Relationship between interannual variations of the river plume and the extent of nursery grounds for the common sole (Solea solea, L.) in Vilaine Bay. Effects on recruitment variability

This study describes the spatial distribution of juvenile sole on the basis of a 10-year beam trawl survey of Vilaine Bay, an estuarine nursery ground within the Bay of Biscay (France). A significant relationship between fluvial discharges in winter-spring and the area covered by high densities of 0-group juveniles was indicative of the favourable effects of freshwater supply on nursery size. The extent of the river plume influences both the larval supply and the size and biotic capacity of habitats in estuarine nursery grounds and determines the number of juveniles produced. The correlation between river flow and sole recruitment for Vilaine Bay was confirmed for the Bay of Biscay stock. As the recruitment of the Bay of Biscay sole stock depends partly on the influence of river plumes on nursery grounds, it appears to be less variable than for other sole stocks affected essentially by larval supply. The balance between the different factors influencing recruitment differs according to the area concerned, and recruitment variability depends on the respective roles of these factors.