By-catch in a 40 mm PE Demersal Trawl Codend

Authors : Yeliz DOĞANYILMAZ ÖZBİLGİN, Zafer TOSUNOĞLU, Hüseyin ÖZBİLGİN

Pages : 179-185

View : 21 | Download : 4

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Demersal trawling in Turkish waters yields a considerable amount of by-catch and discard. Data presented in this study were collected during a demersal trawl codend selectivity trial carried out on board the RV Egesüf insert ignore into journalissuearticles values(27 m, 500 HP); between August 9 and September 4, 2002, in İzmir Bay. In total, 52 species of fish and invertebrate from 40 mm nominal mesh size commercially used PE codend and 24 mm cover were identified, separately weighed, and classified as commercial and non-commercial. In addition, for red mullet insert ignore into journalissuearticles values(Mullus barbatus);, hake insert ignore into journalissuearticles values(Merluccius merluccius);, common pandora insert ignore into journalissuearticles values(Pagellus erythrinus);, axillary sea bream insert ignore into journalissuearticles values(Pagellus acarne);, annular sea bream insert ignore into journalissuearticles values(Diplodus annularis);, and picarel insert ignore into journalissuearticles values(Spicare smaris);, length measurements were taken to the nearest half centimeter, and percentages of by-catch, in terms of numbers of individuals, were calculated using Minimum Landing Size insert ignore into journalissuearticles values(MLS); or, if this was not defined, Length at First Maturity insert ignore into journalissuearticles values(LFM);. Levels of by-catch for these species were also calculated in terms of weight, using length-weight relationships reported in the literature. The results showed that, on average, 63% insert ignore into journalissuearticles values(93 kg); of codend catch was composed of commercial species, while the rest, 37% insert ignore into journalissuearticles values(56 kg);, was unmarketable species. Moreover, although they are commercial species, 5% of red mullet, 92% of hake, 32% of common pandora, and 33% of axillary sea bream were below MLS in terms of weight. In conclusion, it is stressed that the Aegean Sea demersal trawl fishery has a multi-species nature, its by-catch level is rather high, and therefore there is an urgent need for introducing more selective fishing practices.
Keywords : The Aegean Sea, İzmir Bay, trawl, discard, by catch