462 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



SUMMARY 



The data show differences in fecundity between 

 populations of the same species of salmon for 

 different localities — the best examples being the 

 king salmon, Oncorhynchus tshawytscha, of the Sac- 

 ramento and Klamath Rivers; the sockeye salmon, 

 0. nerka, of the Skeena River system; and the 

 chum salmon, 0. keta, of Japan. 



The number of eggs shows a linear relation with 

 the logarithm of fork length; but for Oncorhynchus, 

 in which the size range of the mature adults is 

 slight, the regression of egg number on fork length 

 may more conveniently be treated as linear. 



There is an annual variation in fecundity. 

 Owing possibly to the short life history of the 

 pink salmon, this variation is pronounced in 

 that species. The annual differences in fecundity 

 of pink salmon are shown by covariance analysis 

 to be negatively associated with sea temperature 

 for a Queen Charlotte Island population. 



The number of eggs in the left and in the right 



ovary differs in some species, the left ovary usually 

 having the larger number; but this will vary 

 with the individual fish. This disparity between 

 the two ovaries in egg number is apparently due 

 to one ovary exceeding the other in length because 

 of crowding of the small posterior end of the body 

 cavity by the intestine. 



Fecundity in sockeye salmon was not shown to 

 be affected by length of sojourn in fresh water 

 prior to entering the sea. However, sockeye 

 spending 2 years at sea mature more eggs than 

 sockeye of the same size with 3 years of sea life. 



The four species of fluvial anadromous On- 

 corhynchus have larger eggs than the sockeye, 

 0. nerka, or species of the other genera. 



There is a suggestion of lower fecundity from 

 south to north in Oncorhynchus (except in 0. 

 gorbuscha). This may be caused by a higher age 

 at maturity, and therefore slower growth rates, 

 from south to north. 



REFERENCES 



Allen, George H. 



1956. Age and growth of the brook trout in a Wyoming 

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 Abo, K. v., and G. C. Broadhead. 



1950. Differences between egg counts of sockeye sal- 

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 Beal, Fred R. 



1955. Silver salmon {Oncorhynchus kisutch) reproduc- 

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1893. Life history of the salmon. Bull. U. S. Bureau 

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 Belding, David L. 



1940. The number of eggs and pyloric appendages as 

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 Belding, David L., and Doris M. Hyde. 



1932. Notes on the ocean feeding grounds of the 

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RODD. 



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1910. Notes on the increase in size of fish ova after 

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Brice, John J. 



1898. A manual of fish culture. Rept. of Commis- 

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 Brown, C. J. D., and Gertritde C. Kamp. 



1942. Gonad measurements and egg countsof brown 

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1952. Egg counts of Salvelinus malma from the Clark's 

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Calhoun, A. J. 



1944. Black-spotted trout in Blue Lake, California. 

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Cooper, Edwin L. 



1953. Mortality rates of brook trout and brown trout 

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Curtis, Brian. 



1935. The golden trout of Cottonwood Lakes. Cali- 

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Curtis, Brian, and J. C. Fraser. 



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Dahl, Knut. 



1917. Salmon and trout: a handbook. Salmon and 

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