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Genetics of Reproduction in Domesticated Rainbow Trout¹

University of California, Davis

Abstract

A population consisting of parental, F₁, F₂ and backcrosses among two domestic strains of rainbow trout was used to estimate genetic parameters of reproductive performance for hatchery cultured stocks. Data were collected for post-spawning body weight, volume of eggs spawned, egg size, egg number and egg per 100 g body weight for a total of 1,604 2-year-old female progeny. Heritabilities estimated from full-sub comparisons were similar for all five traits and equal to about .20 ± .05 Dominance and epistatic variance was evident for all traits except number of eggs for which genetic variation appeared to be primarily additive. The coefficient of variation was lowest for egg size (18%), intermediate for body weight (23%) and egg number (25%) and highest for egg volume (28%) and eggs per unit body weight (30%).

Genetic, environmental and phenotypic correlations among the traits were estimated. Generally, egg volume was highly correlated with egg number (.77 ± .07), egg size (-.55 ± .12) and body weight (.56 ± .11), however, egg volume and number were correlated arithmetically. Environmental correlations of egg volume with egg size and body weight also showed a positive relationship but were low. The correlation with egg number was equal to the genetic correlation. The genetic correlations for body weight with egg size and egg number were .46 ± .13 and .39 ± .14, respectively. Egg size was estimated by the volumetric method so negative correlation estimates indicate a positive relationship. The environmental correlation between body weight and egg size was zero. The genetic correlation between egg number and egg size was small and positive while the environmental correlation was about .20. Egg size showed a strong genetic correlation with eggs per unit body weight (.47 ± .13) while the environmental correlation was only .26. The phenotypic correlations were generally midway between estimates of the genetic and environmental correlation and the three always carried the same sign. It was suggested that selection for egg volume may be the most effective means of improving reproductive performance.

¹ Department of Animal Science. Study supported in part by California Department of Fish and Game through Dingell-Johnson Project F-28-R, supported by Federal Aid to Fish Restoration funds.

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