Impact of otter trawling on an eastern Mediterranean commercial trawl fishing ground

Within the scope of the EC Study Project "The environmental impact of demer sal fishing gears on the marine environment", a commercial fishing ground o n the north coast of Crete, Greece, was studied for otter-trawling impacts. The trawling season is limited to eight months between October and May. Th e major trawling lane, at 200 m depth off the port of Heraklion, is narrow because of bottom contouring. Four sampling stations were chosen in the vic inity, two in the lane and one on either side. Sediment chemistry and macro faunal community structure were studied over 11 months, starting before the trawling season and ending well after. During each sampling trip a towed v ideo survey was completed to check seabed conditions. In addition, beam-tra wl samples were taken at the beginning and at the end. Video observations r evealed the extent of trawling activities and showed higher numbers of epif aunal species outside the lane (particularly the echinoderms Leptometra pha langiuin, Stichopus regalis, and Ophiura texturata). The epifauna in the be am-trawl samples also showed lower numbers in the lane. Sediments were pred ominantly clay. Sedimentary organic carbon, chlorophyll, and phaeopigments all exhibited significant differences between stations during the trawling season. Species number, abundance, and biomass were all generally significa ntly lower in the lane during the trawling season, noticeable particularly in the phyla Echinodermata, Sipuncula, and to a lesser extent the Polychaet a. The closed season did not seem to allow recovery to pre-season levels. I mpacts on the less mobile fauna were more pronounced, but degree of robustn ess also seems to play a major role. (C) 2000 International Council for the Exploration of the Sea.