Cumulative selectivity benefits of increasing mesh size and using escape gaps in Australian Portunus armatus traps

Broadhurst, Matt K., Smith, Timonthy M., Millar, Russell B., Hughes, Brian, Raoult, Vincent, and Gaston, Troy F. (2019) Cumulative selectivity benefits of increasing mesh size and using escape gaps in Australian Portunus armatus traps. Fisheries Management and Ecology, 26 (4). pp. 319-326.

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Abstract

The individual and cumulative effects of increasing mesh size (from 56- to 75-mm stretched mesh opening) and installing three escape gaps (36 × 120 mm) in collapsible-netted round traps were assessed to address concerns associated with excessive discarding in an Australian portunid fishery. Compared to conventional traps comprising 56-mm mesh throughout, those with the same mesh size and escape gaps caught significantly fewer (by 54%) undersized blue swimmer crabs, Portunus armatus Milne-Edwards and yellowfin bream, Acanthopagrus australis Günther (by 64%). Irrespective of escape gaps, simply increasing the mesh size to 75 mm did not significantly affect catches of undersized P. armatus, although 87% fewer A. australis were retained. Traps with both 75-mm mesh and escape gaps maintained reductions of A. australis, but had a clear cumulative effect on P. armatus selection, retaining 84% fewer undersized individuals across a larger size at retention. The results support using escape gaps in existing conventional traps, but illustrate the need to configure the minimum legal mesh size to approach the desired target size of P. armatus as a precursor to maximising trap selectivity. Larger-meshed traps also require less material (i.e. plastic), which benefits their manufacture and, equally importantly, reduces environmental costs when lost.

Item ID: 68694
Item Type: Article (Research - C1)
ISSN: 1365-2400
Keywords: crustaceans, escape gap, selectivity, trap, undersize
Copyright Information: © 2019 John Wiley & Sons Ltd
Date Deposited: 16 Jul 2021 02:41
FoR Codes: 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300505 Fisheries management @ 60%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310301 Behavioural ecology @ 20%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 20%
SEO Codes: 10 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 1003 Fisheries - wild caught > 100303 Wild caught crustaceans (excl. rock lobster and prawns) @ 70%
18 ENVIRONMENTAL MANAGEMENT > 1802 Coastal and estuarine systems and management > 180201 Assessment and management of coastal and estuarine ecosystems @ 30%
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