Genetic variation in the growth traits of straight-bred and crossbred black bream (Acanthopagrus butcheri Munro) at 90 days of age

The current slow growth rate of black bream (Acanthopagrus butcheri Munro) impedes their widespread commercial aquaculture across inland southern Australia. We report initial estimates of genetic variation for growth traits at 90 days of age from a diallel cross using two black bream populations. Standard length, total length, and wet weight varied significantly among lines and among half‐sib groups within lines. Differences among half‐sib groups explained 6.8% of the total variance in standard length, 8.3% in total length, and 7.1% in wet weight, giving estimated heritabilities over all lines of 0.27±0.11 for standard length, 0.33±0.13 for total length, and 0.28±0.12 for wet weight. There was no evidence for heterosis in any traits when straight‐bred and crossbred lines were compared. There were high phenotypic (r_P=0.95–0.98) and genetic (r_G=0.63–0.69) correlations among all growth traits.