Characterisation of genetic structure of Dicentrarchus labrax larvae in two nurseries of the Gulf of Lions (NW Mediterranean)

Despite extensive knowledge of the genetic structure of sea bass ( Dicentrarchus labrax) populations, no studies have investigated genetic structure within early life stages, or compared such structure between such stages and ( sub) adults. Using nine newly developed microsatellite loci, we investigated patterns of genetic variation and relatedness among juveniles that settled in two NW Mediterranean nursery grounds in close geographical proximity. There was no evidence for differentiation among samples at settlement (theta= - 0.0010), and no significant genetic relatedness. Nevertheless, significant departures from Hardy- Weinberg equilibrium were detected in each sample, which could not be attributed exclusively to the presence of null alleles and to Wahlund effect. These results are compared with and discussed in relation to the genetic structure of adults described in the same area 10 years ago.