Factors affecting elasmobranch escape from turtle excluder devices (TEDs) in a tropical penaeid-trawl fishery

Campbell, Matthew J., Tonks, Mark L., Miller, Margaret, Brewer, David T., Courtney, Anthony J., and Simpfendorfer, Colin A. (2020) Factors affecting elasmobranch escape from turtle excluder devices (TEDs) in a tropical penaeid-trawl fishery. Fisheries Research, 224. 105456.

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Abstract

The use of turtle excluder devices (TEDs) has resulted in fewer elasmobranchs (i.e. sharks and rays) caught in tropical penaeid-trawl fisheries. However, very few studies in the primary literature have quantified the effects of various TED design aspects affecting the escape of elasmobranchs. Data collected by observers on board commercial trawlers operating in Australia's northern prawn fishery (NPF) during 2001 were re-examined to quantify the effect of TEDs on catches of various elasmobranchs. During this sampling, a total of 6204 elasmobranchs were caught from 1440 net trawls. The 34 species identified, from 15 families and four taxonomic orders, were dominated by small carcharhinids (n = 2160, median total length = 75 cm) and dasyatids (n = 2030, median disc width = 24 cm). The TEDs assessed significantly reduced the numbers of large elasmobranchs caught: increasing fish size was found to result in higher escape for all taxonomic orders. Further, top-shooter TEDs increased the escape of Carcharhiniformes, while bottom-shooter TEDs facilitated greater escape of Myliobatiformes. Grid orientation had no effect on the escape of Orectolobiformes or Rhinopristiformes. Decreasing bar space was found to increase the escape of only one species, the Australian blacktip shark (Carcharhinus tilstoni). The TEDs facilitated the escape of several species of conservation interest including the globally endangered scalloped hammerhead (Sphyrna lewini) and zebra shark (Stegostoma fasciatum). However, the rostrum of the narrow sawfish (Anoxypristis cuspidata) inhibited the escape of this globally important species. Fishery-specific research is required to determine the appropriate TED bar spaces that reduce catches of elasmobranchs while minimising the loss of commercially important species.

Item ID: 62966
Item Type: Article (Research - C1)
ISSN: 0165-7836
Keywords: turtle excluder device, TED, elasmobranch, discards, grid orientation, bar space
Copyright Information: © 2019 Published by Elsevier B.V.
Funders: Fisheries Research and Development Corporation (FRDC), Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Projects and Grants: FRDC Project Number 2000/17
Date Deposited: 18 Mar 2020 07:33
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 35%
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300502 Aquaculture and fisheries stock assessment @ 30%
41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410401 Conservation and biodiversity @ 35%
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