Round scallops and square meshes: a comparison of four codend types on the catch rates of target species and by-catch in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery
Anthony J. Courtney A D , Matthew J. Campbell A , Darren P. Roy A , Mark L. Tonks A B , Keith E. Chilcott A and Peter M. Kyne CA Queensland Department of Primary Industries and Fisheries, Southern Fisheries Centre, PO Box 76, Deception Bay, Qld 4508, Australia.
B Present address: CSIRO Marine and Atmospheric Research, PO Box 120, Cleverland, Qld 4163, Australia.
C School of Biomedical Sciences, University of Queensland, St. Lucia, Qld 4072, Australia.
D Corresponding author. Email: tony.courtney@dpi.qld.gov.au
Marine and Freshwater Research 59(10) 849-864 https://doi.org/10.1071/MF08073
Submitted: 5 March 2008 Accepted: 30 June 2008 Published: 27 October 2008
Abstract
Concern over the amount of by-catch from benthic trawl fisheries and research into the problem have increased in recent years. The present paper demonstrated that by-catch rates in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery can be reduced by 77% (by weight) using nets fitted with a turtle excluder device (TED) and a square-mesh codend, compared with a standard diamond-mesh codend with no TED. This large reduction was achieved with no significant effect on the legal size scallop catch rate and 39% fewer undersize scallops were caught. In total, 382 taxa were recorded in the by-catch, which was dominated by sponges, portunid crabs, small demersal and benthic fish (e.g. leatherjackets, stingerfish, bearded ghouls, nemipterids, longspine emperors, lizard fish, triggerfish, flounders and rabbitfish), elasmobranchs (e.g. mainly rays) and invertebrates (e.g. sea stars, sea urchins, sea cucumbers and bivalve molluscs). Extremely high reductions in catch rate (i.e. ≥85%) were demonstrated for several by-catch species owing to the square-mesh codend. Square-mesh codends show potential as a means of greatly reducing by-catch and lowering the incidental capture and mortality of undersize scallops and Moreton Bay bugs (Thenus australiensis) in this fishery.
Additional keywords: benthic impacts, drag, Great Barrier Reef, selectivity, trawl net.
Acknowledgements
This research was funded by the Australian Government Fisheries Research and Development Corporation (FRDC Project No. 2000/170) and the Queensland Department of Primary Industries and Fisheries. Dr Matt Broadhurst of the New South Wales Department of Primary Industries kindly provided advice on the application and construction of square-mesh codends. We gratefully acknowledge the skills and seamanship provided by Colin, Wayne and Darren Flaherty and for making their vessel FV Southern Intruder available for the charter. Brad May assisted with processing the by-catch. The research charter and by-catch sampling carried out in the Great Barrier Reef Marine Park were undertaken under permit approval number G01/437. Two anonymous referees provide useful comments on an earlier draft of this paper.
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