Cephalopods in shelf and slope Mauritanian waters during Spanish-Mauritanian oceanographic cruises (2007-2010)

Abstract

This poster presents the results of four Spanish-Mauritanian oceanographic cruisers on Mauritanian continental shelf and slope. Cephalopod specimens were collected in 281 bottom-trawling stations carried out between 2007 and 2010. Cephalopods were separated and preliminary identified onboard. Quantitative data of abundance and weight were recorded for each species. Representative cephalopods subsample were fixed and preserved in 4% formaldehyde for further identification using taxonomic keys and specific literature. A total of 16,036 cephalopods (1795 kg) were caught in 281 trawl stations (96.6% of sampled locations). Forty-nine species belonging to 20 families were identified. The maximum numerical abundances corresponded to the Families Ommastrephidae (71.1%), Loliginidae (7.3%), Octopodidae (6.2%) and Sepiidae (5.3%). Ommastrephidae, Loliginidae and Octopodidae were also the dominant families in weight. The highest abundances were observed close to the coast in deep shelf and upper slope, presents two main concentration zones, up to 1000 m depth: one matching the highest abundance areas in the Banc d'Arguin and a second zone located in the middle slope off the central Mauritanian coast. Statistical analysis shows two cephalopods assemblages. The Shelf Assemblage was the most conspicuous group located on the deep shelf and upper slope (80-400 m depth). The Slope Assemblage was located at depths between 400 and 1800 m. In both cases, Ommastrephidae species were the main contributors: Illex coindetii and Todaropsis eblanae accumulated 65.6% of the similarity in the Shelf Assemblage, while Todarodes sagittatus sagittatus, together with the incirrated Octopodidae and Ophisthoteuthis agassizii, contributed 73.8% to the Slope Assemblage similarity.