Designing aquaculture mass selection programs to avoid high inbreeding rates

Summary

A series of replicated stochastic simulations was carried out to determine the effect of the number of breeders selected (4–100 pairs), the number of progeny tested (5–150 progeny per pair) and the magnitude of the heritability (0.1–0.4) on the rate of inbreeding, and the response to selection through 15 generations of mass selection. It was found that to keep inbreeding rates low (about 1% per generation), a minimum of 50 pairs of breeders should be selected and the number of progeny tested should be restricted and standardized to not less than 30–50 progeny per pair. These designs resulted in a response to selection (average per generation) of 5–13% of the base population mean depending on the heritability. Testing larger numbers of progeny resulted in a marginal increase in response to selection. Reducing the number of broodstock pairs might increase the rate of inbreeding to as much as 6–8% per generation. Loss of genetic variation because of inbreeding was then found to reduce the response to selection by more than one third. In addition, a further reduction is likely to occur because of inbreeding depression.