Effects of mesh configuration on the selectivity of demersal trawl codends for nephrops norvegicus (Linnaeus, 1758) (Decapoda, Nephrophidae)

In the present study, we have compared the selectivity of a diamond mesh codend (40D), currently used by Turkish trawl fishermen, and a square mesh codend (40S), which is in the legislation for EU Mediterranean countries (EC 1967/2006). Trawling was carried out onboard the commercial trawler "Niyazi Reis" in the international waters between Turkey and Greece, at depths ranging from 158 to 264 m, in August 2005. Selectivity data were obtained by using the covered codend technique. Selection parameters were estimated by fitting a logistic equation using the maximum likelihood method. Nephrops norvegicus escaped from the codends with retention ratios of 0.98 and 0.91 for 40D and 40S codends, respectively. The selection curves of the two codends are found to be significantly different (p < 0.01). For combined sexes, L 50 values of 16.03 (s.e. 0.41) and 19.38 mm (s.e. 0.51) were estimated in 40D and 40S codends, respectively. The results of this study clearly demonstrate that N. norvegicus took advantage of the increase in escape area provided by the change in mesh configuration from diamond to square. © 2009 Brill Academic Publishers.NECESSITY/501605The authors would like to thank the captain and crew of the commercial trawler “Niyazi Reis”. Thanks are also due to Dr. C. Aydın, Dr. G. Gökçe, S. Leblebici, I. Aydin, and O. Soykan for participating the sea trials. This study was financed by the Commission of the European Union (NECESSITY/501605). -