Media Release Save Our Sharks

Marine conservationists welcome study which finds deterrent technology reduces shark ‘bite-offs’ by up to 65%

September 1, 2021

The Australian Marine Conservation Society (AMCS) says the findings of a study in Western Australia showing the incidence of shark bite-offs being reduced by up to 65% with the use of deterrent technology, provides a promising solution to a frustrating and widespread issue for Australian fishers.

Shark bite-offs – or being ‘sharked’ – is also known as shark depredation and is what happens when a shark preys on a fisher’s catch. In recent years, reports of shark depredation have been increasing, coming in from recreational fishers across the north of Australia.

The tests of three deterrent devices – Shark Banz “Sentry” (magnetic based), Ocean Guardian “Fish01” (electric based) and Shark Stopper (acoustic based) – by the WA Department of Primary Industries (DPIRD) and Recfishwest, reduced the normal depredation rates from 40% of landed fish to as low as only 12% of landed fish.

The tests were carried out in north-west WA, Montebello Islands and Exmouth – all shark depredation hotspots – across a total of 60 sites and 180 hours, split evenly across the two regions.

Importantly, part of the study involved a survey of 1,340 recreational fishers to understand their experiences of depredation and preferred method of avoiding bite-offs.

Approximately 70% of recreational fishers, including charter operators, moved fishing spots, and 15% stopped fishing altogether. Less than 10% used a magnetic or electric-based deterrent.

Other strategies used by recreational fishers to mitigate bite offs included rapid retrieval, heavier fishing line, electric reels, avoiding the use of burley or baits and not dumping fish offal. This is the first study to document the different methods fishers are using.

AMCS shark scientist Dr Leonardo Guida said: “Bite-offs are understandably frustrating, so these results are encouraging. A technical solution to shark bite-offs can improve our co-existence with sharks and the all-round experience for everyone on the water. Tech isn’t a silver bullet however, behavioural responses are important too, and it’s great to see the environmental stewardship many responsible fishers have borne out in these results.”

Underwater video and DNA swabs from bitten fish were also used to identify species responsible for depredation. Responsible species included a variety of whaler species, including grey reef, dusky, and blacktip. Some bite-offs were even found to not be caused by sharks at all, with large reef cod species shown to be responsible.

Dr Guida added: “Being able to tell what species is responsible for bite-offs is a crucial piece of the puzzle. Sharks are typically the go-to culprit, but it is interesting to note they are not the only species responsible. Understanding this important element allows all stakeholders to better understand and address this challenge, particularly when it comes to making decisions about how we manage our recreational and commercial fisheries.

WA has been leading in this space for the past ten years or so. Across the country, particularly in the tropical north of Queensland and the Northern Territory, we can build on what WA has done, tailor it to different regions, and have evidence-based approaches to mitigating bite-offs.

“I would encourage fisheries departments and recreational fishing groups in those regions to follow the lead of WA and instigate their own studies on shark bite-offs so potential solutions can be tailored to their regions.”