Catch composition of non-target species escaping dredge gear of Rapana fisheries in the western coast of the Black Sea

Abstract

ABSTRACT Despite the importance of Rapana fisheries in the Black Sea region, few studies have focused on the non-target species, and determined discard rates from hauls on the deck, with no data on organisms that entered and subsequently escaped the fishing net during the dredge fishing. Rapana venosa is harvested along the entire coast of the Black Sea using dredging or beam-trawl fishing. This study adopted the cover net method to assess the composition and proportion of non-target escapees in Rapana fisheries by dredging along the western coast of the Black Sea. In this method, the dredge net bag (codend net) is covered with a second net bag that has a smaller mesh size to retain those individuals escaping from the dredge net bag. Up to 87% of the total ∼1.4×106 individuals per km (ind. km−2) cover net catches belonged to non-target species. Overall, 24 non-target species were caught in the cover net, with 46% of species belonging to the Teleostei (mostly flatfishes), 21% Malacostraca, 17% Bivalvia, 8% Gastropoda, 4% Amphibia, and 4% Ascidiacea. On the other hand, up to 6.8% of the total ∼0.16×106 ind. km−2 catches of the codend net (dredge net) belonged to non-target species. Compared to the cover net, a total of seven non-target species were retained in the codend net, and six of them belonged to Bivalvia. This study demonstrated an apparent negative impact of Rapana fisheries, particularly on escapees that often go unaccounted for their vulnerability to stress and physical damage.