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This is the first molecular identification of the Arrowhead dogfish Deania profundorum based on the mitochondrial cytochrome oxidase c subunit I (COI) ever made. It is based on four specimens caught in the Cantabrian Sea (north of Spain) during a monitoring survey in the summer of 2009. Three specimens of Deania calcea were also sampled as comparative material. The sequences obtained were in concordance with the identification of the Deania species. The two Deania species shared no COI haplotypes and showed a genetic distance of 3.6% (23 fixed differences out of 652 bp), which is within the range of congeneric species. [ABSTRACT FROM AUTHOR]

The feeding habits of birdbeak dogfish Deania calcea, velvet belly lantern shark Etmopterus spinax and blackmouth catshark Galeus melastomus at Le Danois Bank, Cantabrian Sea, south Bay of Biscay were studied in relation to their bathymetric distribution. Deep-sea sharks were collected during two multidisciplinary surveys carried out in October 2003 and April 2004 at the Le Danois Bank. Two different habitats were defined: (1) the top of the bank, ranging from 454 to 642 m depth and covered by fine-sand sediments with a low percentage of organic matter, and (2) the inner basin located between the bank and the Cantabrian Sea's continental shelf, at depths of 810–1048 m, which was characterized by a high proportion of silt and organic matter. Deania calcea was not present at the top of the bank but was abundant below 642 m, while E. spinax was abundant in the shallower top of the bank but was not found in the deeper inner basin. There was almost no bathymetric overlap between these two deep-sea shark species. Galeus melastomus was found over the whole depth range. There seemed to be an ontogenetic segregation with depth for this species, however, since 80% of the specimens collected at the top of the bank were < 600 mm total length ( LT) (mean 510 mm LT), whereas larger individuals (mean 620 mm LT) inhabited deeper zones. Galeus melastomus exhibited a significantly higher feeding intensity than both E. spinax at the top of the bank and D. calcea in the inner basin. Little dietary overlap between D. calcea and G. melastomus in the inner basin was found, with D. calcea being an ichthyophagous predator while the diet of G. melastomus at these depths was composed of a variety of meso-bathypelagic shrimps ( e.g. Acantephyra pelagica, Pasiphaea spp. and Sergia robusta), cephalopods and fishes. The diets of E. spinax and G. melastomus at the top of the bank showed a high dietary overlap of euphausiids, which represented the main prey taxa for both species. Euphausiids declined in abundance with depth which was reflected in the diet of G. melastomus. The cluster analysis of prey affinities among hauls depicted two major groups, corresponding to the two different habitats (top of the bank and inner basin). Redundancy analysis also indicated top–basin segregation, with euphausiids representing the main prey taxa at the top of the bank and bathypelagic shrimps in the inner basin. Euphausiids and Micromesistius poutassou were key prey within the Le Danois Bank ecosystem since they were positively selected by the three deep-sea shark species. These results show that the feeding ecology of these predators in Le Danois Bank ecosystem is highly influenced by depth-related variables, as a result of changes in prey availability. Overall results were analysed in relation to the deep-sea Le Danois ecosystem structure and functioning. [ABSTRACT FROM AUTHOR]

The blue whiting is the most important demersal species caught by the Spanish trawler fleet in the southern Bay of Biscay. Lesser spotted dogfish are not a commercial by-catch, and are discarded immediately after sorting. During 1994 the contents of 1094 dogfish stomachs were analysed. The results show that lesser spotted dogfish with a total length of >17 cm eat blue whiting throughout the year. The length range of blue whiting found in lesser spotted dogfish stomachs was similar to the length range discarded by the fishery. Blue whiting account for 20% of the stomach volume in lesser spotted dogfish 30–50 cm long. From the state of digestion of blue whiting prey, and the comparative analysis of the size distributions of blue whiting in lesser spotted dogfish stomachs and in the fishery, it appears that many of these blue whiting are discards, consumed when already dead or damaged. The impact of this supplementary food on lesser spotted dogfish abundance is discussed. [ABSTRACT FROM PUBLISHER]