Trawl cod end mesh selectivity of braided PE material for Parapenaeus longirostris (Lucas, 1846) (Decapoda, Penaeidae)

In this study, cod end mesh selectivity of braided polyethylene for the deep-water rose shrimp, Parapenaeus longirostris was investigated in the Aegean Sea. Fishing trials were carried out on the commercial trawler, "Hapuloglu" between 9 and 12 December 2006. Data were collected by a diamond mesh cod end of the 1200 mesh trawl net commercially used. The mean mesh size of the cod end meshes (nominal 46 mm) was measured near to 50 mm by using a calliper rule. Selectivity data were collected by the covered cod end method and analysed by means of a logistic equation with the Maximum Likelihood method. The mean selectivity curves were estimated from the individual hauls that were fitted taking into account the variation between hauls. The 50% retention length and the selection range of combined (male + female) P. longirostris were estimated as 19.6 mm (carapace length) and 6.2 mm, respectively, and there was no significant difference between the L-50 values of the male and female sexes (p < 0.05). Consequently, the cod end showed relatively better selectivity considering the size at 50% sexual maturity of the species, and the effect of increased mesh size and of the material used are of great importance in enhancing the size selectivity and reducing the amount of undersized P. longirostris caught in this fishery.