Genetic characterization of the relict population of the European sturgeon, Acipenser sturio: insights into breeding and conservation programs

Captive and restocking programs have become a common management technique to supplement populations of endangered species. They are generally designed to minimize the genetic risks associated with the loss of genetic diversity and inbreeding and therefore provide more chances for organisms to survive and adapt to environmental changes. Here, we examine the patterns of genetic diversity of individuals of wild origin, captive-wild breeders and five released cohorts of the critically endangered European sturgeon, Acipenser sturio based on the analysis of 18 microsatellite markers. The only remaining population of this species is located in the Gironde basin (France), following continued demographic decline over the last century. A restoration program initiated 20 years ago has resulted in more than one and a half million individuals being stocked. Here, we present main conclusions of this study concerning the levels of genetic variability and structure, effective population size, relatedness and inbreeding within the captive broodstock and the stocked population. Our results indicated that A. sturio genetic diversity is highly reduced, but that the stocked population is not inbred and is no less genetically diverse than in the wild, with most allelic diversity being conserved. Our findings further suggest that a multiple-year stocking strategy associated with a sufficiently high number of unrelated parent pairs may be the best strategy for reintroduction and long-term preservation of genetic diversity of this species (by avoiding inbreeding and increasing the effective population size).