Abstract:

Management of a population’s effective breeding number (N_e) is crucial, because it is inversely related to genetic drift and to inbreeding. Reductions in Ne can irreversibly damage a population’s genetic and biological potential. Recommended N_es for standard reference populations of tilapia are 390-500, and those for farm populations are 100-150. Effective breeding numbers for reference populations must be larger because the management goal is conservation genetics – preventing detrimental levels of inbreeding, preventing the loss of rare alleles and preserving heterozygosity. Effective breeding numbers for farm populations can be smaller because the management goal is to maximize productivity. Acquisition of a foundation stock is the most important aspect of management of a population’s N_e, because the alleles that exist in that sample are those that determine the population’s genetic and biological potential. The fecundity of tilapia can facilitate maintenance of desired N_es; females produce only about 150-500 offspring per spawn, so even moderately-sized farms require hundreds of broodfish.

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Date 1987/12/01

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