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Abstract

M ore than half of the landing (70%) of Red mullet (Mullus barbatus) in Turkey is provided from the Black Sea, which is almost all (96%) with bottom trawls. The effect of demersal trawl codend mesh shape and size on the s electivity of Red mullet in the Black Sea was investigated. Selectivity trials were conducted in August 2014 on a commercial trawl boat with conventional (40D), 36 and 40 mm square mesh (36S and 40S) and turned mesh codends (40T90). Data were collected using the covered codend method with a total of 21 valid hauls and selection parameters were obtained by fitting a logistic equation using maximum likelihood method. The L 50 value was found to be very low at 9.79 cm in the 40D trawl codend, while the L 50 value of 40S (11.89 cm) and 36S (10.59 cm) codends was obtained 21.5% and 8.2% better compared to the 40D, respectively. According to the traditional trawl codend, a L 50 value increase of 5.1% was observed in 40T90 (10.29 cm). Although all these values are below the M inimum Landing Size of the species, changes to the traditional mesh, especially in the shape of the mesh, can lead to significant improvements in size selectivity.

Comparison of selectivity of the trawl codends for whiting (Merlangius merlangus euxinus) in the Black Sea

“…Whiting, which is a cold water fish, is generally found deeper than 40-45 m throughout the year, whereas red mullet is more common in shallow water than 30 m (Zengin et al, 2015). Kaykaç et al, (2018) indicates that a 40S trawl codend will contribute to the preservation of the red mullet stocks. These results support the use of square mesh codends for whiting and red mullet in the region.…”

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“…On the contrary, it was reported that L50 values were below the first maturity size as well as the MLS in experiments where the codends were made from PE material, having the same characteristics in terms of codend circumference, mesh size and shape (Tokaç et al, 2004;Özbilgin, Tosunoğlu, Tokaç & Metin, 2011;Kaykaç, Zengin & Tosunoğlu, 2018). Many researchers have reported that the type of material used for manufacturing the codend also affects the selectivity and PA nets have a superior selectivity than PE nets (Akyol, Tosunoğlu & Tokaç, 2000;Deval, Bök, Ateş & Özbilgin, 2006;Tokaç et al, 2004).…”