a s i t i z e d and  1.  of f i s h  r e l a t i o n s h i p are  i n the  liter-  T_. t r u t t a e  -  presented.  Growth Experiment Comparison of growth r a t e s  shows t h a t  control fish usually  (growth r a t e s not  greater  those f i s h w i t h the  of growth per  grew s l i g h t l y  control trout  f a s t e r than i n f e c t e d  1) fish  that  number o f nematodes grew most s l o w l y .  Fur-  d a t a i n terms of amount o f food consumed and  gram dry weight of f i s h  t i s s u e per  day  ( F i g . 2 and  d e c r e a s i n g growth r a t e s  difference  and  no  appreciable  w i t h i n c r e a s i n g numbers o f p a r a s i t e s d e c r e a s i n g growth r a t e s  have been found by H i s c o x and  at any  Brocksen  3) r e v e a l s i n food  (1973).  slightly  consumption  given r a t i o n l e v e l .  as a f u n c t i o n  rate  compared w i t h numbers  of p a r a s i t e s w i t h which f i s h were i n f e c t e d  gradually  (Fig.  s t a t i s t i c a l l y ) at a l l r a t i o n l e v e l s and  greatest  t h e r e x a m i n a t i o n of the  of i n f e c t e d and  of numbers of T_.  Similar truttae  Whereas these authors  39 noted  i n c r e a s i n g consumption r a t e s i n r e l a t i o n  ( p a r a s i t e numbers), my highest  (4%) and  lowest  creased i n r e l a t i o n 3%.  d a t a suggest  and  be e x p l a i n e d by  the f a c t t h a t H i s c o x  experimental  and  ( s i x t y f i s h p e r group) consumed i t s a l l o t t e d  i t s i n d i v i d u a l r a t e of growth.  amount of food consumed by  f i s h on 2% and  the numbers of p a r a s i t e s suggests these r a t i o n s decrease  Thus, a decrease  ration  ration  i n the  3% r a t i o n s w i t h an i n c r e a s e i n  t h a t growth r a t e s o f i n f e c t e d f i s h  to a s l i g h t l y  on  g r e a t e r degree as a f u n c t i o n of  N e v e r t h e l e s s , d i f f e r e n c e s i n growth r a t e s and  between i n f e c t e d and  fish  dependent on the weight  numbers of worms than do growth r a t e s o f i n f e c t e d f i s h  any  and  d e s i g n assumed t h a t each  t h e r e f o r e amount o f food consumed was  the f i s h and  tions.  de-  examined consumption by measuring the amount o f food consumed  w i t h i n a r a t i o n group  of  amount o f food consumed  to numbers o f p a r a s i t e s a t r a t i o n l e v e l s o f 2%  by i n d i v i d u a l f i s h whereas my  per day  infection  i n c r e a s i n g food i n t a k e o n l y a t the  (1%) r a t i o n l e v e l s ;  These d i f f e r e n c e s may  Brocksen  to degree o f  on 1% o r 4% r a food  c o n t r o l f i s h were not s t a t i s t i c a l l y  consumption  significant  at  level.  Comparison of growth e f f i c i e n c y w i t h numbers o f p a r a s i t e s ( F i g . 4) suggests to  fish  t h a t f o o d consumed by  c o n t r o l s was  more e f f i c i e n t l y  t i s s u e than food eaten by i n f e c t e d f i s h .  converted  These r e s u l t s i n  g e n e r a l c o n f i r m the f i n d i n g s of H i s c o x and Brocksen  (1973) a l t h o u g h  t h e i r v a l u e s f o r growth e f f i c i e n c y are as much as twice as l a r g e as found i n t h i s study.  As  the f i s h i n t h i s experiment were not  those  indivi-  d u a l l y f e d , wastage of f o o d , p a r t i c u l a r l y a t h i g h e r r a t i o n l e v e l s , have r e s u l t e d i n o v e r e s t i m a t i o n of the amount of food consumed and  may hence  40 would lower c a l c u l a t e d growth e f f i c i e n c i e s .  In a d d i t i o n , growth ex-  p e r i m e n t s i n t h i s i n v e s t i g a t i o n were performed and e a r l y f a l l and may  d u r i n g the l a t e summer  have c o i n c i d e d w i t h a p h y s i o l o g i c a l c y c l e i n h e r -  ent i n some salmonids which  decreases the growth r a t e and  growth e f f i c i e n c y , a t t h i s time of y e a r (Brown, 1957). was  performed  and 16°C  a t 9 to 11°C.  t h u s , the  The p r e s e n t study  Brown (1946a) has suggested  t h a t between 9  growth e f f i c i e n c y w i l l be lower than at 7-9°C o r 16-19°C s i n c e  maintenance requirements and m e t a b o l i c r a t e s are h i g h e s t between 9 and 16°C.  In a d d i t i o n , Brown (1946a), and D a v i s  i n growth which which  coincided with genetic s t r a i n s of trout.  these experiments were performed may  than those used by H i s c o x and Brocksen i n c a p a b l e of growing f i s h may  (1934) d e t e c t e d d i f f e r e n c e s  as e f f i c i e n t l y .  The  have been b r e d  trout with  differently  (1973) and hence may  have been  F i n a l l y , some of the 1% y e a r o l d  have been approaching m a t u r i t y and hence may  have been c o n v e r t -  i n g c o n s i d e r a b l e amounts of food energy i n t o r e p r o d u c t i v e p r o d u c t s a t the expense o f f i s h t i s s u e  (Aim 1939,  As a means o f comparing  1949;  M i l l e n b a c h , 1950).  the r e s u l t s o f t h i s growth study w i t h those  of o t h e r i n v e s t i g a t i o n s growth r a t e s and growth e f f i c i e n c i e s were compared w i t h d i f f e r e n t r a t i o n s a s s i g n e d .  Figure 5 i l l u s t r a t e s  the  relation-  s h i p between growth r a t e s of c o n t r o l and i n f e c t e d f i s h and r a t i o n .  While  t h e r e i s no a p p r e c i a b l e d i f f e r e n c e between the s l o p e s o f the curves f o r c o n t r o l and i n f e c t e d f i s h apparent  (confirmed by H i s c o x and B r o c k s e n , 1973)  i t is  t h a t i n c r e a s e s i n growth r a t e are g r e a t e r when 1% t o - 2 % r a t i o n s  are f e d than when 2% to 4% r a t i o n s are a d m i n i s t e r e d ( F i g . 5 a ) .  These r e -  s u l t s are c o n s i s t e n t w i t h those of Le B r a s s e u r (1969) and B r e t t e_t_ a l . (1969) and the i n f l e c t i o n of the curves at 4% r a t i o n s i n d i c a t e s t h a t  the  41  r a t i o n i s being approached at which food presented w i l l no longer r e sult  i n an increase i n growth rate.  By p l o t t i n g growth rate (% i n -  crease i n wet wt/day) and r a t i o n on axes which allow negative growth rates to be displayed (Figure 12) the maintenance (minimum r a t i o n which w i l l allow zero growth) and optimum (ration l e v e l at which maximum growth rate occurs) rations may be determined geometrically (Thompson, 1941; Warren and Davis, 1967; Brett et_ al_. , 1969).  In this manner the tangent  from the o r i g i n to the curve determines the optimum r a t i o n and the maintenance ration i s determined by the point at which the growth curves intercept the l i n e of zero growth.  Using this procedure an estimated  ration of 1.5 to 1.6% per day would result i n maximum growth rates f o r f i n g e r l i n g f i s h (similar values for both control and infected  fish).  Maintenance rations derived i n a similar manner would approximate 0.3% of wet body weight/day.  While these estimates are s l i g h t l y below those  of Brown (1946c) and Brett e_t a l . (1969) who used d i f f e r e n t species of salmonids at d i f f e r e n t times of the year, they provide additional i n f o r mation concerning the growth c h a r a c t e r i s t i c s of the population of f i s h used i n this study.  The use of only two ration levels i n growth studies  with lh year old f i s h (resulting i n a strcug-kt  l i n e rather than a  curve f o r growth vs. ration) precludes derivation of maintenance and optimum rations f o r these animals. Derivation of the maintenance r a t i o n allows further c a l c u l a t i o n of the net growth e f f i c i e n c y (Modified from Brett et_ a l . , 1969) such that Kn = AW/RAt - Rm where Kn = net growth e f f i c i e n c y ; AW = growth rate; RAt = t o t a l food con-  41a  Figure 1 2 .  Geometrical determination of optimum and maintenance rations for f i n g e r l i n g rainbow trout.  Optimum rations determined by a  v e r t i c a l l i n e dropped from the tangent of the growth curves; maintenance r a t i o n determined by the point at which the growth curve b i s e c t s the l i n e of zero growth.  42  43 sumption and Rm = food r e q u i r e d f o r maintenance. Growth e f f i c i e n c y  c a l c u l a t i o n s p r e s e n t e d p r e v i o u s l y i n t h i s paper  were d e r i v a t i o n s o f gross growth e f f i c i e n c y r a t i o n s were not known.  s i n c e v a l u e s . f o r maintenance  Net e f f i c i e n c y v a l u e s d e s c r i b e the a c t u a l  c i e n c y o f c o n v e r s i o n of food i n t o new  effi-  f i s h t i s s u e a f t e r s u b t r a c t i o n of  amounts of food r e q u i r e d f o r maintenance of e x i s t i n g body t i s s u e s has been made ( B r e t t e t a l . , 1969).  Thus, net growth e f f i c i e n c i e s  for a  g i v e n p o p u l a t i o n w i l l be g r e a t e r than gross growth e f f i c i e n c i e s .  Net  growth e f f i c i e n c y v a l u e s o b t a i n e d f o r t h i s  investigation  greatest f o r f i s h  f o r f i s h m a i n t a i n e d on 4% r a -  tions.  f e d 1% r a t i o n s and l e a s t  Comparable  r e s u l t s have been o b t a i n e d by Warren and D a v i s  and B r e t t et_ al_. (1969) , who greater f o r f i s h  (Table V) a r e  found t h a t n e t growth e f f i c i e n c i e s were  f e d lower r a t i o n s than f i s h  f e d l a r g e r amounts o f f o o d .  Comparison of g r o s s growth e f f i c i e n c y w i t h r a t i o n a decrease i n e f f i c i e n c y  (1967)  (Fig.  7) r e v e a l s  ( n e g a t i v e K l i n e ) f o r r a t i o n s over 2% o f wet  body weight/day f o r b o t h i n f e c t e d and c o n t r o l f i n g e r l i n g t r o u t and a s t e a d i l y d e c r e a s i n g e f f i c i e n c y f o r lh y e a r o l d f i s h to more than 1% o f t h e i r wet body weight/day.  fed r a t i o n s  Similar decreasing  e f f i c i e n c i e s have been d e s c r i b e d by Paloheimo and D i c k i e 1966b), Warren and Davis Growth e f f i c i e n c i e s ling  (1967), La B r a s s e u r  i n c r e a s e between  amountin growth  (1965, 1966a,  (1969) and K e r r (1971).  1% and 2% r a t i o n l e v e l s f o r f i n g e r -  t r o u t i n t h i s experiment ( F i g . 7 a ) .  Kerr  (1971) has suggested t h a t  p o s i t i v e K l i n e s such as these a r e a r e s u l t of a lower m e t a b o l i c expendi t u r e on spontaneous a c t i v i t y than i s p r o v i d e d f o r by the r a t i o n f e d .  r Thus, f i s h m a i n t a i n e d on r a t i o n s below that which would r e s u l t growth r a t e  ( i n this  i n optinu  case on r a t i o n s l e s s than 1.5% p e r day) may  be  44  TABLE V GROSS AND NET GROWTH EFFICIENCY OF FINGERLING RAINBOW TROUT  Age  Diet  8mo  1%  »  "  Control  2%  Inf  II  M  Con  «  3%  Inf  Level  Infected  Con  .1  II  Infection  k%  Inf  II  Con  K(gross e f f i c i e n c y )  0.159 0.184  0.186 0.181 0.129 0.119 0.1 0.111  Kn(net  efficiency)  0.244 0.266 0.241 0.22 0.152 0.133 0.111  0.122  45 represented by p o s i t i v e K l i n e s .  Fish fed rations greater than the  optimum would be capable of metabolic expenditures which outreach t h e i r l e v e l s of feeding, hence growth e f f i c i e n c i e s of these f i s h would be described by a negative K l i n e .  Accordingly, gross growth e f f i c i e n c y curves  obtained i n this study r e f l e c t low (positive slope) and intermediate to high (negative slope) r a t i o n levels (Kerr, 1971; Brett and 1975)  Shelbourn,  and adequately describe e f f i c i e n c y - r a t i o n relationships representa-  tive of control and p a r a s i t i z e d trout used i n this investigation.- ' A f i n a l manipulation of growth rate data (Figure 13) compares growth rates of f i n g e r l i n g and 1% year old f i s h on 1% and 3% rations (values for control and infected f i s h combined) with weight.  No s i g n i f i c a n t cor-  r e l a t i o n s between weight and growth were found, i n d i c a t i n g that the a l l o t t e d rations were not i n excess of those required f o r increasing growth (Brett and Shelbourn 1975) .  These data confirm the p o s i t i v e K  l i n e s which appear i n F i g . 7a. A summary of the relationships between control f i s h and those i n f e c ted with J_. truttae according to rations fed appears i n F i g . 8; growth e f f i c i e n c y vs growth rate.  The p o s i t i v e correlations obtained i l l u s t r a t e  a b a s i c trend toward increasing growth e f f i c i e n c y with increasing growth rate at a given r a t i o n l e v e l .  Most e f f i c i e n t use of rations occurs where  lowest rations are presented.  Since these results agree with those pre-  sented by Brown (1957), Paloheimo and Dickie (1966b), Kerr (1971), Brett and Shelbourn  (1975), and others, and since regression l i n e s representing  infected and non-infected f i s h are v i r t u a l l y the same, i t may be concluded that there i s no s i g n i f i c a n t difference i n growth c h a r a c t e r i s t i c s betweer  45a  Figure 1 3 . Growth rate of f i n g e r l i n g and. 1-jr year o l d rainbow trout i n r e l a t i o n to f i s h weight. One percent and three percent ration groups only are represented; data from control and infected f i s h i s combined.  46  47 p a r a s i t i z e d and p a r a s i t e - f r e e  t r o u t which may be a t t r i b u t e d  to the pre-  sence o f T_. t r u t t a e .  2.  Stamina Experiments Importance o f r e l a t i v e c o n d i t i o n  and by and  ("fitness" or "condition  m o r p h o l o g i c a l measurements i n stamina experiments have been d i s c u s s e d Bainbridge  (1960) f o r g o l d f i s h , dace and rainbow t r o u t , B r e t t  Bams (1967) f o r sockeye salmon, B l a x t e r  (1969) f o r v a r i o u s  o f marine f i s h , Webb (1971a,b, 1975) f o r rainbow t r o u t  These authors suggest that  f o r f i s h with condition  1.0 (such as those used i n t h i s s t u d y ) , the.less  well  lative  trout.  f a c t o r s g r e a t e r than  t h e l a r g e r the c o n d i t i o n  factor  f i s h which  a r e a and drag i n stamina chambers (have g r e a t e r r e -  b r e a d t h , w i d t h , depth and weight t o l e n g t h  c r i t i c a l v e l o c i t i e s and f a t i g u e drag.  species  rainbow  t h e f i s h w i l l p e r f o r m i n swimming t e s t s s i n c e  p r e s e n t more s u r f a c e  (1964)  and Jones e t a l .  (1974) f o r v a r i o u s s p e c i e s o f f r e s h - w a t e r f i s h i n c l u d i n g  and  factor")  f a s t e r than f i s h w i t h l e s s s u r f a c e  Therefore, s i m i l a r i t i e s  measurements of a l l f i s h w i t h i n ( T a b l e s 3 and 4 ) , suggest that  r a t i o s ) a t t a i n lower area  i n body morphology and c o n d i t i o n  each r a t i o n c a t e g o r y i n t h i s any d i f f e r e n c e s  measurements o f p a r a s i t i z e d and c o n t r o l  trout  factor  investigation  between observed  stamina  a r e a d i r e c t r e s u l t o f the  p r e s e n c e o f T_. t r u t t a e and do n o t o c c u r as a r e s u l t o f d i f f e r i n g f a c t o r s o r body shapes o f i n f e c t e d o r n o n - i n f e c t e d  condition  fish.  C r i t i c a l v e l o c i t y t e s t s , used as a b a s i s by which to compare maximum sustained  swimming speeds ( F i g . 9 ) , show t h a t  perform e q u a l l y cal  well  a t any r a t i o n l e v e l .  c o n t r o l , and i n f e c t e d  E f f e c t s of p a r a s i t e s  trout  on c r i t i -  swimming speeds o f f i s h have a l s o been t e s t e d by Fox (1965), working  4d w i t h Bolbophorus c o n f u s u s , a s t r i g e i d encyst and  i n the m u s c u l a t u r e o f rainbow t r o u t , Smith and M a r g o l i s  (1970)  Boyce ( p e r s . comm.), who examined Eubothrium s a l v e l i n i , a tapeworm  attached and  trematode whose m e t a c e r c a r i a e  to the p y l o r i c caeca and i n t e s t i n e o f sockeye salmon and B u t l e r  Millemann  (1971), who s t u d i e d the trematode Nanophyetus  e n c y s t e d i n the muscle o f coho salmon and s t e e l h e a d i n v e s t i g a t o r s found decreased swimming a b i l i t i e s  trout.  salmincola A l l o f these  i n i n f e c t e d f i s h but  those w o r k i n g w i t h c e r c a r i a e n o t e d d e f i c i e n c i e s i n stamina o n l y migration  and encystment o f t h e p a r a s i t e s .  during  I t i s p o s s i b l e , t h a t had  s t a m i n a measurements been performed immediately f o l l o w i n g i n f e c t i o n o f the  t r o u t w i t h T_. t r u t t a e i n t h i s  themselves to and i r r i t a t i n g  study  (while  the worms were  t h e c a e c a l mucosa), s i g n i f i c a n t  attaching differences  i n swimming a b i l i t y between c o n t r o l and i n f e c t e d f i s h may have been found. The  d a t a o f Smith and M a r g o l i s  (1970) and Boyce ( p e r s . comm.), however,  suggest t h a t i n t e s t i n a l p a r a s i t e s which a t t a c h  to the mucosa o f the p y l o r i c  caeca may i n f l u e n c e swimming performance r e g a r d l e s s time post  o f the l e n g t h o f  i n f e c t i o n t h a t swimming t e s t s a r e performed.  S i n c e none of the  above s t u d i e s examined the e f f e c t s o f nematode p a r a s i t e s a t t a c h e d i n t e s t i n a l epithelium, through and d e s t r o y  i t i s possible  t h a t p a r a s i t e s which do n o t m i g r a t e  the body m u s c u l a t u r e ( a s do trematode l a r v a e )  do not c o n t i n u e t o grow t o c o n s i d e r a b l e  s i z e while w i t h i n  o r which  the host  tapeworms l i k e E_. s a l v e l i n i ) do not e f f e c t t h e maximum s u s t a i n e d speed o f t h e i r  to the  (as do  swimming  host.  In a d d i t i o n to the comparison o f c o n t r o l and i n f e c t e d f i s h i n r e l a t i o n to t h e i r c r i t i c a l  swimming speeds, i t i s important  t o d i s c u s s the  49 v a r i a t i o n i n the r e l a t i o n s h i p between l e n g t h tween r a t i o n groups. bility  The  groups t e s t e d which showed the  and  critical  v e l o c i t y such that  p e r f o r m r e l a t i v e l y b e t t e r than l o n g e r have been c o n f i r m e d by B r e t t Jones et a l . (1974).  fish  ( F i g . 9d).  (1964, 1965), B r e t t and  F i n g e r l i n g t r o u t f e d 1%,  c o r r e l a t i o n between l e n g t h  and  critical  f i s h of n e a r l y  the same l e n g t h  determinations,  (and  In o r d e r  This  T h i s may  lengths  i s probably  due  imply t h a t when  disguise v a r i a -  critical  be made w i t h v a l u e s  Cox  (1970) .  The  (cm/sec) on l o g e weight i n f e c t e d f i s h and  l i n e whose e q u a t i o n i s y = 2.49  + 0.84x.  e speed on l o g e l e n g t h were n e a r l y  -5.0173 + 0.387x.  and  i n the  compared w i t h  of f i s h used i n the c r i t i c a l v e l o c i t y t e s t s  the r e g r e s s i o n of l o g e speed  and  (1973)  r a t i o n s show no  i n each r a t i o n group are  a f t e r the example of F r y and  s i m i l a r f o r both c o n t r o l and  fish  c o n d i t i o n f a c t o r ) a r e used i n stamina  i n t h i s experiment may  the mean weights and  rela-  size.  l i t e r a t u r e , mean speeds r e c o r d e d  infected fish  Glass  t h a t a comparison between r e s u l t s of a l l the  v e l o c i t i e s obtained  ( F i g u r e 14)  shorter  v a r i a t i o n s i n i n d i v i d u a l performance w i l l  t i o n s i n performance r e l a t i v e to  equations f o r  (g) were v e r y  have been drawn as a s i n g l e  S i m i l a r l y the r e g r e s s i o n s the same f o r i n f e c t e d and  of non-  have been drawn as a s i n g l e l i n e whose e q u a t i o n i s y = The  speed-weight exponent  t h i s study i s s l i g h t l y g r e a t e r  Dickson  greatest v a r i a -  These f i n d i n g s  2% or 4%  velocity.  to s i m i l a r i t y i n s i z e of the f i s h t e s t e d .  in  c r i t i c a l v e l o c i t y be-  i n s i z e ( 1 % y e a r o l d f i s h on 1% r a t i o n s ) e x h i b i t a n e g a t i v e  t i o n s h i p between l e n g t h  log  and  (1959), B a i n b r i d g e  (0.84) r e p r e s e n t i n g  than t h a t r e p o r t e d  (1960, 1962)  and  F r y and  by  Blaxter  Cox  (1970).  the  fish  and Discre-  49a  Figure  14.  C r i t i c a l v e l o c i t i e s a t t a i n e d by f i n g e r l i n g and year o l d rainbow t r o u t i n r e l a t i o n l e n g t h and weight. ration  Mean speeds o n l y o f each  group t e s t e d have been p l o t t e d .  critical  velocities  have been i n c l u d e d  to f i s h  Relative  ( L / s e c ) o f each p o i n t p l o t t e d i n order  t h a t a comparison  w i t h a c t u a l swimming speeds (cm/sec) may be made.  50  L E N G T H 10 I  1  .  1  1  .  1?  2  (CM) 14  15 16 17 181920  22  24  26  28  30  10090-  s p  E E D CM  807060®^3.15  50-|  1%  40-I  3  !  ^"  1j  3%  YEAR  SEC 8 MONTH  3o-a  O CONTROL ©  INFECTED  20-B  10  1 ' i t t 4  5  6  t"'i t 7 8 9 10  L  "T""T* 15  20  1  'I 30  WEIGHT(g)  i I m '  i  1  40  50  100  200  "-n 300  51 p a n c i e s between the r e s u l t s o f these i n v e s t i g a t i o n s and those found i n the  p r e s e n t study may  be a t t r i b u t a b l e to d i f f e r e n c e s i n the types o f  apparatus used to measure c r i t i c a l v e l o c i t i e s .  The  stamina chambers  used by B l a x t e r and D i c k s o n (1959), B a i n b r i d g e (1960, 1962) Cox  and F r y and  (1970) were r o t a t i n g a n n u l a r chambers or doughnut-shaped wheels  r o t a t i n g about a c e n t r a l a x i s i n which both the apparatus and the water were i n motion r e l a t i v e t o the f i s h .  In t h i s study a f l o w - t h r o u g h t u n n e l  was  used i n which  the apparatus and the f i s h were s t a t i o n a r y and o n l y  the  water moved.  The s p e e d - l e n g t h exponent  v e s t i g a t i o n was Brett  (0.387) o b t a i n e d i n t h i s i n -  s l i g h t l y l e s s than t h a t found f o r sockeye salmon  by  (1965) and B r e t t and G l a s s (1973) and a p p r o x i m a t e l y e q u a l to those  found f o r t h r e e s p e c i e s of salmonids by Jones et_ al_. (1974) . In  a d d i t i o n to the a c t u a l c r i t i c a l swimming speeds r e c o r d e d i n cm/sen,  r e l a t i v e c r i t i c a l swimming speeds  ( r e c o r d e d i n Lengths/sec) have been i n -  c l u d e d f o r each p o i n t d e f i n i n g the speed-weight s i o n s p l o t t e d i n F i g u r e 14.  and s p e e d - l e n g t h r e g r e s -  R e l a t i v e swimming speeds  t h i s study) a l l o w comparison o f swimming a b i l i t i e s s i z e s from d i f f e r e n t p o p u l a t i o n s to be made. i n f e c t e d and n o n - i n f e c t e d t r o u t i n t h i s t h i s way.  of f i s h of d i f f e r e n t  Stamina measurements o f  i n v e s t i g a t i o n were compared i n  I t i s e v i d e n t from F i g u r e 14 t h a t w h i l e l a r g e r f i s h  lower r e l a t i v e c r i t i c a l swimming speeds swimming speeds are g r e a t e r . formance  (used throughout  attain  than s m a l l e r f i s h , t h e i r  actual  These same c o n c l u s i o n s about swimming p e r -  i n f i s h have been drawn by B a i n b r i d g e (1960, 1962), B r e t t  1965), F r y and Cox  (1964,  (1970), B r e t t and G l a s s (1973), Jones' e t a l . (1974),  and Webb (1975). Fixed v e l o c i t y  t e s t s , conducted at 90% o f the c r i t i c a l v e l o c i t y  52 measured f o r f i n g e r l i n g s on cant d i f f e r e n c e  (p = 0.05)  2%  rations  (Appendix IV)  between the  c o r r e l a t i o n s of  vs v e l o c i t y of c o n t r o l or p a r a s i t i z e d f i s h  ( F i g . 10).  concur w i t h those o f K l e i n e_t a l . (1969) , who Infected  r e v e a l no time to These  showed t h a t  signififatigue  findings  rainbow t r o u t  w i t h Crepidostomum f a r i o n i s swam as w e l l as u n i n f e c t e d  t r o u t , but  d i s a g r e e w i t h those of B u t l e r  and  Millemann  control  (1971), who  ob-  t a i n e d p o o r e r v a l u e s f o r swimming performance from coho salmon and head t r o u t i n f e c t e d w i t h Nanophyetus s a l m i n c o l a has  been suggested e a r l i e r ,  fered  the  used m i g r a t i n g and  encysting  t i s s u e , thereby i n f l i c t i n g fish.  This  through nor  considerable  author used g u t - i n h a b i t i n g e n c y s t i n muscle t i s s u e . a gut-inhabiting  t o r y or e n c y s t i n g  stage.  the  the  one  parasite  migrate (1969)  (a trematode) w i t h no  that i n h o s t - p a r a s i t e  migra-  systems  t h a t o f K l e i n et^ a l . (1969) , where  t h a t e f f e c t s of the p a r a s i t e on  the  life  welland  cycle.  o b t a i n e d f o r time to f a t i g u e vs v e l o c i t y r e l a t i o n s h i p s  were n e a r l y  the  same f o r both c o n t r o l and  d i f f e r g r e a t l y from e s t a b l i s h e d  Brett  work o f K l e i n et^ al_.  the  the h o s t are minimal i n o r d e r to a s s u r e mutual s u r v i v a l  Correlations  not  authors  i r r i t a t i o n on  nematodes which n e i t h e r The  used i n t h i s study and  t h e r e b y c o n t i n u a n c e of the p a r a s i t e  ( F i g . 10)  M i l l e m a n (1971) d i f -  aforementioned  damage and  It i s possible,  d e f i n i t i v e host i s a f i s h ,  b e i n g of  the  As  trematode c e r c a r i a e which i n f e c t h o s t muscle  likewise u t i l i z e d  such as  than from c o n t r o l s .  study of B u t l e r and  from the p r e s e n t i n v e s t i g a t i o n i n that  steel-  i n f e c t e d f i s h and  f i x e d - v e l o c i t y t e s t v a l u e s found  do by  (1964). S i m i l a r l y , no  m a i n t a i n e d on  significant differences  d i f f e r e n t r a t i o n s were found  i n burst  v e l o c i t i e s of  ( F i g . 11).  fish  However, whereas  53 the time m a i n t a i n e d - b u r s t v e l o c i t y exponents attained  ( F i g . 11)  and maximum b u r s t v e l o c i t i e s  i n t h i s study are s i m i l a r to those  B l a x t e r and D i c k s o n  (1959), B a i n b r i d g e (1960, 1962)  o b t a i n e d by  and B r e t t  the d u r a t i o n of the b u r s t swimming a c t i v i t y i n the p r e s e n t i s v e r y much s h o r t e r  (1964),  investigation  (1/3 sec) than the d u r a t i o n s of b u r s t a c t i v i t y r e -  corded by the above-mentioned authors  (20 s e c ) .  The d i f f e r e n c e s i n the  time m a i n t a i n e d f a c t o r o f the b u r s t v e l o c i t y measurements may  be  account-  ed f o r by examination of the methods used by the o t h e r i n v e s t i g a t o r s i n r e l a t i o n to those employed i n t h i s timed f i s h  study.  B l a x t e r and D i c k s o n  i n open tanks a g a i n s t a r e f e r e n c e background,  (1959)  i n culverts  and  i n tubes towed through the water to get s u b s t a n t i a l f l o w r a t e s a g a i n s t which f i s h were encouraged  to swim.  B a i n b r i d g e (1960, 1962)  r o t a t i n g a n n u l a r tank i n which f i s h remained tank.  He  camera.  employed a  s t a t i o n a r y r e l a t i v e t o the  r e c o r d e d b u r s t v e l o c i t i e s w i t h an o s c i l l o s c o p e and a movieBrett  (1964) e x t r a p o l a t e d d a t a o f o t h e r i n v e s t i g a t o r s to get the  b u r s t v e l o c i t y r e g r e s s i o n l i n e he p r e s e n t e d .  A l l apparatus used to com-  p i l e the above i n f o r m a t i o n on b u r s t swimming a l l o w e d t e s t  f i s h consider-  a b l e freedom of movement, whereas the swimming chamber used i n t h i s restricted lateral  and v e r t i c a l movement c o n s i d e r a b l y , e s p e c i a l l y where  l a r g e r f i s h were used.  I t i s p o s s i b l e t h a t had  a l o n g e r tube w i t h a  g r e a t e r diameter been used f o r b u r s t v e l o c i t y t e s t s i n t h i s times f o r which b u r s t speeds those r e p o r t e d i n the No mum 11).  study  investigation,  c o u l d be m a i n t a i n e d would be comparable to  literature.  d i f f e r e n c e s i n the r e l a t i o n s h i p between time m a i n t a i n e d and maxi-  b u r s t v e l o c i t y a t t a i n e d by c o n t r o l and i n f e c t e d While  similar studies testing  f i s h were found ( F i g .  the b u r s t swimming o f p a r a s i t i z e d  and  54 c o n t r o l f i s h have not been r e p o r t e d i n the l i t e r a t u r e , and  thus  cannot  p r o v i d e a comparison w i t h the r e s u l t s of the p r e s e n t work, t h e s e are a t l e a s t  consistent with  mina measurement amined i n t h i s  those of the o t h e r two  ( c r i t i c a l v e l o c i t y t e s t s and  s e r i e s of swimming  results  components of  sta-  f i x e d v e l o c i t y t e s t s ) ex-  experiments.  Combination o f f i x e d v e l o c i t y  ( F i g . 10)  r e g r e s s i o n s i n t o a s i n g l e graph ( F i g . 15)  and b u r s t v e l o c i t y  ( F i g . 11)  g i v e s a more complete  estima-  t i o n of the approximate swimming a b i l i t i e s of the f i n g e r l i n g t r o u t l e n g t h 14.9  cm)  used i n stamina  tests i n this  study.  Composite swimming  c u r v e s , o b t a i n e d by B r e t t (1964) u s i n g sockeye salmon, and (1960, 1962), who f o r comparison.  In g e n e r a l , the s u s t a i n e d swimming and i n this  the aforementioned  authors.  by  found by  Bainbridge  D u r a t i o n of b u r s t swimming a c t i v i t y i n  s h o r t e r than t h a t measured by  already discussed.  a r e a between the steady  swimming  B u r s t swimming r e g r e s s i o n s c a l c u l a t e d f o r  and B r e t t (1964).  t h i s i n v e s t i g a t i o n was  steady  i n v e s t i g a t i o n are s i m i l a r to those o b t a i n e d  f i s h used i n t h i s study d i s p l a y s l o p e s s i m i l a r to those  f o r reasons  Bainbridge  t e s t e d rainbow t r o u t , have been i n c l u d e d i n F i g u r e 15  r e g r e s s i o n s found  (1960, 1962)  (mean  E x t e n s i o n of a l i n e  swimming and  the above from the  authors  transition  t h e s u s t a i n e d swimming c u r v e s  to  the  y a x i s ( v e l o c i t y a x i s ) i n d i c a t e s t h a t the average c r i t i c a l v e l o c i t y of the e x p e r i m e n t a l s l i g h t l y lower investigation Brett  (1964) .  f i s h i s approximately  3.1  l e n g t h s per  sec.  This i s  than the a c t u a l measured v a l u e s f o r the f i s h used i n t h i s (Appendix IV) and Bainbridge  v e l o c i t y estimates  s l i g h t l y g r e a t e r than v a l u e s r e p o r t e d by  (1962) may  have o b t a i n e d s l i g h t l y lower  than B r e t t (1964) o r the p r e s e n t  critical  investigation d u e  to  54a  Figure 1 5 . Composite swimming curve r e l a t i n g sustained, steady and burst swimming a b i l i t i e s of f i n g e r l i n g rainbow trout (mean length 1 4 . 9 cm).  Included  i n the graph for comparison are the data of Brett  (1964),  who tested sockeye salmon, and  the swimming curves obtained by Bainbridge for rainbow trout.  (1962)  1  2  3  4  5  6  7  8  9  VELOCITY (L/SEC'l  10  11  12  56 h i s use o f l a r g e r Cox,  (20-30 cm) rainbow t r o u t  ( B r e t t , 1964, 1965; F r y and  1970). Once a c c u r a t e d e t e r m i n a t i o n s o f swimming a b i l i t y have been made,  and  speed-weight r e l a t i o n s h i p s have been e s t a b l i s h e d ( F i g . 1 4 ) , d e r i v a t i o n  o f oxygen consumption and t h e r e f o r e o f m e t a b o l i c r a t e s o f e x e r c i s e d f i s h i s p o s s i b l e ( B r e t t and G l a s s , 1973). consumed/Kg body weight/hr) fish  A c t i v e m e t a b o l i c r a t e s ( i n mg 0^  as d e f i n e d by B r e t t  (1964, 1965), o c c u r when  r e a c h t h e i r maximum s u s t a i n e d swimming speed  Standard  (critical  velocity).  m e t a b o l i c r a t e s ( r e p r e s e n t i n g 0^ consumption o f f i s h a t r e s t o r  zero a c t i v i t y ) may be o b t a i n e d by e x t r a p o l a t i n g 0^ consumption v e r s u s v e l o c i t y curves back to zero v e l o c i t y  ( F r y , 1957; B r e t t , 1965).  v e l o c i t i e s and speed-weight r e l a t i o n s h i p s , determined  Critical  for fingerling  t r o u t and lig y e a r o l d t r o u t on 1% r a t i o n s i n t h i s i n v e s t i g a t i o n ,  resemble  c l o s e l y the c r i t i c a l v e l o c i t i e s and speed-weight exponents found by B r e t t (1964, 1965) f o r sockeye  salmon.  T h e r e f o r e , approximate  determinations  o f a c t i v e and s t a n d a r d m e t a b o l i c r a t e s o f the t r o u t t e s t e d at 10°C i n this  study may be made ( F i g u r e 16) u s i n g the temperature-weight  response  s u r f a c e s f o r a c t i v e and s t a n d a r d m e t a b o l i c r a t e s o b t a i n e d by B r e t t and Glass  (1973).  Comparison o f a c t i v e and s t a n d a r d m e t a b o l i c r a t e s o b t a i n e d  i n t h i s manner ( T a b l e VI) shows t h a t s m a l l e r f i s h have g r e a t e r m e t a b o l i c r a t e s p e r u n i t weight than l a r g e r f i s h . and B r e t t and G l a s s  (1964, 1965)  (1973) have made s i m i l a r o b s e r v a t i o n s f o r weight-  m e t a b o l i c r a t e r e l a t i o n s h i p s found fish.  F r y (1957), B r e t t  f o r a v a r i e t y o f f r e s h and s a l t water  S u b t r a c t i o n o f the s t a n d a r d m e t a b o l i c r a t e s from  b o l i c r a t e s o b t a i n e d above, y i e l d s values presented i n Table VI. a means to assess environmental  the a c t i v e meta-  the "scope f o r a c t i v i t y "  ( F r y , 1947)  Scope f o r a c t i v i t y has been c o n s i d e r e d as s t r e s s on f i s h e s  ( B r e t t , 1958), as an  56a  Figure 1 6 .  Temperature-weight  responses f o r a c t i v e  and s t a n d a r d  m e t a b o l i c r a t e s o f f i n g e r l i n g and 1 £ y e a r o l d r a i n bow  trout.  Data r e p r e s e n t i n g  on 1%, 2 % , and k% r a t i o n s and \% r a t i o n s have been i n c l u d e d .  f i n g e r l i n g s maintained 1^- year o l d t r o u t f e d Vertical lines  r e s p o n d i n g to w e i g h t s o f both c o n t r o l and f i s h have been drawn to the temperature equivalent  to the temperature  were conducted ( 1 0 ° C ) . mg O2 consumed/hr. Glass  (1973).  a t which  Metabolic rates  cor-  infected  isopleth swimming  tests  are g i v e n i n  Graph i s drawn a f t e r B r e t t  and  57  58 TABLE VI ACTIVE AND STANDARD METABOLIC RATES AND SCOPE FOR ACTIVITY OF FINGERLING AND l £ YEAR OLD RAINBOW TROUT  Age  Ration  8mo  1%  Infected  27-75  WT  ES  624  »  "  Control  26.06  690  65  625  "  2%  Inf  45.25  685  63  622  "  "  Con  42.27  685  62  623  "  k%  Inf  54.5  681  61  620  " i i yr  "  I n f e c t i o n Level  •  Mean Wt(g) Metabolic Rate* Active Standard  55-29  . Con  681  61  Scope for A c t i v i t y  620  V/o  Inf  277.32  655  47  608  "  Con  256.65  652  46  606  *mg 0  ?  consumed/ Kg f i s h t i s s u e / hr  59 i n d e x o f energy a v a i l a b l e recently  as  ( B r e t t , 1964), and  the  to temperature and  photoperiod f l u c t u a t i o n s ,  onset o f s e x u a l m a t u r i t y  (Dickson and  i n d i c a t e a reduced amount o f energy  f o r swimming o r r e g u l a t i o n  of b o d i l y  environment.  tested  Examination o f the control  fish  i n two  infected e f f e c t on  at the p = 0.05  fish. the  age  categories,  a b i l i t i e s of i n f e c t e d  on  no s i g n i f i c a n t  T_. t r u t t a e has  c o n f i r m the  be  useful  no  non-  measurable  t h e i r metabolism i n  s i m i l a r i t i e s i n swim-  non-infected trout  therefore  para-  at t h r e e r a t i o n l e v e l s ,  f i s h to r e g u l a t e  response to e n v i r o n m e n t a l changes and  of p a r a s i t i s m  i n response to a changing  (Table V I ) , r e v e a l s  These r e s u l t s suggest that  Scope f o r a c t i v i t y v a l u e s may  as  available  l e v e l between " s c o p e s " o f i n f e c t e d and  ming performance of i n f e c t e d and  Lower  approximate scopes f o r a c t i v i t y o f  i n the p r e s e n t i n v e s t i g a t i o n  difference  starva-  such  T_. t r u t t a e would t h e r e f o r e  functions  strains  Kramer, 1971).  scopes f o r a c t i v i t y i n groups of f i s h i n f e c t e d w i t h p a r a s i t e s  s i t i z e d and  more  a means of comparison between responses o f d i f f e r e n t  or species of f i s h t i o n and  f o r swimming i n f i s h  observed i n t h i s  i n assessing  study.  effects  fish.  General Conclusion Given the  environmental conditions  used i n t h i s study, the n i f i c a n t e f f e c t s on  statistically  growth, swimming performance or m e t a b o l i c  sig-  activity  a r e s u l t o f i n f e c t i o n w i t h the p a r a s i t i c nema-  t r u t t a e . S i n c e the  which the p a r a s i t e matures and viable  l e v e l s of p a r a s i t i c i n f e c t i o n  r e s u l t s o b t a i n e d i n d i c a t e no  of rainbow t r o u t o c c u r as tode T r u t t a e d a c n i t i s  and  t r o u t i s the  d e f i n i t i v e host i n  from which the p a r a s i t e  f e r t i l i z e d eggs (evidence from the  continually  releases  present i n v e s t i g a t i o n ) , i t i s  60 r e a s o n a b l e to assume t h a t by not a l t e r i n g o r i n t e r r u p t i n g p h y s i o l o g i c a l activities petuation Lester  e s s e n t i a l t o the h o s t ' s w e l l b e i n g , T_. t r u t t a e i s e n s u r i n g o f i t s own l i f e  cycle.  (M.S. 1969) and B u t l e r  stamina and m e t a b o l i c r a t e ) sented here s i n c e intermediate parasites  Thus, the f i n d i n g s o f Fox (1965),  and Millemann (1971) ( p a r a s i t e s  these a u t h o r s measured e f f e c t s o f l a r v a l p a r a s i t e s on  (not d e f i n i t i v e ) h o s t s .  Continuance o f t h e l i f e  used i n the above s t u d i e s would t h e r e f o r e  by  may t h e r e f o r e  increase  the f i n a l b i r d h o s t they r e q u i r e  cycles of  depend on i n g e s t i o n ( f i s h eating b i r d s ) .  d e c r e a s i n g swimming a b i l i t y o f t r o u t , salmon o r s t i c k l e b a c k  l a r v a l parasites  effect  a r e not d i r e c t l y comparable w i t h those p r e -  of the i n t e r m e d i a t e h o s t by s u i t a b l e d e f i n i t i v e h o s t s By  per-  t h e i r chances o f b e i n g  f o r development i n t o a d u l t  hosts, ingested parasites.  While T_. t r u t t a e had no measurable e f f e c t on swimming and growth under the c o n d i t i o n s al  used i n t h i s study, i t i s p o s s i b l e  environmental s t r e s s f a c t o r s  ( B r e t t , 1958) been i n t r o d u c e d  experimental design, s i g n i f i c a n t reductions c i e n c y may have been found.  t h a t had a d d i t i o n i n t o the  i n growth and swimming  Smith and M a r g o l i s  effi-  (1970) showed t h a t  during  s m o l t i f i c a t i o n and m i g r a t i o n swimming a b i l i t y and growth r a t e s o f sockeye salmon i n f e c t e d w i t h Eubothrium s a l v e l i n i were markedly reduced. t r o u t i n f e c t e d w i t h 5 t o 7 T_. t r u t t a e d i e d 60% f a s t e r than c o n t r o l s when m a i n t a i n e d on s t a r v a t i o n d i e t s Brett  (1958) has suggested t h a t  f l u c t u a t i n g temperatures, changing the p h y s i o l o g i c a l  o f s a l m o n i d s , e s p e c i a l l y i f they harbour c o n s i d e r a b l e  and  variance  non-infected  (Hiscox and Brocksen, 1973).  t i e s and a l t e r e d p h o t o p e r i o d s may a l l i n f l u e n c e  In a d d i t i o n  Rainbow  to the above s t r e s s  salinistate  numbers o f p a r a s i t e s .  f a c t o r s , state of sexual maturity  i n s i z e among e x p e r i m e n t a l f i s h  ( p o s i t i o n which a f i s h  61 o c c u p i e s i n the dominance h i e r a r c h y e s t a b l i s h e d i n the tank and Hoar, 1955) 1957).  may  (Stringer  a l s o i n f l u e n c e growth and m e t a b o l i c r a t e s (Brown,  Thus, use o f spawning o r post-spawning  f i s h or i n f e c t i o n only  o f s m a l l e r t r o u t w i t h i n a g i v e n p o p u l a t i o n o f f i s h may  have r e s u l t e d i n  more pronounced decreases i n growth or swimming e f f i c i e n c y i n f i s h  infec-  ted w i t h J_. t r u t t a e . . In t h e i r d i s c u s s i o n of p o t e n t i a l b i o l o g i c a l and economic e f f e c t s J_* t r u t t a e i n f e c t i o n s , H i s c o x and Brocksen minor decrease i n growth e f f i c i e n c i e s  (1973) have suggested  that  of the  they observed would r e s u l t i n major  f i n a n c i a l e x p e n d i t u r e s i f h a t c h e r y t r o u t h a r b o u r i n g these p a r a s i t e s were raised. fish  While  these p a r a s i t e s may  cultural situations prevail  indeed be important where  artificial  (although p a r a s i t i z e d or diseased  fish  are u s u a l l y e l i m i n a t e d from h a t c h e r y systems as soon as they are d i s covered) , i t i s l i k e l y  that i n n a t u r a l s i t u a t i o n s , environmental  l o g i c a l f a c t o r s such as food a v a i l a b i l i t y , temperature,  and p h y s i o -  photoperiod  and  s t a t e o f s e x u a l m a t u r i t y i n f l u e n c e growth and swimming e f f i c i e n c y t o a much g r e a t e r degree.  That  these nematodes may  be an i m p o r t a n t  s t r e s s imposed on w i l d rainbow t r o u t under c o n d i t i o n s of s e v e r e muscular  a c t i v i t y and d e p l e t i o n of energy  i n g o r a f t e r spawning a c t i v i t i e s ,  additional  starvation,  r e s e r v e s which occur  can o n l y be suggested.  Without  dur-  evidence  from r e s e a r c h on t h i s most e s s e n t i a l aspect o f rainbow t r o u t s u r v i v a l ,  the  o v e r a l l e f f e c t o f T_. t r u t t a e on i t s t r o u t h o s t must be r e g a r d e d as b e i n g insignificant.  62 LITERATURE CITED Aim, G. 1939. I n v e s t i g a t i o n on growth u s i n g d i f f e r e n t K g l . L a n t b r u k s s t y r e l s e n Medd. 15. Aim, G. 1949. of t r o u t .  forms o f t r o u t  I n f l u e n c e o f h e r e d i t y and environment on v a r i o u s forms Rept. I n s t . Freshwater Research D r o t t n i n g h o l m 29: 29-34.  Andrews, J.S. 1938. 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The swimming e n e r g e t i c s o f t r o u t . I I . Oxygen t i o n and swimming e f f i c i e n c y . J . Exp. B i o l . 55: 521-540. Webb, P.W. Res.  consump-  1975. Hydrodynamics and e n e r g e t i c s o f f i s h p o p u l a t i o n . Board Can. B u l l . 190. 158 pp.  W h i t l o c k , J.H. W i s n i e w s k i , L.W. truncatus.  1949.  Fish.  C o r n e l l V e t e r i n a r i a n 39: 146-182.  1932. Zur p o s t e n b r y o n a l e n e n t w i c k l u n g von Cyathocephalus Z o o l . Anz. 48: 7-8.  67 APPENDIX I  EQUATIONS FOR REGRESSION LINES APPEARING IN FIGURES 1,  Figure 2 Growth Rate vs Number o f P a r a s i t e s  Age o f F i s h  Ration  8mo  1% 2%  11 ti 11  I i yr it  Figure 3 Food Consumption vs Number o f P a r a s i t e s  8mo •i it 11  F i g u r e 4. Growth E f f i c i e n c y vs Number o f P a r a s i t e s  7.32 +(-0.059)x  y=  13.17 +(-0.088)x H . 0 5 +(-0.113)x 16.37 +(-0.11)x 5.94 +(-0.019)x 11.68 +(-0.053)x  y=  V/o  y=  y/o  y=  1% 2%  y=  y/o  y=  k%  y=  y=  y=  y= y/o  y=  8mo  1%  y=  it  2%  y=  it  3%  y=  k%  y=  \%  y=  y/o  y=  11  1? tl  yr  of Regression  y=  3% 4%  l£ y r II  Equation  2. AND 3.  41.46 + 0.098x 70.83 +(-0.302)x 113.72 +(-0.926)x 147.34 +(-0.254)x 42.56 + 0.013x 109.83 +(»0.178)x 18.17 18.63 12.43 11.12 13.88 10.62  +(-0.0018)X +(-0.0005)x +(-0.00003)x +(-0.0009)x +(-0.00048)x +(-0„00034)x  Line  APPENDIX I I  EQUATIONS FOR REGRESSION LINES APPEARING IH FIGURE 8 • (GROWTH EFFICIENCY VS GROWTH RATE)  Age  of Fish  8mo  Diet  Infection Level  Equation o f Regression  1 0/  Infected  y=  -0.21+ 0.02ifX  II  il  Control  y=  9.8+  II  2%  Inf  y=  u  n  Con  y=  -0.0029+ 0.015x 0.28+ 0 . 0 1 4 X  it  3%  Inf  y=  0+ O.OIx  ii  H  Con  y=  ti  4%  Inf  y=  it  II  Con  y=  \%  Inf  y=  ti  Con  y=  Inf  y=  Con  y=  H H  ti  it  * a l l regressions  0.012x  -0.052+ 0.0086x 0.026+ 0.0066x 0.0if6+ 0.0068x -0.207+ 0.051x 0.0004+ 0.024x -0.034+ 0.0095x 0.086+ 0.0085x  s i g n i f i c a n t a t p=  0.01  Lines*  APPENDIX I I I  EQUATIONS FOR REGRESSION LINES APPEARING IN FIGURE (TIME MAINTAINED VS BURST VELOCITY. FINGERLING  Ration  I n f e c t i o n Level  FISH)  Equation of Regression  1%  Infected  y= 0.251+ (-O.OH)x**  "  Control  y= 0.334+ (-0.03)x*  y/o " k% "  Inf Con Inf Con  y= 0.251+ y= 0.269* y= 0.317+ y= 0.276+  11  Line  (-0.022)x* (-0.025)x* (-0.026)x* (-0.015)x»*  *= s i g n i f i c a n t c o r r e l a t i o n at p=  0.01  **= s i g n i f i c a n t c o r r e l a t i o n at p=  0.05  70 APPENDIX IV  MEAN LENGTHS, WEIGHTS, AND CRITICAL OF FISH USED IN STAMINA  Age  8mo  Diet  Infection Level  1%  Infected  it  II  Control  ti  2%  Inf  it  it  Con  it  4%  Inf  it  tt  Con  1%  Inf  tt  Con  tt  Mean Lt(cm)  13.34 13.04 15.44 15.03 16.24 16.33 27.91 27.1  VELOCITIES  EXPERIMENTS  Mean Wt(g)  27.75 26.06 45.25 42.27 54.5 55-29 277.32 256.65  Mean C r i t V e l ( L / s e c )  3.87 4.12 . 3.2 3.22 3.15 3.43 2.96 3.13  n  7 7 8 8 7 7 7 7  

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