Growth rate and spawning time in diallel crosses of three strains of rainbow trout (Oncorhynchus mykiss)

Factors controlling individual pre-maturation instantaneous growth rate and female spawning date were examined in two complete sets of diallel crosses of three strains of rainbow trout (Oncorhynchus mykiss ). Hybrids generally performed intermediately to pure strains. For growth rate, the trend among dam strains was opposite to the trend among sire strains. Hybrids grew more like their sire's strain and spawned more like their dam's strain. Males grew faster than females for all strains. Early-maturing individuals weighed more prior to maturation, but grew at the same rate as later-maturing individuals. Spawn date was highly repeatable over seasons. Genetic parameters and breeding values were estimated for 2-year old weight, and 3- and 4-year old spawn dates. All traits had high heritabilities. Negative phenotypic correlations and zero genetic correlations occurred between weight and spawn dates. Recommendations were made for a breeding program that simultaneously increases growth and delays spawning time.