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

Three codends 1. a control, 2. a simplified Nordmore-grid and 3. one with a radial escape section were tested aboard trawl vessels off New South Wales Australia, to determine the effects on the catch of bycatch and target species.  The codend with a radial escape section and the simplified Nordmore-grid retained fewer school prawns by weight 11.5% and 4.6% resepectively, compared to the control net.   The Nordmore-grid codend caught 50% fewer yellowfin bream than the radial escape section net and 55% fewer than the control net.  Both trial codends significantly reduced the predicted mean weight (36% Nordmore-grid and 74.3% radial escape section) and number (17.3% and 49.3%) of bycatch.  The Nordmore-grid codend retained significantly fewer bycatch by weight (59.8%) and number 38.7%) than the radial escape section codend.  In addition, the Nordmore-grid codend retained significantly fewer Ramsey's perchlet than the control (48.3%) and radial escape section (50.7%) and fewer southern herring (69.4% and 57.6% respectively).  Significantly more silver biddy sized 9.5 to 10.5 cm total length were retained inthe control codend compared to the Nordmore-grid and radial escape section codends.