Smoltification in the Net-Pen Culture of Coho Salmon: Quantitative Genetic Analysis

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Abstract
Investigations were conducted with underyearling coho salmon Oncorhynchus kisutch reared in marine net‐pens to determine the extent of genetic involvement in traits associated with smoltiffcation and saltwater adaptation and to assess genetic relationships among these traits. Data were obtained from two brood years (1977 and 1978) of experimental families formed by a nested mating design and consisted of length and weight measurements and morphological smolt assessments at 7 and 11 months postfertilization. Reasonably high heritability estimates (h2 = 0.22–0.29) were obtained for all smoltification traits except survival (h2 = 0.07). Correlation estimates among the variables suggested a strong genetic relationship between size and smoltification traits, with the exception of percent survival. The use of these estimates for genetic improvement was illustrated by two types of selection index. Substantial increases in smoltification and saltwater‐adaptation traits appeared to be possible. Received April 25, 1983 Accepted March 20, 1984