Individual variation in progeny size and quality in rainbow trout, Oncorhynchus mykiss (Walbaum)

Early life history traits of fish are very variable as a result of both genetic and environmental factors. In this study, we examine individual variation in early life history traits in progeny of seven females crossed with one male rainbow trout, Oncorhynchus mykiss (Walbaum). Individual eggs were followed from fertilization through hatching until death of the larvae by starvation. Larvae and yolksac size (size was shown to be a good indicator of energy content) increased with increasing egg size, but there were still differences between families after variation in egg size was accounted for. Incubation time was not correlated with egg size, and did not differ between families. The progeny from the different families utilized the available energy differently, as both longevity and growth-rate without food was independent of yolk-sac size, but strongly dependent on family. The observed between-family differences in early life history traits in rainbow trout were mainly caused by genetically based effects; egg size and thus probably egg quality, which differed strongly bet ween females, could not adequately explain these differences.