Performance of square-mesh codends in reducing discards and by-catch in the Shark Bay scallop fishery

Abstract

Abstract. The performance of square-mesh codends (as opposed to the conventional diamond mesh) was examined as a discard and by-catch reduction device for the Shark Bay saucer-scallop trawl fishery. Of the three different-sized squaremesh codends (50, 55, 60 mm) tested against the standard 100-mm diamond-mesh codend, the 50-mm square-mesh codend performed poorly with relatively high retention of small (,85 mm shell height) scallops, whereas the 55-and 60-mm square-mesh codends retained 22-33% less smaller scallops than did the diamond-mesh codend. Overall, a mean of 5% loss in commercial-sized scallops across all three square-mesh codends and significant by-catch reductions of up to 95% were achieved compared with the diamond mesh. Catch rate of prawns by the square-mesh codend was less than 2% of that of the standard prawn net. The performance of the 60-mm square-mesh codend presents a good basis for its use in commercial trials in the Shark Bay scallop trawl fishery. A move to square-mesh codends could result in a significant reduction of small scallops and by-catch and may potentially increase the catches of commercial-sized scallops as a result in improvements in water flow and net efficiency.

Science behind management of Shark Bay and Florida Bay, two P-limited subtropical systems with different climatology and human pressures

“…The fisheries papers in this special issue build on previous research and increase understanding of the effect of fisheries on the Shark Bay ecosystem. Chandrapavan et al (2012) examined the performance of square mesh panels fitted to standard 100 mm scallop trawls in minimising discards of small scallops and by-catch species. Geostatistical modelling has been used to provide a useful tool for understanding patterns in the abundance and spatial distribution of scallop recruitment in Shark Bay (Mueller et al 2012).…”