Reproductive Investment and Growth History in Female Coho Salmon

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Abstract
The body size, ovary mass, egg mass, and fecundity of coho salmon Oncorhynchus kisutch from three different rearing environments (wild, ranched, and captive) were compared to determine which aspects of growth history affect changes in these reproductive characters. In addition, the growth of individually tagged females reared in captivity throughout the seawater growth phase was measured and related to final reproductive investment. A strong positive relationship existed between ovary mass and body length at spawning; this relationship was maintained over a wide range of final body sizes, and the regression slope was consistent among the rearing environments. However, the relative investment in ovary mass and fecundity (regression intercepts) differed between rearing environments. Fish reared in captivity throughout their life cycle had higher values than did fish reared in the other two environments. A relatively weak positive relationship between egg mass and final body length was common to females from all three rearing environments. In captively reared female coho salmon, growth during the 6 months prior to spawning had the greatest correlation with the reproductive parameters measured at spawning.
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