Atypical size selection of captive school prawns,Metapenaeus macleayi,by three recreational fishing gears in south‐eastern Australia |
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| Authors: | Matt K Broadhurst Russell B Millar Damian J Young Michael E L Wooden Stuart Rowland |
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| Institution: | 1. NSW Department of Primary Industries , Fisheries Conservation Technology Unit , P.O. Box J321, Coffs Harbour, NSW, 2450, Australia E-mail: mbroadhurst@nmsc.edu.au;2. Department of Statistics , University of Auckland , Private Bag 92 019, Auckland, New Zealand;3. NSW Department of Primary Industries , Fisheries Conservation Technology Unit , P.O. Box J321, Coffs Harbour, NSW, 2450, Australia;4. NSW Department of Primary Industries , Grafton Aquaculture Centre , PMB 3, Grafton, NSW, 2460, Australia |
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| Abstract: | Three manipulative experiments were done to estimate the selectivity of conventional and new sizes and configurations of mesh for school prawns, Metapenaeus macleayi, in three south‐eastern Australian recreational fishing gears (haul, push, and scoop nets). The treatment meshes examined were: (1) conventional‐sized, diamond‐shaped mesh used in all gears (20 mm in scoop nets and 30 mm in push and haul nets); (2) 30 mm in scoop nets; and (3) 40‐mm diamond‐ and (4) 23‐mm square‐shaped mesh in all gears. In all experiments, known quantities of school prawns (6–24 mm carapace length (CL)) were placed in purpose‐built enclosures, monitored to ensure no experimental‐induced stress (as measured by changes in L‐lactate in their haemolymph) and the replicate treatments of the various gear configurations deployed. Escapees from the various treatment nets were collected from the enclosures using fine‐meshed nets. Logistic selection curves were derived for all treatment nets and specific comparisons made within and among gears. All nets had 50% retention lengths (L50) comparable to other penaeid‐catching gears with similar mesh sizes, but most had selection ranges (SRs) that were atypically inflated. The large SRs were attributed to a combination of factors that included the mesh geometry and towing speed of the gears and the behaviour of school prawns. The 20‐mm scoop net had the smallest selection parameters, retaining >99% of individuals larger than 13 mm CL. Mesh size in this gear would need to be increased to at least 30 mm to allow some maturing prawns (>18 mm CL) to escape. |
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| Keywords: | selectivity shrimp prawn bycatch reduction mesh size Metapenaeus macleayi lactate |
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