Many fish species realize their life cycle in restricted and variable habitats such as coastal and estuarine nurseries. These habitats are essential for the growth and survival of young fish. The decisive nature of this phase on coastal nurseries explains that the degradation and destruction of these biotopes are among the main causes of the decline of marine species occupying these limited and fragile habitats. Reducing the surface or decreasing the quality of these coastal habitats can affect the size of the fish stocks that depend on them. The characterization of the ecological status and the study of the functionality of these nursery habitats, are essential for the implementation of ecosystem-based management measures that guarantee sustainable fisheries. The NURSE 2021 cruise is part of a time series that started in 1980s. This time series supports public policies by consolidating knowledge on coastal environments. It grants Ifremer on its capacity in terms of expertise vis-à-vis all other non-fishing coastal uses (aggregates extraction, clippings, MRE, etc.). In addition, this time series is now participating in the MSFD through the assessment of Good Environmental Status (GES) of the Descriptor 1 on Biodiversity.

NURSE 2021 aimed to collect data to monitor and understand the functioning of nurseries in the coastal zone, as these essential habitats play a determining role in the recruitment of juveniles of several fish species. Therefore, it aimed at pursuing the standardized sampling of benthic and demersal organisms  (commercial and non-commercial invertebrates and fish) since the 1980's to develop nursery habitat quality indicators and GES indicators for coastal ecosystems. Concurrently, the cruise collected data on coastal marine litter, one of the MSFD descriptor.

This cruise is mainly part of the Popex project of the Department of Biological Resources and Environment (RBE, Ifremer). At the same time, the cruise contributes to other complementary projects in strong collaboration with Dyneco Ifremer Brest Unit and the UMR ESE Unit at Agrocampus Ouest.

The data obtained at the scale of each of the sites studied are all elements that contribute to the understanding of the functioning of coastal ecosystems both at the site scale and at the regional scale (i.e. Bay of Biscay). The data obtained in the context of the NURSE 2021 cruise are used to feed the models on the trophic capacity of coastal marine ecosystems, models developed as part of the CAPANOUR research project and a thesis co-supervised by A. Brind'Amour ( Ifremer) and H. Le Bris (UMR ESE). All the data obtained from the cruise are added to those already existing in order to develop GES indicators for coastal fish and cephalopods and marine coastal litter under MSFD.

The study areas of this cruise correspond to three flatfish nurseries in the Bay of Biscay: the two pertuis charentais and the bay of Vilaine. The work carried out on the three nurseries proposes a quantitative and biogeographical description of the ecosystems. They consisted of sampling by beam trawl according to a standardized protocol. The species thus caught have been identified, measured and weighed. Dissolved oxygen measurements have also been taken for each tow to characterize this environmental pressure at the scale of the coastal areas.