Opisthobranch molluscs from the subtidal trawling grounds off Blanes (Girona, north-east Spain)

Studies on the opisthobranch molluscs inhabiting the continental platform in areas not accessible by SCUBA diving are rare in the subtidal bottoms of the Iberian Peninsula. Data obtained from trawls are not adequate for quantitative analysis, due to the indirect method used and the high number of variables which affect the capture of the samples. However, with the aim of obtaining qualitative information oil the opisthobranch molluscs inhabiting the subtidal trawling grounds off Blanes, we took more than 500 sample, over a two-year period, oil the non-commercial fraction of the trawling fisheries, finding opisthobranchs in 306 samples. We analysed samples from 16 trawling sites, at depths between 50 and 300 in, by using ten fishing boats of the 'Confraria de Pescadors del Port de Blanes. We obtained 4.295 specimens of opisthobranchs belonging to 29 species. From these, 4 are Cephalaspidea s.s., 1 Anaspidea, 1 Umbraculacea, 3 Pleurobranchacea and 20 Nudibranchia (3 Arminina, 3 Dendronotina and 14 Doridina). The most abundant species were Gastropteron rubrum and Scaphander lignarius, both cephalaspideans present during all seasons, and the dendronotacean Tethys fimbria. For Scaphander lignarius it was possible to distinguish three size-groups, from Which the smallest one was usually found in summer. Other interesting species found were, among others, Armina tigrina, Baptodoris cinnabarina, Thordisa filix and Kaloplocamus ramosus. The richest trawling grounds in species numbers and abundances were La Planassa and Els Capets. The total number of opisthobranch species reported for the trawling grounds off Blanes is now 48.