The Bay of Málaga is located in a high biodiversity and productivity area that harbours a wide variety of commercial species exploited by different fishing fleets. Benthic and demersal fauna from circalittoral soft bottoms have been studied using a benthic dredge (BD) (8 sampling stations) and an otter trawl (OT) (8 sampling stations on a seasonal basis). Some sediment and water column variables, as well as the trawling activity, have also been studied and used for analysing their linkage with the fauna. A total of 287 species have been found in these bottoms and fish, molluscs and crustaceans represented the most diverse and abundant faunistic groups. A new record of the decapod Hippolyte leptometrae for Spanish waters is also included in this study. Some multivariate analyses using BD samples indicated the presence of three assemblages, but these seem to represent different facies of a single benthic community due to the absence of acute sediment changes and significant differences in the fauna. OT samples only displayed differences related to seasons but not to sediment types or depth. These seasonal differences seem to be linked to biological and ecological features of both dominant and/or commercial species. Mud and organic matter contents (%OM) in sediment, as well as the temperature, were the main variables linked to the spatial distribution of the benthic community identified with BD, whereas medium and coarse sand as well as gravel contents were the main variables linked to the changes of the epibenthic and demersal assemblage resulting from OT samples. The information of this study is of importance for improving the knowledge on the biodiversity of circalittoral soft bottoms of the Mediterranean and Alboran Sea as well as for the potential creation of a Marine Fisheries Reserve in the Bay of Málaga.

The composition and structure of sublittoral faunal assemblages inhabiting soft bottoms (15–72 m depth) within the Marine Protected Area ‘Acantilados y Fondos Marinos de Calahonda-Castell de Ferro’ in southern Spain (North Alboran Sea, Mediterranean) have been studied in relation to sediment and water column variables. Three assemblages were identified and corresponded to mixed bottom, unstable bottom and coastal detritic bottom assemblages, based on Pérès & Picard's (1964) benthic classification. A total of 14,318 individuals were collected and 218 species identified, molluscs being the best represented group (141 species). Species richness displayed significant differences with depth and transect, with the highest values observed in the medium to very fine sand and muddy bottoms with bioclasts located at the shallowest sampling stations. The presence of some rare and poorly known invertebrates that are scarce in other areas of the Mediterranean Sea is remarkable, such as the crustacean decapods Bythocaris cosmetops and Pagurus mbizi, Atlantic species with no records in the Mediterranean Sea, and the bathyal molluscs Poromya granulata and Alvania testae, collected at shallow depths. The spatial distribution of faunal assemblages was mainly related to depth and percentage of gravel and clay according to the canonical correspondence analysis. The geographic location of the area, the heterogeneity of soft bottoms and the presence of upwellings in the area may favour the high biodiversity found in the studied soft bottoms. This study increases the scarce knowledge of the circalittoral fauna of sedimentary habitats of the Alboran Sea, providing a baseline for the management of this interesting SCI and for the EU Marine Strategy Framework Directive.

We report the first mono-specific facies of Parazoanthus axinellae from the western Portuguese coast. The habitat was recorded using a MiniRov Observer on a large outcrop at ca. 55–60 m in the Luiz Saldanha Marine Park. A method to estimate the maximum uncertainty of the ROV position is illustrated and the occurrence of the facies is discussed.

One new dorvilleid species belonging to the genus Ophryotrocha Claparède & Mecznikow, 1869 is described. The studied material was collected in circalittoral seabeds (70–100 m depth) in the Cantabrian Sea (north-east Atlantic Ocean). The new species Ophryotrocha cantabrica is characterized by having well-developed antennae and palps, parapodia with long dorsal cirrus, sub-triangular acicular lobes and inferior chaetal lobe well-developed, as well as the presence of P-type maxillae and bifid mandibles slightly tagged. The most closely related Ophryotrocha species are O. longidentata Josefson, 1975 and O. lobifera Oug, 1978; however, both species have biarticulated palps. Other differences with O. cantabrica sp. nov. are: body size and shape, parapodia morphology and number of setae, as well as the shape of mandibles and maxillae.