A new species of holothurian of the genus Psolus Oken, 1815 is described. Psolus rufus sp. nov. was found in the central Cantabrian slope (Bay of Biscay) at 1500 m depth. The new species is characterized by having: ovoid body, reddish colour in vivo; dorsal area enclosed in a complete test composed of imbricating scales; 10 triangular plates of the same size surrounding mouth; 10 oral tentacles; no dorsal papillae; tube feet in two rows in the ventrolateral radii but one single row in the medial third or the body; ossicles are big dorsal plates and small plates in the sole, which are smooth, irregular and perforated. The molecular study of the COI gene supports the morphological results, grouping P. rufus sp. nov. together with other members of the genus. However, the new species is genetically distinct from the two groups (Antarctic and Canadian) of the available sequenced Psolus species. Furthermore, a key to the Psolus species of the north-eastern Atlantic Ocean is provided.

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.

Seventeen chondrichthyan species were caught in the Cantabrian Sea (southern Bay of Biscay) during a multidisciplinary survey carried out in the Avilés canyon system in May 2011. This survey provided the first records of three species (Galeus murinus, Neoraja iberica, and Neoraja caerulea) in these waters, and a further record of Rajella kukujevi. To confirm the identity of these species, the cytochrome c oxidase subunit I (COI) of the specimens was sequenced. Genetic analyses revealed that the DNA sequences of the two Neoraja species were identical in all the specimens analysed. Morphometric analyses, based on 40 characters, showed 3.66% dissimilarity between the two species. The morphometric character that contributed most to this discrepancy was disc width.

The analyses presented in this paper provide evidence that several community metrics and indicators of the inner shelf community in the Cantabrian Sea show response to placement of anti-trawling reefs. Total biomass, species richness, and to a lesser extent, maximum length and percentage of large fish, were sensitive to exclusion of trawling. Density, diversity and average trophic level did not show this sensitivity. The main species profiting from trawl exclusion were seabreams (Sparidae), catsharks and skates (Elasmobranchii), red mullets (Mullidae), gurnards (Triglidae) and John Dory (Zeus faber). Conversely, the main fishery target species (hake, anglerfish and megrim) showed a progressive decrease in abundance during the study period, a pattern which was also shown by their total stock biomass in the totality of the shelf area. Sea urchins, cephalopods and gastropods also increased in relative abundance with trawl exclusion. Reef age was identified as a key factor in reef development. After reef deployments, two periods were identified: (1) a recovery period, in which total biomass increased, mainly as a consequence of the increase in generalist species (e.g. catsharks); and (2) a consolidation period, during which biomass increased again, mainly as a consequence of an increase in specialized stenoic species (e.g. sparids), while biomass of generalist species remained constant or declined.

The main objective of this study was to describe the reproductive cycle of the sea urchin Paracentrotus lividus on the Cantabrian coast (north of Spain), and assess its relationship with environmental factors. To achieve this, samples were taken monthly from three localities during 17 months in two different habitats. At least 15 individuals from each location and habitat were collected during each sampling occasion and used for assessments of gonad index and histological sections. The water temperature and the chlorophyll concentration were also measured. The breeding season of P. lividus in Cantabria started in March and continued until September with one or two main spawning periods per year (depending on year and population), the first one in the beginning of spring and the second one in the summer. The most important differences in the gonad cycle were observed among localities, and the smallest among habitats. Temperature, photoperiod and nutritive stage are important factors controlling the gonad cycle. The beginning of spawning in the Cantabrian populations coincides with the spring phytoplankton bloom and the rise in temperature, which may act as environmental triggers.

Following the accident of the oil tanker ‘Prestige’, we surveyed the large scale fuel deposition patterns on the Cantabrian shore (northern Spain) covering three regions (from west to east): (i) Asturias, west of Cape Peñas (24 segments surveyed); (ii) Asturias, east of Cape Peñas (33 segments surveyed); and (iii) Cantabria (also east of Cape Peñas, 256 segments surveyed). Fuel arrived to the Cantabrian Coast as a single oil wave which was more intense to the east than to the west of Cape Peñas. The mean percentage of coast length affected was 25, 41 and 15% in western Asturias, eastern Asturias and Cantabria, respectively. However, less than 10% of the substrate was covered by fuel in oiled patches, thus the impact was moderate. We conclude that these patterns are consistent with fuel transport by the Iberian Poleward Current, a hydrographic feature typical of this region during winter.