Trawl selectivity studies on Nephrops norvegicus (L.) in the eastern Mediterranean Sea

The trawl codend selectivity on Nephrops norvegicus was studied using diamo nd meshes of 16 mm, 20 mm, 24 mm and 26 mm nominal side mesh size. The cove r codend method was applied for the sampling. The logistic function for the probability of retention by the codend was used for the estimation of sele ctivity parameters from all data combined. The results indicated that the 1 6 mm mesh size was not selective and that almost all individuals were retai ned. The 24 mm and 26 mm mesh size showed quite similar results and were a little more selective than the 20 mm mesh size. None of the experimental me sh sizes proved to be adequate for N. norvegicus, since all estimated value s of length of 50% retention (L50) were lower than the length at first matu rity and those of length of 25% retention (L25) were lower than the legisla ted minimum landing size. It is suggested that mesh size should be much lar ger than 20 mm, the size legislated by E.U. for the Mediterranean.