The English Channel, a crossroads between the Atlantic Ocean and the North Sea, characterized by its megatrial regime, is an area rich in species of boreal (cod, whiting...), temperate (bar, red gurnard...) and Lusitano fish (hake, monkfish...), flat (sole, plaice...) and pelagic fish (mackerel, sardines ...), selacians (rays, dogfish ...), crustaceans and cephalopods of commercial interest (cuttlefish, squid). It is an open maritime region, a place of continuous exchanges (biological, hydrological, etc.), where many key habitats are identified: nurseries, spawning grounds and migration ways. The Channel is also a spatial entity characterized by the preponderance of its socio-economic activities in relation with the maritime environment: it represents nearly 20% of the world marine traffic, but also 40% of the fish catches of France in the North-East Atlantic, carried out by more than 1300 small fishing vessels, registered along the Channel coast.

The CGFS survey, conducted annually since 1988, is the only way of collecting science data with a Large Vertical Opening bottom trawl in the English Channel. The resulting data are used annually by the ICES International Stock Assessment Working Groups. The main objective of the CGFS 2020 survey is therefore to collect the data necessary for the evaluation of the fish stocks of the 7d (Eastern Channel) and 7e (Western Channel) divisions, and more specifically to obtain abundance at age indexes for species evaluated analytically in 7d (red mullet, plaice...) or global abundance indexes (bar, horse mackerel, cuttlefish, squids). As such, this survey is largely funded by Europe through the European Fund for Maritime Affairs and Fisheries.

In addition, the CGFS is identified in the monitoring program of the MSFD (Marine Strategy Framework Directive): its secondary objective is thus to collect in the Channel data on the biotic and abiotic environment of the exploited species, for better understand their dynamics within the ecosystem. The series of CGFS surveys will allow the monitoring of the ecological status of the French waters of the Channel, by providing data allowing the calculation of indicators for the descriptors D1-biodiversity, D2-invasive species, D3-commercial species, D4-trophic networks, D5-eutrophication, D8-contaminants, D9-sanitary issues, D10-waste and D11-noise.

The survey is organized in two periods of 16 days of work at sea each, respectively in Western Channel and Eastern Channel. Nearly 120 tows, made during the daylight, are programmed. The abiotic parameters are measured either by station with a rosette or continuously. Sampling of fish eggs is done continuously.

After the survey, all data will be validated and provided to national and European databases (SIH, Harmonie, Sismer, DATRAS).