Management techniques to minimize the loss of genetic variability in hatchery fish populations

Inbreeding in hatchery fish populations causes loss of genetic variability. This reduces the effective population size (Ne) for breeding programs. Seven ways to increase Ne are suggested: (1) mate each available female with a single male; (2) include both early- and late-maturing fish in matings and avoid selection for other traits; (3) import fertilized eggs from areas within the hatchery\u27s drainage or from adjacent drainages; (4) import sperm from wild or adjacent hatchery populations; (5) rear about 20 independent families that can be tagged to estimate family-size variance; (6) store sperm from in-house males cryogenically for later out-crosses; and (7) ensure that progeny of all matings are represented among released fish and replacement brook stock. Practical considerations determine which of these suggestions apply to particular hatchery operations, but the success of each depends on sustained commitment by management, careful monitoring, and objective evaluation