RETAINED AND DISCARDED BY-CATCH FROM OCEANIC PRAWN TRAWLING IN NEW-SOUTH-WALES, AUSTRALIA

The catches and by-catches of oceanic prawn trawlers were identified a nd quantified in a stratified, randomized, observer survey of four of the most important fleets in NSW, Australia. For each port, catches we re sampled from all tows done during replicate fishing trips in each s eason from winter 1990 to autumn 1992. Data were examined using analys es of variance of relative abundances of individual species and groups of species, multi-dimensional scaling of the full by-catch dataset, e stimates of retained by-catches and discards by the four ports (incorp orating estimates of fishing effort) and length-frequency distribution s of common discards. The results revealed a latitudinal gradient in b y-catch and discarding with larger quantities occurring northwards. Ho wever, significant species-specific variations in abundances were dete cted at all spatial and temporal scales sampled such that the occurren ces and abundances of particular by-catch species depended on the loca tion, season and year examined. In catching an estimated 1 579t of pra wns during the two-year survey, the oceanic prawn trawlers from the fo ur ports were estimated to have caught approx. 16 435t of by-catch (a by-catch-to-prawn ratio of 10.4: 1). Of this by-catch, 2 952t were est imated to have been retained for sale and 13 458t were discarded - inc luding several million individuals of commercially and recreationally important species (e.g. snapper, eastern blue-spot flathead, red-spot whiting). We discuss the results in terms of the spatial and temporal variations in these discards and the relative effectiveness of various ways to reduce them, including fixed and flexible closures to trawlin g and selective trawl gears and fishing practices. (C) 1998 Elsevier S cience B.V. All rights reserved.