Gill net selectivity for by-catch species in red mullet net off the Çanakkale coast

In this study, the selectivity of a considerable amount of by-catch species ((painted comber (Serranus scriba), peacock wrasse (Symphodus tinca), blotched picarel (Spicara maena), black scorpionfish (Scorpaena porcus) ve axillary seabream (Pagellus acarne)) caught by mullet gill with nets 18, 20 and 22 mm mesh size were estimated on the coast of Çanakkale. The SELECT method was used for the determination of the selectivity parameters. Five different functional models (normal location, normal scale, gamma, lognormal and bimodal) were used to fit the selectivity curve to the catch data. Bi-model function gave the best fit for painted comber and peacock wrasse. Log normal model for blotched picarel and black scorpionfish and Gamma model for axillary seabream were the best suitable fit. Model lengths for gill nets with 18, 20 and 22 mm mesh size estimated as 15,62 cm, 17,36 cm and 19,10 cm for the painted comber (S. scriba); 13,26 cm, 14,73 cm, 16,21 cm for the peacock wrasse (S. tinca); 14,70 cm, 16,33 cm, 17,96 cm for the blotched picarel (S. maena); 9,64 cm, 10,71 cm, 11,78 cm for the black scorpionfish (S. porcus) and 12,31 cm, 13,68 cm 15,05 cm for the axillary seabream (P. acarne), respectively.The length at first maturity of the by-catch species were compared with the model lengths and found that the nominal mesh size with 22 mm must be used.