Effect of an invasive mollusc, American slipper limpet Crepidula fornicata, on habitat suitability for juvenile common sole Solea solea in the Bay of Biscay

This study describes the effect of an invasive mollusc, the slipper limpet Crepidula fornicata, on the distribution and abundance of young-of-the-year sole Solea solea in coastal nursery areas, based on beam-trawl surveys in the Bay of Biscay (France) over a 3 yr period (2000 to 2002). As habitat suitability for juvenile sole varies according to bathymetry and sediment structure, these factors and the density of the slipper limpet were used as descriptors in generalised linear models of habitat suitability to characterise the distribution of juvenile sole. The models were based on a delta distribution, coupling a binomial model testing for the presence of juvenile sole with a log-normal distribution for density when juveniles were known to be present. These linear models were used to quantify the effect of the presence and density of the slipper limpet on the density of young-of-the-year sole in nursery habitats. Despite large variability in the data set, this quantitative approach emphasised the negative role of the mollusc on juvenile sole density in the Bay of Biscay. There was no apparent effect of the slipper limpet on the extent of the sole nursery grounds, but the density of young-of-the-year sole was significantly lower where this invasive species was established. The negative effect of this invasive species on nursery habitat capacity and sole stock recruitment is discussed.