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Abstract

In this study, factors (depth, season and mesh size) influencing the catch and discards of whiting (Merlangius merlangus euxinus) gillnet fishery on the Black Sea coasts of Turkey were investigated. A total of 19 species were identified and the target species, whiting (Merlangius merlangus euxinus), dominated 87.56% of the total catch and followed by red mullet (Mullus barbatus) with 6.32%. While 82.02% of the total catch had commercial value, 17.98% was discarded. The percentage of the discarded red mullet and whiting under MLS (<13 cm) were found to be 16.03% and 13.27%, respectively. The highest discard amount was observed in winter and the lowest one in summer. The discard rate was highest in the 55-74 m depth group and the 32 mm mesh size. One-way analysis of similarity (ANOSIM) showed that there were significant differences in the discard species compositions between spring and summer, as well as 32 and 40 mm, 32 and 44 mm mesh sizes (P<0.05). These results on the discard information in gillnet fishery can contribute to the literature on ecosystem-based sustainable fisheries management by highlighting relevant results on the protection of species and ecosystem.

Effects of depth and season on catch volume of bottom gillnets employed along the Fatsa coasts of the South-eastern Black Sea

“…Red mullet was mostly caught in the shallow waters, with catches decreasing with increasing water depth. However, this is contrasted by Kalaycı and Yeşilçiçek (2014) finding along the Rize coasts (South-eastern Black Sea) the highest red mullet CPUE in the 55-74 m depth strata. Apparently, the depth distribution of this species may depend on the fluctuations in water temperature.…”

“…As a cold-water fish, its seasonal vertical distribution depends on the sea water temperature and during summer the fish stays mainly below the thermocline (30-40 m; ca 7.5-8.5 °C). Contrary to results of Kalaycı and Yeşilçiçek (2014), the results of our study agree with these informations.…”

“…From late spring and throughout the summer red mullets prefer shallow coastal waters where they reproduce. During our study, the most red mullet was caught in the spring, followed by summer, winter and autumn, respectively, whereas, Kalaycı and Yeşilçiçek (2014) reported the highest CPUE during the winter period. According to Genç et al (2002), red mullets migrate into shallow waters toward spring and they are caught by gillnets in this season.…”

“…Catch volume estimate in deeper waters was not possible. Kalaycı and Yeşilçiçek (2014) found a linear correlation between the whiting catch volume and water depth. Erdem et al (2007) reported that whiting catch was greater in the waters deeper than 50 m in the coasts of Samsun.…”

“…Thus, all studies show that whiting prefers waters deeper than 15 m. Seasonality of whiting catch shows some trends, however firm conclusion can not be drawn because of missing data for July and August. Kalaycı and Yeşilçiçek (2014) reported different results from the Rize coasts of the South-eastern Black Sea reaching, the highest CPUE in spring. As indicated by Knudsen et al (2010), excluding the summer period in the South-eastern Black Sea whiting yields abundant catch throughout the year.…”