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    Body shape and trawl cod end selectivity for nine commercial fish species
    (Cambridge Univ Press, 2003) Tosunoglu, Z; Ozbilgin, YD; Ozbilgin, H
    This study investigates the catch components of a commercially used demersal trawl cod end in Izmir Bay, and reveals some of the morphological characteristics of nine commercial fish species; red mullet (Mullus barbatus), hake (Merluccius merluccius), whiting (Merlangius merlangus euxinus), poor cod (Trisopterus minutus capelanus), tub gurnard (Trigla lucerna), common pandora (Pagellus erythrinus), axillary sea bream (Pagellus acarne), picarel (Spicara smaris) and annular sea bream (Diplodus annularis) in relation to mesh size and shapes. furthermore selectivity of 40-mm polyethylene netting cod end for red mullet, hake, common pandora, axillary sea bream, picarel and annular sea bream is presented. The results are discussed in a way to understand the probable effects of fish body shape on mesh selectivity.
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    By-catch in a 40 mm PE demersal trawl codend
    (Scientific Technical Research Council Turkey-Tubitak, 2006) Ozbilgin, YD; Tosunoglu, Z; Ozbilgin, H
    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 Egesuf (27 m, 500 HP) between August 9 and 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 merluccius), common pandora (Pagellus erythrinus), axillary sea bream (Pagellus acarne), annular sea bream (Diplodus annularis), and picarel (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 (MLS) or, if this was not defined, Length at First Maturity (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% (93 kg) of codend catch was composed of commercial species, while the rest, 37% (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.
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    Determination of the appropriate hanging ratios to ease the escape of juvenile red mullet (Mullus barbatus L., 1758) and annular sea bream (Diplodus annularis L., 1758) from a trawl codend
    (Scientific Technical Research Council Turkey, 2003) Tosunoglu, Z; Ozbilgin, YD; Ozbilgin, H
    This study investigates the relationship between total length (TL) and fork length (FL), girth (G), height (H) and width (W) of red mullet (Mullus barbatus) (n = 953) and annular sea bream (Diplodus annularis) (n = 944) collected during trawl selectivity trials carried out in Izmir Bay between July 1996 and February 1997. The FL, G, H and W of red mullet were 89, 53, 20 and 11% of the TL, respectively. For annular sea bream these values were 91, 80, 34 and 11 %, respectively. The ratios for average body thickness (W/H) were 0.573 for red mullet and 0.319 for annular sea bream. The hanging ratios (E-RM and E-AS8) of codends designed to ease the escape of juveniles of these species were 0.497 for red mullet and 0.304 for annular sea bream.