Effects of an area closed to.sheries on the composition of the benthic fauna in the southern North Sea

Abstract

The effects of.shery exclusion on the composition of the macrofauna were determined by comparing the.shery-exclusion zone around a gas production platform in the southern North Sea (Frisian Front) with nearby regularly.shed areas. A Triple-D dredge was used, in addition to a standard box corer, to collect the relatively rare and larger species. Multivariate analysis showed greater species richness, evenness, and abundance of mud shrimps (Callianassa subterranea, Upogebia deltaura) and fragile bivalves (Arctica islandica, Thracia convexa, Dosinia lupinus, Abra nitida, Cultellus pellucidus) in the Triple-D samples from the exclusion area. Although box cores did con.rm the higher abundance of both mud shrimps in the exclusion zone and demonstrated greater densities of the brittlestar Amphiura.liformis, they did not clearly reveal the distinctness of the exclusion zone. This is attributed to the large proportion of small, short-living species in the samples and the relative scarcity of vulnerable larger species common to all the box core samples. There was no evidence of greater recruitment in the relative small exclusion zone, despite its positive effect on adult survival. The observation that the.shery affects deep-living mud shrimps may point to consequences for the functioning of the benthic ecosystem other than simple loss of biodiversity. © 2007 International Council for the Exploration of the Sea.