Synthèse de l’état des stocks dans le golfe Normand-Breton. Réponse à une demande d'expertise

This report incorporates the latest available information on the state of stocks fished in the Normandy-Breton Gulf. For whelk, the standardised LPUE, used here as a proxy for abundance, suggests a steady decline in stock biomass since 2017, with a further decline observed in 2024. Landings are following this trend, generally with a one-year lag. This stock seems to be more fragile than ever. A number of factors suggest that rapidly changing environmental conditions in the Western Channel could be a major contributor to this deterioration in the state of the stock. For spider crab, abundance has particularly increased in the Norman-Breton Gulf in recent years, the main fishing area in France. However, this situation is highly heterogeneous, with spider crab abundance currently lower in other areas, such as southern Brittany. We still lack the information needed to understand this dynamic, but the milder winter conditions, with cooler temperatures, are likely to favour the survival of juveniles. For edible crab, LPUE trends indicate that the state of the stock is low. Low recruitment in recent years and/or an increase in mortality unrelated to fishing could explain this sharp drop in landings; work is underway to validate these hypotheses. The state of the lobster stock is considered to be generally good, although no length-based indicators or other stock assessments are yet available for these stocks, except in Granville Bay, where the decline has been confirmed for 10 years now. Some work is underway to develop assessments that will be adjusted using a global SPiCT model. For scallops, the CMSY+ and SPiCT models have been used to assess the Normandy-Breton Gulf stock. The stock in the Bay of Saint-Brieuc has shown a steady increase in biomass and abundance indices over the last 10 years. The model results confirm that the stock is in excellent condition, with catches below the estimated MSY. No information is available for other bivalve stocks.