The impact of otter trawling on mud communities in the northwestern Mediterranean

We report the findings of an experiment conducted in the northwestern Mediterranean to evaluate the short-term effects of otter trawling on a muddy-sediment infaunal community. A commercial fishing vessel, using conventional otter trawling gear, fished two waylines repeatedly until each had been disturbed entirely either once or twice. Infaunal samples were collected from replicate sites located within the fished and adjacent undisturbed control areas. Univariate analyses of species richness and diversity indicated that the infaunal community did not alter during the first 102 h after fishing in the area that was trawled once. However, the abundance of a number of species decreased significantly on the unfished line compared with the fished line 150 h after fishing. No differences were detected on the line that was fished twice, but this part of the experiment was terminated after 72 h. Multivariate analyses revealed that the communities in both fished and unfished areas changed in a similar manner through time and that there was no apparent effect of fishing until 150 h after fishing. These short-term changes are discussed in the light of recent studies of infaunal changes in other habitats.