Publication Abstract

Demersal assemblages in the Irish Sea, St George's Channel and Bristol Channel

J. R. Ellis, S. I. Rogers and S.M. Freeman

Macro-epibenthic invertebrate and demersal fish assemblages are described from 101 beam trawl stations in the Irish Sea, St George’s Channel and Bristol Channel. Cluster analysis was used to identify those stations where catches were similar, in terms of species composition and biomass, and six assemblages were identified. The average similarity within these assemblages ranged from 44 to 58%. Species that were indicative of the di.erences between the six assemblages were used to describe their biological characteristics. Plaice and dab dominated on fine substrates in inshore waters (Pleuronectes–Limanda assemblage), whereas sea urchins and sun-stars dominated on the coarser substrates further o.shore (Echinus–Crossaster assemblage). Thickback sole and hermit crabs were typical of the transitional area (Microchirus–Pagurus assemblage). Norway lobster and witch dominated on the muddy sediments in the Irish Sea (Nephrops–Glyptocephalus assemblage). Dead man’s fingers beds (Alcyonium assemblage) occurred on coarse substrates in inshore waters throughout the study area, whereas common spider crabs were only dominant in the Bristol Channel (Maja assemblage). The common starfish (Asterias rubens) was an important component of all assemblages. The distribution of these assemblages was primarily correlated with depth, temperature and substrate type. Their spatial distribution was similar to previously described distribution patterns of sediments and infaunal communities in the area.

Reference:

J. R. Ellis, S. I. Rogers and S.M. Freeman, 2000. Demersal assemblages in the Irish Sea, St George's Channel and Bristol Channel. Estuarine, Coastal and Shelf Science, 51(3): 299-315.