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Effects of Mesh Configuration on the Selectivity of Demersal Trawl Codends for Nephrops Norvegicus (Linnaeus, 1758) (Decapoda, Nephrophidae)

2009; Brill; Volume: 82; Issue: 12 Linguagem: Francês

10.1163/001121609x12487811051705

1568-5403

M. Hakan Kaykaç, Hüseyin Özbilgin, Adnan Tokaç,

Fish Biology and Ecology Studies

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. Dans cette etude, nous avons compare la selectivite du cul de chalut a maille diamant (40D), actuellement utilise par les pecheurs turcs, et du cul de chalut a maille carree (40S), qui est dans la legislation concernant les pays mediterraneens de l'UE (EC 1967/2006). Le chalutage a ete mene a bord du chalutier commercial Niyazi Reis dans les eaux internationales entre la Turquie et la Grece, a des profondeurs de 158 a 264 m, en Aout 2005. Les mesures de selectivite ont ete obtenues par la technique du cul de chalut couvert. Les parametres de selection ont ete estimes en appliquant une equation logistique utilisant la methode du maximum de vraisemblance. Nephrops norvegicus s'echappait des culs de chalut avec des taux de retention de 0,98 et 0,91 pour les culs de chalut 40D et 40S, respectivement. Les courbes de selection des deux culs de chalut etaient significativement differents (p < 0.01). Pour les deux sexes ensemble, les valeurs de L 50 de 16,03 (s.e. 0,41) et 19,38 mm (s.e. 0,51) ont ete estimes, pour, respectivement, les culs de chalut 40D et 40S. Les resultats de cette etude demontrent clairement que N. norvegicus tire avantage par l'augmentation de sa capacite d'echappement, induite par le changement de la structure de la maille, de diamant a carree.