A novel grid-net design to eliminate bycatch in beam trawl fishing for the veined rapa whelk in the south-eastern Black Sea

Abstract

Beam trawl fisheries in the Black Sea target the veined rapa whelk (Rapana venosa) while other species of fish and crabs are returned to the sea dead or alive. Smaller bivalves and crabs are also packed with the catch without elimination. in this study, novel grid-net designs (GNDs) with two different bar spacings were tested to reduce the bycatch. Thirty hauls (15 hauls for each bar spacing) were carried out in the south-eastern Black Sea between 17 and 26 August 2017. Bycatch compositions were compared by towing a commercial diamond mesh and one of the grid-net beam trawls simultaneously onboard a commercial vessel. There were statistically significant (p<0.01. 78% and 83%) decreases in the mean bycatch weight for 20 mm and 30 mm grid-nets, respectively. the estimated commercial loss was 14% in the 20 mm GND and 39% in the 30 mm GND in the landing values as compared to the commercial gear. in conclusion, the use of grid-net design for beam trawl fishing in the south-eastern Black Sea can significantly reduce the bycatch of most benthic species. There is a trade-off between the reduction in the bycatch and some commercial loss, which could be offset with some compensation to fisheries, such as an extension of the fishing season.