Family heterozygosity and progeny body length in pink salmon Oncorhynchus gorbuscha (Walbaum)

The relationship between multiple-locus heterozygosity at eight polymorphic enzyme loci and progeny body length was examined in 20 experimental pink salmon families differing in parental heterozygosity. It was shown that: (1) the effect of individual heterozygosity on body length within the families was not statistically significant; (2) a considerable part of the between-family component of variance of body length was largely attributed to the differences in family heterozygosity; (3) there was no association between the mean family heterozygosity and the coefficient of variation of body length. In the groups of families with the low, intermediate and high heterozygosity the highest value of mean progeny body length was recorded in the intermediate heterozygosity group. There was no significant effect of heterozygosity at single loci on these differences among families. The results are explained by the hypothesis of epistasis and the hypothesis of maintenance of an optimal heterozygosity level in populations.