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The relationship between growth rate and precocious sexual maturation in rainbow trout (Oncorhynchus… Lamont, Carole Ann 1990

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THE RELATIONSHIP BETWEEN GROWTH RATE AND PRECOCIOUS SEXUAL MATURATION IN RAINBOW TROUT (Oncorhynchus mykiss) AND COHO  SALMON ( 0 . .kisutch)  by CAROLE ANN LAMONT B.Sc.  ( B i o l o g y ) Simon F r a s e r U n i v e r s i t y , 1984  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF ANIMAL SCIENCE) We accept t h i s t h e s i s as c o n f o r m i n g to the required  standard  THE UNIVERSITY OF BRITISH COLUMBIA December, 1990. (c) C a r o l e A. Lamont, 1990.  In  presenting this  degree at the  thesis in  University of  partial  fulfilment  of  of  department  this or  thesis for by  his  or  requirements  British Columbia, I agree that the  freely available for reference and study. I further copying  the  representatives.  an advanced  Library shall make  it  agree that permission for extensive  scholarly purposes may be her  for  It  is  granted  by the  understood  that  head of copying  my or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department The University of British Columbia Vancouver, Canada  Date  DE-6 (2/88)  ABSTRACT  Rainbow kisutch)  trout  {Oncorhynchus  mykiss)  produce males which mature  age.  The  objectives  of  this  and coho  at an abnormally  study  were  d e s c r i b e the r o l e o f growth r a t e i n e a r l y of  male  salmonids by m o n i t o r i n g  to  using and  rainbow t r o u t  coded t a g s .  These f i s h  (0.  early  critically  sexual maturation  growth r a t e  and  s e x u a l development i n i n d i v i d u a l l y i d e n t i f i e d  Underyearling  salmon  fish.  were i n d i v i d u a l l y were r e a r e d  precocious  identified  at 9°C and  15°C  growth was monitored twice a month i n both groups over a  9 month p e r i o d  starting  January 24,  1989.  The  number of  p r e c o c i o u s males i n the 9°C and 15°C groups were 11% and 18% respectively.  Yearling  coho  salmon were s i m i l a r l y tagged,  r e a r e d at ambient temperature, and monitored f o r growth over an 8 month p e r i o d s t a r t i n g March 22nd, the  coho  1989.  salmon matured p r e c o c i o u s l y .  there  was  early  s p r i n g and p r e c o c i o u s m a t u r a t i o n .  fish  that  maturing  a  similar  matured  relationship  declined  individuals.  relationship)  was  Ten percent of  In both experiments  between  fast  autumn  relative  Condition  factor  (length  among  those  in  The growth r a t e of  in  greater  growth  fish  to  non-  t o weight  that  matured  iii  p r e c o c i o u s l y . . Plasma coho salmon. of the assay number  of  suggested.  Most  growth hormone was  samples f e l l  below the d e t e c t i o n  (1.5. t o 3.0 ng/ml). precocious  males  monitored i n the  in  A strategy cultured  limits  t o reduce the salmonids  is  TABLE OF CONTENTS ABSTRACT  i  LIST  OF T A B L E S  LIST  OF F I G U R E S  i v v  ACKNOWLEDGEMENTS. .  v i  INTRODUCTION MATERIALS Fish  .  AND  Stocks  i  1  METHODS and Culture  Conditions.....  Coho Salmon G r o w t h Hormone S t u d y Radioimmunoassay Procedures Data C o l l e c t i o n and A n a l y s i s Salmon G r o w t h Hormone A n a l y s i s  15 18 19 23 25  RESULTS Rainbow Trout Study Coho Salmon Study G r o w t h Hormone A n a l y s i s  26 37 42  DISCUSSION  46  Conclusions  and F i s h  Culture  Implications  REFERENCES....  55 58  APPENDICES Appendix  1:  Mean w e i g h t , l e n g t h , a n d s a m p l e s i z e , by sample d a t e f o r mature a n d immature rainbow t r o u t males r e a r e d a t 9 ° C .  79  A p p e n d i x 2: Mean w e i g h t , l e n g t h , a n d s a m p l e s i z e , by sample d a t e f o r mature a n d immature rainbow t r o u t males reared a t 15°C  80  A p p e n d i x 3: Mean w e i g h t , l e n g t h , a n d s a m p l e s i z e , by sample d a t e f o r mature and immature coho salmon males  81  L I S T OF TABLES  Table 1. Reports of p o s i t i v e c o r r e l a t i o n o f growth r a t e and maturation i n salmonids... Table 2 . Pooled length-weight r e l a t i o n s h i p s o f male rainbow t r o u t and coho salmon Table 3 . Mean plasma growth hormone l e v e l s (ng/ml), s t a n d a r d d e v i a t i o n , and range f o r immature male, mature male, and female coho salmon i n May, June, and September f o r each assay  V  LIST OF FIGURES F i g u r e 1. The e f f e c t o f t e m p e r a t u r e on p r e c o c i o u s m a t u r a t i o n . Mean w e i g h t (g) +/- 1 S.E. as a f u n c t i o n o f time i n rainbow t r o u t r e a r e d a t 9°C a n d 1 5 ° C . The warm w a t e r g r o u p h a d a s i g n i f i c a n t l y h i g h e r mean w e i g h t (P<0.05) f r o m M a r c h 2 8 t h , 198 9 t o t h e e n d o f t h e s t u d y . . . . . .  27  F i g u r e 2. Mean s p e c i f i c g r o w t h r a t e s (%g/d) +/- 1 S.E. o f male r a i n b o w t r o u t r e a r e d a t 9 ° C . * i n d i c a t e s s i g n i f i c a n t d i f f e r e n c e s (P<0.05) ....... . 28 F i g u r e 3. Mean s p e c i f i c g r o w t h r a t e s (%g/d) +/- 1 S.E. o f male r a i n b o w t r o u t r e a r e d a t 1 5 ° C . * i n d i c a t e s s i g n i f i c a n t d i f f e r e n c e s (P<0.05)  30  F i g u r e 4. C o n d i t i o n f a c t o r o f m a t u r e a n d immmature r a i n b o w t r o u t r e a r e d a t 9 ° C . The m a t u r e m a l e s h a d a s i g n i f i c a n t l y h i g h e r c o n d i t i o n f a c t o r (P< 0.05) f r o m M a r c h 2 8 t h , 1989 t o t h e e n d o f t h e s t u d y . . . . . . .  32  F i g u r e 5. C o n d i t i o n f a c t o r o f m a t u r e a n d immmature r a i n b o w t r o u t r e a r e d a t 1 5 ° C . The m a t u r e m a l e s h a d a s i g n i f i c a n t l y h i g h e r c o n d i t i o n f a c t o r (P< 0.05) f r o m M a r c h 2 8 t h , 1989 t o t h e e n d o f t h e s t u d y  33  F i g u r e 6. Frequency d i s t r i b u t i o n o f weight i n male r a i n b o w t r o u t r e a r e d a t 9°C i n J u n e and A u g u s t , 1989  35  F i g u r e 7. Frequency d i s t r i b u t i o n o f weight i n male r a i n b o w t r o u t r e a r e d a t 15°C i n J u n e and A u g u s t , 198 9  36  F i g u r e 8. Mean s p e c i f i c g r o w t h r a t e s (%g/d) o f m a t u r e a n d immature male coho s a l m o n . * i n d i c a t e s s i g n i f i c a n t d i f f e r e n c e s (P<0.05)...  38  F i g u r e 9. C o n d i t i o n f a c t o r o f m a t u r e a n d immature male coho s a l m o n . The m a t u r e m a l e s h a d a s i g n i f i c a n t l y h i g h e r c o n d i t i o n f a c t o r (P< 0.05) f r o m A p r i l 20, 198 9 t o t h e e n d o f t h e s t u d y  39  F i g u r e 10. F r e q u e n c y d i s t r i b u t i o n o f w e i g h t i n male coho s a l m o n i n J u l y a n d November, 198 9  41  Figure  51  11. D a y l e n g t h i n h o u r s a t 4 9 ° l a t i t u d e .  vi  ACKNOWLEDGEMENTS  First  and foremost,  inspiring  I wish t o thank  me t o pursue t h i s  degree,  Scott  J . Smith f o r  and f o r h i s continuous  over the past 2 y e a r s .  support and encouragement t  I  would  also  like  s u p e r v i s o r , Dr. George Ed  Donaldson,  to  thank  my  graduate  Iwama, and my a d v i s o r y  Dr. Ted Down  and Dr. R.  studies  committee, Dr.  Ra jamahendran  for  t h e i r guidance and a s s i s t a n c e .  I s i n c e r e l y thank t h e s t a f f o f t h e F i s h C u l t u r e Section Dye, it the  at t h e West Vancouver  Research  Laboratory, e s p e c i a l l y Helen  whose committment t o the coho salmon study ensured t h a t  r a n smoothly. Fisheries  technical particularly  I would Research  suport, talented  and L a r r y  like  Section  especially  government bureaucracy. Rempel  also  t o thank for  their  Kanji  at o r c h e s t r a t i n g  the s t a f f of  Tsmura, miracles  invaluable who within  S p e c i a l thanks t o Bob Land,  Mitchell  at the F r a s e r  Valley  hatchery and Andy Lamb at the West Vancouver their f i s h culture expertise.  is a  Morley  Research  Laboratory f o r  vii  I would l i k e U.B.C,  t o thank t h e F i s h e r i e s  the Ministry of Agriculture  Department  of Fisheries  and Oceans,  Research Section at  and F i s h e r i e s , for providing  and t h e financial  s u p p o r t , equipment, f i s h , and f a c i l i t i e s .  I  would  sincerely  Aquahut: e s p e c i a l l y  like  t o thank  my  colleagues  at the  C a r l Mazur, James McGeer, John  Morgan,  and Tim Y e s a k i ; and C h a r l e n e H i g g i n s and B e t h S c o t t a t t h e Institute  o f A n i m a l Resource  Ecology.  Thankyou  f o r your  generous s u p p o r t , and f o r making t h e t i m e spent a t U.B.C. so enjoyable.  T h i s t h e s i s i s d e d i c a t e d t o my p a r e n t s : R u s s e l l A. Lamont who  introduced  Lamont  me  (nee S t a f )  pursuits.  t o n a t u r e and b i o l o g y ,  and Bernece  who was t h e impetus b e h i n d my  G.  academic  1  INTRODUCTION  P h e n o t y p i c v a r i a t i o n f o r t h e age a t s e x u a l m a t u r a t i o n is  common  f o r many a n i m a l  conditional  species.  response t h a t maximizes  M a t u r a t i o n age i s a f i t n e s s by t r a d i n g o f f  the r i s k s a s s o c i a t e d w i t h e a r l y maturation against the costs of  maturing  at a later  age (Dominey,  1984) .  In species  where t h e t y p i c a l male mating p a t t e r n i s h i g h l y  competitive,  i n d i v i d u a l males may adopt s t r i k i n g l y d i f f e r e n t b e h a v i o u r a l m a t i n g p a t t e r n s ; o f t e n termed a l t e r n a t i v e m a t i n g b e h a v i o u r s (Alcock,  1979) .  alternative younger  mating  males  populations male  An  tactics  in  size  of this  that or  males  submissive  The t y p i c a l  t o adopt  tactics  while  t e r r i t o r i a l l y dominant  behaviour  a r e used age  t o s u c c e s s f u l l y compete  phenotypes.  smaller  example  pattern  "sneaking"  older  breeding or larger  i s f o r younger o r  behaviour  the larger  the  by s m a l l e r o r  polymorphic with  is  or older  (Dominey, 1984).  This  o r t o use males a r e  s p e c i f i c type  o f a l t e r n a t i v e m a t i n g t a c t i c has been demonstrated t o e x i s t in  bees  (Alcock,  (Christenson lizards red  deer  1979)/  and G o i s t ,  ( T r i v e r s , 1976), (Clutton-Brock  beetles 1979),  (Eberhard, 1982), bullfrogs  elephant seals e t a l . , 1979),  spiders  (Howard,  1984),  (Le Boeuf,  1974),  and many  fishes  2  (Constanz,  1975;  and Hoffman,  Warner  1980;  Gross,  Among S a l m o n i d a e , that  is  younger  species  or  sneaking  nest of  this  mating  the  to  be  Size  large  size  enough  However,  the  individual use,  fish  physiological,  at  large  of  Warner  of  that  i n the  favors  precocious the  size  the  the  males  gonads  that  mating  at  on and a  males  and  and  age  (Gross,  age  the  success  undetected  develop  population  and h e n c e ,  employ  Precocious  selection  age  particular  and f e r t i l i z e  enough t o  control  an  territorially  relatively  small  at  "jacks"  older,  maintains  1984) .  which  an  strategy  it  mediated  by  understood.  any age  of  or  1984).  remain  is  environmental,  interrelationship regulation  well  their  an i m p o r t a n t r o l e  spawning  matures,  are not  larger,  selection;  mechanisms  Maturation  the  to  but  the  for  salmonids  (Gross,  males,  within  1980;  commonly m a t u r e  gain access to,  distribution  dominant  polymorphism  avoid  strategy  small  Dominey,  average  male  plays  Disruptive  bimodal  will  to  spawning grounds,  spawn.  the  i n order to  "redd".  1975;  1985).  Young  behaviour  or  need  al.  some m a l e s  than  stock.  dominant males  et  a complex and  genetic  t h e s e mechanisms  sexual  process  maturation  components.  and t h e i r is  influence  uncertain  The on  (Billard,  3  1983) .  The mechanisms c o n t r o l l i n g p r e c o c i o u s m a t u r a t i o n a r e  particularly  obscure.  not  by any s i n g l e  mediated  I t i s probable that  a number o f i n t e r r e l a t e d 1984) ,  physiological  conditions  This precocious between  maturation,  relationship been  attain  menarche  (Bullough, forced  by  slowly slider  start  platyfish and than  and also  and  sticklebacks  earlier  Mitra, delay  when  they  1986).  and K o e l l a ,  r a t e has  Among 1986),  women  maturity  when  t o grow  more  Slower  growing  male  e t a l . , 1981).  t o reproduce  15  females  stress,  nourished are  A  malnourished  delay  of  relationship  maturation.  (Gibbons  start  poorly  (Wootton,  slower growing  rats  maturity  the  aspects  and growth  than  1963).  Drosphila  Koella,  (Stearns  and g e n e t i c  W e l l - f e d human  or temperature  o l d whereas  reproducing  (Stearns  precocious  species.  years  nutritional  11 d a y s  1976; Bye,  the physiological  Laboratory  uncrowded  a l . , 1986),  i n particular  and  i n many  1981).  turtles  c o n t r o l l e d by  (Gardner,  age a t m a t u r a t i o n  2-5  (Kennedy  Well-fed, are  between  on  and  rate  demonstrated  et  age i s  1985).  focuses  growth  but rather  environmental  (Randall  (Gjedrem,  thesis  factor,  maturation  when  o r crowded  days fish, plaice  o l d or faster (Pitt,  they flies later  growing 1975),  1973) m a t u r e and a t a y o u n g e r age  conspecifics.  4  Policansky conditions, rapidly to  do  growth  (1983)  with  abundant  and m a t u r e  so. rate  postulated  as  soon  Among s a l m o n i d s , and  Improved f e e d i n g  precocious  food as  that  supply,  they  this  are  stable  fish  maturation  rearing  should  grow  developmentally  able  relationship  a n d / o r g r o w t h have  in maturation rates  under  is  between  well  resulted  f o r many s a l m o n i d s p e c i e s  in  rapid  documented. differrences  (Table  1).  Table 1. Reports o f p o s i t i v e c o r r e l a t i o n o f growth and m a t u r a t i o n r a t e i n salmonids.  Species Oncorhynchus  Reference spp.  Chinook salmon Coho salmon (0. Masu salmon Pink salmon  (0.tshawytscha) kisutch)  (0. masou) (0. gorbuscha)  Sockeye salmon (0. nerka) Rainbow t r o u t (0. mykiss)  Amago salmon 0. Salmo  rate  rhodurus  •Fla'in, 1970 Hager and Noble, 197 6 B i l t o n e t a l . , 1982 Utoh, 1976 MacKinnon and Donaldson, 1976 R i c k e r , 1938 Aim, 1959 Kato, 1975 Houston, 1981 Schmidt and House, 197 9 Skarphedinsson e t a l . , 1985 T o f t e b e r g and Hansen, 1986 Tsumura and Hume, 198 6 Nagahama e t a l . , 1982  spp.  A t l a n t i c salmon  Brown t r o u t  (S.  Salvelinus  spp.  A r c t i c char (S. Brook t r o u t (S.  (S.  salar)  trutta)  alpinus) fontinalis)  D o l l y Varden (5. malma) Lake t r o u t (S. namycush)  Aim, 1959 L e y z e r o v i c h , 1973 Mitans, 1973 Glebe e t a l . , 1978 Naevdal e t al.,1978 Thorpe and Morgan, 1978 Lundqvist, 1980 B a i l e y e t a l . , 1980 Saunders e t a l . , 1982 D a l l y e t a l . , 1983 Thorpe e t . a l . , 1983 Aim, 1959 Jonsson and Hindar, 1982  Grainger, 1953 Jonsonn and Hindar, 1982 McCormick and Naima'n, 1984 Jonsson and Hindar, 1982 Aim, 1959 Hanson and Wickwire, 1967  I  This widespread rate  and  maturation  initiation  of  dependant  upon  MacKinnon et  and  al.,1980;  with  basis  the  has  concept  et that  1976;  alone  t o mature.  in  smaller  size  basis,  they  threshold it  achieving  matured  at  the  the  although  for  the  a critical  size  is  dictate  1983) .  a l o n e may  concurs major  Achieving  predispose  age,  meet of  at  On  a  this  minimum  critical  to  found  and  lake.  a  a  (Salvelinus  of maturation.  development  Bailey  a  Varden  that  order  1957;  e t . a l . (1984)  younger  achieving a  in  salmonids  necessarily  concept  initiation  the  hypothesis  Dolly a  that  a l . , 1977;  can  Jonsson  and  necessary  requirements  not  clarki)  rejected  that  physically  may  growth  (Elson,  t h a n t h e same s p e c i e s i n a n o t h e r  dictates  appears  This size  F o r example,  lake  et  (Smith-Gill,  however,  (0.  one  Refstie  critical  in  threshold  a l . , 1986).  critical  malma)  proposal  size  minimum  Myers  cutthroat  the  a  conversion  that  to  maturation  developmental  a fish  led  precocious  Donaldson,  size  f o r a r e l a t i o n s h i p between  size  Therefore, size the  gonadal  may  be  energy tissue,  not n e c e s s a r i l y  initiate  maturation.  Thorpe a  better  than  size  (1986)  factor alone.  argued  on He  which  that to  argued  instantaneous  base that  growth-rate  "developmental size  alone  is  decisions"  i s a measure  of  7  past  performance;  consumed, in  the  which  size  stages  are  alone,  reached  Salmonids spawning  environmental the  seasonal time  initiation  of  within  an e n v i r o n m e n t a l  (Houston,  initiation 1981;  maturation  process  for  energy  be  summer  (Salmo  to  growing  maturation  is  salar)  fish  time  period.  into In  by  (Lundqvist,  in  It  the  to  temperate temperate  event,  gonads  and  been  p e r i o d would  addition, in  that  spring  Atlantic is  of  allow  during  evidence  it  in  proposed  late  growth  of  and spawn  The i n i t i a t i o n  gonadal  and  by  entrainment  has  1990a).  photoperiod 1980)  by  during  time  For  restricted  "windows"  occurs  during this  directed  are  spawning  window.  period  regulated  the  potential  1979).  can develop  Rowe and T h o r p e ,  the  and  is  developmental  physiological to  been  predicted  which  Therefore, the  had  the  not  and B e r v e n ,  or  way  determined.  is  at  spawners  be made p r i o r  o r i e n t e d way so t h e  the  be  had  growth-rate  which  can  rate  periods  a time  that  the  conditions.  m a t u r a t i o n must  upon  it  and t h e  material  metamorphosis  (Smith-Gill  are  food  instantaneous  and s p a w n i n g  by  of  assimilated and  performance  but  in definite  climate,  hand,  amphibians,  age  quantity  energy  other  current  the  h a d been  acquired  maturation  in  or  it  of  sexual  example,  efficiency  On t h e  measure  for  is  that  allocated. a  that  the that  salmon  initiated  8  under i n c r e a s i n g and  day  Thorpe,  198 9)  Rapid  growth  spring  has  Bilton  (1980)  rate  earlier  age  at  than  (1989)  that an  extending  photoperiod  February,  increased  Atlantic during  salmon  the  individually 1990a) . spring  reduced  Thorpe, period ability  be  of the  during the  fall  Variation influence rearing  the  1990b). may  a  rate  another  reduction of  important  or the next  temperature  matured  Adams  an and  water  temperature  in  sexual  maturation  in  rapid  growth  rate  sexual maturation  salmon  (Rowe  feed  males  rate  mechanism gonads and  and  during  precocious  growth  at  by  study,  in  example,  opportunity  early  Atlantic  the  kisutch)  fingerlings.  of  to  For  months  increasing  number  during  in  Thorpe,  the  early  (Rowe this  determining  spawn  in  and time the  successfully  spring.  environment  precocious  8  and  f i s h to develop  in  to  growth  Therefore, an  6  enhancing  linked  Adams  during  (Oncorhynchus  that  identified  Moreover,  studies.  growing  In  1983;  salmonids  salmon  of  the  was  many  coho  age  parr.  spring  Sumpter,  theory.  in  slower  showed  and  among m a t u r i n g  observed  found  faster  (Scott  support t h i s  been  growing  Thorpe  lengths  has  maturation. promoted  sexual  also For  been  example,  maturation  shown  to  increased in  rainbow  9  trout  (0. mykiss)  (Titarev,  1975) as  anadromous form, s t e e l h e a d t r o u t , and i n p i n k salmon  well  as  i n the  (Schmidt and House, 1979),  (0. gorbuscha)  (MacKinnon and Donaldson,  197 6) .  S i n c e growth i s d i r e c t l y r e l a t e d t o t e m p e r a t u r e and  ration,  the influence  o f temperature  on m a t u r a t i o n may be  m e d i a t e d t h r o u g h i t s e f f e c t on growth r a t e .  Some  previous  studies  d i d not  find  a  positive  c o r r e l a t i o n between p r e c o c i o u s m a t u r a t i o n and growth Glebe  e t a l . (1980)  between growth salmon;  Naevdal  rate  d i d n o t show  a positive  e t a l . (1978)  showed t h a t  the c o r r e l a t i o n  m a t u r a t i o n and growth  for  and G j e r d e  Atlantic  salmon,  salmon  correlation  and p r e c o c i o u s m a t u r a t i o n i n A t l a n t i c  between age a t f i r s t Atlantic  rate.  males  were  (1984)  the  rate  was s m a l l  found t h a t m a t u r i n g  smallest  parr.  This  d i s c r e p a n c y c o u l d be r e s o l v e d i f i t c o u l d be d e t e r m i n e d t h a t m a t u r i n g males a r e l a r g e r t h a n non-maturing males and  then  Leyzerovich  Other  grow  more  slowly  i n autumn,  as  initially,  suggested  by  (1973)/ D a l l e y e t a l . (1983), and G j e r d e (1984).  experiments  have  shown  that  w i n t e r and s p r i n g i n f l u e n c e t h e i n i t i a t i o n A t l a n t i c salmon p a r r .  Rowe and Thorpe  lipid  levels  in  of maturation i n  (1990b)  examined t h e  e f f e c t o f d i e t r e s t r i c t i o n on f a t u t i l i z a t i o n and p r e c o c i o u s  10  maturation  in Atlantic  salmon p a r r .  Growth was  suppressed  by f a s t i n g f i s h i n a l t e r n a t e weeks d u r i n g s e q u e n t i a l 2 month periods.  Significant  occurred  i n populations  June.  They  also  utilisation matured  r e d u c t i o n s i n male  found  and storage  and those  which  restricted that  maturation  during A p r i l ,  the seasonal  differed  between  d i d not.  May,  pattern  those  rates  of f a t  fish  The g r e a t e s t  which  difference  o c c u r r e d i n l a t e winter, when males d e s t i n e d t o mature down new  stores of v i s c e r a l  f a t , while  and  immature  laid  fish did  not.  In h i g h e r v e r t e b r a t e s such as r a t s , r e p r o d u c t i v e success  i s positively  during  the e a r l y  levels  play a similar  fat  maturation role  cattle,  correlated to f a t stores  stages  (Frisch,  i n maturation  1988).  i n fish,  s t o r e s i n l a t e w i n t e r would probably prevent  that year. winter storage  In a d d i t i o n ,  would at  maturation  restriction  process  time. in  This fish  might  with  Iffat then low  maturation  of feed intake i n late  n e c e s s i t a t e the m o b i l i s a t i o n that  and humans,  r a t h e r than f a t  further  otherwise  block  the  adequate f a t  stores.  Other evidence i n d i c a t e s t h a t maturation r a t e s are a l s o genetically  controlled  (Donaldson  and Olson,  1955; Thorpe,  11  1975;  Naevdal  e t a l . , 1978;  1984;  Gjedrem,  1985).  growth  and  Thorpe,  early  (1986)  development early  stimulated 1983), will  therefore  by  the  acquire  sufficient  starts  objective  will  and  that  prevents  late,  energy  (Scott  be t r i g g e r e d  It i s likely  i s adaptive  season  The  daylength  this  rivers They the  Coho  fall  lengths  and w i n t e r  study  was  April  stream migrate  where  they  for fish  the to  on  examine  coho s a l m o n and  i n the small  streams,  Pacific  Ocean.  i n freshwater  streams  during  t o December.  i n freshwater  competing  feed  when  East  October  approximately  are t e r r i t o r i a l ,  growth-related  to c r i t i c a l l y  the North  a n d spawn  and remain  o f time,  reside  along  from  Sumpter,  and m a t u r a t i o n  and i s t o o s h o r t  salmon  and t r i b u t a r i e s  are  r e s e r v e s f o r spawning.  of this  a r e anadromous,  around  fry  trout.  and  of  i n the  systems  maturation  the growth p a t t e r n s o f p r e c o c i o u s l y maturing rainbow  rate  level  hormone  fast  linked.  provided  determined  gonadotropic  maturation  growing  Gjerde,  genetically  that,  a genetically  entrained.  maturation  were  proposed  increasing  gonadal  be  maturation  when  e t a l . , 1983;  T h o r p e e t a l . (1983) showed t h a t  i s above  spring,  Thorpe  streams  one y e a r .  At t h i s  for specific  aquatic  t o the sea the following  F r y emerge f o r varying stage, the  areas  within a  invertebrates.  spring,  and e i t h e r  Smolts remain  12  in  the  nearshore  coastal  zone  salmon  will age  in  will  returning  prior  to  spawn  Gonadal to  British  coho  desirable  .  within  usually  the  or  gonads  c a r r y the  before  occurs  popular  1980).  at  Coho  sea  before  or  "jacks"  males,  returning to  during the  coast  and t h e i r  due  to  to  the  species,  reside  in  to  spawn  the  early  better  due  chinook high  coho  or  during  the  outlet  of  salmon  summer months  associated in  with  of  became  winter. spawning,  subsequent  years.  and  under (0.  less  lakes.  tributaries  lakes.  prior  their  precocious  streams  streams  to  salmon  rate  on  1980's,  endurance  spawn d u r i n g s p r i n g i n s m a l l e r  spawn  at  summer m o n t h s ,  farm  freshwater  g o n a d mass o v e r t h e  to  during  species  relative  inlet  mortality  ability  months  Precocious  sea  C.)  this  trout  rivers,  (Hart,  around the  fall.  (B.  However,  Rainbow  high  at  growth r a t e  farm.  develop  a  a  to  They w i l l  18  3.  development  conditions  maturation  and  6 months  were  tshawytscha)  Pacific  spend age  or migrate  s a l m o n f a r m i n g i n d u s t r y was g r o w i n g r a p i d l y  initial  culture  of  at  Columbia  salmon  faster  Northern  spawning i n the  When t h e the  the  and c h a n n e l s  generally  spend o n l y 2.  straits  to  They  spawning,  Although there these The  fish  is  have  number  of  13  fish  spawning  more t h a n  and C r o s s m a n , are  3 to  1973).  5 years  Precocious salmonids likely  Normally,  old.  is  improved  effects  susceptibility  to  growth  rate,  flesh  quality, fish  Sterilization  in  and  the  the all  these  success.  This  study  was  the  role  of  maturation  cultured  information gained  used to  In were  a i d i n the  this  study,  monitored  species.  in  Rainbow  maturation;  used  designed  management  results  of  of  this  patterns  individually were  of  to  had  manage limited  a  in  better  precocious  anticipated this  study  that  c a n be  problem.  and  sexual  identified  grown  all-female  methods  rate  of  fisheries.  acquire  is  reduced  precociously  have  It  The  increased  wild  to  most  deterioration  these  as  2.  is  invasions,  growth  from t h e  trout  rates.  and  salmonids.  growth  growth  of  they  cultured  This  techniques  of  age  among  production  been  maturation;  understanding  m a t u r e when  and t h e  aquaculture  (Scott  1983).  fungal  value  precocious  the  with  10%  mature at  and  mortality,  and g r a d i n g have  in  males  feeding  techniques,  fish  (Billard,  bacterial  limit  than  more p r e v a l e n t  associated  increased  less  these  Precocious  maturation  to  deleterious  stocks,  c a n be  than i n w i l d stocks  due  maturing  once  at  two  development  fish  of  temperatures  both in  14  order  to  examine  precocious  the  effect  maturation.  investigation  was  to test  of The  goal  the hypothesis  p a t t e r n of p r e c o c i o u s l y maturing immature f i s h .  enhanced  growth  of  the  that  rate  on  present  t h e growth  f i s h d i f f e r e d from t h a t o f -  To a c e r t a i n e x t e n t t h i s work p a r a l l e l s work  done w i t h A t l a n t i c  salmon t h a t was  Rowe and Thorpe (1990a).  recently published  by  As p a r t o f t h e coho s t u d y , plasma  growth hormone was m o n i t o r e d  to investigate i t ' s potential  r o l e i n p r e c o c i o u s m a t u r a t i o n i n coho salmon.  15  MATERIALS AND METHODS  Fish  Stocks  and C u l t u r e C o n d i t i o n s  Rainbow egg  trout  collection  approximately during Trout at  e g g s were station,  50km  t h e annual hatchery  3 years  NW  gathered  located  a t t h e Pennask  at  50°  o f Summerland,  B. C. M i n i s t r y  egg c o l l e c t i o n .  B.  00'N/120°  C,  08'W,  i n June  o f Environment  This  Creek  1988  Summerland  stock n o r m a l l y matures  o f age, b u t many m a l e s m a t u r e p r e c o c i o u s l y a t age  2.  The  fertilized  hatchery until  where  they  September  transferred  eggs were  to  were  Valley  Trout  hatchery  B.  where  they  C.  fiberglass  fish  were  tank  and  C.  were  with  transferred  hatched,  this  time,  Ministry  of  held  Two  transponder  reared  At  (research  tanks.  intraperitoneally integrated  incubated,  1988. t h e B.  t r a n s p o r t e d t o t h e Summerland  3  m  thousand an  15,000  in  individually  i n 9.0°C  well  water  circular  were  injected  coded  passive  (PIT) t a g i n J a n u a r y , t o a 2 m diameter  Fraser  Abbotsford,  diameter  fish  reared  f r y were  Environment  section)  in  and  1989.  circular and under  These  fiberglass simulated  v.  natural  photoperiod.  In March  1989  one h a l f  of the  fish  16  (approximately 2 m diameter  1000)  circular fiberglass  were h e l d u n d e r both  fed  a r a t i o n of  of  the  in  both  2% o f  groups to  warm w a t e r  (9°C) was  were  pelleted  31,  maturity  Sex  fish  sacrificed in  in  each  from  males  (ovaries)  at  fish, index  28,  determined incised  examine by  the  orange  two  this  fish  and t h e y  were  automatically duration  individual  weeks time,  fish  507  fish  from t h e  were  fish  from J a n u a r y  cool  and s a c r i f i c e d .  from water  The  assessed  (GSI)(Robertson, were  15°C  of  f o r the  of  males  from b o t h groups  and  order to  At  g r o u p and 598  on September  was  dispensed  every  1989.  m a t u r i t y by g o n a d o s o m a t i c remaining  food  randomly s e l e c t e d  determined  Both groups  and w e i g h t s  monitored  (15°C)  g r o u p were  tank.  an a d j a c e n t  natural photoperiod  Lengths  August  into  t h e i r mean body w e i g h t  experiment.  1989  the  simulated  Oregon m o i s t  at  24,  were t r a n s f e r r e d  1958).  s e x e d and a s s e s s e d  sex for The for  1989.  by  visual  laterally  examination. along  the  Fish  ventral  were  surface  gonads.  Females  were  distinguished  colored  granular  oval  enlargements  the  anterior portion of  the  ovaries  most  cases,  were  the  naked  eye,  although  examination  under  low p o w e r .  gonadal  clearly some  attachment.  distinguishable required  Immature male  In with  microscopic  testes  were  pale  17  colored  and  smooth t e x t u r e d .  white lobes,  For  River  coho  Salmon  were used.  2.4  m  and  of  study,  322  coho  Fisheries  and  Oceans  Enhancement  Program  in July  1988,  salmon  hatchery  F i s h were t r a n s f e r r e d t o the  diameter  water.  salmon  Department  Laboratory  1987  DFO  circular  tanks  were  selected  in  order  to  year  West Vancouver  in  in  outdoor  ambient fork  maximize  well length  maturation  rates.  Each f i s h was  i n j e c t e d i n t r a p e r i t o n e a l l y with a  tag  March  As  in  bacterial treated  1989.  infection, food  following pelleted  food  to  were v a c c i n a t e d dilute  et  1989  f o r V.  salmonicida  by  al.,  fed  0.673%  1986)  s a t i a t i o n several for V i b r i o  30,  treatment  for  1989.  against  oxytetracycline  a  3  week  times d a i l y  anguillarum of  the  by  period  bacteria  Yersinia  .  The  ruckeri,  (Biomed)  for  again on and  four  days  from  June  20,  June  Ltd).  at a r a t e of 1989  to  20  Aeromonas  i n t r a p e r i t o n e a l i n j e c t i o n (Aqua H e a l t h to seawater g r a d u a l l y  fish  immersing them i n  F i s h were v a c c i n a t e d  anguillarum,  every  PIT  Coho salmon were hand f e d Oregon moist  F i s h were i n t r o d u c e d increments  prophylactic were  inactivated culture  seconds on May 5,  fish  (Piper  tagging.  a  the  Capilano  brood  where they were r e a r e d  fiberglass  from  (DFO)  For t h i s experiment, salmon f r y of 18 cm  longer  large  a l s o smooth i n t e x t u r e .  the  Canadian  Mature male t e s t e s were  July  25% 2,  18  1989.  Fork  l e n g t h s and  weights  i n t e r v a l s from  of  individual fish  taken  a t monthly  1989.  The s t o c k n o r m a l l y spawns i n l a t e November.  S p e c i f i c growth r a t e factor  25  t o November  (% body weight/day)  and  and immature males  t e m p e r a t u r e groups  i n both  and among t h e mature  and  1,  condition  ( l e n g t h t o weight r e l a t i o n s h i p ) were c a l c u l a t e d  compared between mature trout  March  were  and  rainbow immature  coho salmon.  Coho Salmon Hormone Study  To p r o v i d e an i n i t i a l plasma sample, b l o o d was drawn by syringe  from t h e d o r s a l  t a g g e d on March growth  aorta  22, 1989.  experiment.  was  41  fish  that  were  not  These f i s h were not used i n the  B l o o d was  f i s h by t h e same method on May 1989.  from  t a k e n from t h e e x p e r i m e n t a l 25, J u l y 31, and November 30,  Samples were kept on i c e , c e n t r i f u g e d , and t h e plasma separated  and  stored  a n a l y z e d f o r growth hormone.  at  -25°C  until  they  could  be  19  Radioimmunoassay P r o c e d u r e s  Plasma  salmon  radioimmunoassay  growth hormone l e v e l s were measured (RIA)  using  the  procedure  described  by by  Wagner and McKeown (1986) w i t h s e v e r a l m o d i f i c a t i o n s by Dr. Manuel  Diez,  a  Laboratory.  visiting  Recombinant  scientist salmon  at  t h e West  growth hormone  used f o r t h e s t a n d a r d  s o l u t i o n s and as a t r a c e r .  was  T.  a gift  Japan.  from Dr.  Abe,  Vancouver (rsGH) The  Sciences, widely  by  Dr.  B.  A.  Simon F r a s e r  rsGH  Kyowa Hakko Kogyo Co. L t d . ,  A n t i s e r u m t o n a t u r a l salmon growth hormone (sGH)  provided  was  McKeown,  Department  University.  This  tested for i t ' s s u i t a b i l i t y  of  was  Biological  antibody  has  been  f o r RIA purposes (Wagner  and McKeown, 198 6 ) .  The  i o d i n a t i o n b u f f e r was  g/1 monobasic sodium phosphate S t . L o u i s , MO)  a 0.5M  and 60 g/1 d i b a s i c sodium phosphate  made w i t h  (S-0876,  Sodium phosphate b u f f e r  iodination buffer d i l u t e d 10-fold  d i s t i l l e d w a t e r t o 0.05M.  (S-2002, Sigma) i n SPB.  buffer)  was  0.05M  SPB  with  The column b u f f e r was made w i t h 2  g/1 b o v i n e serum albumin (A-9627, Sigma) and 0.1 g/1 azide  (71  (S-0751, Sigma C h e m i c a l Co.,  Sigma) i n d i s t i l l e d water, pH 7.4. (SPB) was  phosphate b u f f e r  sodium  The hormone assay b u f f e r  containing  20  g/1  EDTA  (RIA  (S-311,  20  Fisher), normal  9  g/1  rabbit  sodium  serum  chloride  (S-9625,  (NRS)(869019,  Sigma)  Calibiochem)  i n 5.0 mis double d i s t i l l e d water), 100 mg/1 g/1 bovine J.  serum  albumin and 1.0  g/1  20  ml/1  (1 v i a l  NRS  sodium a z i d e , 2  Triton  X-100  (X198-7,  Baker).  Recombinant  was  iodinated  f o l l o w i n g the chloramine T method as i n Greenwood  and Hunter  (1963). was  A total  growth  Kyowa  T  ( i n 10 (in  sequentially. 160  ug  Fisher)  containing  10  ul  iodination  ul  iodination  Following  o f sodium  iodination  vial  a small  The s t i r bar was turned on and 10 u l 0.5M rsGH  chloramine  hormone  of 2.5 mCi Nal25I (5 ul)(IMS-30, Amersham),  added t o a s c i n t i l l a t i o n  s t i r bar. ug  salmon  ( i n 100  and  and  buffer)  were  30 seconds of constant  metabisulfate  buffer)  buffer)  200  u l column  ug  (S-244,  Fisher)  potassium  buffer)  were  SPB,  10  40  ug  added  agitation, ( i n 10 u l  iodide  added  glass  to  (P-411 , c  stop  the  reaction.  The r e a c t i o n mixture t o t a l 57 cm Sephadex G50 0.145  ml  through were  had with  (Pharmacia Ltd.) column.  been column  collected  volume was put onto a 0.5 x  drawn  into  buffer.  i n 12  x  75  the  column,  Fractions mm  When the e n t i r e i t was  flushed  containing  6 drops  polystyrene  culture  tubes,  21  b e g i n n i n g when t h e f i r s t column. a  Picker  0.145  ml was  first  p u t onto t h e  Ten u l a l i q u o t s from each f r a c t i o n were counted on S p e c t r o s c a l e r 4R  f o r 6 seconds  c o n t a i n e d t h e most  each  to  determine  which  protein.  These f r a c t i o n s were combined and r e t a i n e d a t 4°C  for  fractions  counter  radiolabelled  a s s a y s , and a l l r e m a i n i n g f r a c t i o n s were d i s c a r d e d .  F o r t h e radioimmunoassay o f sGH, d u p l i c a t e polystyrene  c u l t u r e tubes were s e t up t o c o n t a i n 50 u l o f  t h e a p p r o p r i a t e rSGH s t a n d a r d 50 u l o f r s G H - I activity  i n RIA  (0.2 - 100 ng/ml) o r  (5, 000 cpm,  1 2 5  buffer),  antiserum d i l u t i o n  and  diluted 50  ul  both  of  antibody.  o f 1:10, 000 bound 50% ' o f l a b e l l e d  maximum b i n d i n g c o n t r o l s were p r e p a r e d by standard  substituting Standards  and  antibody  standard  were  plasma,  t o the appropriate  (5,000 cpm) under t h e c o n d i t i o n s o f t h e a s s a y . and  12 x 75 mm  freshly  alone  with  RIA  prepared  rsGH  Non-specific substituting  buffer  w i t h RIA b u f f e r  An  and  by  respectively.  and s t o r e d a t 4°C  f o r no  l o n g e r t h a n one week.  These t u b e s were v o r t e x e d and then b r i e f l y The t u b e s  were i n c u b a t e d f o r 24 hours  a d d i t i o n o f lOOul globulin  centrifuged.  a t 4°C p r i o r  t o the  (1 u n i t ) o f goat a n t i b o d y t o r a b b i t gamma-  (GARGG)(Calbiochem 539844, p r e p a r e d by t h e a d d i t i o n  22  of  12.5 ml 0.05M  tubes at  SPB t o 1 v i a l  1,500  Finally,  counted  For tubes  and t h e r a d i o a c t i v i t y  f o r 1 minute  (cpm)  2 hours  the supernatant  was  of the remaining p e l l e t  was  each.  calculation  first  The  t h e t u b e s were c e n t r i f u g e d a t  (3500 rpm) a t 4°C f o r 30 m i n u t e s ,  aspirated,  o f sGH  concentration,  had t h e n o n - s p e c i f i c  binding  counts  counts  for  a l l  p e r minute  s u b t r a c t e d , a n d were t h e n e x p r e s s e d as a p e r c e n t a g e o f  maximum b i n d i n g  binding curves  should  cpm.  always  determine  In t h i s  fall  o f p e r c e n t bound  concentration  0  a n d 100%.  (Y-axis) p l o t t e d  o f hormone  standards  against  (X-axis)  sGH c o n c e n t r a t i o n i n t h e s a m p l e s . than  standard  t h e samples  curve) ,  detectable interassay plasma  way, v a l u e s f o r p e r c e n t a g e  between  b o u n d was g r e a t e r  each  GARGG) .  were v o r t e x e d a n d i n c u b a t e d f o r an a d d i t i o n a l  room t e m p e r a t u r e .  the  of lyophilized  were  assay.  levels  80% ( i . e . ,  f o r the  precision, evaluated  eight  taken  assay.  In  samples  from  f o r plasma  growth  l o g of the  were  used  to  I f the percent  o f fthe linear  were  Standard  part  t o have order a  less to  common  hormone  of the than  assess pool of  levels i n  23  Data C o l l e c t i o n and A n a l y s i s  Lengths were  and  monitored  individual  coho  growth r a t e s  w e i g h t s o f each twice  i n d i v i d u a l rainbow  monthly.  Lengths  salmon were t a k e n once  and  weights  a month.  (SGR) were c a l c u l a t e d between  trout of  Specific  sample p e r i o d s as  follows: SGR = lnS2 - l n S l x 100 x d-1  where l n i s t h e n a t u r a l l o g a r i t h m ,  S l and S2 a r e t h e w e i g h t s  at t i m e 1 and 2, and d-1 i s t h e number o f days between 1 and 2 ( C l a r k e and S h e l b o u r n ,  Differences between  i n mean  maturing  and  1986).  size  and  non-maturing  specific males  growth  were  d a t a were t e s t e d  for  homogeneity  1937 of  analysis  by  Bartletts test  When d e p a r t u r e s from t h e s e assumptions  of  test  compared by was  used  variance  Student's t - t e s t . to  m a t u r a t i o n between  and  (Bartlett,  occurred,  logarithmic  t r a n s f o r m a t i o n s were a p p l i e d p r i o r t o t h e a n a l y s i s . were  by  period.  f o r n o r m a l i t y by p r o b a b i l i t y p l o t  of variance  i n Zar, 1984).  rate  tested  a n a l y s i s o f v a r i a n c e f o r each group f o r each sample All  time  compare  The  differences  Means  Chi-squared in  t h e two t e m p e r a t u r e groups  the  (X ) 2  percent  (Zar, 1984).  24  In  this  case,  expected  t h e mean  value.  rejected  with  o f t h e two p e r c e n t s  was u s e d  F o r a l l comparisons t h e n u l l a  significance  level  as t h e  hypothesis  of alpha  less  was  than  or  e q u a l t o 0.05.  Length calculated provides being  t o weight using  allometric  (cm),  K  (Bolger  when  lengths  analysis  100W/L  immature  of variance.  a significance  level  =  weight total  1975), between  198 9)  was  which groups  and g r o w t h i s  b  W  i s weight  Mean males  using  The n u l l of alpha  o f both  i s length  compared  between  Kruskal-Wallis  one-way  h y p o t h e s i s was r e j e c t e d  l e s s than  testes  body w e i g h t  (g) , L  of the regression ofl o g  c o n d i t i o n was  was c a l c u l a t e d u s i n g t h e f o r m u l a  GSI  vary  factor)  1951) :  on l o g l e n g t h . and  (Ricker,  and C o n n o l l y ,  i s condition factor,  mature  (condition  formula  and b i s t h e s l o p e c o e f f i c e n t  weight  GSI  index  (Le C r e n ,  K =  where  Flicker's  the best  compared  relationship  o r e q u a l t o 0.05.  by R o b e r t s o n  (g) x 100  (g)  with  (1958):  25  GSI 0.05%,  values  whereas  of  all  those  non-maturing  of  maturing  males  fish  were  were  less  than  greater  than  1.4%.  Effort date.  was  However,  mortalities  to  sample  In of  n  figure  legends.  differences  are  fish  (n) avoid  listed  in  fish  at  cases  n  sample  measurement, each  and  population. every  sample  representation,  appendix  where  each  almost  confusing the  at  elude  from  changed  to  In  every  managed t o  some  size  order  values  measure  some f i s h  removed  Therefore, date.  made  rather  was  than  greater  i n n w o u l d have no b e a r i n g on t h e  the  in  than  the 100,  results.  Salmon G r o w t h Hormone A n a l y s i s  Samples analysed  by  maturation were  above  the  detection  analysis  and  sample  evaluated.  of  variance.  date  Each  assay  was  in  the  position  differences  in  the  concentration  be  combined.  of  allow the  of  The  on p l a s m a  Differences  p o o l e d plasma d i d not  limits  the  effects  growth  of  results  sex, levels  individually.  standard growth  were  of  hormone  evaluated  the  assay  curve  hormone  from t h e  and/or in  3 assays  the to  26  RESULTS  Rainbow T r o u t Study  When t h e f i s h were s p l i t February 21st.,  1989,  i n t o two t e m p e r a t u r e groups on  t h e r e was no s i g n i f i c a n t  i n mean w e i g h t between t h e two g r o u p s .  difference  However, from March  28th onward, t h e warm water group had a s i g n i f i c a n t l y h i g h e r mean w e i g h t ( F i g u r e 1) .  The r a t e o f p r e c o c i o u s  maturation  i n t h e warm water group was a t a s i g n i f i c a n t l y h i g h e r (18%)  rate  t h a n t h e c o o l water group (11%) ( F i g u r e 1 ) .  At- 9°C, t h e m a t u r i n g males had a h i g h e r s p e c i f i c growth rate  (% body w e i g h t / day) t h a n t h e immature males a t each  two week sample p e r i o d from F e b r u a r y 21/22 t o June 6/7, 1989 (except f o r March 11/12 when s p e c i f i c mature  and immature groups were equal)  June 20/21, t o August 30/September rate  o f t h e two groups was e q u a l  period  growth r a t e s i n b o t h  on J u l y  specific  (Figure  2) .  1, t h e s p e c i f i c (except  From growth  f o r one s a m p l i n g  19/20 when t h e immature males had a h i g h e r  growth r a t e )  ( F i g u r e 2) .  On September  l a s t s a m p l i n g day, t h e immature males had a h i g h e r growth r a t e t h a n t h e mature males ( F i g u r e 2 ) .  28th, t h e specific  27.  0-1  1  Feb  1  1  Mar  Apr  1  1  1  May June July  1  1  Aug Sept  \—  Oct  F i g u r e 1. The e f f e c t o f t e m p e r a t u r e on p r e c o c i o u s m a t u r a t i o n . Mean w e i g h t (g) +/- 1 S.E. as a f u n c t i o n o f t i m e i n r a i n b o w t r o u t r e a r e d a t 9°C and 1 5 ° C . From March 2 8 t h , 1989 t o t h e e n d o f t h e s t u d y , t h e warm w a t e r g r o u p h a d a s i g n i f i c a n t l y h i g h e r mean w e i g h t (P<0.05) .  28  F i g u r e 2. Mean s p e c i f i c g r o w t h r a t e s (%g/d) +/- 1 S.E. ofmale r a i n b o w t r o u t r e a r e d a t 9 ° C . * i n d i c a t e s s i g n i f i c a n t d i f f e r e n c e s b e t w e e n means a t e a c h sample point (P<0.05).  29  At 15°C, t h e m a t u r i n g males had a h i g h e r s p e c i f i c growth rate two  (% body w e i g h t / day) t h a n t h e immature males a t each week  sample  period  (except f o r A p r i l mature  from  March  14/15 t o J u l y  19/20  11/12 when s p e c i f i c growth r a t e s i n b o t h  and immature  groups were  equal).  Specific  growth  r a t e f o r b o t h mature and immature groups was e q u a l f o r t h e p e r i o d from August 1/2 t o August 30/ September 1.  Specific  growth r a t e was g r e a t e r i n immature males t h a n mature males on t h e l a s t sample d a t e , September 28 ( F i g u r e 3 ) .  The p o o l e d male d a t a f o r t h e l e n g t h - w e i g h t gave a r e g r e s s i o n s l o p e o f 2.971 (Table 2 ) . used f o r c a l c u l a t i n g c o n d i t i o n f a c t o r .  relationships T h i s v a l u e was  C o n d i t i o n f a c t o r was  e q u a l f o r males i n b o t h t e m p e r a t u r e groups from t h e s t a r t o f t h e s t u d y on January 24 t o March 15.  From t h e next sample  date t o t h e end o f t h e s t u d y , t h e c o n d i t i o n m a t u r i n g males was s i g n i f i c a n t l y immature  males  significant  (Figure  effect  4,  5) .  on c o n d i t i o n .  f a c t o r of the  greater than that Temperature The f i s h  also  of the had a  i n t h e warmer  water had a s i g n i f i c a n t l y g r e a t e r c o n d i t i o n f a c t o r from t h e first  sample d a t e a f t e r  t h e y were t r a n s f e r r e d  water t o t h e end o f t h e s t u d y .  t o t h e warm  30  -1.CH  —I  Feb  1 Mar  —I  Apr  1  H  1  May June July  1  1—  r-  Aug Sept Oct  gure 3. Mean s p e c i f i c growth r a t e s (%g/d) +/- 1 S.E. o f male rainbow t r o u t r e a r e d at 15°C. * i n d i c a t e s s i g n i i c a n t d i f f e r e n c e s between means at each sample point (P<0.05).  31  T a b l e 2. P o o l e d l e n g t h - w e i g h t d a t e o f male r a i n b o w t r o u t  Species  No. of fish  r e l a t i o n s h i p s from a n d coho s a l m o n .  Correlation coefficient  Regression parameters  (r)  Rainbow Coho  Trout  Salmon  13,982 775  each  a  b  sample  ANOVA P<  0.972  -11.303  2.971  0.001  0.800  -  2.027  0.000  6.494  32  1.7 A — A MATURE A A IMMATURE  1.6 1.5 1.4 1.3 + 1.2 1.1 1.0 0.9 Feb  Mar  Apr  May June July Aug Sept Oct  gure 4. Mean c o n d i t i o n f a c t o r +/- 1 S.E. o f mature and immmature r a i n b o w t r o u t r e a r e d a t 9°C. The mature males had a s i g n i f i c a n t l y h i g h e r mean c o n d i t i o n f a c t o r t h a n t h e immature males (P< 0.05) from March 28th, 1989 t o t h e end o f t h e s t u d y .  33  F i g u r e 5. Mean c o n d i t i o n f a c t o r +/- 1 S.E. o f mature and immmature rainbow t r o u t r e a r e d a t 15°C. The mature males had a s i g n i f i c a n t l y h i g h e r mean c o n d i t i o n f a c t o r t h a n t h e immature males (P<0.05) from March 28th, 1989 t o t h e end o f t h e s t u d y .  34  In b o t h 9°C and 15°C groups o f f i s h , t h e w e i g h t / f r e q u e n c y d i s t r i b u t i o n o f mature and immature males o v e r l a p p e d f o r t h e duration  o f the study  (Figure  6,7) .  p r e c o c i o u s males were s i g n i f i c a n t l y the  n o n - p r e c o c i o u s males  In addition,  the  l o n g e r and h e a v i e r t h a n  f o r the duration  o f the study  (Appendix 1,2).  Gonadal  development  was  first  observed  among  the  i n c i d e n t a l m o r t a l i t i e s from t h e 15°C group on June 7, 1989, and from t h e 9°C group on J u l y 2.9%  t o 8.5% i n t h e c o l d  19, 1989.  water mature  13.6% i n t h e warm w a t e r mature males. males was l e s s t h a n 0.5%.  GSI ranged from  males  GSI f o r a l l  varied  observation  i s subjective.  immature  E x t e r n a l d a r k e n i n g was apparent  i n some, b u t n o t a l l o f t h e p r e c o c i o u s males. darkening  and 1.4% t o  individually,  and  The degree o f  therefore  A l l o f t h e female t r o u t  immature a t t h e end o f t h e s t u d y .  this were  35  June 250 MMATURE  200 150 100  50 0  1  MATURE  ii  i III  Is i i  40  80  Weight (g)  120  August 250 MMATURE  200 150 100  50 0  1  MATURE  iii  lists 40  Weight (g)  120  F i g u r e 6. Frequency d i s t r i b u t i o n o f w e i g h t i n male rainbow t r o u t r e a r e d a t 9oC i n June and August 1989.  June M/ATURE MATURE  August 175| MMATURE  150  MATURE  125 100 75 50 251  1 ^ ^ ^ BP ^1  50  ffl  tjt  100 Weight (g)  tJLjJLfL^jqL^jm  150  200  g u r e 7. F r e q u e n c y d i s t r i b u t i o n o f w e i g h t i n male t r o u t r e a r e d a t 15oC i n J u n e and A u g u s t 1989.  rainbow  37  Coho Salmon Study  The mature coho males had a s i g n i f i c a n t l y h i g h e r growth r a t e  specific  t h a n t h e immature males a t each sample  from t h e s t a r t o f t h e study March 22nd t o J u l y 1 0 t h . and  immature  males  had  equal  specific  sample d a t e s J u l y 31 and September 9.  growth  date  Mature  rates  for  However, by t h e end  o f s t u d y November 30, t h e immature males had a s i g n i f i c a n t l y higher  specific  growth r a t e t h a n t h e mature males  (Figure  8) .  S p e c i f i c growth r a t e f o r female f i s h was e q u a l t o t h a t o f t h e immature males a t each sample date f o r t h e d u r a t i o n o f the  study.  A l l females were  immature - a t t h e end o f t h e  study.  The  pooled  relationships  monthly  value  for  gave a r e g r e s s i o n  slope  the  length-weight  o f 2.027  (Table 2 ) .  T h i s v a l u e was used f o r c a l c u l a t i n g coho c o n d i t i o n  factors.  C o n d i t i o n f a c t o r among males was e q u a l a t t h e b e g i n n i n g t h e s t u d y on March 22nd.  of  From t h e next sample date t o t h e  end o f t h e s t u d y , t h e c o n d i t i o n f a c t o r o f m a t u r i n g males was significantly (Figure 9).  greater  relative  to that  o f immature  males  38  2.0  T  Q_  in  -1.0 4  1 Mar  1  1  1  h  1  1  1  r—  Apr May June July Aug Sept Oct Nov  F i g u r e 8. Mean s p e c i f i c growth r a t e s (%g/d) +/- 1 S.E. o f mature and immature male coho salmon. * indicates s i g n i f i c a n t d i f f e r e n c e s between means at each sample p o i n t (P< 0.05).  39  Mar  Apr  May June July Aug Sept Nov Dec  F i g u r e 9. C o n d i t i o n f a c t o r +/- 1 S.E. of mature and immature male coho salmon. The mature males had a s i g n i f i c a n t l y h i g h e r mean c o n d i t i o n f a c t o r than the immature males (P< 0.05) from A p r i l 20, 1989 t o the end of the study.  40  The  weight/frequency  duration were  o f t h e study  significantly  p r e c o c i o u s males  Gonadal  mature for  males  immature  the maturing the  study.  (Figure  longer  and  was  first  on J u l y . 31, 1989. was  10) .  overlapped The  heavier  g r e a t e r than  males. males.  External  observed  f o r the  precocious than  f o r the d u r a t i o n o f the study  development  mortalities  distribution  the  Gonadosomatic index  incidental (GSI)  4.3%. GSI was  less  darkening  variable  A l l females  non-  (Appendix 3 ) .  among  was  males  than  for  0.6% among  were immature a t t h e e n d o f  41  July 301 MMATURE MATURE  201  10  100 Weight  50  150  November 30 MMATURE MATURE  20  10  S 50  i l i i i 100 Weight (g)  F i g u r e 10. Frequency d i s t r i b u t i o n J u l y and November, 1989.  150  o f male coho salmon i n  42  Growth Hormone Analyses Inter-assay hormone  variation  measurements  i n the mean p o o l e d  and  i n the  position  curves made p o o l i n g data from i n d i v i d u a l Further,  the d e t e c t i o n l i m i t s  plasma  o f the  growth  standard  assays i m p o s s i b l e .  of each assay run v a r i e d ,  and  most o f the samples f e l l below those d e t e c t i o n l i m i t s  (Assay  #1,  24/41  < 1.5  Assay  #3,  87/98  <  limits The  were  ng/ml;  4.0  Assay #2,  ng/ml).  between  interpretation  1.9  The ng/ml  o f the data  36/56 < 3.0  ng/ml;  samples  above  the  and  ng/ml  (Table  20  i s limited  detection 3a-c).  due t o the  number o f samples below the d e t e c t i o n l i m i t s t h a t  large  c o u l d not  be i n c l u d e d i n the a n a l y s e s .  The  plasma  detection No  growth  limits  correlation  hormone  were e v a l u a t e d between  plasma  measurements separately growth  s p e c i f i c growth r a t e was e s t a b l i s h e d . measurements by  level. each  had no Small  sample  significant between  the  f o r each assay.  hormone  level  and  Plasma growth hormone  f o r the 3 sample dates were p o o l e d and grouped  sex and male  factors  above  maturation significant  sample  date.  difference  sample d a t e s .  effect  size With  status  t o determine t h a t  on plasma growth hormone  prevented both  in  these  comparisons f o r  sexes pooled,  plasma  these  growth  there hormone  was  no  level  43  Table 3a. Coho salmon growth hormone assay r e s u l t s f o r assay #1. Mean plasma sGH l e v e l , s t d . dev., range and sample s i z e f o r mature males, immature males and females i n May, June and September. Detection l i m i t of the assay was 1.5 ng/ml. May  Mean sGH (ng/ml)  Std Dev.  Range  n  n below detection limits  Mature Males  3.60  2.97  1 .5 -  5. 7  2  1  Immature Males  6.05  1.89  3 .9 -  7. 6  3  2  Females  6.44  8.44  2 .0 - 19. 0  4  3  Range  n  n below detection limits  -  0  2  2  2  3  .6  June  Mean sGH (ng/ml) -  Mature Males  Std Dev.  -  Immature Males  4 .75  4 .10  1 .8 -  Females  6.83  5.30  2 .0 - 12. 5,  September  Mean sGH (ng/ml)  -.  Mature Males Immature Males  Std Dev.  -  15.75  6.01  5.5  0.42  Females Pooled Plasma =5.6  ng/ml  7. 6  n  Range  n below detection limits  -  0  o  11 .5 - 20. 0  2  4  2  4  5 .2 -  5. 8  44  Table 3b. Coho salmon growth hormone assay r e s u l t s f o r assay #2. Mean plasma sGH l e v e l , s t d . dev., range and sample s i z e f o r mature males, immature males and females i n May, June and September. Detection l i m i t of t h e assay was 3.0 ng/ml. May  Mature Males  Mean sGH Std Dev. (ng/ml)  -  Range  n  n below detection limits  -  0  3  Immature Males  4.87  2.52  3.05 - 10 .5  8  2  Females  6. 63  4. 77  3.25 - 10 .0  2  . 4  Std Dev.  Range  n  n below detection limits  1  2  1  8  1  6  n  n below detection limits  June  Mean sGH (ng/ml)  Mature Males  3.2  Immature Males  5.0  Females  5.6  September  Mature Males  Mean sGH (ng/ml)  Std Dev.  Range  8.8  1.70  7.6 - 10 . 0  2  1  Immature Males  10.13  2 .90  6.9 - 12 .5  3  6  Females  10.37  6. 18  3.4 - 15 .2  3  4  Pooled Plasma = 5.6 ng/ml  45  Table 3c. Coho salmon growth hormone assay r e s u l t s f o r assay #3. Mean plasma sGH l e v e l , s t d . dev., range and sample s i z e f o r mature males, immature males and females i n May, June and September. D e t e c t i o n l i m i t o f t h e assay was 3.0 ng/ml. May  Mean sGH (ng/ml)  Std  Dev.  Range  n  n below detection limits  -  0  5  Mature Males  -  Immature Males  -  -  -  0  15  9.2  -  -  1  10  Range  n  -  0  6  2  16  -  1  12  Range  n  Females June  Mature Males Immature Males Females September  Mean sGH (ng/ml)  .  -  Std  Dev.  -.  -  4 .75  0.49  17.50 Mean sGH (ng/ml)  -  Std  Dev.  Mature Males  9.3  5.94  Immature Males  6.8  -  Females  6.93  2.35  P o o l e d Plasma = 3.7 ng/ml  4 .4 -  5. 1  5 .1 - 13. 5 -  4 .3 -  9. 1  n below detection limits  n below detection limits  2  3  . 1  12  4  8  46  DISCUSSION  W h i l e many s t u d i e s o f w i l d and h a t c h e r y - r e a r e d s a l m o n i d s have found a p o s i t i v e  c o r r e l a t i o n between  h i g h growth  rate  and p r e c o c i o u s m a t u r a t i o n (Table 1 ) , t h e r e has not been any study t h a t c r i t i c a l l y d e s c r i b e s t h e s p e c i f i c growth p a t t e r n o f p r e c o c i o u s l y m a t u r i n g rainbow t r o u t and coho salmon. a r e c e n t paper by Rowe and Thorpe  (1990a) t h e growth p a t t e r n  o f i n d i v i d u a l l y marked p r e c o c i o u s l y m a t u r i n g A t l a n t i c parr  was d e s c r i b e d .  In  I t i s interesting  t o note  growth p a t t e r n t h e y d e s c r i b e w i t h A t l a n t i c  salmon  salmon  that the from t h e  genus Salmo concur w i t h t h e f i n d i n g s o f t h i s s t u d y w i t h coho salmon and rainbow t r o u t from t h e genus  Oncorhynchus.  In t h i s s t u d y , t h e s p e c i f i c growth rate" f o r p r e c o c i o u s l y mature the This  male rainbow t r o u t and coho  immature  males  agrees w i t h  with A t l a n t i c not  found  during  a  the spring  the findings  salmon.  salmon was g r e a t e r than and summer  months.  o f Rowe and Thorpe  (1990b)  C o n v e r s e l y , some o t h e r s t u d i e s have  positive  correlation  between  m a t u r a t i o n and growth r a t e i n A t l a n t i c salmon 1980;  Naevdal  present salmon  study,  e t a l . , 1978; and G j e r d e , specific  and rainbow  trout  growth were  rates  precocious  (Glebe e t a l . ,  1984).  In the  among m a t u r i n g  coho  comparatively greater  than  47  t h o s e o f immature males d u r i n g t h e s p r i n g months, s i m i l a r t o immature males d u r i n g August, and by  the  end  of  September.  l e s s than  Rowe  and  immature males  Thorpe  (1990a)  and  Saunders e t a l . (1982) have a l s o r e c o r d e d t h e same p a t t e r n of  faster  initial  growth f o l l o w e d by  i n autumn among m a t u r i n g A t l a n t i c the  correlation  maturation period,  between  appears  and  may  to  be  be  decreased  growth r a t e  salmon p a r r .  Therefore,  growth  rate  dependant  upon  non-existant  or  e x t e r n a l i n d i c a t o r s o f m a t u r a t i o n are  The  use  study.  o f PIT  t a g s was  This enabled  critical  a critical  and a  precocious  specific  negative  by  time  the  time  to the design of  this  apparent.  description  of the  growth  p a t t e r n o f p r e c o c i o u s l y m a t u r i n g f i s h on an i n d i v i d u a l b a s i s when m a t u r a t i o n was  not  evident.  In t h i s  way,  the  growth  p a t t e r n o f i n d i v i d u a l s c o u l d be r e c o r d e d on a r e g u l a r b a s i s and  the  sexual  status of  e v a l u a t e d at a l a t e r d a t e . i n rainbow  c o u l d be  examination were  of the  fish  could  study.  easily  read  A l s o , i t was i n order  l a r g e number o f f i s h  required for this  be  In a d d i t i o n , t h e t a g s were used E x t e r n a l tags  t o t h e r i s k o f t a g l o s s over t h e  month d u r a t i o n o f t h e tags  individual  t r o u t t h a t weighed l e s s than 5 g.  c o u l d not be used due  the  those  study.  This  to  necessary facilitate  (Appendix  number o f  8-9 that the  1)  that  fish  were  48  n e c e s s a r y because the r a t e o f p r e c o c i o u s m o r t a l i t i e s associated with It  was  more  involved  in  efficient the  study  frequent  to  increase  than  i s was  m a t u r a t i o n and  s a m p l i n g were unknown. the to  experiment i f the number of p r e c o c i o u s  i s possible  among m a t u r i n g endogenous anabolic  that  males  the  conditions. and  increasing  will  feed  the  Some  increase  intake  weight  and  (Donaldson e t a l . , 1979).  steroid  entire  study.  growth  rate  i s maintained  by  hormones  can  be  fish  by  gains  improving  fish  insufficient  higher  spring  of  the  f i s h was  relatively  during  number  repeat  f o r s t a t i s t i c a l a n a l y s i s at the end o f the  It  the  in  feed  utilization  Hunt e t al.. (1982) r e c o r d e d s m a l l  peaks i n plasma t e s t o s t e r o n e  concentration  i n February-March  i n A t l a n t i c salmon t h a t matured i n the f o l l o w i n g autumn, but no  increased  Therefore,  elevations  responsible s p r i n g and  As  for  during  in  those in  androgen  maintaining  maturation progresses,  of  fish  the  that  did  not  mature.  concentration  increased  may  growth  be  during  summer among p r e c o c i o u s l y m a t u r i n g males.  concentration levels  levels  may  n e g a t i v e l y i n f l u e n c e growth r a t e .  androgens  maturation  f u r t h e r e l e v a t i o n s o f androgen  were  i n the  suspected  platyfish,  of  retarding  Xiphophorus  Higher growth  maculatus,  49  (Schreibman of  mature  declines  and K a l l m a n , males  at  Thorpe,  (1990a)  maturing  Atlantic  the  fall  salmon  rate  observed  in this  increased 9°C  to  gonadal  similar growth  rate  of  to  18%  in  males  those  and  reduce  rate  by  of  energy  and  appetite  time.  that  in this  Similarly,  and coho  salmon due  or b o t h .  sources  from  may have  elevated  to In  somatic  played  the  not  of  a  role  effecting  of  from  able  for  on  subsequently gonads  11% i n  findings to  warmer w a t e r faster  the acts via  upon t h e  are  trout  influences  growth  associated  an a f f e c t  pituitary  the  promote  rainbow  T e m p e r a t u r e may h a v e  acting  the  spawning  the  temperature  These  who was  known i f  independent  either  maturation  (1975)  time  is  water  15°C water.  Titarev  It  gonadotropin which directly  in  s t u d y may a l s o h a v e b e e n  precocious  w i t h warmer t e m p e r a t u r e s . maturation  males  Rowe  suggested  that  development  the  of  by 1 y e a r .  maturation  reduction  at  growth  immature  maturation.  and t h e y  study,  the  to  the  rate.  present  water  and  and r e d u c e d a p p e t i t e ,  reallocation  r e d u c e d growth  the  autumn  fish,  among r a i n b o w t r o u t  the  growth  these  of  h i g h androgen l e v e l s  addition,  In  time  parr  androgen l e v e l s  in  females  an  increased  tissue  to  the  found  r e d u c e d growth  i n the  In  relative  sharply  may be due t o  1977).  to  gonads,  steroidogenic  on  produce or  by  enzymes  50  (Kime,  1979).  improved  However,  growth  maturation  rates  trout  r a t e has r e s u l t e d  rate  independant  (McCormick and Naiman, improved  i n brook  growth  rate w i l l  temperature  Therefore,  result  fontinalis)  i n increased precocious  of  1984).  (S.  increase.  i t appears t h a t  i n increased  r e g a r d l e s s o f t h e endogenous e f f e c t s  of  maturation temperature  d e s c r i b e d above.  The and  maturing  occupied  f i s h were s i g n i f i c a n t l y h e a v i e r and l o n g e r the  upper  mode  of  distribution  f o r the entire  distribution  of lengths  and w e i g h t s  mature  overlapped  f o r the duration  fish  study.  t h e weight  frequency  However, t h e f r e q u e n c y f o r mature  and non-  of the  study.  T h e r e f o r e , i t appears t h a t a l t h o u g h a c e r t a i n s i z e t h r e s h o l d is  necessary,  size  alone  cannot  be a s u f f i c i e n t c o n d i t i o n  f o r maturation t o proceed.  In  the present  work,  growth r a t e among m a t u r i n g  the pattern fish  of higher  relative  specific  t o immature  fish  d u r i n g s p r i n g and summer was e v i d e n t i n t h e coho study and for  both  This  pattern  (Figure start  temperature  11) . both  also  regimes  i n t h e rainbow  coincides  Changes  with  i n photoperiod  vitellogenesis  and  trout  study.  increasing  daylength  cue a d u l t  salmon t o  spermatogenesis  (Billard,  24  "i  30  Figure  11.  i — i — i — i — i — i — i — i — i — i — r  60  Daylength  90  120  150  i n hours  180  210  TME  (d)  at  49°  240  270  300  latitude  330  360  (List,  1966)  52  start  both  1983).  vitellogenesis If  maturation  the  at  and  spermatogenesis  environmental  any  age  are  (Billard,  mechanisms  similar,  initiating  then  changes  in  p h o t o p e r i o d would a l s o cue p r e c o c i o u s m a t u r a t i o n .  Photoperiod  may  also  maturation process. is  positively  al.,  play  an  additional  role  i n the  S e v e r a l authors have noted t h a t  influenced  by i n c r e a s i n g  daylength  growth  (Gross e t  1965/ Saunders and Henderson, 1970; Komourdjian e t a l . ,  1976) .  Therefore,  provide  the f i s h  increasing  with  may p l a y a secondary  photoperiod  a cue f o r maturation  role  may  not  only  t o occur, but  i n p r e c o c i o u s m a t u r a t i o n v i a the  mechanisms a s s o c i a t e d with i n c r e a s e d growth r a t e .  In t h i s study, c o n d i t i o n f a c t o r was s i g n i f i c a n t l y g r e a t e r i n maturing of  March  factor  during  et  Thorpe, be  the  maturing  has  Atlantic  Comparatively  r e l a t e d t o gonadal  before  spring  a l . , 1982; Johnston 1990a).  however,  and coho salmon from t h e end  t o t h e end o f t h e study.  precociously Hunt  male rainbow t r o u t  also salmon  been  condition  found  among  ( L e y z e r o v i c h 1973;  e t a l . 1987; and Rowe and greater condition  f a c t o r may  development d u r i n g t h e summer months,  the d i f f e r e n c e  gonadal  Increased  observed  development  was  i n March  first  occurred  observed  long  i n June and  53  July.  Condition  factor  has  been  shown  to  be  directly  r e l a t e d t o f a t content o f A t l a n t i c salmon p a r r d u r i n g  spring  months  fat i s  the  (Pinder and E a l e s ,  primary  sockeye  salmon  Therefore, spring  determinant (Parker  the  1969). of  condition  and  increase  condition  i n body  an  energy  essential  costs  internal  o f maturation  during  the  Thorpe  (1990b).  and  maturation  in  fat. store  offset process  factor  study  to  a reduction  1970).  during  T h i s body needed  as  immature  Groves,  observed i n t h i s  r e l a t e d t o an i n c r e a s e  body  factor  Vanstone,1966;  in  among maturing males  In a d d i t i o n ,  the  may  be  f a t may  be  support  i n food  suggested by  the  intake  Rowe  and  However, i n order t o make any q u a n t i t i a t i v e  assessment  concerning the r o l e  maturation  among salmon  of f a t s t o r e s  and t r o u t ,  they  i n precocious  s h o u l d be  measured  directly.  Hypophysectomy  1967)  and  supplemental growth hormone experiments (Down e t a l . ,  1989)  have  (Donaldson  established  component  to  dependant  growth  that  growth  growth  and  McBride,  hormone  i n salmonids.  is  In a d d i t i o n ,  response t o exogenous  growth  been demonstrated s e v e r a l times (Down e t a l . , al.,  1978).  The  growth hormone RIAs  development  and  a  necessary a dose-  hormone  has  1988; Higgs et  validation  of  salmonid  (Bolton e t a l . 1986; Wagner and Mckeown,  54  198 6)  has  endogenous  l e d to several growth  hormone  r e l a t i o n s h i p between  investigations in fish.  of the r o l e  In s p i t e  of t h i s ,  t h e l e v e l s o f endogenous plasma  hormone and growth has n o t been e s t a b l i s h e d .  of a  growth  T h i s may  stem  from t h e c o m p l e x i t y o f growth and t h e n a t u r e and f u n c t i o n o f growth hormone i t s e l f .  The r e s u l t s  study  d i d not  o f t h e growth  assays  i n this  between  growth hormone and growth, sex, o r m a t u r a t i o n .  l a r g e number o f samples  falling  establish  a  hormone  relationship  below t h e d e t e c t i o n  The  limits  o f t h e assay b r i n g s q u e s t i o n t o t h e v a l i d i t y o f t h e r e s u l t s . The plasma growth hormone l e v e l s f o r coho salmon r e p o r t e d i n the  literature  1989; coho  Sweeting obtained  range  from 4 t o 450 ng/ml  and McKeown,  1987) .  this  a t t h e West Vancouver  s t u d y appear  radioisotope  laboratory  amount  amount  of  into  10%)  t h e hormone.  unlabelled  using the  lower.  During the  o f t h e growth hormone, o n l y a s m a l l  (approximately  incorporated  al.,  The r e s u l t s o b t a i n e d  t o be g e n e r a l l y  labelling  et  Previous results f o r  same assay ranged from 2 t o 100 ng/ml. in  (Clarke  hormone  of  the  radioisotope  was  The p r e s e n c e o f t h e l a r g e in  the  assay  may  have  i n t e r f e r r e d w i t h t h e p r o p o r t i o n o f l a b e l l e d and n o n - l a b e l l e d a n t i b o d y b i n d i n g d u r i n g t h e assay, r e s u l t i n g i n fewer sample growth hormone m o l e c u l e s b i n d i n g t o t h e a n t i b o d y t h a n would n o r m a l l y be e x p e c t e d .  I n a d d i t i o n , t h e 12 t o 15 months c o l d  55  storage  may have r e s u l t e d i n t h e d e t e r i o r a t i o n o f t h e growth  hormone w i t h i n t h e plasma samples.  Conclusions  The  and F i s h C u l t u r e  most  significant  Implications  finding  from  this  study  i s the  p a t t e r n o f r e l a t i v e i n c r e a s e d growth r a t e among p r e c o c i o u s l y m a t u r i n g rainbow t r o u t and coho salmon d u r i n g t h e s p r i n g and early  summer, f o l l o w e d by a d e c r e a s e i n growth r a t e  t h e l a t e summer and e a r l y f a l l .  during  T h i s p a t t e r n was e v i d e n t i n  t h e rainbow t r o u t grown under two t e m p e r a t u r e regimes and i n the  coho  salmon.  Therefore,  restriction  of  rate  reduce  number  the  growth of  i t is  during  fish  possible  the  maturing  early  that  the  spring  may  precociously.  In  a d d i t i o n , i f growth i s slowed by r e s t r i c t i n g f e e d i n such a way t h a t compensatory growth mechanisms a r e a c t i v a t e d , t h e n , reduced  feed  intake  for a  short  necessarily r e s u l t i n a smaller method  has  been  used  period  fish  successfully  of time w i l l  (Quinton, to  reduce  m a t u r a t i o n i n A t l a n t i c salmon  (Rowe and Thorpe,  requires  Pacific  trout.  further  study  with  salmon  1989).  not This  precocious 1990b), but and  rainbow  56  Conversely, also  be  the  useful  promotion  in  been  used  precocious  as  a  treatment  genotypic  females  1986) . males  If to  spawn  may  have linked  coho  salmon,  known.  to the  the  The  consequences  i n v o l v e s the  males  induce the  use  to  of of  cause  (Donaldson,  these  costs  that  Myers  lipids  of  phenotypic maintaining  the  et  initiation  al.,  i n commercial  1986).  direct  biological  The  affected the  fish  by  method  feed  may  maturation.  indicate  systems  of  of f a t reserves  Consequently,  maturation  the  hormonal  stocks  accumulation  1982).  of  however,  all-female  i s most s i g n i f i c a n t l y  study  determinant  influences not  of t h i s  rarely  c o u l d be e l i m i n a t e d .  promote p r e c o c i o u s  results  important  could  may  salmonids  the  as p h e n o t y p i c  1986;  with  maturation  differentiation  speculated  (Watanabe,  of r e p l a c i n g p r o t e i n  The  sex  year  o f body l i p i d s  inadvertently  avoid  technique  growth  (Thorpe,  lipids  to  p r e c o c i o u s l y , then  be  spring  composition dietary  during  to develop  authors  maturation  This  additional  Several  Female  production of  technique  improved  them f o r an  during  the  maturation.  androgen  precocious  aquaculture.  m a t u r e p r e c o c i o u s l y and has  of  that in  growth r a t e rainbow  pathway  by  controlling property  i s an  trout  which  growth  maturation triggering  and  is the  57  maturation factor reserves are  process  strongly  involved,  several  not  be  growth  correlated  to  growth  or l i p i d and  may  storage. that  physiological  initiated.  itself, rate  It is likely it  may  thresholds  be  but  such  another  as  energy  that other  factors  necessary before  to  achieve  maturation  is  58  REFERENCES  Alcock,  J.  1979.  variation  The  among  Hemipepsis  G.  1959.  fishes.  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Biochem.  78  Wootton, R.  1973. The e f f e c t o f s i z e o f f o o d r a t i o n on egg  production: Gasterosteus  The  female  aculeatus.  three-spined  stickleback,  J . F i s h B i o l . 5: 89-96.  Zar, J.H. 1984. B i o s t a t i s t i c a l a n a l y s i s . P r e n t i c e - H a l l I n c . , Englewood C l i f f s , N.J. 718 pp.  79  Appendix 1: Mean weight ( g ) , l e n g t h , and sample s i z e , by sample d a t e f o r mature and immature rainbow t r o u t males r e a r e d a t 9oC. The mature males had a s i g n i f i c a n t l y g r e a t e r mean w e i g h t and mean l e n g t h t h a n t h e immature males (P< 0.05) f o r t h e d u r a t i o n of t h e s t u d y . Date  Mature n  wt (g)  Immature s t d dev.  n  wt. (g)  s t d dev.  i  Jan. Feb Feb. Mar. Mar. Apr. Apr. May May June June July July Aug. Aug. Aug. Sept  24-27 7/8 21/22 14 29 12 25 9 23 6 20 4 20 1 15 31 .28  104 103 104 89 101 102 102 102 102 100 102 102 102 101 101 101 35  Date  Jan. 24-27 Feb 7/8 Feb. 21/22 Mar. 14 Mar. 29 Apr. 12 Apr. 25 9 May May 23 June 6 June 20 July 4 J u l y 20 1 Aug. Aug. 15 Aug. 31 Sept .28  7.5 7.5 8.8 10.4 13.4 16.0 20.1 25.0 29.5 33.9 39.5 44.6 49.4 47.7 48.8 49.5 72 .2  2.49 2.50 3.02 4.05 5.31 6.29 8.08 9.82 11.41 13.01 14.59 16.35 18.24 17. 63 17.84 18.61 22 .72  Mature n  len(mm)  104 103 104 89 101 102 102 102 102 100 102 102 102 101 101 101 35  89.2 89.7 93.5 99.8 106.1 111.3 118.4 127.2 134.2 139.5 146.2 154.1 160.4 161.5 163.8 167.2 182.3  362 358 362 328 359 362 362 360 360 361 360 361 361 358 360 359 121  4.8 4.8 5.4 6.3 . 7.7 8.9 10.5 12.7 14.4 16.5 19.0 21.4 23. 6 22.8 23.8 24.2 34.7  1.75 1.69 2.00 2.42 3.08 3.58 4.37 5.39 6.26 7.33 8.57 9.88 11.46 11.03 11.70 11.96 18.27  n  len(mm)  s t d dev  362 358 362 328 359 362 362 360 360 361 360 361 361 358 360 359 121  76.1 77.0 7 9.3 83.7 88.7 93.2 97.8 103.3 108.7 112.9 117.8 124.0 129.0 129. 9 132.1 134 . 6 155.5  9.45 9.45 9. 95 10.96 11.52 12.15 13.02 14.77 15.02 15. 97 17.10 18.32 19.44 19.79 22.06 20.90 23.21  Immature s t d dev. 9.42 12. 64 10.31 12.35 13.00 16.73 17.31 15 .44 16.14 16.59 17.24 17.73 18.22 18.41 18.67 19.07 17.38  80  A p p e n d i x 2: M e a n w e i g h t ( g ) , l e n g t h , a n d s a m p l e s i z e , b y sample d a t e f o r mature and immature r a i n b o w t r o u t males r e a r e d a t 15oC. The mature males h a d a s i g n i f i c a n t l y g r e a t e r mean w e i g h t a n d mean l e n g t h t h a n t h e i m m a t u r e m a l e s (P< 0.05) f o r t h e d u r a t i o n o f t h e s t u d y .  Date  Mature n  Jan. Feb. Feb. Mar. Mar. Apr. Apr. May May June June July July Aug. Aug. Sept. Sept.  24-27 7/8 21/22 15 28 11 26 10 24 7 21 5 19 2 16 1 28  158 161 160 158 158 158 157 158 158 158 158 158 153 150 150 148 55  Date  J a n . 24-27 F e b . 7/8 F e b . 21/22 M a r . 15 M a r . 28 A p r . 11 A p r . 26 May 10 May 24 7 June J u n e 21 July 5 J u l y 19 Aug. 2 A u g . 16 Sept . 1 S e p t .28  .  wt  (g)  6.4 6.6 7.6 9.0 13.3 16.1 20.5 26.4 31.1 35. 6 41.3 50.7 61.0 62. 6 69.0 64.1 72.2  Immature s t d dev.  n  3.38 2.48 3.07 3.52 5.22 6.47 8.96 11.32 13.26 15.35 17.80 22.04 27.54 28.03 30.97 32.99 22.72  252 249 253 252 252 252 252 252 251 251 250 245 245 237 236 235 65  Mature n  len(mm)  158 161 160 158 158 158 157 158 158 158 158 158 153 150 150 148 55  84.5 86.0 88.7 93.8 103.9 110.8 119.0 128.2 134.9 141.0 147.9 156.2 164.3 168.8 174.5 173.2 182.3  wt  (g)  4.6 4.6 5.2 6.0 8.8 10.4 12.5 15. 6 17.6 19.5 21.8 26.1 30.4 29.7 33.0 34.7 34.7  s t ddev.  1.82 1.92 2.13 2.42 3.61 4.38 5.46 7.07 8.20 9.18 10.37 12.34 16.34 14.49 17 .74 17.19 18.27  Immature std  dev.  10.35 10.23 11.02 11.82 13.05 14.09 15.57 16.82 17.85 18.91 20.08 21.14 22.87 23.41 25.11 28.29 17.38  n  l e n (mm)  252 249 253 252 252 252 252 252 251 251 250 245 245 237 236 235 65  75.5 75.8 78.0 82.1 90.7 96.4 102 .1 108.9 113.9 117.9 122.4 129.4 134.1 137.2 139.5 145.4 144.5  std  de  1  9.53 10.41 10.38 10.70 12.10 13.00 13 . 88 15.23 16.29 17.15 19.50 19.05 20.18 2 1 . 01 26.68 22.48 23.21  81 A p p e n d i x 3: Mean w e i g h t ( g ) , l e n g t h , and sample s i z e , by sample d a t e f o r m a t u r e and immature coho s a l m o n m a l e s . The m a t u r e m a l e s h a d a s i g n i f i c a n t l y g r e a t e r mean w e i g h t and mean l e n g t h t h a n t h e immature m a l e s (P< 0.05) f o r t h e duration of the study.  Date  Mature _n  Mar. 22 Mar. 31 A p r . 21 May 15 May 25/26 J u l y 10 J u l y 31 Sept. 9 Nov. 30  18 4 22 22 22 22 24 19 17  Date  (g) s t d d e v .  27 . 9 25.4 31.3 41.8 45. 9 86.2 100.6 122.0 95.0  5. 42 3. 20 6. 37 10. 67 12. 79 23. 22 23. 51 35. 23 28. 19  Mature n  Mar. 22 Mar. 31 A p r . 21 May 15 May 25/26 . J u l y 10 J u l y 31 Sept. 9 Nov. 30  wt  Immature  18 4 22 22 22 22 24 19 17  wt  (g)  24.1 25.2 26.0 30.7 32.9 45.7 51.9 68.8 70.0  70 12 77 82 83 83 85 66 60  s t d dev. 3. 97 3. 75 4 .88 7 . 68 8. 45 13. 70 16. 42 22. 54 31. 06  Immature  len(mm) s t d 134 . 6 132.8 14 0.4 152.7 161.5 189.9 198.2 211. 6 211.2  n  dev.  7.58 4.19 7.62 9.35 10 . 95 12.32 12.79 16.38 17.09  n 69 12 77 82 83 83 85 66 60  len(mm) 12 8.1 129.7 131.4 139.0 144 .1 161.1 166. 8 176.5 186.7  std  de-  6.75 7.69 7.89 10.03 21. 68 13. 62 14.29 26.06 24.04  

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