Genetic studies of growth in domesticated rainbow trout

The heritability of body weight and the form of the growth curve was investigated in two crossbred strains of domesticated rainbow trout. Growth rate was nearly exponential at young ages but slowed to nearly linear at older ages. An empirical equation was derived that related exponential growth constants to the observed growth patterns. Heritabilities of body weight based on full-sib families were estimated at six ages for each stock. Estimates made at young ages were similar to other estimates of body weight in salmonid fish. However, non-additive genetic variance, culling bias and common environmental effects may have inflated estimates made at older ages, as the estimates were extremely high, and these possible sources of confounding were known to exist in the experimental design.