LOW EFFECTIVE SIZES IN HATCHERY POPULATIONS OF THE EUROPEAN OYSTER (OSKEA-EDULIS) - IMPLICATIONS FOR THE MANAGEMENT OF GENETIC-RESOURCES

Data on allozyme frequencies were used to estimate the effective sizes (N-e) of three hatchery-obtained populations of Ostrea edulis from Sp ain and France in the first hatchery generation. Two methods of N-e es timation were used: the so-called ''temporal method,'' based on the ch anges of allele frequencies across generations, and the ''heterozygosi ty method,'' based on the decrease of hererozygosity with respect to t he parental wild population from which the broodstock animals were obt ained. For comparison, the effective size of the wild progenitor popul ation of one of the Spanish hatchery populations (Ortigueira) was also estimated by the temporal method. Large differences between the numbe r of individuals used as broodstock and N-e were observed. More import ant, the estimates indicate that the N-e of hatchery populations is sm aller than that of the wild population studied. Introduction in the wi ld of such low-variability hatchery-produced oysters could result in t he reduction of inbreeding and variance N-e of the wild populations.