Gear selectivity of large-mesh nets and drumlines used to catch sharks in the Queensland Shark Control Program

  • WD Sumpton
  • SM Taylor
  • NA Gribble
  • G McPherson
  • T Ham

Abstract

Catches of sharks and bycatch in large-mesh nets and baited drumlines used by the Queensland Shark Control Program were examined to determine the efficacy of both gear types and assess fishing strategies that minimise their impacts. There were few significant differences in the size of both sharks and bycatch in the two gear types, apart from significantly smaller (p < 0.05) tiger sharks Galeocerdo cuvier being taken on drumlines and smaller green turtles Chelonia mydas in nets. Catch per unit effort showed orders of magnitude differences among species, even within the same family. Hammerhead sharks and rays were particularly vulnerable to net capture, whereas higher catch rates of tiger sharks were observed for drumlines. Nets caught more marine mammals, teleost fish and rays, whereas drumlines exhibited higher catch rates of the threatened loggerhead turtle Caretta caretta. Survival of most taxa (particularly obligate ram ventilators) was lower in nets than drumlines. Bycatch species (turtles and marine mammals) were able to swim to the surface to breathe when they were hooked on drumlines, enhancing their survival potential. Fishing strategies that recognise the different selectivity patterns of the gear can be developed to suit local biotic and abiotic conditions, although it is recognised that quantification of both ecological risk and risk to bathers is not a simple task.

Keywords: bycatch, drumlines, mesh nets, shark control

African Journal of Marine Science 2011, 33(1): 37–43

Author Biographies

WD Sumpton
Queensland Department of Employment Economic Development and Innovation, Southern Fisheries Centre, PO Box 76, Deception Bay 4508, Australia
SM Taylor
Queensland Department of Employment Economic Development and Innovation, Primary Industries Building, 80 Ann St, Brisbane 4001, Australia
NA Gribble
Queensland Department of Employment Economic Development and Innovation, Northern Fisheries Centre, 38–40 Tingira Street, Cairns 4870, Australia
G McPherson
Queensland Department of Employment Economic Development and Innovation, Northern Fisheries Centre, 38–40 Tingira Street, Cairns 4870, Australia
T Ham
Queensland Department of Employment Economic Development and Innovation, Primary Industries Building, 80 Ann St, Brisbane 4001, Australia
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X