HALIEUTIQUE MER ET LITTORAL

Estuaries and coastal areas are essential habitats for many fish species. These habitats act as nurseries for a large proportion of species of fisheries interest. Their coastal distribution at juveniles stage makes them particularly vulnerable to anthropogenic pressures. However, a comprehensive analysis of the impacts of nursery habitat degradation for exploited fish species is still lacking. Our study aims at assessing the effects of degradation/restoration of nursery habitat common to four Eastern English Channel species of large fisheries interest: sole, plaice, whiting and seabass. A generic simulation model representing the dynamics of exploited populations and the dependence of recruitment on juvenile habitats is used. It evaluates the combined effect of nursery degradation and fisheries exploitation on stock dynamics. The model was calibrated for each species based on the results of stock assessments complemented by literature. Restoration of both surface and quality for nursery habitats were built using estimated area losses since 1870 and literature. Surface restoration had a smaller impact than quality restoration on biomass and catch gains at MSY (Maximum Sustainable Yield) for the four species. The species with the higher level of concentration on shallow nursery areas were the most sensitive to the habitat restoration scenarios. The response also depends to life history traits; species with lower steepness exhibit a stronger response to habitat scenarios.