THE IMPACT OF HYDRAULIC DREDGING FOR RAZOR CLAMS ENSIS SP ON AN INFAUNAL COMMUNITY

The impact of fishing for razor clams (Ensis sp.) by hydraulic dredging on the associated infaunal community has been examined in a manipulative field experiment executed in autumn in a Scottish sea loch at 7 m depth. Infaunal samples from replicate fished and unfished plots were examined after 1 and 40 days. Major effects on the total number of individuals were observed immediately after fishing and sign test revealed a reduction in the abundance of a significant proportion of species in fished areas. However, after 40 (mostly stormy) days no effects of fishing could be detected and no visible signs of fishing remained on the sea bed. We hypothesize that active migration into the water column and passive suspension during wind- and tide-induced sediment transport dilute localized effects and conclude that, given the restricted depth at which fishing is possible at present, hydraulic dredging is unlikely to have persistent effects on most of the infaunal community in most habitats. The effects on long-lived bivalve species could, however, be more serious.