Projet Barfray. Montage d’une opération pilote de marquage conventionnel sur frayère

The Barfray project aimed at improving the knowledge on the essential habitats of the European sea bass (Dicentrachus labrax) on the French Atlantic coast (English Channel and Bay of Biscay). One of the research need concerns the diversity of feeding areas contributing to the main spawning grounds. Here we present the setting up of a conventional tagging pilot operation on spawning ground, a prerequisite to carry out this research. The operation initially aimed to tag 2,000 adult sea bass by mobilising a pair of pelagic trawlers for 10 days of fishing on an offshore spawning ground in the Bay of Biscay. This operation had to be reorganised and reduced in duration as no pelagic trawlers agreed to participate. Ifremer therefore carried out a sea bass spawning tagging campaign with the help of two longliners from La Cotinière (Oléron Island) from 20 to 24 February 2019 off the Gironde. This campaign allowed the tagging of 321 adult sea bass with one or two external tags. The weather conditions did not allow the operation to start earlier in the sea bass fishing season on this spawning ground, when longline yields are usually better. Communication operations were set up to encourage the various stakeholders (e.g. professional and recreational fishermen) to return the tags to Ifremer in exchange for a reward. The expected results concern the analysis of the apparent movement of fish between the tagging area (the spawning ground) and their recapture locations in the following 6 months. The data should allow quantifying the contribution of the sampled spawning area to the coastal summer feeding grounds. The study area covers the whole Bay of Biscay and the Western English Channel. The project should ultimately enable the adaptation and/or reinforcement of the management measures implemented for this species, which is experiencing a decline in abundance, particularly in the Celtic Sea - Channel - North Sea, but also in the Bay of Biscay.