New Zealand Journal of Marine and Freshwater Research abstracts
Atypical size selection of captive school prawns, Metapenaeus macleayi,
by three recreational fishing gears in south-eastern Australia
Matt K. Broadhurst
NSW Department of Primary Industries
Fisheries Conservation Technology Unit
P.O. Box J321
Coffs Harbour
NSW 2450, Australia
email: mbroadhurst@nmsc.edu.au
Russell B. Millar
Department of Statistics
University of Auckland
Private Bag 92 019
Auckland, New Zealand
Damian J. Young
Michael E. L. Wooden
NSW Department of Primary Industries
Fisheries Conservation Technology Unit
P.O. Box J321
Coffs Harbour
NSW 2450, Australia
Stuart Rowland
NSW Department of Primary Industries
Grafton Aquaculture Centre
PMB 3, Grafton
NSW 2460, Australia
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 (6Ð24
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.
Keywords selectivity; shrimp; prawn; bycatch reduction;
mesh size; Metapenaeus macleayi; lactate
M04055; Online publication date 24 November 2004 Received 5 March 2004;
accepted 30 August 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38: 755–766
0028–8330/04/3805–0755 © The Royal Society of New Zealand 2004
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