The effects of beam-trawl disturbance on infaunal communities in different habitats

摘要: Beam-trawling is a source of physical disturbance to marine sedimentary communities in areas less than 50m deep, on the western European continental shelf. Chains attached between beam-trawl shoes are designed penetrate upper few cm sediment, which leads damage or removal some infaunal and epifaunal species. In areas, beam-trawling may be frequent intense, leading speculation that it generate long-term changes local benthic fauna. As part larger MAFF study examining ecological effects beam-trawling, we investigated its impact an community north-eastern Irish Sea. Studies this type complicated by heterogeneity environment, hence adopted replicated, paired control treatment design maximize chances detecting any due trawling. A side-scan sonar survey revealed experimental area was characterized mobile megaripples south-eastern sector stable sediments with uniform topography north-western sector. Multivariate analysis species abundances from separated fauna into two distinct corresponded different substratum characteristics. Data regions were therefore treated separately when testing for sector, trawling led 58% decrease mean abundance taxa 50% reduction number per sample. differences fished sites largely common These apparent had naturally impoverished high level heterogeneity. Univariate variables, such as total sample, indicated variation replicate samples increased result disturbance. However, examination data using index multivariate dispersion no difference unfished areas. This suggests fishing consistent samples. Fishing demersal gears modifies relatively sediments. Frequent repeated lead structure these habitats.