By-catch in a 40 mm PE Demersal Trawl Codend

摘要

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 Egesiif (27 m, 500 HP) between August 9and September 4, 2002, in izmir 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 (Mullus barbatus), hake (Merluccius merlucdus), common pandora (Pagellus erythrinus), axillary sea bream (Pagellus acarne). annular sea bream (Diplodus annularis), and picarel (Spicare smarts), 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 (MLS) or, if this was not defined, Length at First Maturity (LFM). Levels of by-catch for these species were also calculated interms of weight, using length-weight relationships reported in the literature. The results showed that, on average, 63% (93 kg) of codend catch was composed of commercial species, while the rest, 37% (56 kg), was unmarketable species. Moreover, althoughthey 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, itsby-catch level is rather high, and therefore there is an urgent need for introducing more selective fishing practices.