Genetic stock structure analysis revealed single population units in the shared stocks of Adriatic demersal species

Two genetic research projects (financed in parallel by FAO-AdriaMed and by the Italian Ministry of Agriculture and Forestry Policies) have been carried out to identify population status and structure within the Adriatic shared demersal fish stocks, which are bioeconomically relevant for SCSA in the Mediterranean (see Annexes 1 and 2). The sampling and genetic methodologies adopted by both projects were standardised as much as possible for all species by the use of MEDITS samplings and microsatellite marker analyses. Genetic estimators for population status (i.e. genetic polymorphism in terms of allelic diversity, heterozygosity, and fitting of Hardy-Weinberg equilibrium) and structure (i.e. genetic differentiation in terms of fixation indexes and gene flow rates) were applied using specific statistical software. High levels of genetic polymorphism and correlation with Hardy-Weinberg equilibrium were scored in most species, implying good status of stocks. Similarly, high levels of genetic homogeneity were observed among geographical samples in most species, clearly suggesting the occurrence of single population units within the Adriatic shared stocks. Low genetic polymorphism and weak genetic divergences were occasionally found, probably related to specific bio-ecological and behavioural features, and/or to methodological artefacts. In populations of marine species, such a pattern of genetic features can be related to largesize and unfragmented populations (a fishery question: Can it also be associated with undepleted stocks?). This initial picture of the population structure of several Adriatic marine fishery resources needs to be integrated by further genetic analyses carried out at a finer scale as well as by data obtained from other methodological approaches.