ASSESSMENTS OF MODIFIED CODENDS THAT REDUCE THE BY-CATCH OF FISH IN 2ESTUARINE PRAWN-TRAWL FISHERIES IN NEW-SOUTH-WALES, AUSTRALIA

Four experiments, comparing catches and by-catches from a conventional codend with several modified codends, were done in two estuarine praw n-trawl fisheries in New South Wales, Australia, The modified codends were designed to reduce by-catch and included panels of square-mesh, s oft mesh separating panels and a Nordmore-grid. Compared to a conventi onal codend, the codends with square-mesh panels showed no significant differences in catches of school prawns (Metapenaeus macleayi) nor by -catches. The codends with soft mesh separating panels showed differen t results between locations. In the Clarence River estuary, these desi gns significantly reduced by-catch (up to 70%) with no reduction in ca tches of school prawns, while similar designs tested in Botany Bay sho wed significant reductions in by-catches and catches of king prawns (P enaeus plebejus) (up to 58% and 34% respectively). In the Clarence Riv er the codend with the Nordmore-grid, showed a significant reduction i n by-catch (77%) with no reduction in catches of school prawns compare d to a conventional codend. The results are discussed in terms of the probable behaviour of fish and prawns in the modified trawls, the need for fishery-specific designs of by-catch reducing trawl modifications and the implications of introducing such designs into normal commerci al practice.