Use of bycatch reducing devices for brachyurids by small scale trawl fishing

Abstract

Bycatch reduction devices (BRD) are technical modifications installed in the codend of trawl nets in order to avoid or to reduce  unwanted fishing mortality. We conducted four experiments to assess the BRD performance for brachyurids exclusion small-scale  trawl fishery (10-m length canoe, 18HP) from Paraná State coast. We tested two Nordømore grids with different bar spaces (24- mm – G24; 37-mm – G37), a 28-mm square-mesh codend (MQ) and a 28-mm square-mesh codend with a 96-mm upper escape panel  (JE). The BRDs were compared against a control net during 60-min paired deployments (total of 6 replicates of each configuration  on each season). Nordømore grids retained less total brachyurids (G24: 62%; G37: 53%, p<0,05) than conventional design (control),  especially for  Callinectes sp.,  Libinia ferreirae and  Arenaeus cibrarius but not significant for  Persephona sp. and  Hepatus  pudibundus . Modified codends (MQ and JE) did not significantly reduce brachyurids (p>0,05). All tested modifications reduced total  Xiphopenaeus kroyeri although not significant (G24: 15,77%; G37: 32,08%; J.E: 8,01%; M.Q: 2,41%; p>0,05). Nordømore grids  had shown better efficiency for brachyurids. Yet target-species losses must be better understood in order to promote a better dialogue  with artisanal fisherman and decision-makers. Thereby, results provided preliminary reference points for an ecosystem approach to  trawl fisheries management.