Evaluation du stock de coquilles Saint-Jacques Pecten maximus du gisement de la baie de Seine. Résultats de la campagne scientifique COMOR 2025 (07 au 22 juillet 2025)

The bay of Seine King scallop (Pecten maximus) stock assessment survey (COMOR2024) took place for the first time on the R/V Côtes de la Manche in July 2024, in a normal configuration. The usual sampling plan was applied, with 156 points to be sampled. At the end of the survey, 158 dredge tows were made, 100 valid tows in the Bay of Seine (French territorial waters) and 57 valid tows in the area "Extérieur Bay of Seine" (between the 12 miles limit on the South and the 49°48 parallel on the North). The analysis of these data confirms a very high level of exploitable biomass, which continues to increase in the Bay of Seine (but also outside the Bay of Seine), reaching a level in 2024 that has never been seen since the beginning of the historical series. Outside the Bay of Seine, biomass was estimated at 34947 tonnes, well above the average for the last decade. This is the record level for the “Extérieur” Bay of Seine. In the Bay of Seine, the estimated biomass is again very high, and is also the highest ever estimated (102729 tonnes, compared with 72614 tonnes in 2023, +41%). This biomass is made up of the largest cohort of 2-year-old King scallops ever estimated, arriving in the fishery for the first time (confirming what was identified last year with the highest abundance index of 1-year-old juvenile scallops) and a particularly abundant adult scallops remaining in the fishery after the last fishing season (64% and 36% of the biomass respectively). This is the third year in a row that a relatively balanced population of recruits and adults has been observed, especially since adults aged 3 and over are more abundant in 2024, for all age classes. The population is evenly distributed across the different areas of the Bay of Seine. However, the highest densities are found in the western part of the bay.