UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

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

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1991_A6_7 L36.pdf [ 3.5MB ]
Metadata
JSON: 831-1.0098584.json
JSON-LD: 831-1.0098584-ld.json
RDF/XML (Pretty): 831-1.0098584-rdf.xml
RDF/JSON: 831-1.0098584-rdf.json
Turtle: 831-1.0098584-turtle.txt
N-Triples: 831-1.0098584-rdf-ntriples.txt
Original Record: 831-1.0098584-source.json
Full Text
831-1.0098584-fulltext.txt
Citation
831-1.0098584.ris

Full Text

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. (Biology) Simon Fraser 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 i n THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF ANIMAL SCIENCE) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH December, 1990. (c) Carole A. Lamont, COLUMBIA 1990. In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying 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 trout {Oncorhynchus mykiss) and coho salmon (0. kisutch) produce males which mature at an abnormally early age. The objectives of t h i s study were to c r i t i c a l l y describe the role of growth rate i n early sexual maturation of male salmonids by monitoring growth rate and precocious sexual 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 f i s h . Underyearling rainbow trout were i n d i v i d u a l l y i d e n t i f i e d using coded tags. These f i s h were reared at 9°C and 15°C and growth was monitored twice a month i n both groups over a 9 month period s t a r t i n g January 24, 1989. The number of precocious 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, reared at ambient temperature, and monitored for growth over an 8 month period s t a r t i n g March 22nd, 1989. Ten percent of the coho salmon matured precociously. In both experiments there was a s i m i l a r r e l a t i o n s h i p between fast growth i n early spring and precocious maturation. The growth rate of f i s h that matured declined i n autumn r e l a t i v e to non-maturing i n d i v i d u a l s . Condition factor (length to weight relationship) was greater among those f i s h that matured i i i precociously. . Plasma growth hormone was monitored i n the coho salmon. Most samples f e l l below the detection l i m i t s of the assay (1.5. to 3.0 ng/ml). A strategy to reduce the number of precocious males i n cultured salmonids i s suggested. TABLE OF CONTENTS ABSTRACT i i L I S T OF TABLES i v L I S T OF FIGURES v ACKNOWLEDGEMENTS. . v i INTRODUCTION . 1 MATERIALS AND METHODS F i s h S t o c k s and C u l t u r e C o n d i t i o n s . . . . . 15 Coho Salmon Growth Hormone S t u d y 18 Ra d i o i m m u n o a s s a y P r o c e d u r e s 19 D a t a C o l l e c t i o n a nd A n a l y s i s 23 Salmon Growth Hormone A n a l y s i s 25 RESULTS Rainbow T r o u t S t u d y 2 6 Coho Salmon S t u d y 37 Growth Hormone A n a l y s i s 42 DISCUSSION 4 6 C o n c l u s i o n s and F i s h C u l t u r e I m p l i c a t i o n s 55 REFERENCES.... 58 APPENDICES A p p e n d i x 1: Mean w e i g h t , l e n g t h , and sample s i z e , by sample d a t e f o r mat u r e and immature r a i n b o w t r o u t m a l e s r e a r e d a t 9 ° C . 7 9 A p p e n d i x 2: Mean w e i g h t , l e n g t h , and sample s i z e , by sample d a t e f o r mat u r e and immature r a i n b o w t r o u t m a l e s r e a r e d 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 , 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 81 LIST 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 of growth rate and maturation i n salmonids... Table 2 . Pooled length-weight relationships of male rainbow trout and coho salmon Table 3 . Mean plasma growth hormone leve l s (ng/ml), standard deviation, and range for immature male, mature male, and female coho salmon i n May, June, and September for each assay V LIST OF FIGURES F i g u r e 1. The e f f e c t o f temperature on p r e c o c i o u s m a t u r a t i o n . Mean weight (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 at 9°C and 15°C. The 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 weight (P<0.05) from March 28th, 198 9 t o the end of the study...... 27 F i g u r e 2. Mean s p e c i f i c growth r a t e s (%g/d) +/- 1 S.E. of male rainbow t r o u t r e a r e d at 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 growth r a t e s (%g/d) +/- 1 S.E. of 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 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 of mature and immmature rainbow t r o u t r e a r e d at 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 c o n d i t i o n f a c t o r (P< 0.05) from March 28th, 1989 t o the end of the study....... 32 F i g u r e 5. C o n d i t i o n f a c t o r of mature and immmature rainbow t r o u t r e a r e d at 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 c o n d i t i o n f a c t o r (P< 0.05) from March 28th, 1989 to the end of the study 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 rainbow t r o u t r e a r e d at 9°C i n June and August, 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 rainbow t r o u t r e a r e d at 15°C i n June and August, 198 9 36 F i g u r e 8. Mean s p e c i f i c growth r a t e s (%g/d) of mature and immature male coho salmon. * 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 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 c o n d i t i o n f a c t o r (P< 0.05) from A p r i l 20, 198 9 t o the end of the study 3 9 F i g u r e 10. Frequency d i s t r i b u t i o n of weight i n male coho salmon i n J u l y and November, 198 9 41 F i g u r e 11. Daylength i n hours at 49° l a t i t u d e . 51 v i ACKNOWLEDGEMENTS F i r s t and foremost, I wish to thank Scott J. Smith for i n s p i r i n g me to pursue t h i s degree, and for his continuous support and encouragement over the past 2 years. t I would also l i k e to thank my graduate studies supervisor, Dr. George Iwama, and my advisory committee, Dr. Ed Donaldson, Dr. Ted Down and Dr. R. Ra jamahendran for t h e i r guidance and assistance. I sincerely thank the s t a f f of the Fish Culture Research Section at the West Vancouver Laboratory, e s p e c i a l l y Helen Dye, whose committment to the coho salmon study ensured that i t ran smoothly. I would also l i k e to thank the s t a f f of the F i s h e r i e s Research Section for t h e i r invaluable tec h n i c a l suport, e s p e c i a l l y Kanji Tsmura, who i s p a r t i c u l a r l y talented at orchestrating miracles within a government bureaucracy. Special thanks to Bob Land, Morley Rempel and Larry M i t c h e l l at the Fraser Valley Research hatchery and Andy Lamb at the West Vancouver Laboratory for t h e i r f i s h culture expertise. v i i I would l i k e to thank the F i s h e r i e s Research Section at U.B.C, the M i n i s t r y of A g r i c u l t u r e and F i s h e r i e s , and the Department of F i s h e r i e s and Oceans, f o r p r o v i d i n g f i n a n c i a l support, equipment, f i s h , and f a c i l i t i e s . I would s i n c e r e l y l i k e to thank my colleagues at the Aquahut: e s p e c i a l l y C a r l Mazur, James McGeer, John Morgan, and Tim Yes a k i ; and Charlene Higgins and Beth Scott at the I n s t i t u t e of Animal Resource Ecology. Thankyou f o r your generous support, and f o r making the time spent at U.B.C. so enjoyable. This t h e s i s i s dedicated t o my parents: R u s s e l l A. Lamont who introduced me t o nature and b i o l o g y , and Bernece G. Lamont (nee Staf) who was the impetus behind my academic p u r s u i t s . 1 INTRODUCTION Phenotypic v a r i a t i o n f o r the age at sexual maturation i s common f o r many animal spec i e s . Maturation age i s a c o n d i t i o n a l response that maximizes 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 l a t e r age (Dominey, 1984) . In species where the 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 behavioural mating 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 mating behaviours (Alcock, 1979) . An example of t h i s behaviour i s the a l t e r n a t i v e mating t a c t i c s that are used by smaller or younger males i n s i z e or age polymorphic breeding popu l a t i o n s t o s u c c e s s f u l l y compete w i t h o l d e r or l a r g e r male phenotypes. The t y p i c a l p a t t e r n i s f o r younger or small e r males t o adopt "sneaking" behaviour or to use submissive t a c t i c s while the l a r g e r or o l d e r males are t e r r i t o r i a l l y dominant (Dominey, 1984). This s p e c i f i c type of a l t e r n a t i v e mating t a c t i c has been demonstrated t o e x i s t i n bees (Alcock, 1979)/ b e e t l e s (Eberhard, 1982), spiders (Christenson and Go i s t , 1979), b u l l f r o g s (Howard, 1984), l i z a r d s ( T r i v e r s , 1976), elephant s e a l s (Le Boeuf, 1974), red deer (Clutton-Brock et a l . , 1979), and many f i s h e s 2 (Constanz , 1975; Warner e t a l . 1975; Dominey, 1980; Warner and Hoffman, 1980; G r o s s , 1985). Among Salmonidae , some males commonly mature at an age t h a t i s younger than the average f o r t h e i r p a r t i c u l a r s p e c i e s or s t o c k . Young male sa lmonids or " jacks" employ s n e a k i n g b e h a v i o u r to a v o i d l a r g e r , o l d e r , t e r r i t o r i a l l y dominant males i n o r d e r t o g a i n access t o , and f e r t i l i z e the nes t or " r e d d " . S i z e p l a y s an impor tant r o l e i n the success o f t h i s mat ing s t r a t e g y (Gross , 1984) . P r e c o c i o u s males need t o be s m a l l enough to remain r e l a t i v e l y u n d e t e c t e d on the spawning grounds , but l a r g e enough t o d e v e l o p gonads and spawn. D i s r u p t i v e s e l e c t i o n ; s e l e c t i o n t h a t f a v o r s a b i m o d a l s i z e d i s t r i b u t i o n o f s m a l l p r e c o c i o u s males and l a r g e dominant males , m a i n t a i n s the s i z e and age po lymorphism w i t h i n the spawning p o p u l a t i o n (Gross , 1984) . However, the mechanisms t h a t c o n t r o l the age at which an i n d i v i d u a l f i s h matures , and hence, the mat ing s t r a t e g y i t w i l l use , are not w e l l u n d e r s t o o d . M a t u r a t i o n at any age i s a complex p r o c e s s media ted by p h y s i o l o g i c a l , e n v i r o n m e n t a l , and g e n e t i c components. The i n t e r r e l a t i o n s h i p o f these mechanisms and t h e i r i n f l u e n c e on the r e g u l a t i o n o f s e x u a l m a t u r a t i o n i s u n c e r t a i n ( B i l l a r d , 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 maturation are p a r t i c u l a r l y obscure. I t i s probable t h a t maturation age i s not mediated by any s i n g l e f a c t o r , but r a t h e r c o n t r o l l e d by a number of i n t e r r e l a t e d environmental (Gardner, 1976; Bye, 1984) , p h y s i o l o g i c a l (Randall et a l . , 1986), and g e n e t i c c o n d i t i o n s (Gjedrem, 1985). T h i s t h e s i s focuses on the p h y s i o l o g i c a l aspects of p r e c o c i o u s maturation, and i n p a r t i c u l a r the r e l a t i o n s h i p between growth r a t e and p r e c o c i o u s maturation. A r e l a t i o n s h i p between age at maturation and growth r a t e has been demonstrated i n many s p e c i e s . W e l l - f e d human females a t t a i n menarche 2-5 years e a r l i e r than malnourished women (Bullough, 1981). Laboratory r a t s d elay m a t u r i t y when f o r c e d by n u t r i t i o n a l or temperature s t r e s s , t o grow more sl o w l y (Kennedy and M i t r a , 1963). Slower growing male s l i d e r t u r t l e s a l s o d elay m a t u r i t y (Gibbons et a l . , 1981). W e l l - f e d , uncrowded Drosphila s t a r t t o reproduce when they are 11 days o l d whereas p o o r l y n o u r i s h e d or crowded f l i e s s t a r t r e p r o d u c i n g when they are 15 days o l d or l a t e r (Stearns and K o e l l a , 1986). Among f i s h , f a s t e r growing p l a t y f i s h (Stearns and K o e l l a , 1986), p l a i c e ( P i t t , 1975), and s t i c k l e b a c k s (Wootton, 1973) mature and at a younger age than slower growing c o n s p e c i f i c s . 4 P o l i c a n s k y (1983) p o s t u l a t e d t h a t under s t a b l e r e a r i n g c o n d i t i o n s , w i t h abundant food s u p p l y , f i s h s h o u l d grow r a p i d l y and mature as soon as they are d e v e l o p m e n t a l l y a b l e t o do so . Among s a l m o n i d s , t h i s r e l a t i o n s h i p between r a p i d growth r a t e and p r e c o c i o u s m a t u r a t i o n i s w e l l documented. Improved f e e d i n g a n d / o r growth have r e s u l t e d i n d i f f e r r e n c e s i n m a t u r a t i o n r a t e s f o r many s a l m o n i d s p e c i e s (Table 1 ) . Table 1. Reports of po s i t i v e c o r r e l a t i o n of growth rate and maturation rate i n salmonids. Species Reference Oncorhynchus spp. Chinook salmon (0.tshawytscha) Coho salmon (0. kisutch) Masu salmon (0. masou) Pink salmon (0. gorbuscha) Sockeye salmon (0. nerka) Rainbow trout (0. mykiss) Amago salmon 0. rhodurus Salmo spp. A t l a n t i c salmon (S. salar) Brown trout (S. trutta) Salvelinus spp. A r c t i c char (S. alpinus) Brook trout (S. fontinalis) Dolly Varden (5. malma) Lake trout (S. namycush) •Fla'in, 1970 Hager and Noble, 197 6 B i l t o n et a l . , 1982 Utoh, 1976 MacKinnon and Donaldson, 1976 Ricker, 1938 Aim, 1959 Kato, 1975 Houston, 1981 Schmidt and House, 197 9 Skarphedinsson et a l . , 1985 Tofteberg and Hansen, 1986 Tsumura and Hume, 198 6 Nagahama et a l . , 1982 Aim, 1959 Leyzerovich, 1973 Mitans, 1973 Glebe et a l . , 1978 Naevdal et al.,1978 Thorpe and Morgan, 1978 Lundqvist, 1980 Bailey et a l . , 1980 Saunders et a l . , 1982 Dally et a l . , 1983 Thorpe et. 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 T h i s widespread b a s i s f o r a r e l a t i o n s h i p between growth r a t e and maturation has l e d to the p r o p o s a l t h a t the i n i t i a t i o n o f p r e c o c i o u s maturation i n salmonids i s dependant upon a minimum s i z e t h r e s h o l d (Elson, 1957; MacKinnon and Donaldson, 1976; R e f s t i e et a l . , 1977; B a i l e y et al.,1980; Myers et a l . , 1986). T h i s h y p o t h e s i s concurs w i t h the concept t h a t c r i t i c a l s i z e can d i c t a t e a major developmental c o n v e r s i o n ( S m i t h - G i l l , 1983) . A c h i e v i n g a c r i t i c a l s i z e alone however, may not n e c e s s a r i l y p r e d i s p o s e a f i s h t o mature. For example, Jonsson e t . a l . (1984) found t h a t c u t t h r o a t (0. clarki) and D o l l y Varden (Salvelinus malma) i n one l a k e matured at a younger age, and at a s m a l l e r s i z e than the same s p e c i e s i n another l a k e . On t h i s b a s i s , they r e j e c t e d the concept t h a t a minimum s i z e t h r e s h o l d d i c t a t e s the i n i t i a t i o n of maturation. Therefore, i t appears t h a t although a c h i e v i n g a c r i t i c a l s i z e may be p h y s i c a l l y necessary i n order t o meet the energy requirements f o r the development of gonadal t i s s u e , a c h i e v i n g a c r i t i c a l s i z e alone may not n e c e s s a r i l y i n i t i a t e m a t u r a t i o n . Thorpe (1986) argued t h a t instantaneous growth-rate i s a b e t t e r f a c t o r on which to base "developmental d e c i s i o n s " than s i z e alone. He argued t h a t s i z e alone i s a measure of 7 p a s t per formance ; t h a t i s the q u a n t i t y o f food i t had consumed, the e f f i c i e n c y i t had been a s s i m i l a t e d and the way i n which t h a t a c q u i r e d energy and m a t e r i a l had been a l l o c a t e d . On the o t h e r hand, i n s t a n t a n e o u s g r o w t h - r a t e i s a measure o f c u r r e n t performance upon which the p o t e n t i a l f o r s e x u a l m a t u r a t i o n and spawning can be d e t e r m i n e d . F o r example, i n amphib ians , metamorphosis i s not p r e d i c t e d by s i z e or age a l o n e , but by the r a t e at which deve lopmenta l s tages are r e a c h e d ( S m i t h - G i l l and B e r v e n , 1979) . Sa lmonids are s e a s o n a l spawners and are r e s t r i c t e d to spawning i n d e f i n i t e t ime p e r i o d s or "windows" by temperate e n v i r o n m e n t a l c o n d i t i o n s . T h e r e f o r e , i n the temperate c l i m a t e , the i n i t i a t i o n o f the p h y s i o l o g i c a l en tra inment o f m a t u r a t i o n must be made p r i o r t o the spawning event , and i n a t ime o r i e n t e d way so the f i s h can deve lop gonads and spawn w i t h i n an e n v i r o n m e n t a l t ime window. I t has been proposed t h a t the i n i t i a t i o n p e r i o d o c c u r s d u r i n g l a t e s p r i n g (Houston, 1981; Rowe and Thorpe , 1990a) . The i n i t i a t i o n o f the m a t u r a t i o n p r o c e s s d u r i n g t h i s t ime p e r i o d would a l l o w f o r energy t o be d i r e c t e d i n t o gonadal growth d u r i n g the summer growing p e r i o d . In a d d i t i o n , e v i d e n c e t h a t m a t u r a t i o n i s r e g u l a t e d by p h o t o p e r i o d i n A t l a n t i c salmon (Salmo salar) ( L u n d q v i s t , 1980) and t h a t i t i s i n i t i a t e d 8 under i n c r e a s i n g day lengths (Scott and Sumpter, 1983; Adams and Thorpe, 198 9) support t h i s t heory. Rapid growth r a t e among maturing salmonids d u r i n g the s p r i n g has been observed i n many s t u d i e s . For example, B i l t o n (1980) found t h a t coho salmon (Oncorhynchus kisutch) growing f a s t e r at an age of 6 to 8 months matured at an e a r l i e r age than slower growing f i n g e r l i n g s . Adams and Thorpe (1989) showed t h a t enhancing growth o p p o r t u n i t y by extending p h o t o p e r i o d and i n c r e a s i n g water temperature i n February, i n c r e a s e d the r a t e of sexual maturation i n A t l a n t i c salmon p a r r . In another study, r a p i d growth r a t e d u r i n g the s p r i n g was l i n k e d t o e a r l y s exual maturation i n i n d i v i d u a l l y i d e n t i f i e d A t l a n t i c salmon (Rowe and Thorpe, 1990a) . Moreover, a r e d u c t i o n i n feed d u r i n g the e a r l y s p r i n g reduced the number of p r e c o c i o u s males (Rowe and Thorpe, 1990b). Therefore, growth r a t e d u r i n g t h i s time p e r i o d may be an important mechanism i n d e t e r m i n i n g the a b i l i t y o f the f i s h t o develop gonads and spawn s u c c e s s f u l l y d u r i n g the f a l l or the next s p r i n g . V a r i a t i o n i n environment has a l s o been shown to i n f l u e n c e p r e c o c i o u s maturation. For example, i n c r e a s e d r e a r i n g temperature promoted sexual maturation i n rainbow 9 t r o u t (0. mykiss) ( T i t a r e v , 1975) as w e l l as i n the anadromous form, steelhead t r o u t , (Schmidt and House, 1979), and i n pink salmon (0. gorbuscha) (MacKinnon and Donaldson, 197 6) . Since growth i s d i r e c t l y r e l a t e d t o temperature and r a t i o n , the i n f l u e n c e of temperature on maturation may be mediated through i t s e f f e c t on growth r a t e . Some previous s t u d i e s d i d not f i n d a p o s i t i v e c o r r e l a t i o n between precocious maturation and growth r a t e . Glebe et a l . (1980) d i d not show a p o s i t i v e c o r r e l a t i o n between growth r a t e and precocious maturation i n A t l a n t i c salmon; Naevdal et a l . (1978) showed t h a t the c o r r e l a t i o n between age at f i r s t maturation and growth r a t e was small f o r A t l a n t i c salmon, and Gjerde (1984) found t h a t maturing A t l a n t i c salmon males were the sma l l e s t p a r r . This discrepancy could be r e s o l v e d i f i t could be determined that maturing males are l a r g e r than non-maturing males i n i t i a l l y , and then grow more slow l y i n autumn, as suggested by Leyze r o v i c h (1973)/ D a l l e y et a l . (1983), and Gjerde (1984). Other experiments have shown th a t l i p i d l e v e l s i n winter and s p r i n g i n f l u e n c e the i n i t i a t i o n of maturation i n A t l a n t i c salmon p a r r . Rowe and Thorpe (1990b) examined the e f f e c t of 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 precocious 10 maturation in A t l a n t i c salmon parr. Growth was suppressed by f a s t i n g f i s h i n alternate weeks during sequential 2 month periods. S i g n i f i c a n t reductions i n male maturation rates occurred i n populations r e s t r i c t e d during A p r i l , May, and June. They also found that the seasonal pattern of fat u t i l i s a t i o n and storage d i f f e r e d between those f i s h which matured and those which did not. The greatest difference occurred i n late winter, when males destined to mature l a i d down new stores of v i s c e r a l fat, while immature f i s h did not. In higher vertebrates such as rats, c a t t l e , and humans, reproductive success i s p o s i t i v e l y correlated to fat stores during the early maturation stages (Frisch, 1988). I f fat lev e l s play a s i m i l a r role i n maturation i n f i s h , then low fat stores i n late winter would probably prevent maturation that year. In addition, r e s t r i c t i o n of feed intake i n late winter would necessitate the mobilisation rather than fat storage at that time. This might further block the maturation process i n f i s h with otherwise adequate fat stores. Other evidence indicates that maturation rates are also g e n e t i c a l l y c o n t r o l l e d (Donaldson and Olson, 1955; Thorpe, 11 1975; Naevdal et a l . , 1978; Thorpe et a l . , 1983; Gjerde, 1984; Gjedrem, 1985). Thorpe et a l . (1983) showed t h a t f a s t growth and e a r l y maturation were g e n e t i c a l l y l i n k e d . Thorpe, (1986) t h e r e f o r e proposed t h a t , p r o v i d e d r a t e o f development i s above a g e n e t i c a l l y determined l e v e l i n the e a r l y s p r i n g , when the gonadotropic hormone systems are s t i m u l a t e d by i n c r e a s i n g daylength (Scott and Sumpter, 1983), gonadal maturation w i l l be t r i g g e r e d and maturation w i l l be e n t r a i n e d . I t i s l i k e l y t h a t t h i s g r o w t h - r e l a t e d maturation i s adap t i v e and prevents maturation when the growing season s t a r t s l a t e , and i s too short f o r f i s h t o a c q u i r e s u f f i c i e n t energy r e s e r v e s f o r spawning. The o b j e c t i v e of t h i s study was t o c r i t i c a l l y examine 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 coho salmon and rainbow t r o u t . Coho salmon r e s i d e i n the s m a l l streams, r i v e r s and t r i b u t a r i e s along the North East P a c i f i c Ocean. They are anadromous, and spawn i n freshwater streams d u r i n g the f a l l and w i n t e r from October t o December. F r y emerge around A p r i l and remain i n freshwater streams f o r v a r y i n g l e n g t h s o f time, approximately one year. At t h i s stage, the f r y are t e r r i t o r i a l , competing f o r s p e c i f i c areas w i t h i n a stream where they feed on a q u a t i c i n v e r t e b r a t e s . Smolts migrate t o the sea the f o l l o w i n g s p r i n g , and e i t h e r remain 12 i n the n e a r s h o r e s t r a i t s and channe l s or m i g r a t e around the c o a s t a l zone i n the N o r t h e r n P a c i f i c (Hart , 1980) . Coho salmon w i l l g e n e r a l l y spend 18 months at sea b e f o r e r e t u r n i n g t o spawn at age 3. P r e c o c i o u s males , or " jacks" w i l l spend o n l y 6 months at sea b e f o r e r e t u r n i n g t o spawn at age 2. Gonadal development o c c u r s d u r i n g the summer months, p r i o r to spawning i n the f a l l . When the salmon farming i n d u s t r y was growing r a p i d l y on the B r i t i s h Columbia (B. C . ) coas t d u r i n g the e a r l y 1980's , coho salmon were a p o p u l a r s p e c i e s t o farm due to t h e i r f a s t e r i n i t i a l growth r a t e and t h e i r b e t t e r endurance under c u l t u r e c o n d i t i o n s r e l a t i v e to ch inook salmon (0. tshawytscha) . However, due to the h i g h r a t e o f p r e c o c i o u s m a t u r a t i o n w i t h i n t h i s s p e c i e s , coho salmon became l e s s d e s i r a b l e t o farm. Rainbow t r o u t r e s i d e i n f r e s h w a t e r streams and l a k e s . They w i l l u s u a l l y spawn d u r i n g s p r i n g i n s m a l l e r t r i b u t a r i e s o f r i v e r s , o r i n l e t or o u t l e t streams o f l a k e s . They d e v e l o p gonads d u r i n g the summer months p r i o r t o spawning, and c a r r y the gonad mass over the w i n t e r . A l t h o u g h t h e r e i s a h i g h m o r t a l i t y a s s o c i a t e d w i t h spawning, these f i s h have the a b i l i t y to spawn i n subsequent y e a r s . The number o f 13 f i s h spawning more than once can be l e s s t h a n 10% (Scott and Crossman, 1973). N o r m a l l y , these f i s h mature when they are 3 t o 5 y e a r s o l d . P r e c o c i o u s males mature at age 2. P r e c o c i o u s m a t u r a t i o n i s more p r e v a l e n t among c u l t u r e d sa lmonids than i n w i l d s t o c k s ( B i l l a r d , 1983) . T h i s i s most l i k e l y due t o improved f e e d i n g and growth r a t e s . The d e l e t e r i o u s e f f e c t s a s s o c i a t e d w i t h m a t u r a t i o n ; i n c r e a s e d s u s c e p t i b i l i t y to b a c t e r i a l and f u n g a l i n v a s i o n s , r educed growth r a t e , i n c r e a s e d m o r t a l i t y , and the d e t e r i o r a t i o n o f f l e s h q u a l i t y , l i m i t the v a l u e o f these p r e c o c i o u s l y m a t u r i n g f i s h i n a q u a c u l t u r e and w i l d f i s h e r i e s . S t e r i l i z a t i o n t e c h n i q u e s , the p r o d u c t i o n o f a l l - f e m a l e s t o c k s , and g r a d i n g have a l l been used as methods to manage p r e c o c i o u s m a t u r a t i o n ; these t e c h n i q u e s have had l i m i t e d s u c c e s s . T h i s s tudy was d e s i g n e d t o a c q u i r e a b e t t e r u n d e r s t a n d i n g o f the r o l e o f growth r a t 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 c u l t u r e d s a l m o n i d s . I t i s a n t i c i p a t e d t h a t the i n f o r m a t i o n g a i n e d from the r e s u l t s o f t h i s s tudy can be used t o a i d i n the management o f t h i s p r o b l e m . In t h i s s t u d y , growth p a t t e r n s and s e x u a l development were m o n i t o r e d i n i n d i v i d u a l l y i d e n t i f i e d f i s h o f b o t h s p e c i e s . Rainbow t r o u t were grown at two t emperatures i n 14 order t o examine the e f f e c t of enhanced growth ra t e on precocious maturation. The goal of the present i n v e s t i g a t i o n was to t e s t the hypothesis t h a t the growth p a t t e r n of p r e c o c i o u s l y maturing f i s h d i f f e r e d from t h a t of-immature f i s h . To a c e r t a i n extent 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 that was r e c e n t l y p u b l i s h e d by Rowe and Thorpe (1990a). As part of the coho study, plasma growth hormone was monitored t o i n v e s t i g a t e i t ' s p o t e n t i a l r o l e i n precocious maturation i n coho salmon. 15 MATERIALS AND METHODS F i s h Stocks and C u l t u r e C o n d i t i o n s Rainbow t r o u t eggs were gathered at the Pennask Creek egg c o l l e c t i o n s t a t i o n , l o c a t e d at 50° 00'N/120° 08'W, approximately 50km NW of Summerland, B. C , i n June 1988 d u r i n g the annual B. C. M i n i s t r y of Environment Summerland Trout hatchery egg c o l l e c t i o n . T h i s stock n o r m a l l y matures at 3 years o f age, but many males mature p r e c o c i o u s l y at age 2. The f e r t i l i z e d eggs were t r a n s p o r t e d t o the Summerland hatchery where they were incubated, hatched, and r e a r e d u n t i l September 1988. At t h i s time, 15,000 f r y were t r a n s f e r r e d t o the B. C. M i n i s t r y o f Environment F r a s e r V a l l e y Trout hatchery ( r e s e a r c h s e c t i o n ) i n Abbotsford, B. C. where they were h e l d i n 3 m diameter c i r c u l a r f i b e r g l a s s tanks. Two thousand f i s h were 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 w i t h an i n d i v i d u a l l y coded p a s s i v e i n t e g r a t e d transponder (PIT) t a g i n January, 1989. These f i s h were t r a n s f e r r e d t o a 2 m diameter c i r c u l a r f i b e r g l a s s tank and r e a r e d i n 9.0°C w e l l water and under s i m u l a t e d v. n a t u r a l p h o t o p e r i o d . In March 1989 one h a l f o f the f i s h 16 (approx imate ly 1000) were t r a n s f e r r e d i n t o an a d j a c e n t 1 5 ° C 2 m d i a m e t e r c i r c u l a r f i b e r g l a s s t a n k . Both groups o f f i s h were h e l d under s i m u l a t e d n a t u r a l p h o t o p e r i o d and they were b o t h f e d Oregon mois t p e l l e t e d food d i s p e n s e d a u t o m a t i c a l l y at a r a t i o n o f 2% o f t h e i r mean body weight f o r the d u r a t i o n o f the e x p e r i m e n t . Lengths and weights o f i n d i v i d u a l f i s h i n b o t h groups were m o n i t o r e d every two weeks from January 24, 1989 t o August 31, 1989. A t t h i s t i m e , 507 f i s h from the warm water ( 1 5 ° C ) group and 598 f i s h from the c o o l water ( 9 ° C ) group were randomly s e l e c t e d and s a c r i f i c e d . The sex was d e t e r m i n e d i n each f i s h , males were a s s e s s e d f o r m a t u r i t y by gonadosomatic index ( G S I ) ( R o b e r t s o n , 1958). The r e m a i n i n g f i s h from b o t h groups were sexed and a s s e s s e d f o r m a t u r i t y on September 28, 1989. Sex was de termined by v i s u a l e x a m i n a t i o n . F i s h were s a c r i f i c e d and i n c i s e d l a t e r a l l y a l o n g the v e n t r a l s u r f a c e i n o r d e r t o examine the gonads. Females were d i s t i n g u i s h e d from males by orange c o l o r e d g r a n u l a r o v a l enlargements ( o v a r i e s ) at the a n t e r i o r p o r t i o n o f gonadal a t tachment . In most c a s e s , the o v a r i e s were c l e a r l y d i s t i n g u i s h a b l e w i t h the naked eye , a l t h o u g h some r e q u i r e d m i c r o s c o p i c e x a m i n a t i o n under low power. Immature male t e s t e s were p a l e 17 colored and smooth textured. Mature male testes were large white lobes, also smooth in texture. For the coho salmon study, 322 coho salmon from the Canadian Department of Fisheries and Oceans (DFO) Capilano River Salmon Enhancement Program hatchery 1987 brood year were used. Fish were transferred to the DFO West Vancouver Laboratory i n July 1988, where they were reared i n outdoor 2.4 m diameter fiberglass c i r c u l a r tanks i n ambient well water. For t h i s experiment, salmon fry of 18 cm fork length and longer were selected i n order to maximize maturation rates. Each f i s h was injected i n t r a p e r i t o n e a l l y with a PIT tag i n March 1989. As a prophylactic treatment against b a c t e r i a l i n f e c t i o n , f i s h were fed 0.673% oxytetracycline treated food (Piper et a l . , 1986) for a 3 week period following tagging. Coho salmon were hand fed Oregon moist p e l l e t e d food to s a t i a t i o n several times d a i l y . The f i s h were vaccinated for V i b r i o anguillarum by immersing them in d i l u t e i n a c t i v a t e d culture of the bacteria (Biomed) for 20 seconds on May 30, 1989. Fish were vaccinated again on June 5, 1989 for V. anguillarum, Yersinia ruckeri, and Aeromonas salmonicida by 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 Health Ltd). Fish were introduced to seawater gradually at a rate of 25% increments every four days from June 20, 1989 to July 2, 18 1989. Fork lengths and weights of i n d i v i d u a l f i s h were taken at monthly i n t e r v a l s from March 25 t o November 1, 1989. The stock normally spawns i n l a t e November. S p e c i f i c growth r a t e (% body weight/day) and c o n d i t i o n f a c t o r (length to weight r e l a t i o n s h i p ) were c a l c u l a t e d and compared between mature and immature males i n both rainbow t r o u t temperature groups and among the mature and immature coho salmon. Coho Salmon Hormone Study To provide an i n i t i a l plasma sample, blood was drawn by syringe from the d o r s a l aorta from 41 f i s h t h a t were not tagged on March 22, 1989. These f i s h were not used i n the growth experiment. Blood was taken from the experimental f i s h by the same method on May 25, J u l y 31, and November 30, 1989. Samples were kept on i c e , c e n t r i f u g e d , and the plasma was separated and s t o r e d at -25°C u n t i l they could be analyzed f o r growth hormone. 19 Radioimmunoassay Procedures Plasma salmon growth hormone l e v e l s were measured by radioimmunoassay (RIA) using the procedure de s c r i b e d 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 v i s i t i n g s c i e n t i s t at the West Vancouver Laboratory. Recombinant salmon growth hormone (rsGH) was used f o r the standard s o l u t i o n s and as a t r a c e r . The rsGH was a g i f t from Dr. T. Abe, Kyowa Hakko Kogyo Co. L t d . , Japan. Antiserum to n a t u r a l salmon growth hormone (sGH) was provided by Dr. B. A. McKeown, Department of B i o l o g i c a l Sciences, Simon Fraser U n i v e r s i t y . This antibody has been widely t e s t e d f o r i t ' s s u i t a b i l i t y 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 a 0.5M phosphate b u f f e r (71 g/1 monobasic sodium phosphate (S-0751, Sigma Chemical Co., St. L o u i s , MO) and 60 g/1 d i b a s i c sodium phosphate (S-0876, Sigma) i n d i s t i l l e d water, pH 7 .4 . Sodium phosphate b u f f e r (SPB) was made w i t h i o d i n a t i o n b u f f e r d i l u t e d 1 0 - f o l d w i t h d i s t i l l e d water to 0.05M. The column b u f f e r was made wit h 2 g/1 bovine serum albumin (A-9627, Sigma) and 0.1 g/1 sodium azide (S-2002, Sigma) i n SPB. The hormone assay b u f f e r (RIA b u f f e r ) was 0.05M SPB c o n t a i n i n g 20 g/1 EDTA (S-311, 20 Fisher), 9 g/1 sodium chloride (S-9625, Sigma) 20 ml/1 normal rabbit serum (NRS)(869019, Calibiochem) (1 v i a l NRS in 5.0 mis double d i s t i l l e d water), 100 mg/1 sodium azide, 2 g/1 bovine serum albumin and 1.0 g/1 Triton X-100 (X198-7, J. Baker). Recombinant salmon growth hormone was iodinated following the chloramine T method as i n Greenwood and Hunter (1963). A t o t a l of 2.5 mCi Nal25I (5 ul)(IMS-30, Amersham), was added to a s c i n t i l l a t i o n v i a l containing a small glass s t i r bar. The s t i r bar was turned on and 10 u l 0.5M SPB, 10 ug Kyowa rsGH (in 10 u l iodination buffer) and 40 ug chloramine T (in 10 u l iodination buffer) were added sequentially. Following 30 seconds of constant agitation, 160 ug of sodium metabisulfate (S-244, Fisher) (in 10 u l iodination buffer) and 200 ug potassium iodide (P-411 c, Fisher) (in 100 u l column buffer) were added to stop the reaction. The reaction mixture t o t a l volume was put onto a 0.5 x 57 cm Sephadex G50 (Pharmacia Ltd.) column. When the entire 0.145 ml had been drawn into the column, i t was flushed through with column buffer. Fractions containing 6 drops were c o l l e c t e d i n 12 x 75 mm polystyrene culture tubes, 21 beginning when the f i r s t 0.145 ml was f i r s t put onto the column. Ten u l a l i q u o t s from each f r a c t i o n were counted on a P i c k e r S p e c t r o s c a l e r 4R counter f o r 6 seconds each to determine which f r a c t i o n s contained the most r a d i o l a b e l l e d p r o t e i n . These f r a c t i o n s were combined and r e t a i n e d at 4°C f o r assays, and a l l remaining f r a c t i o n s were di s c a r d e d . For the radioimmunoassay of sGH, d u p l i c a t e 12 x 75 mm po l y s t y r e n e c u l t u r e tubes were set up t o c o n t a i n 50 u l of the appropriate rSGH standard (0.2 - 100 ng/ml) or plasma, 50 u l of r s G H - I 1 2 5 (5, 000 cpm, d i l u t e d t o the appropriate a c t i v i t y i n RIA b u f f e r ) , and 50 u l of antibody. An antiserum d i l u t i o n of 1:10, 000 bound 50% ' of l a b e l l e d rsGH (5,000 cpm) under the c o n d i t i o n s of the assay. N o n - s p e c i f i c and maximum b i n d i n g c o n t r o l s were prepared by s u b s t i t u t i n g both standard and antibody w i t h RIA b u f f e r and by s u b s t i t u t i n g standard alone w i t h RIA b u f f e r r e s p e c t i v e l y . Standards were f r e s h l y prepared and s t o r e d at 4°C f o r no longer than one week. These tubes were vortexed and then b r i e f l y c e n t r i f u g e d . The tubes were incubated f o r 24 hours at 4°C p r i o r to the a d d i t i o n of lOOul (1 u n i t ) of goat antibody to r a b b i t gamma-g l o b u l i n (GARGG)(Calbiochem 539844, prepared by the a d d i t i o n 22 of 12.5 ml 0.05M SPB to 1 v i a l of l y o p h i l i z e d GARGG) . The tubes were v o r t e x e d and incubated f o r an a d d i t i o n a l 2 hours at room temperature. F i n a l l y , the tubes were c e n t r i f u g e d at 1,500 (3500 rpm) at 4°C f o r 30 minutes, the supernatant was a s p i r a t e d , and the r a d i o a c t i v i t y of the remaining p e l l e t was counted f o r 1 minute each. For c a l c u l a t i o n of sGH c o n c e n t r a t i o n , counts f o r a l l tubes f i r s t had the n o n - s p e c i f i c b i n d i n g counts per minute (cpm) s u b t r a c t e d , and were then expressed as a percentage of the maximum b i n d i n g cpm. In t h i s way, v a l u e s f o r percentage b i n d i n g should always f a l l between 0 and 100%. Standard curves of percent bound (Y-axis) p l o t t e d a g a i n s t l o g of the c o n c e n t r a t i o n o f hormone standards (X-axis) were used t o determine sGH c o n c e n t r a t i o n i n the samples. I f the percent bound was g r e a t e r than 80% ( i . e . , o f f the l i n e a r p a r t o f the standard curve) , the samples were taken t o have l e s s than d e t e c t a b l e l e v e l s f o r the assay. In order t o assess i n t e r a s s a y p r e c i s i o n , e i g h t samples from a common p o o l of plasma were e v a l u a t e d f o r plasma growth hormone l e v e l s i n each assay. 23 Data C o l l e c t i o n and A n a l y s i s Lengths and weights of each i n d i v i d u a l rainbow t r o u t were monitored twice monthly. Lengths and weights of i n d i v i d u a l coho salmon were taken once a month. S p e c i f i c growth r a t e s (SGR) were c a l c u l a t e d between sample periods as f o l l o w s : SGR = lnS2 - l n S l x 100 x d-1 where l n i s the n a t u r a l logarithm, S l and S2 are the weights at time 1 and 2, and d-1 i s the number of days between time 1 and 2 (Clarke and Shelbourn, 1986). D i f f e r e n c e s i n mean s i z e and s p e c i f i c growth ra t e between maturing and non-maturing males were t e s t e d by a n a l y s i s of variance f o r each group f o r each sample p e r i o d . A l l data were t e s t e d f o r normality by p r o b a b i l i t y p l o t and f o r homogeneity of variance by B a r t l e t t s t e s t ( B a r t l e t t , 1937 i n Zar, 1984). When departures from these assumptions of a n a l y s i s of variance occurred, l o g a r i t h m i c transformations were a p p l i e d p r i o r to the a n a l y s i s . Means were compared by Student's t - t e s t . The Chi-squared (X 2) t e s t was used to compare d i f f e r e n c e s i n the percent maturation between the two temperature groups (Zar, 1984). 24 In t h i s case, the mean of the two percents was used as the expected v a l u e . For a l l comparisons the n u l l h y p o thesis was r e j e c t e d with a s i g n i f i c a n c e l e v e l of alpha l e s s than or equal t o 0.05. Length t o weight r e l a t i o n s h i p ( c o n d i t i o n f a c t o r ) was c a l c u l a t e d u s i n g Flicker's formula (Ricker, 1975), which p r o v i d e s the best index when lengths vary between groups b e i n g compared (Bolger and Connolly, 198 9) and growth i s a l l o m e t r i c (Le Cren, 1951) : K = 100W/Lb where K i s c o n d i t i o n f a c t o r , W i s weight (g) , L i s l e n g t h (cm), and b i s the slope c o e f f i c e n t o f the r e g r e s s i o n of l o g weight on l o g l e n g t h . Mean c o n d i t i o n was compared between mature and immature males u s i n g K r u s k a l - W a l l i s one-way a n a l y s i s o f v a r i a n c e . The n u l l h y p o t h e s i s was r e j e c t e d with a s i g n i f i c a n c e l e v e l of alpha l e s s than or equal t o 0.05. GSI was c a l c u l a t e d u s i n g the formula by Robertson (1958): GSI = weight of both t e s t e s (g) x 100 t o t a l body weight (g) 25 GSI v a l u e s o f a l l n o n - m a t u r i n g males were l e s s than 0.05%, whereas those o f m a t u r i n g f i s h were g r e a t e r than 1.4%. E f f o r t was made t o measure every f i s h at each sample d a t e . However, some f i s h managed to e lude measurement, and m o r t a l i t i e s removed some f i s h from each p o p u l a t i o n . T h e r e f o r e , sample s i z e (n) changed at a lmost e v e r y sample d a t e . In o r d e r t o a v o i d c o n f u s i n g r e p r e s e n t a t i o n , the v a l u e s o f n are l i s t e d i n the appendix r a t h e r than i n the f i g u r e l e g e n d s . In cases where n was g r e a t e r t h a n 100, d i f f e r e n c e s i n n would have no b e a r i n g on the r e s u l t s . Salmon Growth Hormone A n a l y s i s Samples above the d e t e c t i o n l i m i t s o f the assay were a n a l y s e d by a n a l y s i s o f v a r i a n c e . The e f f e c t s o f sex, m a t u r a t i o n and sample date on plasma growth hormone l e v e l s were e v a l u a t e d . Each assay was e v a l u a t e d i n d i v i d u a l l y . D i f f e r e n c e s i n the p o s i t i o n o f the s t a n d a r d c u r v e a n d / o r d i f f e r e n c e s i n the c o n c e n t r a t i o n o f growth hormone i n the p o o l e d plasma d i d not a l l o w the r e s u l t s from the 3 assays to be combined. 26 RESULTS Rainbow Trout Study When the f i s h were s p l i t i n t o two temperature groups on February 21st., 1989, there was no s i g n i f i c a n t d i f f e r e n c e i n mean weight between the two groups. However, from March 28th onward, the warm water group had a s i g n i f i c a n t l y higher mean weight (Figure 1) . The rat e of precocious maturation i n the warm water group was at a s i g n i f i c a n t l y higher r a t e (18%) than the co o l water group (11%) (Figure 1). At- 9°C, the maturing males had a higher s p e c i f i c growth r a t e (% body weight / day) than the immature males at each two week sample p e r i o d from February 21/22 t o June 6/7, 1989 (except f o r March 11/12 when s p e c i f i c growth ra t e s i n both mature and immature groups were equal) (Figure 2) . From June 20/21, t o August 30/September 1, the s p e c i f i c growth r a t e of the two groups was equal (except f o r one sampling p e r i o d on J u l y 19/20 when the immature males had a higher s p e c i f i c growth rate) (Figure 2) . On September 28th, the l a s t sampling day, the immature males had a higher s p e c i f i c growth r a t e than the mature males (Figure 2 ) . 27. 0-1 1 1 1 1 1 1 1 1 \— Feb Mar Apr May June July Aug Sept Oct F i g u r e 1. The e f f e c t o f temperature on p r e c o c i o u s m a t u r a t i o n . Mean weight (g) +/- 1 S.E. as a f u n c t i o n of time i n rainbow t r o u t r e a r e d at 9°C and 15°C. From March 28th, 1989 to the end of the study, the 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 weight (P<0.05) . 28 F i g u r e 2. Mean s p e c i f i c growth r a t e s (%g/d) +/- 1 S.E. of-male rainbow t r o u t r e a r e d at 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 between means at each sample p o i n t (P<0.05). 29 At 15°C, the maturing males had a higher s p e c i f i c growth r a t e (% body weight / day) than the immature males at each two week sample p e r i o d from March 14/15 t o J u l y 19/20 (except f o r A p r i l 11/12 when s p e c i f i c growth ra t e s i n both mature and immature groups were equal ) . S p e c i f i c growth r a t e f o r both mature and immature groups was equal f o r the p e r i o d from August 1/2 to August 30/ September 1. S p e c i f i c growth r a t e was greater i n immature males than mature males on the l a s t sample date, September 28 (Figure 3). The pooled male data f o r the length-weight r e l a t i o n s h i p s gave a r e g r e s s i o n slope of 2.971 (Table 2 ) . This value was 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 . C o n d i t i o n f a c t o r was equal f o r males i n both temperature groups from the s t a r t of the study on January 24 t o March 15. From the next sample date t o the end of the study, the c o n d i t i o n f a c t o r of the maturing males was s i g n i f i c a n t l y g r eater than t h a t of the immature males (Figure 4, 5) . Temperature a l s o had a s i g n i f i c a n t e f f e c t on c o n d i t i o n . The f i s h i n the warmer water had a s i g n i f i c a n t l y greater c o n d i t i o n f a c t o r from the f i r s t sample date a f t e r they were t r a n s f e r r e d t o the warm water t o the end of the study. 30 - 1 . C H —I 1 —I 1 H 1 1 1— r-Feb Mar Apr May June July Aug Sept Oct gure 3. Mean s p e c i f i c growth rates (%g/d) +/- 1 S.E. of male rainbow trout reared at 15°C. * indicates s i g n i i c a n t differences between means at each sample point (P<0.05). 31 Table 2. Pooled length-weight r e l a t i o n s h i p s from each sample date o f male rainbow t r o u t and coho salmon. Species No. C o r r e l a t i o n R e g r e s s i o n ANOVA of c o e f f i c i e n t parameters f i s h (r) a b P< Rainbow Trout Coho Salmon 13,982 775 0.972 0.800 -11.303 2.971 0.001 - 6.494 2.027 0.000 32 1.7 1.6 1.5 1.4 1.3 + 1.2 1.1 1.0 0.9 A — A MATURE A A IMMATURE 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. of mature and immmature rainbow t r o u t reared at 9°C. The mature males had a s i g n i f i c a n t l y higher mean c o n d i t i o n f a c t o r than the immature males (P< 0.05) from March 28th, 1989 to the end of the study. 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. of mature and immmature rainbow t r o u t reared at 15°C. The mature males had a s i g n i f i c a n t l y higher mean c o n d i t i o n f a c t o r than the immature males (P<0.05) from March 28th, 1989 to the end of the study. 34 In both 9°C and 15°C groups of f i s h , the weight/frequency d i s t r i b u t i o n of mature and immature males overlapped f o r the du r a t i o n of the study (Figure 6,7) . In a d d i t i o n , the precocious males were s i g n i f i c a n t l y longer and heavier than the non-precocious males f o r the d u r a t i o n of the study (Appendix 1,2). Gonadal development was f i r s t 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 the 15°C group on June 7, 1989, and from the 9°C group on J u l y 19, 1989. GSI ranged from 2.9% t o 8.5% i n the c o l d water mature males and 1.4% to 13.6% i n the warm water mature males. GSI f o r a l l immature males was l e s s than 0.5%. E x t e r n a l darkening was apparent i n some, but not a l l of the precocious males. The degree of darkening v a r i e d i n d i v i d u a l l y , and t h e r e f o r e t h i s o b s e r v a tion i s s u b j e c t i v e . A l l of the female t r o u t were immature at the end of the study. 35 June 250 200 150 100 50 0 Is 1 i III i i i i MMATURE MATURE 40 80 Weight (g) 120 August 250 200 150 100 50 0 1 iii l i s t s MMATURE MATURE 40 Weight (g) 120 F i g u r e 6. Frequency d i s t r i b u t i o n of weight i n male rainbow t r o u t reared at 9oC i n June and August 1989. June M/ATURE MATURE August 175| 150 125 100 75 50 251 1 ^ ^ ^  50 BP 1^ ffl tjt tJLjJLfL^jqL^jm MMATURE MATURE 100 Weight (g) 150 200 gure 7. Frequency d i s t r i b u t i o n o f weight i n male rainbow t r o u t r e a r e d at 15oC i n June and August 1989. 37 Coho Salmon Study The mature coho males had a s i g n i f i c a n t l y higher s p e c i f i c growth r a t e than the immature males at each sample date from the s t a r t of the study March 22nd to J u l y 10th. Mature and immature males had equal s p e c i f i c growth rates f o r sample dates J u l y 31 and September 9. However, by the end of study November 30, the immature males had a s i g n i f i c a n t l y higher s p e c i f i c growth ra t e than the mature males (Figure 8) . S p e c i f i c growth ra t e f o r female f i s h was equal t o th a t of the immature males at each sample date f o r the d u r a t i o n of the study. A l l females were immature - at the end of the study. The pooled monthly value f o r the length-weight r e l a t i o n s h i p s gave a r e g r e s s i o n slope of 2.027 (Table 2). This value 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 f a c t o r s . C o n d i t i o n f a c t o r among males was equal at the beginning of the study on March 22nd. From the next sample date to the end of the study, the c o n d i t i o n f a c t o r of maturing males was s i g n i f i c a n t l y greater r e l a t i v e to that of immature males (Figure 9). 38 2.0 T Q_ in -1.0 4 1 1 1 1 h 1 1 1 r — Mar Apr May June July Aug Sept Oct Nov Figure 8. Mean s p e c i f i c growth rates (%g/d) +/- 1 S.E. of mature and immature male coho salmon. * indicates s i g n i f i c a n t differences between means at each sample point (P< 0.05). 39 Mar Apr May June July Aug Sept Nov Dec Figure 9. Condition factor +/- 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 higher mean condition factor than the immature males (P< 0.05) from A p r i l 20, 1989 to the end of the study. 40 The weight/frequency d i s t r i b u t i o n o verlapped f o r the d u r a t i o n o f the study (Figure 10) . The 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 longer and h e a v i e r than the non-p r e c o c i o u s males f o r the d u r a t i o n o f the study (Appendix 3). Gonadal development was f i r s t observed among i n c i d e n t a l m o r t a l i t i e s on July. 31, 1989. Gonadosomatic index (GSI) f o r mature males was g r e a t e r than 4.3%. GSI was l e s s than 0.6% f o r immature males. E x t e r n a l darkening was v a r i a b l e among the maturing males. A l l females were immature at the end of the study. July 41 301 201 10 50 MMATURE MATURE 100 Weight 150 N o v e m b e r 30 20 10 S i l i i i 50 100 Weight (g) 150 MMATURE MATURE F i g u r e 10. Frequency d i s t r i b u t i o n of male coho salmon i n J u l y and November, 1989. 42 Growth Hormone Analyses Inter-assay v a r i a t i o n i n the mean pooled plasma growth hormone measurements and in the po s i t i o n of the standard curves made pooling data from i n d i v i d u a l assays impossible. Further, the detection l i m i t s of each assay run varied, and most of the samples f e l l below those detection l i m i t s (Assay #1, 24/41 < 1.5 ng/ml; Assay #2, 36/56 < 3.0 ng/ml; Assay #3, 87 /98 < 4.0 ng/ml). The samples above the detection l i m i t s were between 1 .9 ng/ml and 20 ng/ml (Table 3a-c). The i n t e r p r e t a t i o n of the data i s l i m i t e d due to the large number of samples below the detection l i m i t s that could not be included i n the analyses. The plasma growth hormone measurements above the detection l i m i t s were evaluated separately for each assay. No c o r r e l a t i o n between plasma growth hormone l e v e l and s p e c i f i c growth rate was established. Plasma growth hormone measurements for the 3 sample dates were pooled and grouped by sex and male maturation status to determine that these factors had no s i g n i f i c a n t e f f e c t on plasma growth hormone l e v e l . Small sample size prevented these comparisons for each sample date. With both sexes pooled, there was no s i g n i f i c a n t difference i n plasma growth hormone l e v e l between sample dates. 43 Table 3a. Coho salmon growth hormone assay r e s u l t s for assay #1. Mean plasma sGH l e v e l , std. dev., range and sample size for 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 l i m i t s 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 June Mean sGH (ng/ml) Std Dev. Range n n below detection l i m i t s Mature Males - - - 0 2 Immature Males 4 .75 4 .10 1 .8 - 7. 6 2 2 Females 6.83 5.30 2 .0 - 12. 5, 3 .6 September Mean sGH (ng/ml) Std Dev. Range n n below detection l i m i t s Mature Males -. - - 0 o Immature Males 15.75 6.01 11 .5 - 20. 0 2 4 Females 5.5 0.42 5 .2 - 5. 8 2 4 Pooled Plasma =5.6 ng/ml 44 Table 3b. Coho salmon growth hormone assay re s u l t s for assay #2. Mean plasma sGH l e v e l , std. dev., range and sample size for mature males, immature males and females i n May, June and September. Detection l i m i t of the assay was 3.0 ng/ml. May Mean sGH (ng/ml) Std Dev. Range n n below detection l i m i t s Mature Males - - 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 June Mean sGH (ng/ml) Std Dev. Range n n below detection l i m i t s Mature Males 3.2 - 1 2 Immature Males 5.0 - 1 8 Females 5.6 - 1 6 September Mean sGH (ng/ml) Std Dev. Range n n below detection l i m i t s Mature Males 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 of the assay was 3.0 ng/ml. May Mean sGH (ng/ml) Std Dev. Range n n below d e t e c t i o n l i m i t s Mature Males - . - - 0 5 Immature Males - - - 0 15 Females 9.2 - - 1 10 June Mean sGH (ng/ml) Std Dev. Range n n below d e t e c t i o n l i m i t s Mature Males -. - - 0 6 Immature Males 4 .75 0.49 4 .4 - 5. 1 2 16 Females 17.50 - - 1 12 September Mean sGH (ng/ml) Std Dev. Range n n below d e t e c t i o n l i m i t s Mature Males 9.3 5.94 5 .1 - 13. 5 2 3 Immature Males 6.8 - - . 1 12 Females 6.93 2.35 4 .3 - 9. 1 4 8 Pooled Plasma = 3.7 ng/ml 46 DISCUSSION While many st u d i e s of w i l d and hatchery-reared salmonids have found a p o s i t i v e c o r r e l a t i o n between high growth rate and precocious maturation (Table 1), there has not been any study t h a t c r i t i c a l l y describes the s p e c i f i c growth p a t t e r n of p r e c o c i o u s l y maturing rainbow t r o u t and coho salmon. In a recent paper by Rowe and Thorpe (1990a) the growth p a t t e r n of 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 maturing A t l a n t i c salmon p a r r was described. I t i s i n t e r e s t i n g t o note t h a t the growth p a t t e r n they describe w i t h A t l a n t i c salmon from the genus Salmo concur w i t h the f i n d i n g s of t h i s study w i t h coho salmon and rainbow t r o u t from the genus Oncorhynchus. In t h i s study, the 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 male rainbow t r o u t and coho salmon was greater than the immature males during the s p r i n g and summer months. This agrees w i t h the f i n d i n g s of Rowe and Thorpe (1990b) w i t h A t l a n t i c salmon. Conversely, some other s t u d i e s have not found a p o s i t i v e c o r r e l a t i o n between precocious maturation and growth r a t e i n A t l a n t i c salmon (Glebe et a l . , 1980; Naevdal et a l . , 1978; and Gjerde, 1984). In the present study, s p e c i f i c growth rates among maturing coho salmon and rainbow t r o u t were comparatively greater than 47 those of immature males during the s p r i n g months, s i m i l a r to immature males during August, and l e s s than immature males by the end of September. Rowe and Thorpe (1990a) and Saunders et a l . (1982) have a l s o recorded the same p a t t e r n of f a s t e r i n i t i a l growth followed by decreased growth r a t e i n autumn among maturing A t l a n t i c salmon p a r r . Therefore, the c o r r e l a t i o n between growth r a t e and precocious maturation appears to be dependant upon a s p e c i f i c time p e r i o d , and may be non-existant or negative by the time e x t e r n a l i n d i c a t o r s of maturation are apparent. The use of PIT tags was c r i t i c a l to the design of t h i s study. This enabled a c r i t i c a l d e s c r i p t i o n of the growth p a t t e r n of p r e c o c i o u s l y maturing f i s h on an i n d i v i d u a l b a s i s when maturation was not evident. In t h i s way, the growth p a t t e r n of i n d i v i d u a l s could be recorded on a r e g u l a r b a s i s and the sexual s t a t u s of those i n d i v i d u a l f i s h could be evaluated at a l a t e r date. In a d d i t i o n , the tags were used i n rainbow t r o u t t h a t weighed l e s s than 5 g. E x t e r n a l tags could not be used due to the r i s k of t a g l o s s over the 8-9 month d u r a t i o n of the study. A l s o , i t was necessary that the tags could be e a s i l y read i n order t o f a c i l i t a t e the examination of the l a r g e number of f i s h (Appendix 1) that were r e q u i r e d f o r t h i s study. This number of f i s h were 48 necessary because the r a t e of precocious maturation and the m o r t a l i t i e s a s s o c i a t e d w i t h frequent sampling were unknown. I t was more e f f i c i e n t t o increase the number of f i s h i n v o l v e d i n the study than i s was t o repeat the e n t i r e experiment i f the number of precocious f i s h was i n s u f f i c i e n t 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 of the study. I t i s p o s s i b l e t h a t the r e l a t i v e l y higher growth ra t e among maturing males during the s p r i n g i s maintained by endogenous c o n d i t i o n s . Some s t e r o i d hormones can be a n a b o l i c and w i l l increase weight gains i n f i s h by i n c r e a s i n g feed i n t a k e and improving feed u t i l i z a t i o n (Donaldson et a l . , 1979). Hunt et al.. (1982) recorded small peaks i n plasma t e s t o s t e r o n e c o n c e n t r a t i o n i n February-March i n A t l a n t i c salmon that matured i n the f o l l o w i n g autumn, but no i n c r e a s e d l e v e l s i n those f i s h t h a t d i d not mature. Therefore, e l e v a t i o n s i n androgen c o n c e n t r a t i o n may be r e s p o n s i b l e f o r maintaining the increased growth during s p r i n g and summer among p r e c o c i o u s l y maturing males. As maturation progresses, f u r t h e r e l e v a t i o n s of androgen co n c e n t r a t i o n 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 . Higher l e v e l s of androgens were suspected of r e t a r d i n g growth durin g maturation i n the p l a t y f i s h , Xiphophorus maculatus, 49 (Schreibman and K a l l m a n , 1977). In these f i s h , the growth o f mature males r e l a t i v e t o females and immature males d e c l i n e s s h a r p l y at the t ime o f m a t u r a t i o n . Rowe and Thorpe , (1990a) found an autumn r e d u c t i o n i n a p p e t i t e i n m a t u r i n g A t l a n t i c salmon p a r r and they sugges ted t h a t t h i s may be due t o h i g h androgen l e v e l s at t h a t t i m e . S i m i l a r l y , the r e d u c e d growth r a t e among rainbow t r o u t and coho salmon i n the f a l l observed i n t h i s s tudy may a l s o have been due t o i n c r e a s e d androgen l e v e l s and reduced a p p e t i t e , or b o t h . In a d d i t i o n , the r e a l l o c a t i o n o f energy s o u r c e s from somat ic t i s s u e growth to gonadal development may have p l a y e d a r o l e i n r e d u c e d growth r a t e . In the p r e s e n t s t u d y , e l e v a t e d water t emperature i n c r e a s e d the r a t e o f p r e c o c i o u s m a t u r a t i o n from 11% i n the 9 ° C water t o 18% i n the 1 5 ° C water . These f i n d i n g s are s i m i l a r t o those o f T i t a r e v (1975) who was a b l e to promote growth and reduce the t ime o f spawning f o r ra inbow t r o u t males by 1 y e a r . I t i s not known i f warmer water i n f l u e n c e s m a t u r a t i o n r a t e independent o f the f a s t e r growth a s s o c i a t e d w i t h warmer t e m p e r a t u r e s . Temperature may have an a f f e c t on m a t u r a t i o n by e i t h e r a c t i n g on the p i t u i t a r y t o produce g o n a d o t r o p i n which s u b s e q u e n t l y a c t s upon the gonads, or by d i r e c t l y e f f e c t i n g the gonads v i a s t e r o i d o g e n i c enzymes 50 (Kime, 1979). However, i n brook t r o u t (S. fontinalis) improved growth r a t e has r e s u l t e d i n incre a s e d precocious maturation r a t e independant of temperature i n c r e a s e . (McCormick and Naiman, 1984). Therefore, i t appears that improved growth r a t e w i l l r e s u l t i n increased maturation r a t e s r e g a r d l e s s of the endogenous e f f e c t s of temperature d e s c r i b e d above. The maturing f i s h were s i g n i f i c a n t l y heavier and longer and occupied the upper mode of the weight frequency d i s t r i b u t i o n f o r the e n t i r e study. However, the frequency d i s t r i b u t i o n of lengths and weights f o r mature and non-mature f i s h overlapped f o r the d u r a t i o n of the study. Therefore, i t appears that although a c e r t a i n s i z e t h r e s h o l d i s necessary, s i z e 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, the p a t t e r n of higher s p e c i f i c growth r a t e among maturing f i s h r e l a t i v e t o immature f i s h d u ring s p r i n g and summer was evident i n the coho study and f o r both temperature regimes i n the rainbow t r o u t study. This p a t t e r n a l s o c o i n c i d e s w i t h i n c r e a s i n g daylength (Figure 11) . Changes i n photoperiod cue adult salmon to s t a r t both v i t e l l o g e n e s i s and spermatogenesis ( B i l l a r d , 24 " i i — i — i — i — i — i — i — i — i — i — r 60 120 180 240 300 360 30 90 150 210 270 330 TME (d) F i g u r e 11. D a y l e n g t h i n h o u r s a t 49° l a t i t u d e ( L i s t , 1966) 52 s t a r t both v i t e l l o g e n e s i s and spermatogenesis ( B i l l a r d , 1983). I f the environmental mechanisms i n i t i a t i n g maturation at any age are similar, then changes i n photoperiod would also cue precocious maturation. Photoperiod may also play an additional role i n the maturation process. Several authors have noted that growth i s p o s i t i v e l y influenced by increasing daylength (Gross et a l . , 1965/ Saunders and Henderson, 1970; Komourdjian et a l . , 1976) . Therefore, increasing photoperiod may not only provide the f i s h with a cue for maturation to occur, but may play a secondary role i n precocious maturation v i a the mechanisms associated with increased growth rate. In t h i s study, condition factor was s i g n i f i c a n t l y greater in maturing male rainbow trout and coho salmon from the end of March to the end of the study. Increased condition factor during the spring has also been found among precociously maturing A t l a n t i c salmon (Leyzerovich 1973; Hunt et a l . , 1982; Johnston et a l . 1987; and Rowe and Thorpe, 1990a). Comparatively greater condition factor may be rel a t e d to gonadal development during the summer months, however, the difference observed i n March occurred long before gonadal development was f i r s t observed i n June and 53 July. Condition factor has been shown to be d i r e c t l y r e l a t e d to fat content of A t l a n t i c salmon parr during spring months (Pinder and Eales, 1969). In addition, body fat i s the primary determinant of condition factor i n immature sockeye salmon (Parker and Vanstone,1966; Groves, 1970). Therefore, the increase i n condition factor during the spring among maturing males observed i n t h i s study may be re l a t e d to an increase i n body f a t . This body fat may be an e s s e n t i a l i n t e r n a l energy store needed to support the costs of maturation and offset a reduction i n food intake during the maturation process as suggested by Rowe and Thorpe (1990b). However, i n order to make any q u a n t i t i a t i v e assessment concerning the role of fat stores i n precocious maturation among salmon and trout, they should be measured d i r e c t l y . Hypophysectomy (Donaldson and McBride, 1967) and supplemental growth hormone experiments (Down et a l . , 1989) have established that growth hormone i s a necessary component to growth i n salmonids. In addition, a dose-dependant growth response to exogenous growth hormone has been demonstrated several times (Down et a l . , 1988; Higgs et a l . , 1978). The development and v a l i d a t i o n of salmonid growth hormone RIAs (Bolton et a l . 1986; Wagner and Mckeown, 54 198 6) has l e d to s e v e r a l i n v e s t i g a t i o n s of the r o l e of endogenous growth hormone i n f i s h . In s p i t e of t h i s , a r e l a t i o n s h i p between the l e v e l s of endogenous plasma growth hormone and growth has not been e s t a b l i s h e d . This may stem from the complexity of growth and the nature and f u n c t i o n of growth hormone i t s e l f . The r e s u l t s of the growth hormone assays i n t h i s study d i d not e s t a b l i s h a r e l a t i o n s h i p between growth hormone and growth, sex, or maturation. The la r g e number of samples f a l l i n g below the d e t e c t i o n l i m i t s of the assay b r i n g s question to the v a l i d i t y of the r e s u l t s . The plasma growth hormone l e v e l s f o r coho salmon reported i n the l i t e r a t u r e range from 4 to 450 ng/ml (Clarke et a l . , 1989; Sweeting and McKeown, 1987) . Previous r e s u l t s f o r coho obtained at the West Vancouver l a b o r a t o r y using the same assay ranged from 2 to 100 ng/ml. The r e s u l t s obtained i n t h i s study appear to be g e n e r a l l y lower. During the r a d i o i s o t o p e l a b e l l i n g of the growth hormone, only a small amount (approximately 10%) of the r a d i o i s o t o p e was i n c o r p o r a t e d i n t o the hormone. The presence of the lar g e amount of u n l a b e l l e d hormone i n the assay may have i n t e r f e r r e d w i t h the p r o p o r t i o n of l a b e l l e d and n o n - l a b e l l e d antibody b i n d i n g during the assay, r e s u l t i n g i n fewer sample growth hormone molecules b i n d i n g to the antibody than would normally be expected. In a d d i t i o n , the 12 t o 15 months c o l d 55 storage may have r e s u l t e d i n the d e t e r i o r a t i o n of the growth hormone w i t h i n the plasma samples. Conclusions and F i s h Cu l t u r e I m p l i c a t i o n s The most s i g n i f i c a n t f i n d i n g from t h i s study i s the p a t t e r n of r e l a t i v e increased growth r a t e among p r e c o c i o u s l y maturing rainbow t r o u t and coho salmon during the s p r i n g and e a r l y summer, fol l o w e d by a decrease i n growth r a t e during the l a t e summer and e a r l y f a l l . This p a t t e r n was evident i n the rainbow t r o u t grown under two temperature regimes and i n the coho salmon. Therefore, i t i s p o s s i b l e t h a t the r e s t r i c t i o n of growth ra t e during the e a r l y s p r i n g may reduce the number of f i s h maturing p r e c o c i o u s l y . 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 feed i n such a way th a t compensatory growth mechanisms are a c t i v a t e d , then, reduced feed i n t a k e f o r a short p e r i o d of time w i l l not n e c e s s a r i l y r e s u l t i n a smaller f i s h (Quinton, 1989). This method has been used s u c c e s s f u l l y to reduce precocious maturation i n A t l a n t i c salmon (Rowe and Thorpe, 1990b), but r e q u i r e s f u r t h e r study w i t h P a c i f i c salmon and rainbow t r o u t . 56 Conversely, the promotion of p r e c o c i o u s maturation may a l s o be u s e f u l i n a q u a c u l t u r e . Female salmonids r a r e l y mature p r e c o c i o u s l y and the p r o d u c t i o n of a l l - f e m a l e stocks has been used as a technique to a v o i d the consequences of p r e c o c i o u s maturation. T h i s technique i n v o l v e s the use of androgen treatment d u r i n g sex d i f f e r e n t i a t i o n t o cause g e n o t y p i c females to develop as phenotypic males (Donaldson, 1986) . I f improved growth c o u l d induce these phenotypic males t o spawn p r e c o c i o u s l y , then the c o s t s o f m a i n t a i n i n g them f o r an a d d i t i o n a l year c o u l d be e l i m i n a t e d . S e v e r a l authors have s p e c u l a t e d t h a t the i n i t i a t i o n of m aturation may be l i n k e d t o the accumulation of f a t r e s e r v e s d u r i n g s p r i n g (Thorpe, 1986; Myers et a l . , 1986). The composition of body l i p i d s i s most s i g n i f i c a n t l y a f f e c t e d by d i e t a r y l i p i d s (Watanabe, 1982). Consequently, the method of r e p l a c i n g p r o t e i n with l i p i d s i n commercial f i s h feed may i n a d v e r t e n t l y promote p r e c o c i o u s m a t u r a t i o n . The r e s u l t s of t h i s study i n d i c a t e t h a t growth r a t e i s an important determinant of maturation i n rainbow t r o u t and coho salmon, however, the d i r e c t pathway by which growth i n f l u e n c e s the hormonal systems c o n t r o l l i n g maturation i s not known. The b i o l o g i c a l p r o p e r t y t r i g g e r i n g the 57 maturation process may not be growth i t s e l f , but another f a c t o r s t r o n g l y c o r r e l a t e d to growth r a t e such as energy reserves or l i p i d storage. I t i s l i k e l y t h a t other f a c t o r s are i n v o l v e d , and t h a t i t may be necessary to achieve s e v e r a l p h y s i o l o g i c a l t h r e s h o l d s before maturation i s i n i t i a t e d . 58 REFERENCES A l c o c k , J . 1979. The b e h a v i o u r a l consequences o f s i z e v a r i a t i o n among males o f the t e r r i t o r i a l wasp, Hemipepsis ustulata (Hymenoptera: P o m p i l i d a e ) . B e h a v i o u r . 71: 322-335. A i m , G . 1959. C o n n e c t i o n s between m a t u r i t y , s i z e and age i n f i s h e s . I n s t . Freshwat . Res . Drot tn inghom, 40: 5-145. Adams, C E . and J . E . T h o r p e . 1989. P h o t o p e r i o d and t empera ture e f f e c t s on e a r l y development and r e p r o d u c t i v e investment i n A t l a n t i c sa lmon, Salmo s a l a r L . A q u a c u l t u r e . 79: 403-409. B a i l e y , J . K . , R . L . Saunders , and M . I . B u z e t a . 1980. I n f l u e n c e o f p a r e n t a l smolt age and sea age on growth and s m o l t i n g o f h a t c h e r y r e a r e d A t l a n t i c salmon (Salmo salar). C a n . J . F i s h . A q u a t . S c i . 37: 1379-1386. B a r t l e t t , M . S . 1937. Some examples o f s t a t i s t i c a l methods o f r e s e a r c h i n a g r i c u l t u r e and a p p l i e d b i o l o g y . J . R o y a l S t a t i s t . Soc . S u p p l . 4: 137-170. 59 B i l l a r d , R. 1983. Environmental f a c t o r s i n salmon c u l t u r e and the c o n t r o l of r e p r o d u c t i o n . In: Symposium on Reproduction i n Salmonids. R.N. Iwamoto and S.A. Sower e d i t o r s . Washington Sea Grant, S e a t t l e , WA. pp. 70-87. B i l t o n , H.T. 1980. Experimental r e l e a s e s of.coho salmon i n B r i t i s h Columbia. In: Salmon Ranching. J.E. Thorpe e d i t o r . Academic Press, London, pp. 305-324. B i l t o n , H.T., A l d e r d i c e , D.F., and Schnute, J.T. 1982. I n f l u e n c e of time and s i z e of r e l e a s e of j u v e n i l e coho salmon (Oncorhynchus kisutch) on r e t u r n s at m a t u r i t y . Can. J . F i s h . Aquat. S c i . 39: 426-447. Bolger, T. and Connolly, P.L. 1989. The s e l e c t i o n of s u i t a b l e i n d i c e s f o r f i s h c o n d i t i o n . J . F i s h . B i o l . 34: 171-182. B o l t o n , J.P., Takahashi, A., Kawauchi, H., Kubota, J . and Hirano, T. 1986. Development and v a l i d a t i o n o f a salmon growth hormone radioimmunoassay. Gen. Comp. Endo. 62: 230-238. 60 Bullough, V.L. 1981. Age at menarche: A misunderstanding. S c i e n c e . 213: 365-366. Bye, V . J . 1984. The r o l e of environmental f a c t o r s i n the t i m i n g of r e p r o d u c t i v e c y c l e s . In: F i s h Reproductive S t r a t e g i e s and T a c t i c s . G.W. P o t t s and R.J. Wooton e d i t o r s , pp. 187-205. Academic P r e s s . London. C l a r k e , W.C, Shelbourn, J.E., Ogasawara, T., and Hirano, T. 1989. E f f e c t of i n i t i a l d aylength on growth, seawater a d a p t a b i l i t y and plasma growth-hormone l e v e l s i n u n d e r y e a r l i n g coho, chinook, and chum salmon. Aqua. 82 (1-4) : 51-62. C l a r k e , W.C. and Shelbourn, J.E. 1986. Delayed p h o t o p e r i o d produces more uniform growth and g r e a t e r seawater a d a p t a b i l i t y i n u n d e r y e a r l i n g coho salmon (Oncorhynchus kisutch) Aquaculture. 56: 267-276. Clu t t o n - B r o c k , T.H., Albon, S.D., Gibson, R.M. and Guinness, F.E. 1979. The l o g i c a l s t a g : A daptive aspects of f i g h t i n g i n r e d deer (Cervus elaphus L . ) . Anim. Behav. 27: 211-225. 61 C h r i s t e n s o n , T . E . and G o i s t , K . C . , J r . 1979. C o s t s and b e n e f i t s o f male-male c o m p e t i t i o n i n the orb weaving s p i d e r , Nephila clavipes. Behav. E c o l . S o c i o b i o l . 5: 87-92. C o n s t a n z , G . D . 1975. B e h a v i o u r a l e c o l o g y o f mat ing i n the male G i l a topminnow, Poeciliopsis occidentalis ( C y p r i n o d o n t i f o r m e s : P o e c i l i i d a e ) . E c o l o g y 56: 966-973. D a l l e y , E . L . , Andrews, C W . and Green , J . W . 1983. P r e c o c i o u s male salmon p a r r (Salmo salar) i n i n s u l a r Newfoundland. C a n . J . F i s h . A q u a t . S c i . 40: 647-652. Dominey, W . J . 1984. A l t e r n a t i v e mat ing t a c t i c s and e v o l u t i o n a r i l y s t a b l e s t r a t e g i e s . Amer. Z o o l . 24: 385-396. Dominey, W . J . 1980. Female mimicry i n male b l u e - g i l l s u n f i s h - A g e n e t i c polymorphism? N a t u r e . 284: 546-548. Dona ldson , E . M . 1986. The i n t e g r a t e d development and a p p l i c a t i o n o f c o n t r o l l e d r e p r o d u c t i o n t e c h n i q u e s i n P a c i f i c s a l m o n i d a q u a c u l t u r e . F i s h P h y s i o . Biochem. 2 ( 1 - 4 ) : 9-24. 62 Donaldson, E.M., Fagerlund, U.H.M., Higgs, D.A., and McBride, J.R. 1979. Hormonal enhancement of growth. In: F i s h P h y s i o l o g y . V o l 8. W.S. Hoar, D.J. Ra n d a l l and J.R. B r e t t e d i t o r s , pp. 456-597. Academic Press, New York. Donaldson, E.M. and McBride, J.R. 1967. The e f f e c t s of hypophysectomy i n the rainbow t r o u t Salmo gairdneri (Rich.) with s p e c i a l r e f e r e n c e t o the p i t u i t a r y -i n t e r r e n a l a x i s . Gen. Comp. E n d o c r i n o l . 9: 93-101. Donaldson, L.R. and Olson, P.R. 1955. Development of rainbow t r o u t brood stock by s e l e c t i v e b r e e d i n g . Trans. Am. F i s h . Soc. 85: 93-101. Down, N.E., Donaldson, E.M., Dye, H.M., Boone, T . C , Langley, K. and Souza, L.M. 1989. A potent analog of recombinant bovine somatotropin a c c e l e r a t e s growth i n j u v e n i l e coho salmon (Oncorhynchus kisutch). Can. J . F i s h . Aqua. S c i . 46: 178-183. 6 3 Down, N.E., Donaldson, E.M., Dye, H.M., Langley, K. and Souza, L.M. 1 9 8 8 . Recombinant bovine somatotropin more than doubles the growth ra t e of coho salmon (Oncorhynchus kisutch) acclimated t o seawater and ambient winter c o n d i t i o n s . Aquaculture. 6 8 : 1 4 1 - 1 5 5 . Eberhard, W.G. 1 9 8 2 . B eetle horn dimorphism: Making the best of a bad l o t . Amer. Natur. 1 1 9 : 4 2 0 - 4 2 6 . E l s o n , P.F. 1 9 5 7 . The importance of s i z e i n the change from p a r r to smolt i n A t l a n t i c salmon. Can. F i s h C u l t . 2 1 : 1 - 6 . F l a i n , M. 1 9 7 0 . Precocious male quinnat salmon (Oncorhynchus tshawytcha) i n New Zealand. New Zealand J . Mar. Freshw. Res., 4: 2 1 7 - 2 2 2 . F r i s c h , R.E. 1 9 8 8 . Fatness and f e r t i l i t y . S c i e n t i f i c American. March 1 9 8 8 . pp. 7 0 - 7 7 . Gardner, M.L.G. 1 9 7 6 . A review of f a c t o r s which may i n f l u e n c e the sea-age and maturation of A t l a n t i c salmon, Salmo salar L. F i s h B i o l . 9: 2 8 9 - 3 2 7 . 64 G i b b o n s , J . W . , S e m l i t s c h , R . D . , Greene, J . L . and Schubauer, J . P . 1981. V a r i a t i o n i n age and s i z e at m a t u r i t y o f the s l i d e r t u r t l e (Pseudemys scripta) . Amer. N a t u r . 17: 841-845. Gjedrem, T . 1985. G e n e t i c v a r i a t i o n i n age at m a t u r i t y and i t s r e l a t i o n t o growth r a t e . I n : Symposium on R e p r o d u c t i o n i n Sa lmonids . R . N . Iwamoto and S . A . Sower e d i t o r s . Washington Sea G r a n t , S e a t t l e , WA. pp 52-61 . G j e r d e , B . 1984. Response t o i n d i v i d u a l s e l e c t i o n f o r age at s e x u a l m a t u r i t y i n A t l a n t i c sa lmon. A q u a c u l t u r e . 38: 229-240. G l e b e , B . D . , R . L . Saunders and A . S r e e d h a r a n . 1978. G e n e t i c and e n v i r o n m e n t a l i n f l u e n c e i n e x p r e s s i o n o f p r e c o c i o u s s e x u a l m a t u r i t y o f h a t c h e r y - r e a r e d A t l a n t i c salmon (Salmo salar) p a r r . C a n . J . Genet . C y t o l . 20: 444. G r a i n g e r , E . H . 1953. On the age, growth, m i g r a t i o n , r e p r o d u c t i v e p o t e n t i a l and f e e d i n g h a b i t s o f the A r c t i c c h a r (Salvellnus alpinus) o f F r o b i s h e r Bay, B a f f i n I s l a n d . J . F i s h . Res . B d . C a n . 10: 326-370. 65 Greenwood, F.C. and Hunter, W.M. and J.S. Glover. 1963. The pr e p a r a t i o n of 1 ^ ^ I - l a b e l l e d human growth hormone of high s p e c i f i c r a d i o a c t i v i t y . Biochem. J . 89: 114-123. Gross, M.R. 1985. D i s r u p t i v e s e l e c t i o n f o r a l t e r n a t i v e l i f e h i s t o r i e s i n salmon. Nature (London);313: 47-48. Gross, M.R. 1984. Sunfish, salmon and the e v o l u t i o n of a l t e r n a t i v e reproductive s t r a t e g i e s and t a c t i c s i n f i s h e s . In: Reproductive S t r a t e g i e s and T a c t i c s . G.W. Po t t s and R.J. Wooton e d i t o r s , pp. 55-75. Gross, W.L., Roelofs, E.W. and Fromm, P.O., 1965. Influence of photoperiod on growth of green s u n f i s h Lepomis cyanellus. J . F i s h . Res. Board Can. 22: 1379-1386. Groves, T.D.D. 1970. Body compositon changes during growth i n young sockeye (Oncorhynchus nerka) i n f r e s h water. J . F i s h . Res. Bd. Can. 27: 929-942. Hagar, R.C. and R.E. Noble. 1976. R e l a t i o n of s i z e at r e l e a s e of hatchery-reared coho salmon t o age, s i z e , and sex composition of r e t u r n i n g a d u l t s . Prog. F i s h . C u l t . 38: 144-147. 66 Hanson, J.H. and R.H. Wickwire. 1967. Fecundity and age at maturation of Lake Trout i n Lake Tahoe. C a l i f . F i s h and Game. 53: 154-164. Hart, J.L. 1980. P a c i f i c f i s h e s of Canada. B u l l . 180. F i s h . Res. Bd. Can. 74 0 pp. Higgs, D.A., Donaldson, E.M., McBride, J.R. and Dye, H.M. 1978. E v a l u a t i o n of the p o t e n t i a l f o r us i n g a chinook salmon (Oncorhynchus tshawytscha) p i t u i t a r y e x t r a c t versus bovine growth hormone t o enhance the growth of coho salmon (Oncorhynchus kisutch). Can. J . Zool. 56: 1226-1231. Howard, R.D. 1984. A l t e r n a t i v e mating behaviours of young male b u l l f r o g s . Amer. Zool. 24: 297-406. Houston, C. 1981. Factors a f f e c t i n g precocious sexual development i n male rainbow t r o u t . MSc. Thesis. U n i v e r s i t y of B r i t i s h Columbia. 67 Hunt, S.M.V., Simpson, T.H. and Wright, R.S. 1982. Seasonal changes i n the l e v e l s of 11-oxotestosterone and t e s t o s t e r o n e i n the serum of male salmon, Salmo salar L., and t h e i r r e l a t i o n s h i p to growth and the maturation c y c l e . J . F i s h B i o l . 20: 105-119. Jonsson, B. and K. Hindar. 1982. Reproductive s t r a t e g y of dwarf and normal A r c t i c charr (Salvelinus alpinus) from Vangsvatnet Lake, Western Norway. Can. J . F i s h . Aquat. S c i . 39: 1404-1413. Jonsson, B., K. Hindar, and T.G. Northcote. 1984. Optimal age at sexual maturity of sympatric and experimentally a l l o p a t r i c c u t t h r o a t t r o u t and D o l l y Varden charr. Oecologia 61: 319-325. Johnston, C.E., Gray, R.W., McLennan, A. and Paterson, A. 1987. E f f e c t s of photoperiod, temperature and d i e t on the r e c o n d i t i o n i n g response, blood chemistry and gonad maturation of A t l a n t i c salmon k e l t s (Salmo salar) h e l d i n freshwater. Can. J . F i s h . Aqua. S c i . 44: 702-711. 68 Kato, T. 1975. The r e l a t i o n between the growth and repro d u c t i v e c h a r a c t e r i s t i c s of rainbow t r o u t (Salmo gairdneri). B u l l . Freshw. F i s h . Res. Lab. Tokyo. 25: 83-115. Kennedy, G.C., and M i t r a , J . 1963. Body weight and food i n t a k e as i n i t i a t i n g f a c t o r s f o r puberty i n the r a t . J . P h y s i o l . 166: 408-418. Kime, D.E. 1979. The e f f e c t of temperature on t e s t i c u l a r s t e r o i d o g e n i c enzymes of the rainbow t r o u t , Salmo gairdneri. Gen. Comp. E n d o c r i n o l . 39: 290-296. Komourdjian, M.P., Saunders, R.L. and Fenwick, J.C. 1976. Evidence f o r the r o l e of growth hormone as a part of a ' l i g h t - p i t u i t a r y a x i s ' i n growth and s m o l t i f i c a t i o n of A t l a n t i c salmon (Salmo salar). Can. J . Zool. 54:544-551. Le Boeuf, B.J. 1974. Male-male competition and reproductive success i n elephant s e a l s . Amer. Zool. 14: 163-176. 69 Le Cren, C D . 1951. The length-weight r e l a t i o n s h i p and seasonal c y c l e i n gonad weight and c o n d i t i o n i n the perch (Perca f l u v i a t i l i s ) . J . Anim. E c o l . 20: 201-219. L e y z e r o v i c h , K.A. 1973. Dwarf males i n the hatchery p r o p a g a t i o n of the A t l a n t i c salmon (Salmo salar). J . I c h t h y o l . 13: 382-392. L i s t , R.J. 1966. Smithsonian m e t e o r o l o g i c a l t a b l e s . Smithsonian m i s c e l l a n e o u s c o l l e c t i o n s . V o l . 114. 527 PP-Lundg v i s t , H. 1980. I n f l u e n c e of p h o t o p e r i o d on growth i n B a l t i c salmon (Salmo salar) w i t h s p e c i a l r e f e r e n c e t o the e f f e c t o f p r e c o c i o u s sexual maturation. Can. J . Z o o l . 58: 940-944. MacKinnon, C N . and Donaldson, E.M. 1976. E n v i r o n m e n t a l l y induced p r e c o c i o u s sexual development i n male pink salmon. J . F i s h . Res. Bd. Can. 33: 2602:2605. McCormick, S.D. and Naiman, R.J. 1984. Some determinants of maturation i n brook t r o u t , Salvelinus fontinalis. A q u a c u l t u r e . 43: 269-278. 70 Mitans, A.R. 1973. Dwarf males and the sex s t r u c t u r e of a B a l t i c salmon (Salmo salar) p o p u l a t i o n . J . I c h t h y o l . 13: 192-197. Myers, R.A., Hutchings, J.A. and Gibson, R.J. 1986. V a r i a t i o n i n male p a r r maturation w i t h i n and among p o p u l a t i o n s of A t l a n t i c salmon. Can. J . F i s h . Aquat. S c i . 43: 1242-1248. Naevdal, G., Holm, M., I n g e b r i g t s e n , 0. and D. M o l l e r . 1978. V a r i a t i o n i n age at f i r s t spawning i n A t l a n t i c salmon (Salmo s a l a r ) . J . F i s h . Res. Board Can. 35: 145-147. Nagahama, Y.S. Adachi, F. T a s h i r o , and E.G. Grau. 1982. Some endocrine f a c t o r s a f f e c t i n g the development o f seawater t o l e r a n c e d u r i n g p a r r - s m o l t t r a n s f o r m a t i o n of the amago salmon Oncorhynchus rhodurus. Aquaculture 28: 81-90. Parker, R.R. and Vanstone, W.E. 1966. Changes i n chemical composition of c e n t r a l B r i t i s h Columbia pi n k salmon d u r i n g e a r l y sea l i f e . J . F i s h . Res. Bd. Can. 23: 1353-1397. 71 Pinder, L . J . and Eales, J.G. 1969. Seasonal buoyancy changes i n A t l a n t i c salmon (Salmo salar) p a r r and smolt. J . F i s h . Res. Bd. Can. 26: 2093-2100. P i p e r , R.G., McElwain, I.B., Orme, L.E., McCraren, J.P., Fowler, L.G., Leonard, J.R. 1986. F i s h Hatchery Management. U.S. Dept. of the I n t e r i o r . F i s h and W i l d l i f e S e r v i c e . Washington, D.C. 517pp. P i t t , T.K. 1975. Changes i n abundance and c e r t a i n b i o l o g i c a l c h a r a c t e r i s t i c s of Grand Bank . American P l a i c e , Hippoglossoid.es platessoides. J . F i s h . Res. Bd. Can. 32: 1383-1389. P o l i c a n s k y , D. 1983. S i z e , age and demography of metamorphosis and sexual maturation i n f i s h e s . Amer. Zool. 23: 57-63. Quinton, J.C. 1989. The e f f e c t of c y c l e p e r i o d , r a t i o n l e v e l and r e p e t i t i v e c y c l i n g on the compensatory growth response i n rainbow t r o u t , Salmo gairdneri Richardson. Msc. Thesis. U n i v e r s i t y of B r i t i s h Columbia. 72 R a n d a l l , B.G., Thorpe, J.E., Gibson, R.J. and Reddin, D.B. 1986. B i o l o g i c a l f a c t o r s a f f e c t i n g age at m a t u r i t y i n A t l a n t i c Salmon (Salmo salar) In: Salmonid age at m a t u r i t y . Can. Spec. Publ. F i s h . Aquat. S c i . 89. D.J. Meerbury e d i t o r , pp 90-96. R e f s t i e , T., S t e i n e , T.A. and Gjedrem, T. 1977. S e l e c t i o n experiments wi t h salmon. I I . P r o p o r t i o n of A t l a n t i c salmon s m o l t i f y i n g at 1 year of age. A q u a c u l t u r e . 10: 231-242. R i c k e r , W.E. 1975. Computation and i n t e r p r e t a t i o n o f b i o l o g i c a l s t a t i s t i c s o f f i s h p o p u l a t i o n s . F i s h . Res. Bd. Can. B u l l . 191. 382 pp. R i c k e r , W.E. 1938. " R e s i d u a l " and kokanee salmon i n C u l t u s l a k e . J . F i s h . Res. Bd. Can. 4: 192-218. Robertson, O.H. 1958. A c c e l e r a t e d development of t e s t i s a f t e r u n i l a t e r a l gonadectomy wi t h o b s e r v a t i o n s on normal t e s t i s o f rainbow t r o u t . U.S. F i s h and W i l d l i f e Serv. F i s h . B u l l . 127: 9-30. 73 Rowe, D.K. and Thorpe, J.E. 1990a. D i f f e r e n c e s i n growth between maturing and non-maturing male A t l a n t i c salmon, Salmo salar L., p a r r . J . F i s h B i o l . 36: 643-658. Rowe, D.K. and Thorpe, J.E. 1990b. Suppression o f maturation i n male A t l a n t i c salmon (Salmo salar L.) p a r r by r e d u c t i o n i n f e e d i n g and growth i n s p r i n g months. A q u a c u l t u r e . 86: 291-313. Saunders, R.L. and Henderson, E.B. 1970 I n f l u e n c e of p h o t o p e r i o d on smolt development and growth of A t l a n t i c salmon. Journ. F i s h . Res. Bd. Can. 27: 1295-1311. Saunders, R.L., Henderson, E.B., and Glebe, B.D. 1982. Pr e c o c i o u s sexual maturation and s m o l t i f i c a t i o n i n male A t l a n t i c salmon (Salmo salar). A q u a c u l t u r e . 28: 211-229. Schmidt, S. and House, E.W. 1979. P r e c o c i o u s sexual development i n h a t c h e r y - r e a r e d and la b - m a i n t a i n e d male s t e e l h e a d t r o u t (Salmo gairdneri) J . F i s h . Res. Bd. Can. 36: 90-93. 74 Schreibman, M.P. and Kallman, K.D. 1977. The g e n e t i c c o n t r o l -of the p i t u i t a r y - g o n a d a l a x i s i n the p l a t y f i s h Xiphophorous maculatus. J . Exp. Zool. 200: 277-294. Scot t , A.P. and Sumpter, J.P. 1983. The c o n t r o l of t r o u t r e p r o d u c t i o n : b a s i c and a p p l i e d research on hormones. In: C o n t r o l Processes i n F i s h Physiology. J.C. Rankin, T.J. P i t c h e r and R. Duggan e d i t o r s . Croom Helm, London, pp. 176-199. Scot t , W.B. and Crossman, E.J. 1973. Freshwater f i s h e s of Canada. B u l l . 184. F i s h . Res. Bd. Can. 766 pp. Skarphedinsson, 0., Bye, V.J. and A.P. S c o t t . 1985. The i n f l u e n c e of photoperiod on sexual development i n u n d e r y e a r l i n g rainbow t r o u t , Salmo gairdneri, Richardson. J . F i s h . B i o l . 27: 319-326. S m i t h - G i l l , S.J. 1983. Developmental p l a s t i c i t y : developmental conversion versus phenotypic modulation. Amer. Zool. 23: 47-55. S m i t h - G i l l , S.J. and Berven, K.A. 1979. P r e d i c t i n g amphibian metamorphosis. Amer. Zool. 23: 47:55. 75 Stearns, S.C. and K o e l l a , J.C. 1986. The e v o l u t i o n of phenotypic p l a s t i c i t y i n l i f e - h i s t o r y t r a i t s : p r e d i c t i o n s of r e a c t i o n norms f o r age and s i z e at m a t u r i t y . E v o l u t i o n . 40: 893-913. Sweeting, R.M. and McKeown, B.A. 1987. Growth hormone and seawater adaptation i n coho salmon Oncorhynchus kisutch. Comp. Biochem. 88: 147-151. Thorpe, J.E. 1975. E a r l y maturation i n male A t l a n t i c salmon. S c o t t . F i s h . B u l l . 42: 15-17. Thorpe, J.E. 1986. Age at f i r s t m a t u rity i n A t l a n t i c salmon, Salmo salar: freshwater p e r i o d i n f l u e n c e s and c o n f l i c t s w i t h smolting. In: Salmonid age at m a t u r i t y . D.J. Meerburg e d i t o r . Can. Spec. Publ. F i s h . Aquat. S c i . 89. P. 7-14. Thorpe, J.E., Morgan, R.I.G., Talbot, C. and M i l e s , M.S. 1983. Inhe r i t a n c e of developmental r a t e s i n A t l a n t i c salmon, Salmo salar L. Aquaculture. 33: 119-128. 76 Thorpe, J.E. and Morgan, R.I.G. 1978. Growth r a t e and s m o l t i n g r a t e of progeny of male A t l a n t i c salmon p a r r , Salmo salar L. J . F i s h . B i o l . 13: 549-556. T i t a r e v , Y.F. 1975. A c c e l e r a t i o n of m a turation i n the Rainbow Trout (Salmo gairdneri) under the i n f l u e n c e of i n c r e a s e d water temperature. J . I c t h y o l . 15: 507-509. T o f t e b e r g , P. and T. Hansen. 1986. R e l a t i o n s h i p between age at m a t u r i t y and growth r a t e i n farmed rainbow t r o u t , Salmo gairdneri. EIFAC/FAO Symposium on S e l e c t i o n , H y b r i d i z a t i o n and Genetic E n g i n e e r i n g i n A q uaculture of F i s h and S h e l l f i s h f o r Consumption and S t o c k i n g . Bordeaux (France), 27-30 May 1986. 35 pp. T r i v e r s , R.L. 1976. Sexual s e l e c t i o n and r e s o u r c e - a c c r u i n g a b i l i t i e s i n Anolis garmani. E v o l u t i o n 30: 253-269. Tsmura, K. and Hume, J . 1986. A comparison o f p r e c o c i o u s n e s s i n t h r e e graded s i z e c l a s s e s of h a t c h e r y - r e a r e d rainbow t r o u t (Salmo gairdneri) . F i s h e r i e s T e c h n i c a l C i r c u l a r No. 75. M i n i s t r y of Environment and Parks. P r o v i n c e of B r i t i s h Columbia. 10 pp. 77 Utoh, H. 1976. Study of the mechanism of d i f f e r e n t i a t i o n between the stream r e s i d e n t form and the seaward migratory form i n masu salmon, Oncorhynchus masou Brevoort. I. Growth and sexual m a t u r i t y of precocious salmon p a r r . B u l l . Fac. F i s h . , Hokkaido Univ. 26: 321-326. Wagner, G.F. and McKeown, B.A. 1986. Development of a salmon growth hormone radioimmunoassay. Gen. Comp. Endo. 62: 452-458. Warner, R.R., Roberson, D.R. and Leigh, E.G., J r . 1975. Sex change and sexual s e l e c t i o n . Science. 190: 633-638. Warner, R.R. and Hoffman, S.G. 1980. L o c a l p o p u l a t i o n s i z e as a determinant of mating system and sexual composition i n two t r o p i c a l marine f i s h e s (Thalassoma spp.) E v o l u t i o n 34: 508-518. Watanabe, T. 1982. L i p i d n u t r i t i o n i n f i s h . Comp. Biochem. P h y s i o l . 73B(1): 3-15. 78 Wootton, R. 1973. The e f f e c t of s i z e of food r a t i o n on egg pro d u c t i o n : The female three-spined s t i c k l e b a c k , Gasterosteus aculeatus. 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 Inc., Englewood C l i f f s , N.J. 718 pp. 79 Appendix 1: Mean weight (g), length, and sample s i z e , by sample date f o r mature and immature rainbow t r o u t males reared at 9oC. The mature males had a s i g n i f i c a n t l y g r e ater mean weight and mean length than the immature males (P< 0.05) f o r the dur a t i o n of the study. Date Mature Immature n wt (g) st d dev. n wt. (g) i s t d dev. Jan. 24-27 104 7.5 2.49 362 4.8 1.75 Feb 7/8 103 7.5 2.50 358 4.8 1.69 Feb. 21/22 104 8.8 3.02 362 5.4 2.00 Mar. 14 89 10.4 4.05 328 6.3 2.42 Mar. 29 101 13.4 5.31 359 . 7.7 3.08 Apr. 12 102 16.0 6.29 362 8.9 3.58 Apr. 25 102 20.1 8.08 362 10.5 4.37 May 9 102 25.0 9.82 360 12.7 5.39 May 23 102 29.5 11.41 360 14.4 6.26 June 6 100 33.9 13.01 361 16.5 7.33 June 20 102 39.5 14.59 360 19.0 8.57 J u l y 4 102 44.6 16.35 361 21.4 9.88 J u l y 20 102 49.4 18.24 361 23. 6 11.46 Aug. 1 101 47.7 17. 63 358 22.8 11.03 Aug. 15 101 48.8 17.84 360 23.8 11.70 Aug. 31 101 49.5 18.61 359 24.2 11.96 Sept .28 35 72 .2 22 .72 121 34.7 18.27 Date Mature Immature n len(mm) s t d dev. n len(mm) s t d dev Jan. 24-27 104 89.2 9.42 362 76.1 9.45 Feb 7/8 103 89.7 12. 64 358 77.0 9.45 Feb. 21/22 104 93.5 10.31 362 7 9.3 9. 95 Mar. 14 89 99.8 12.35 328 83.7 10.96 Mar. 29 101 106.1 13.00 359 88.7 11.52 Apr. 12 102 111.3 16.73 362 93.2 12.15 Apr. 25 102 118.4 17.31 362 97.8 13.02 May 9 102 127.2 15 .44 360 103.3 14.77 May 23 102 134.2 16.14 360 108.7 15.02 June 6 100 139.5 16.59 361 112.9 15. 97 June 20 102 146.2 17.24 360 117.8 17.10 J u l y 4 102 154.1 17.73 361 124.0 18.32 J u l y 20 102 160.4 18.22 361 129.0 19.44 Aug. 1 101 161.5 18.41 358 129. 9 19.79 Aug. 15 101 163.8 18.67 360 132.1 22.06 Aug. 31 101 167.2 19.07 359 134 . 6 20.90 Sept .28 35 182.3 17.38 121 155.5 23.21 80 A p p e n d i x 2: 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 mature and immature r a i n b o w t r o u t m a l e s r e a r e d a t 15oC. The mat 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 d u r a t i o n o f t h e s t u d y . D a t e M a t u r e Immature n . wt (g) s t d dev. n wt (g) s t d dev. J a n . 24-27 158 6.4 3.38 252 4.6 1.82 F e b . 7/8 161 6.6 2.48 249 4.6 1.92 F e b . 21/22 160 7.6 3.07 253 5.2 2.13 Mar. 15 158 9.0 3.52 252 6.0 2.42 Mar. 28 158 13.3 5.22 252 8.8 3.61 A p r . 11 158 16.1 6.47 252 10.4 4.38 A p r . 26 157 20.5 8.96 252 12.5 5.46 May 10 158 26.4 11.32 252 15. 6 7.07 May 24 158 31.1 13.26 251 17.6 8.20 June 7 158 35. 6 15.35 251 19.5 9.18 June 21 158 41.3 17.80 250 21.8 10.37 J u l y 5 158 50.7 22.04 245 26.1 12.34 J u l y 19 153 61.0 27.54 245 30.4 16.34 Aug. 2 150 62. 6 28.03 237 29.7 14.49 Aug. 16 150 69.0 30.97 236 33.0 17 .74 S e p t . 1 148 64.1 32.99 235 34.7 17.19 S e p t . 28 55 72.2 22.72 65 34.7 18.27 D a t e M a t u r e Immature n len(mm) s t d d ev. n l e n (mm) s t d de 1 J a n . 24-27 158 84.5 10.35 252 75.5 9.53 F e b . 7/8 161 86.0 10.23 249 75.8 10.41 F e b . 21/22 160 88.7 11.02 253 78.0 10.38 Mar. 15 158 93.8 11.82 252 82.1 10.70 Mar. 28 158 103.9 13.05 252 90.7 12.10 A p r . 11 158 110.8 14.09 252 96.4 13.00 A p r . 26 157 119.0 15.57 252 102 .1 13 . 88 May 10 158 128.2 16.82 252 108.9 15.23 May 24 158 134.9 17.85 251 113.9 16.29 June 7 158 141.0 18.91 251 117.9 17.15 June 21 158 147.9 20.08 250 122.4 19.50 J u l y 5 158 156.2 21.14 245 129.4 19.05 J u l y 19 153 164.3 22.87 245 134.1 20.18 Aug. 2 150 168.8 23.41 237 137.2 21. 01 Aug. 16 150 174.5 25.11 236 139.5 26.68 S e p t . 1 148 173.2 28.29 235 145.4 22.48 S e p t .28 55 182.3 17.38 65 144.5 23.21 81 Appendix 3: Mean weight (g), len g t h , and sample s i z e , by sample date f o r mature and immature coho salmon males. 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 weight and mean l e n g t h than the immature males (P< 0.05) f o r the d u r a t i o n of the study. Date Mature Immature _ n wt (g) s t d dev. n wt (g) s t d dev. Mar. 22 18 27 . 9 5. 42 70 24.1 3. 97 Mar. 31 4 25.4 3. 20 12 25.2 3. 75 Apr. 21 22 31.3 6. 37 77 26.0 4 . 88 May 15 22 41.8 10. 67 82 30.7 7 . 68 May 25/26 22 45. 9 12. 79 83 32.9 8. 45 J u l y 10 22 86.2 23. 22 83 45.7 13. 70 J u l y 31 24 100.6 23. 51 85 51.9 16. 42 Sept. 9 19 122.0 35. 23 66 68.8 22. 54 Nov. 30 17 95.0 28. 19 60 70.0 31. 06 Date Mature Immature n len(mm) s t d dev. n len(mm) s t d de-Mar. 22 18 134 . 6 7.58 69 12 8.1 6.75 Mar. 31 4 132.8 4.19 12 129.7 7.69 Apr. 21 22 14 0.4 7.62 77 131.4 7.89 May 15 22 152.7 9.35 82 139.0 10.03 May 25/26 . 22 161.5 10 . 95 83 144 .1 21. 68 J u l y 10 22 189.9 12.32 83 161.1 13. 62 J u l y 31 24 198.2 12.79 85 166. 8 14.29 Sept. 9 19 211. 6 16.38 66 176.5 26.06 Nov. 30 17 211.2 17.09 60 186.7 24.04 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0098584/manifest

Comment

Related Items