Karadeniz’in Güney-doğu Kıyılarında Yapılan Galsama Ağları ile Avcılıkta Av Kompzisyonu ve Iskarta Oranı Üzerine Mevsim ve Derinliğin Etkisi

Abstract

Effects of depth and season on species composition of catch and discard rate in the gillnet fishery on the south-eastern coast of the Black Sea was investigated in this study. for this purpose, fishing trials were carried out in the four different depth strata (0-14 m, 15-29 m, 30-49 m and 50 m≥) using multifilament gilnets with mesh sizes of 32, 34, 36 and 38 mm, from March 2013 to February 2014. In the fishing trials, a total of 2506 individuals (133.729 g) belongs to eight fish species were obtained which were whiting (Merlangius merlangus), red mullet (Mullus barbatus), pontic shad (Alosa immaculata), mediterranean horse mackerel (Trachurus mediterraneus), black scorpionfish (Scorpoena porcus), stargazer (Urascopus scaber), seahorse (Hippocampus sp.) and black-striped pipefish (Syngnathus abaster). Allmost catches for whiting, red mullet, pontic shad and mediterranean horse mackerel were of economic value, while all catches for the other species were were discarded. In the shallow waters varying between 0-14 m depth, red mullet and mediterranean horse mackerel were mostly caught. However, catches of especially mediterranean horse mackerel were decreased gradually with increasing water depth. The most caught fish species in deeper water strata more than 15 m was whiting. In the evaluation of the effect of the season on the species composition of catch, the whiting was the most caught fish species by the trial gillnets in all seasons. These fish species, except autumn season (in autumn, potic shad and Mediterranean horse mackerel) followed by red mullet in all seasons. On the orher hand, the rate of discard was determined as 10.2% in number and 15.9% in biomass. It has been found that the discard rate decreases gradually due to the increase in water depth. Seasonally, the lowest discard rate was calculated in winter, followed by autumn, spring and summer, respectively.