Bathyal suprabenthic assemblages from the southern margin of the Capbreton Canyon (“Kostarrenkala” area), SE Bay of Biscay

The bathyal suprabenthic fauna of the Kostarrenkala area (Capbreton Canyon, SE Bay of Biscay) was sampled during daytime at eight stations located on a bathymetric transect between 175 and 1000 m depth using a multinet suprabenthic sled. Two hundred and five suprabenthic taxa were recorded in this area, mainly amphipods, cumaceans, isopods and mysids. Total abundances ranged from 752 to 2640 ind./100 m2, showing a decreasing trend with depth. Diversity values (H′) ranged between 3.83 and 5.72, increasing significantly with depth. Multivariate analysis of abundance data discriminated three assemblages according to depth: shelf break (72 sp., 1924 ind./100 m2), upper slope (93 sp., 1485 ind./100 m2) and mid slope (135 sp., 857 ind./100 m2) assemblages. Each assemblage was characterised by a distinct dominant species: the shelf amphipod Westwoodilla caecula at the shelf break, the isopod Munnopsurus atlanticus on muddy sand bottoms of the upper bathyal, and the amphipod Rhachotropis gracilis on mid-slope muddy bottoms below the mud line. Such a structure of bathyal assemblages seems to be generalised for the whole margin of the Bay of Biscay.