Selection for increased weight at 9 months in redclaw crayfish (Cherax quadricarinatus)

Abstract

Two lines of redclaw crayfish (Cherax quadricarinatus) were maintained for four generations. One line was selected for increased harvest weight at 9 months, and the other maintained as an unselected control. To increase the heritability and limit inbreeding, lines were subdivided into cohorts with selection based on weight differences from cohort means. Selection increased harvest weight. In generation 4, weights averaged 61.6 g for the selected line and 49.3 g for the control line (s.e. diff. 2.3). The percentage of females carrying eggs at harvest was 9.8 in the selected line and 18.1 in the control line (s.e. diff. 4.0) suggesting that selection may have diverted energy from breeding activity to growth by delaying sexual maturity. Selection increased the carapace and tail length of females relative to their body weight. Estimates of realised heritabilities for harvest weight varied from 0.38±0.06 in year 1 to 0.13±0.02 in year 4. A practical selection program for redclaw could include periods of closed line selection alternating with test crossing with outside stocks to replenish genetic variation.