Evolving and devolving bycatch reduction devices in an Australian penaeid-trawl fishery

Since bycatch reduction devices (BRDs) were first tested in Australian penaeid-trawl fisheries almost 20 years ago, there have been ongoing refinements to a discrete range of legislated designs; mostly in response to dynamic fishery-specific operational requirements. This study assesses the relative utility of the latest versions of two generic BRDs that have evolved/devolved in an estuarine fishery. Compared with a codend containing no BRD, a simplified Nordmøre-grid and radial escape section significantly reduced the total weight of bycatch by 74 and 36%, respectively. Catches of the targeted school prawns (Metapenaeus macleayi) were also reduced by 4 and 11%, respectively, although, at least for the Nordmøre-grid, these losses were apparently offset by the practicality of the revised design in terms of a simpler and cheaper construction. The presence of large quantities of displaced submerged plants (e.g. Egeria densa and Hydrilla verticillata) on the trawl grounds at certain times (which preclude using the Nordmøre-grid) may similarly compensate for the reduced efficiency of the radial escape section. In addition to quantifying the performance of the revised BRDs, the results provide direction for their future refinement in this and other similar fisheries.

► The evolution and devolution of bycatch reduction devices (BRDs) is described for a penaeid-trawl fishery. ► Simple modifications to trawls reduced bycatch, with minimal impacts to catches of shrimp. ► The results provide direction for the further refinement of BRDs.