The Marine Strategy Framework Directive recommends that Member States achieve a good environmental status (GES) of their marine waters by 2020. The definition of the GES is described by 11 descriptors, including descriptors assessing (commercial or not) species biodiversity (D1 and D3). D1 stipulates that biological diversity of the fish and cephalopod components is maintained and D3 stipulates that populations of all commercially exploited fish and shellfish are within safe biological limits, exhibiting a population age and size distribution that is indicative of a healthy stock.

The French assessment of the GES was conducted in 2018 in the bay of Biscay. The evaluation consisted in a quantitative and qualitative assessments. For the D3, the quantitative evaluation was based on results from the stock assessment using the fishing mortality and the spawning stock biomass as the two criteria. Whereas, the D1 evaluation was based on time series analyses (i.e. breakpoint analysis) of the abundance of populations of demersal species sensitive to fishing pressure, using data from the French scientific surveys. Qualitative analyses were done for fish species for which either data or methodological aspects were lacking.

For the D3, the evaluation was based on 17% of the stocks assessed by the EU. Thirty percent of those stocks were estimated in GES (i.e. defined by the MSY) whereas 70% were not. For the D1, the evaluation was done on 10% of the diversity of the demersal fish species of the continental shelf. Forty one percent of the populations were estimated in GES, whereas 10% were not. Nearly 50% of assessed population displayed no evolution in the studied time series. Qualitative assessment for the other groups of species (e.g. pelagic species, coastal and deep water species) gave general information of global diversity patterns, fisheries essential habitats, and abundance and biomass temporal evolutions.