EFFECTS OF TOWED DEMERSAL FISHING GEAR ON BIOGENIC SEDIMENTS: A 5-YEAR-STUDY

Abstract

Experimental scallop fishing was carried out using towed commercial dredges on sediments deposited by unattached coralline algae in order to quantify their sensitivity to damage from current fishing practices. These biogenic sediments are patchily distributed in European coastal waters (to -30 m depth around the UK and to -120 m in the Mediterranean) and are of international conservation importance. This paper describes the short and long-term effects of scallop dredging on previously unfished and fished areas of biogenic algal sediment in SW Scotland. Sediment cores taken biannually from 1994-99 were used to assess live coralline abundance on marked test and control plots. Living corallines had <3% cover at a fished site and experimental dredging had no discernible effect on their abundance. Dense populations of live coralline thalli (~20% cover) were located on a previously unfished ground. Although coralline cover remained high in control plots on the unfished site, experimental fishing led to ~ 70% reduction in live corallines on test plots with no signs of recovery over the subsequent 5 years.