ABSTRACT

The deepwaters of the UK's Atlantic Margin are now subject to the environmental pressures of two major Industries oil and gas, and fisheries The former has attracted considerable environmental concern, the other generally receives little comment other than in respect of fish stocks Nevertheless, trawling can have a very significant detrimental impact on seabed fauna and habitats whether In shallow or deepwater Recent surveys of the deep waters to the north and west of Scotland have revealed widespread indications of the impact of trawling Examples of lost or abandoned gear, seabed trawl marks and core samples revealing disturbed seabed conditions are presented The potential impact of trawling on encrusting / epifaunal communities, including the coral and sponge habitats that occur in these areas, is discussed together with the possible influence trawling may have on infaunal benthos

INTRODUCTION

The deep sea environment of the UK's Atlantic Margin has recently been the focus of environmental concern, principally In relation tothe development of the deepwater oil and gas industry This area is, however, subject to environmental pressures from another major commercial activity, the fishing industry Regulation of fisheries is typically based on the management of exploited fish stocks rather than their potentla1 environmental impact in toto In the case of deepwater trawling, physical disturbance of the seabed may be of particular concern Lost or discarded fishing gear is one of the signs of possible environmental impact In the case of set nets and fish traps, lost gear may continue to fish for some time - so called ghost fishing - with a resultant impact on fish and Invertebrate populations (Aikman, 1997) This impact may be less significant in the case of trawl gear The physical presence of discarded trawl gear on the deep sea floor, and other man-made Items as discussed by the other authors in this-volume, may be relatively benign excepting where there IS some specific hazard associated with the material (e g toxicity, see Crawford, this volume)

Although deepwater fishing and other commercial exploitation of the deep-sea floor IS relatively recent, the deepsea floor throughout the world's oceans is littered with man's debris - in the form of clinker (Heezen and Hollister, 1971) The presence of this burnt coal from the age of steam does not appear to have a detrimental impact and may indeed act to increase habitat diversity and consequently biological diversity Many deepwater habitats have little or no hard substrates on which encrusting life can develop, such that the presence of clinker can extend the distribution of individual species (van Praet, Rice and Thurston, 1990) and enhance the species composition of the benthic fauna as a whole (Briggs, Richardson and Young, 1996) The presence of discarded trawl gear on the deep sea floor may act in a similar relatively benign fashion However, the act of trawling itself is likely to be rather more damaging The potential environmental impacts resulting from the physical action of trawling have been the subject of numerous studies in shallow water settings

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