The objective of the survey is to collect data to help monitoring and understanding the functioning of nurseries, as these critical habitats play a key role in the recruitment of juveniles of several fish species. The survey falls in a time series since the early 1980s and is therefore a recurring survey in support of public policies. Indeed, this time series consolidates knowledge of coastal environments by giving Ifremer an increased capacity of its expertise in all coastal uses, other than fishing (extraction of aggregates, clapages, EMR, etc.). It also participates in the Marine Strategy Framework Directive (MSFD) through the development of Good Ecological Status (GES) indicators, in particular those of the D1- Biodiversity.

It has been stated that the Bay of Vilaine, the Bay of Bourgneuf, the outer estuary of the Loire, the outer estuary of the Gironde and the Pertuis Charentais are amongst the most important flatfish nursery sites in the Bay of Biscay. Four of these sites, representing the main coastal nursery areas of the Bay of Biscay, has been sampled during the NURSE18 : the mouth of the Gironde, the mouth of the Loire, Bourgneuf Bay and Vilaine Bay. A sampling effort was directed towards the Gironde, where supplementary information on trophic interactions at the mouth of this nursery. was gathered. NURSE18 had the following objectives:

• Continuing the standardized sampling of benthic and demersal community (invertebrates, commercial and non-commercial fish species) since the 1980s in order to develop quality indicators for nursery habitats and GES indicators for coastal communities as stipulated by the MSFD;
• Characterize the trophic structure determining the dependence of fish on the different habitats of the Gironde.

The data obtained will be used to feed trophic capacity models of marine coastal ecosystems, models developed in previous work through a research project (CAPANOUR) and two co-directed theses between A. Brind'Amour (Ifremer) and H. Le Bris (UMR ESE).