Investigations on drift-net fishery for swordfish (Xiphias gladius L.) in the Aegean sea

Abstract

This study reports an investigation carried out on swordfish drift-net fishery at 2 main swordfish fishing ports, Sivrice (northern) and Fethiye (southern), in the Aegean Sea in 2001-2002. Forty-five boats are used for swordfish fishing in the Turkish Aegean Sea. In these major areas, the highest number of boats 6-10 m in length and 11.5-80 hp in engine power was in the Sivrice area, while the highest number 10-14 m in length and 85-135 hp in engine power was in the Fethiye area. Almost all of the boats were made of wood. Swordfish drift-netting accurs in practice between Sivrice and the island of Lesvos and in both national and international waters between Fethiye and Rhodes. The drift nets are made of multiflament polyamide (PA) netting yarn, 210d/54-60 no, are about 3 to 7 km long, have a 500 mm mesh opening and are 20 meshes deep at Sivrice. They are about 14 km long, made up of various nets mixed together with 4 km for leerfish (Lichia amia) and 6 km for bullet tuna (Auxis rochei), have a 440 mm mesh opening, and are 30 meshes deep in the part for swordfish in Fethiye. Illuminated buoys are attached to each side of the net. Fishing effort and catch per unit effort (CPUE) in the swordfish biomass were rather low at Sivrice. The low CPUE in the biomass was probably the result of worsening meteorological conditions in the region. In each area, bluefin tuna (Thunnus thynnus), little tunnies (Euthynnus alletteratus), Mediterranean spearfish (Tetrapturus belone), albacores (Thunnus alalunga), bullet tuna (Auxis rochei), dolphinfish (Coryphaena hippurus), dolphins (Delphinus delphis). manta rays (Mobula mobular), sunfish (Mola mola) and sharks (Mustelus vulgaris) were recorded as non-target catches.