Retained and discarded by-catch from oceanic prawn trawling in New South Wales, Australia

• Published in: Fisheries research 1998-06, Vol.36 (2), p.217-236
• Main Authors: Kennelly, S.J, Liggins, G.W, Broadhurst, M.K
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; By-catch; BYCATCH; CAPTURE ACCESSOIRE; CHALUTAGE; CREVETTE; DESCARTES; Discards; ECHANTILLONNAGE; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fundamental and applied biological sciences. Psychology; GAMBAS Y CAMARONES; IDENTIFICACION; IDENTIFICATION; Marine; MUESTREO; NEW SOUTH WALES; NOUVELLE GALLES DU SUD; NUEVA GALES DEL SUR; Observer programme; PESCA A LA RASTRA; Prawn trawling; PRAWNS AND SHRIMPS; Retained catches; SAMPLING; TRAWLING
• ISSN: 0165-7836; 1872-6763
• DOI: 10.1016/S0165-7836(98)00091-5

The catches and by-catches of oceanic prawn trawlers were identified and quantified in a stratified, randomized, observer survey of four of the most important fleets in NSW, Australia. For each port, catches were sampled from all tows done during replicate fishing trips in each season from winter 1990 to autumn 1992. Data were examined using analyses of variance of relative abundances of individual species and groups of species, multi-dimensional scaling of the full by-catch dataset, estimates of retained by-catches and discards by the four ports (incorporating estimates of fishing effort) and length–frequency distributions of common discards. The results revealed a latitudinal gradient in by-catch and discarding with larger quantities occurring northwards. However, significant species-specific variations in abundances were detected at all spatial and temporal scales sampled such that the occurrences and abundances of particular by-catch species depended on the location, season and year examined. In catching an estimated 1 579t of prawns during the two-year survey, the oceanic prawn trawlers from the four 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 estimated to have been retained for sale and 13 458t were discarded – including 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 trawling and selective trawl gears and fishing practices.