Number of contributing subpopulations and mating design in the base population when establishing a selective breeding program for fish
2006
Holtsmark, M. | Sonesson, A.K. | Gjerde, B. | Klemetsdal, G.
Fish-breeding programs may be based on fish from wild or from domesticated populations. The knowledge of the genetic properties of these populations is often poor. One alternative is to assume that all fish are unrelated, having the same genetic variance within subpopulations, but different genetic means. The effects of increasing the number of subpopulations in the base (1-8) and the mating design in the base (mating within subpopulations, or at random, within and across subpopulations) on genetic variance, genetic gain and the contributions of the different subpopulations in the following generations were studied for a base population with a realistic number of families (160 or 240) and a somewhat low number of offspring per family (20 or 30). Stochastic simulation was used, assuming an infinitesimal additive genetic model. Selection was carried out for 10 generations, applying optimal contribution selection on phenotype, which maximizes genetic gain at a fixed rate of inbreeding. The largest genetic gain was obtained when sampling fish from at least four subpopulations, and mating within subpopulation(s) in the base. Given a genetic variance within and between subpopulations of 0.2, increasing the number of subpopulations from one to four and from four to eight led to an improvement of the genetic level in generation 11 by 7.0% and 0.3%, respectively. Standard deviations of genetic level, i.e., risk, were also lower from sampling from a larger number of subpopulations. However, sampling from a larger number of subpopulations may introduce larger costs connected with sampling of fish from more locations.
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