Genetic parameters of growth in rainbow trout, Salmo gairdneri, as a function of age and maturity

Abstract

The relative magnitude of additive genetic effects, non-additive genetic effects and maternal effects was determined for size, growth, condition factor and age at sexual maturity for rainbow trout at 2.5 and 4 years of age using a factorial mating system. The data consisted of 747 fish from seventeen 2×2 factorial mating sets. Heritability estimates for length and weight ranged from 0.13±0.17 to 0.38±0.22. Condition factors were more heritable than size, with heritability estimates ranging from 0.46±0.24 to 0.66±0.27. The heritability estimate of age at sexual maturity was 0.21±0.14. Maternal effects were not important for any traits. Non-additive genetic effects were important for all size and growth traits except instantaneous growth rate for weight at 2.5 years of age. Physiological status with respect to maturation and smolting was related to size and affected growth rates. Some of the additive and non-additive genetic variation in size and growth was due to family differences in physiological status. Selection on size after physiological differentiation should take into account the physiological status and history of each fish, if possible. Crossing of lines may be helpful for improving size in maturing fish. Genetic correlations between size or condition factors measured at different ages were all positive. Hence, selection at one stage should improve size or condition factor at another.