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.