Study

Evaluation of exclusion grids to reduce the catch of dolphins, turtles, sharks and rays in Pilbara trawl fishery. DBIF Funded Project

  • Published source details Stephenson P.C., Wells S. & King J.A. (2006) Evaluation of exclusion grids to reduce the catch of dolphins, turtles, sharks and rays in Pilbara trawl fishery. DBIF Funded Project. Department of Fisheries Western Australia report, 171.

Actions

This study is summarised as evidence for the following.

Action Category

Install exclusion and/or escape devices for mammals on fishing nets

Action Link
Marine and Freshwater Mammal Conservation
  1. Install exclusion and/or escape devices for mammals on fishing nets

    A controlled study in 2005–2006 of a pelagic area in the Indian Ocean, Western Australia (Stephenson et al. 2006; same study area as Allen et al. 2014) reported that trawl nets with exclusion and escape devices installed had fewer trapped common bottlenose dolphins Tursiops truncatus than those without devices, but some dolphins exited the net dead or in distress. Results are not based on assessments of statistical significance. Eight dolphins/1,000 trawls were trapped in nets with exclusion devices, whereas 15–22 dolphins/1,000 trawls were trapped in nets without exclusion devices. Three of seven dolphins were observed exiting nets alive, through the escape opening or the mouth of the net. The other four dolphins died or were in distress and fell through the escape opening dead. Six commercial fishing vessels deployed trawl nets with exclusion devices (2006: total 1,156 trawls) and without (2005: 659 trawls; 2006: 229 trawls). Exclusion devices were semi-flexible metal grids (1.2 x 2 m; 15.5 cm vertical bar spacing) attached to the start of the net extension, 10 m from the end of the net, with an escape opening below. Onboard observers recorded trapped dolphins during each haul in 2005–2006. Underwater video cameras recorded the activity of seven dolphins in trawl nets with exclusion devices in 2006.

    (Summarised by: Anna Berthinussen)

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