Effects of demersal trawling along the west coast of southern Africa: multivariate analysis of benthic assemblages

作者：Lara Atkinson, JG Field, L. Hutchings · 发表于：Marine Ecology Progress Series · 年份：2010 · DOI：10.3354/meps08956 · 被引用次数：71 · 研究领域：Marine and fisheries research、Marine Biology and Ecology Research、Marine Bivalve and Aquaculture Studies

This study is the first to examine the benthic impacts of the otter-trawl fishery on hake in the southern Benguela upwelling region. Infauna were sampled at 4 sites, from southern Namibia to Cape Town by means of 5 replicate grab samples at each of 2 trawling treatments (heavily and lightly trawled areas), paired at each site. The large invertebrate epifauna was also sampled at 2 of these sites using a fine-meshed otter trawl. Sites ranged in depth from 350 to 450 m. Environmental attributes (sediment particle size, total organic carbon, depth, salinity, temperature and dissolved O 2 concentration) were examined along with faunal assemblage composition. Vertical profiles of water mass characteristics showed little long-shore variation, apart from slightly lower O 2 concentrations in the north. Difficulties of pseudo-replication in benthic impact studies are discussed, and methods for circumventing these suggested. There were significant differences in sediment characteristics among the 4 sites, but only 2 sites showed different sediment characteristics between trawling treatments. Studies of species richness, evenness and numbers of infaunal individuals showed little difference between trawling treatments at 3 sites and species diversity was similar between treatments at all 4 sites. Multivariate analyses show marked differences in both infaunal and epifaunal assemblages among the sites and between trawling treatments at all sites. The analyses suggest that differences in tra...