Small pelagic fish are keystone species in the ecosystem because of their central place in the food chain. In order to assess stocks and propose appropriate management methods, it is therefore important to have a good knowledge of these species and to have data that are independent of fishing. The Ifremer fisheries laboratory in Sète has therefore been monitoring these populations since the 1990s. In 2002, the EU asked the Member States to contractualise certain operations; it is within this framework that the PELMED campaign was part of the extended contractualisation programme for biomass assessment (DCF). Thus, each year France is required to assess the biomass of small pelagic species in the Mediterranean, in order to determine the state of the stocks and to propose management measures.

The cruise consists of a systematic survey of the entire Gulf of Lion, from Port-Vendres to Marseilles, along radial lines spaced 12 NM apart, perpendicular to the coast, during the day (6 a.m. to 10 p.m.), over the entire length of the shelf and the beginning of the slope. Identification trawls are required to make the specific biomass assessment.

• Sample plan(s) :

In the Gulf of Lion, the survey is carried out along parallel radials 12 nautical miles apart and perpendicular to the coast (9 radials in the Gulf of Lion) on the continental shelf (15-200m depth).

• Precision on the type of data :

The acoustic data is acquired continuously in order to observe the shape and intensity of the echoes that materialise the schools of fish. The echo sounder used is a SIMRAD ER60 38, 70, 120, 200 and 333 kHz coupled to the ME70 multibeam sounder.

After each trawl, the team sorts and weighs all the pelagic species collected, as well as counting and measuring a subsample of the 8 main species (anchovy, sardines, sprats, mackerel, horse mackerel and hake). A set of additional biological parameters is also collected on a sample of the target species (anchovies, sardines, and sprats): sex, maturity, fat content, otoliths, weight by size class. Finally, numerous samples are taken and then frozen for further manipulation on return to the laboratory.

After each trawl, a hydrological station is also carried out with measurements of temperature, conductivity, density, oxygen, pH, radiance and fluorescence along the water column via a bathysonde, collection of seawater using a Niskin bottle for the analysis of phytoplankton (taxonomic composition, biomarker pigments) and nutritive salts, and vertical zooplankton net hauls (WP2). The phytoplankton and zooplankton water samples brought back to the laboratory are analysed in the year following the campaign. Samples of surface microplastics are also taken using a Manta net.

Finally, throughout the campaign, an observer is taken on board to identify and count the birds and marine mammals.

• Parameter(s) observed or measured :

Number of individuals, weight per species, size structure, age.

Acoustics, Bathysonde, Trawling, WP2, Niskin, Manta, Pocket ferrybox.

• Resolution of parameter(s) :

By fishing operation, continuous survey (CUPES), systematic analysis of scientific fishing catches

• Format(s):

The available data exist in the following format: csv

Acoustic data exist in the format: HAC