Review of dolphin acoustic deterrent device mitigation in inshore fisheries

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MIT2019-01: Dolphin acoustic deterrent device mitigation in inshore fisheries (PDF, 1,949 K)

Summary

Dolphin Acoustic Deterrent Devices (ADD; also commonly referred to as pingers) are thought to limit interactions between dolphins and fishing nets by emitting high frequency signals that persuade animals to avoid the noise source. While there is little quantitative data or empirical evidence from New Zealand (NZ) research as to the efficacy of ADDs, there is anecdotal information that they may be effective in reducing dolphin bycatch in set net fisheries. In New Zealand, ADDs are being used by some fishers in the deep-water jack mackerel trawl fishery and also in some inshore set net fisheries, targeting a range of different species, but their efficacy in these various settings has not been formally tested. However, there is some international evidence for their success in overseas fisheries. The Cawthron Institute was contracted by the Department of Conservation to carry out a literature review of ADD use internationally and to provide recommendations for a potential experimental trial of these devices in NZ inshore commercial fisheries.

The main conclusions drawn from the ADD literature as it relates to Hector’s and Māui dolphin bycatch mitigation are:

• while success rates across marine mammal species have been variable, there have been significant examples of large reductions in bycatch through the use of ADDs
• limited ADD trials with Hector’s and Māui dolphins in New Zealand have produced ambiguous results, but provide some indication that Hector’s dolphins display avoidance behaviour around active ADDs
• ADDs appear most successful for cetaceans that are neophobic (i.e. fear of anything new), are easily startled, and have large home-ranges. They are, therefore, more likely to be effective for phocoenids (i.e. porpoises) than coastal delphinids such as Hector’s and Māui dolphins which are boat-positive and unlikely to be strongly neophobic. As such, ADDs may be a less effective mitigation method for Hector’s and Māui dolphins but this requires testing to confirm. Assessment of ADD efficacy will not be possible to assess without well designed, repeatable field trials
• prior to undertaking field trials, the ADD effectiveness must be evaluated against several key considerations:
  • What reductions in bycatch are achievable?
  • Are any reductions likely to meet management goals?
  • What sample sizes would be necessary in order to yield sufficient statistical power to quantify effectiveness?
• if ADDs are implemented, assessment of long-term effectiveness would require dedicated enforcement and compliance monitoring regimes as well as high levels of observer coverage
• the focus of this review has been on mitigating impacts from commercial inshore fisheries; however, any effective mitigation option should also be applied to recreational fisheries wherever possible.

Based on this review, there is evidence to support the trial of ADDs as a mitigation tool to reduce bycatch of Hector’s and Māui dolphin in NZ inshore fisheries. Therefore, it is recommended that a staged approach to research is undertaken and that initial trials that pose no risk to dolphins should be undertaken. Results from initial trials will provide critical data needed to evaluate the potential of progressing research to a pilot scale field study.

Publication details

Childerhouse, S., Johnson, O. and Tremblay-Boyer, L. 2020. Review of dolphin acoustic deterrent device mitigation in inshore fisheries. Prepared for the Conservation Services Programme, Department of Conservation. Cawthron Report No. 3507. 34 p + appendices.