Bycatch reduction device assessment in the trawling fishing from sea-bob shrimp fishery

Abstract

The shrimp fishery is done by otter trawls, with a great impact on marine ecosystems. To reduce these impacts, a few countries have implemented and tested devices to reduce bycatch (collectively termed ‘bycatch reduction devices’ or ‘BRDs’). The effectiveness of four BRDs (including separating grids and square-mesh codends) were assessed in a sea-bob shrimp fishery off the coast of Paraná. A total of 108 hauls (1 hour each) were done over nine months of sampling, with 27 hauls for each BRD. Two identical nets were deployed simultaneously on each side of the vessel. In one net, a standard codend was used, while in the other net, a BRD was inserted anterior to the codend. In total, the four modified nets caught 187.00 kg of fish and 485.26 kg of shrimp. For the fish, there were significant reductions by all BRDs (Test t: P<0.05), with the largest mean reduction in weight by a grid G24 (56.71%) and the lowest reduction by a square-mesh codend (MQ) (17.98%). The grid (G37) and a square-mesh panel (JE) reduced bycatch by 52.92 and 34.46%, respectively. For the shrimp, only the MQ caught similar quantities of shrimp as the control (Test t: P = 0.57). The largest reduction in shrimp occurred in the trawl containing the G37 (32.08%). The mean reductions in shrimp by the G24 and JE were 15.77 and 8.01%, respectively. It was concluded that the four BRDs were effective in excluding fish bycatch, but only the MQ did not significantly reduce the shrimp catch.