Bycatch in the commercial beam trawl fishery for Rapa Whelk in the Black Sea

Abstract

The current study was aimed to investigate the bycatch in commercial beam trawls used in the rapa whelk (Rapana venosa) fishery during September 1, 2015, and April 30, 2016. Four commercial boats using beam trawls were chartered and catch data were recorded from a total of 87 hauls. the hauls were performed at a depth of 7.1-28.3 meters for a duration of 20-77 min and the hauling speed varied between 1.4-2.7 knots. About 28 species were identified as bycatch, on an average this amounted to 11.4% of the total number of specimens. There were identified two different groups in the bycatch (G1: 7-18 m, G2: 19-26 m) based on the depth. Although there was noticed a decline in the volume of bycatch in group G2, it was not significant between the groups (p> 0.05). According to the results of the Generalized Additive Models (GAM), the variables affecting the by-catch amount were identified as a fishing area, depth, haul duration, and the amount of captured rapa whelk (p< 0.01). in addition, a large proportion of immature individuals of striped venus clams (Chamelea gallina), blood cockles (Anadara kagoshimensis), Mediterranean mussels (Mytilus galloprovincialis) and wedge clams (Donax trunculus) were caught as bycatch during the exploration. the current piece of work discusses the impact of commercial beam trawls on the demersal macrofauna.