Estimates of heritability and genetic correlation for growth traits at harvest in redclaw crayfish, Cherax quadricarinatus

The current study assessed genetic parameters of three growth traits in redclaw crayfish Cherax quadricarinatus, including body weight (BW), body length (BL) and carapace length (CL), and explored how the number of families affected the heritability estimates of these traits. A total of 350 families were produced, and seven family levels containing 50, 100, 150, 200, 250, 300 and 350 families respectively were designed. After a 170 d communally rearing period for 350 families, males had significantly higher BW and BL averages (P < 0.001), but significantly lower CL average than females (P < 0.001). Heritability estimates of BW, BL and CL based on 350 families were 0.138 +/- 0.051, 0.123 +/- 0.048 and 0.073 +/- 0.035, with common environmental effects of 0.049 +/- 0.024, 0.053 +/- 0.023 and 0.039 +/- 0.017, respectively. There were strong positive genetic correlations (0.863 +/- 0.089-0.970 +/- 0.028) between these growth traits. Among different family levels, heritability estimates ranged from 0.030 +/- 0.090 to 0.138 +/- 0.051, 0.010 +/- 0.091 to 0.123 +/- 0.048, and 0 to 0.073 +/- 0.035, and common environmental effects ranged from 0.045 +/- 0.101 to 0.092 +/- 0.046, 0.053 +/- 0.023 to 0.100 +/- 0.047, and 0.038 +/- 0.043 to 0.062 +/- 0.033, for BW, BL and CL, respectively. Only heritability estimates of BW and BL based on 300 and 350 families, and that of CL based on 350 families, were significantly different from zero (P < 0.05), which suggested that larger numbers of families could contribute to more accurate estimation of heritability. The results indicate that there exists some genetic variation for our selection population to improve growth in C. quadricarinatus. However, the future program for redclaw crayfish needs to include crossing with outside stocks to replenish genetic variation of selection population.