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ESR 46:121-135 (2021)  -  DOI:

Potential of electric fields to reduce bycatch of highly threatened sawfishes

Kátya Abrantes1,2,*, Adam Barnett1,2, Maarten Soetaert3, Peter M. Kyne4, Adrianne Laird5, Lyle Squire6, Jamie Seymour7, Barbara E. Wueringer8, Jessica Sleeman7, Charlie Huveneers9

1College of Science and Engineering, James Cook University, Townsville, Qld 4811, Australia
2Biopixel Oceans Foundation, Cairns, Qld 4870, Australia
3Institute for Agricultural and Fisheries Research, Animal Sciences - Fisheries, Ankerstraat 1, 8400 Oostende, Belgium
4Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT 0815, Australia
5Northern Prawn Fishery Industry Pty Ltd, Caloundra, Qld 4551, Australia
6Cairns Marine, Cairns, Qld 4870, Australia
7Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Qld 4870, Australia
8Sharks and Rays Australia, PO Box 575, Bungalow, Cairns, Qld 4870, Australia
9College of Science and Engineering, Flinders University, Bedford Park, Adelaide, SA 5042, Australia
*Corresponding author:

ABSTRACT: Sawfishes are among the most threatened families of marine fishes and are susceptible to incidental capture in net fisheries. Since bycatch reduction devices currently used in trawl fisheries are not effective at reducing sawfish catches, new methods to minimise sawfish bycatch are needed. Ideally, these should affect sawfish behaviour and prevent contact with the fishing gear. We tested the effects of electric fields on sawfish behaviour to assess the potential of electric pulses in mitigating sawfish bycatch. Experiments were conducted in a tank where 2 electrodes were suspended in the water column, connected to a pulse generator, and placed across the swimming path of sawfish. Two largetooth sawfish Pristis pristis were tested in control conditions, in the presence of a baseline pulse, and of 5 variations of that pulse where 1 parameter (polarity, voltage, frequency, pulse shape, pulse duration) was altered at a time. Conditional inference trees were used to identify the effects of various parameters (e.g. treatment, individual) on reaction type, reaction distance, twitching presence and duration, and inter-approach times. Sawfish reacted to electric fields, but reaction distances were small (typically <1.2 m), and no field tested consistently led to reactions conducive to escaping from moving nets. The following parameters induced the most response in both individuals: bipolar current, rectangular shaped, 5-10 Hz, ~1500 µs duration, and 100 V. We recommend further research focussing on moving nets, testing a V-shaped electric array preceding the net mouth by at least 5 m, and testing a setup similar to electrotrawling.

KEY WORDS: Bycatch reduction devices · Electric repellents · Sawfish · Prawn fisheries · Pristis pristis · Trawl fisheries

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Cite this article as: Abrantes K, Barnett A, Soetaert M, Kyne PM and others (2021) Potential of electric fields to reduce bycatch of highly threatened sawfishes. Endang Species Res 46:121-135.

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