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Catch-and-release deters sharks from beaches

Catch-and-release deters sharks from beaches

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An approach to managing shark populations near beaches involving catching and releasing them, not only deters sharks from coastal areas but offers a promising solution to the challenge of balancing human safety with marine conservation.

If a shark or other animal is captured, the pressure on the line triggers the communications unit, which then sends an alert via phone call, email and text message to a boat crew who will respond to the animal within 30 minutes. If it is a target shark, namely a white, bull or tiger shark, it will be tagged and then released one kilometre offshore. All other marine animals caught are released immediately.

Researchers conducted trials using SMART drumlines in New South Wales, Australia, to catch and release sharks, particularly White Sharks. The study aimed to quantify the short-term post-release movements and the longer-term fate of these sharks.

Sharks were caught using SMART drumlines deployed about 500 meters from shore. Once captured, they were quickly secured to a research vessel, minimising potential injuries. The sharks were tagged with satellite-linked radio transmitting tags and acoustic transmitters to monitor their movements post-release.

Effective short-term deterrent

The study found that after release, White Sharks moved offshore before gradually returning to nearshore waters. This movement pattern suggests that the catch-and-release method effectively deters sharks from beaches in the short term. Additionally, the rapid response to SMART drumline captures indicated no long-term harm to the sharks, supporting the utility of this method as a non-lethal bather protection tool.

The approach aligns with conservation goals by minimising harm to sharks. It also provides a means of reducing shark-human interactions, a critical concern in areas with high recreational use. The study's findings are particularly relevant for endangered species like the White Shark, offering a humane alternative to lethal control methods. 

Fact file

What are SMART drumlines?

‘SMART’ stands for Shark-Management-Alert-In-RealTime. SMART drumlines consist of an anchor, two buoys and a satellite-linked GPS communications unit attached to a hook baited with one sea mullet.

A triggering magnet is attached to the communications unit. When a shark takes the bait and puts pressure on the line, the magnet is released, alerting the boat crew and DPI scientists that there is an animal on the line. Once alerted, the team responds immediately (within 30 minutes) to tag and release the shark or other marine animal.

SMART drumlines are set every morning (weather dependent) approximately 500m offshore at a depth between 8-15m of water. They are collected at the end of each day and are not left overnight.

— NSW Government  |  Department of Primary Industries

Sources
Biology
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Press releases from Divers Alert Network (DAN)