Fishing effects in northeast Atlantic shelf seas: patterns in fishing effort, diversity and community structure. IV. Can comparisons of species diversity be used to assess human impacts on demersal fish faunas?

Patterns in the abundance of commercially important and non-target demersal fish species collected by beam trawl survey from the coastal waters of the northeast Atlantic are described. Catches were dominated by a small number of species, which occurred in large numbers and at high biomass. The most abundant species (plaice and dab) were typical of shallow, uniform sandy an d muddy seabed which occurred extensively throughout the southern North Sea , and to a limited extent in UK western waters. Renyi's diversity index fam ily was used to rank the diversity of coastal sectors throughout the region . The less species-rich North Sea fauna, partly a result of the uniform nat ure of the seabed, was largely responsible for lower diversity of North Sea coastal faunas compared to those in the Channel and west of the UK. West o f the Dover Strait, the more heterogeneous substrate supported a more diver se fauna of smaller sized fish, with the occurrence of southern species suc h as red gurnard and thickback sole and an increasing abundance of elasmobr anchs. In the Irish Sea, fish biomass was dominated by plaice and dab, but to a lesser extent than on the continental coast of the North Sea. Sole, le sser spotted dogfish and cod were also important in this assemblage. Patter ns in community structure over such a wide spatial scale, and without histo rical perspective, can be explained by biogeographic factors, seabed struct ure and the influence of regional hydrography. Inferring from these pattern s an impact of anthropogenic factors (such as towed fishing gears) is unlik ely to be achieved. Identifying vulnerable species, and use of fishing effo rt distribution data of high resolution, may be a more fruitful approach. C rown copyright (C) 1999 Published by Elsevier Science B.V. All rights reser ved.