Evaluations locales des populations de bivalves dans le golfe de normand breton. Résultats de la campagne BIVALVES2002

The exploited stocks of wild bivalves (common cockles, dog cockles, clams, and spisules) in the Norman-Breton gulf vary according to the fishing activity and the environmental conditions. Different studies, carried out by the Ifremer in this region (between 1982 and 1998), enabled the evaluation of the stocks available for fishing as well as the collection of data on these species (demographic structure, growth...). For more information on the 1993-1994 studies and a presentation of the site and the fishery please refer to the reports by Berthou, 1987 and Noël et al, 1995. The bivalve expedition conducted in May 2002, enabled us to update the data on the populations of dog cockles and banded carpet shells, then of spisules and clams, using the same demographic analysis, growth and evaluation protocol. In addition to this halieutic study, the obtained data will be used to validate a dynamic model on the evolution of bivalve stocks in the English Channel. This expedition also contributed to the update of the data on limpet fresh weight abundance.The studied species are:- The banded carpet shell Tapes rhomboids- The dog cockle Glycymeris glycymeris- The spisule Spisula ovalis- The clam Venus verrucosa.