Modelling larval dispersal of Pecten maximus in the English Channel: a tool for the spatial management of the stocks

International audienceThe great scallop Pecten maximus supports one of the most important and valuable commercial fisheries around the British Isles and in thenorthwest of France, but the resource is mainly managed at the scale of each local fishing ground through a combination of European, nationaland local measures. To analyse the larval dispersal pathways and connectivity patterns among fishing grounds of the great scallop inthe Celtic Sea and the English Channel, a particle tracking model was developed. The model combined a 3D physical circulation model thatsimulated currents and temperature fields and a scallop larval submodel that took into account a temperature-dependent planktonic larvalduration and an active vertical swimming behaviour. Due to the lack of stock assessment at the regional scale, the location of the main fishinggrounds was established by combining different sources (e.g. grey literature, unpublished scientific surveys, vessel monitoring data, fishermen)while the spawning biomass of each stock was estimated from landings data. Results indicated that each local stock could not be consideredas a single independent management unit and that all stocks except that of the Bay of Brest were connected to neighbouring stocks, suggestingthat the management should be defined in a metapopulation context. Three major groups of strongly interconnected stocks includingtwo or three stocks exhibiting high retention and self-recruitment rates and some peripheral stocks with a low self-recruitment rate were defined:the North Brittany and Channel Islands, the eastern English Channel, and the SW of England. Our results were discussed in terms of thedefinition of management units in comparison with genetic and phenotypic data, and in terms of resource management in a transnationalcontext