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The Conversation

  • Written by Nathan Hart, Associate Professor of Biological Sciences, Macquarie University

The recent spate of shark attacks in New South Wales has led to the announcement by NSW Premier Mike Baird and Primary Industries Minister Niall Blair of an expansion of the Shark Meshing Bather Protection Program. New shark nets are being installed at five locations in the Ballina and Evans Head area of the state’s north coast.

However, shark nets are controversial because they are designed to kill potentially dangerous sharks. In the process, nets may also injure or kill non-target animals, including endangered and protected species.

Whether or not shark nets actually reduce the risk of an attack is also a tricky question, although there has only been one fatal attack at a netted beach since the NSW meshing program began in 1937.

While some people welcome more nets, there is increasing support for the use of non-lethal shark attack mitigation measures. This is largely driven by concerns about the potential ecological impacts of shark nets. However, there are also substantial economic and logistical constraints on deploying nets at all locations where people might enter the water.

Beyond shark nets

So what other strategies can we use? As well as large-scale initiatives to reduce the chance of shark attacks at popular beaches, such as the installation of shark-proof barriers and enhancing public awareness of attack risk, concern about shark attacks has also led to a proliferation of personal shark deterrent technologies – so much so that there are now too many to list and describe in detail.

Broadly, the devices include those that produce strong electrical or magnetic fields, those that produce a repulsive light, sound or odour, and those that reduce the visibility of the wearer to sharks.

image Shark net trial locations, NSW north coast. NSW Department of Primary Industries.

Can new devices prevent attacks?

Because of the upsurge in technologies being developed to reduce shark attacks, shark researchers are often asked which are the most effective deterrent devices and which do not work.

However, many of these technologies are still in development. Fewer still have undergone independent testing of their effectiveness in deterring sharks under different conditions. This means that the general public have limited information when deciding if a particular shark deterrent might be suitable and whether it is worth purchasing, especially given that most commercially available devices cost several hundred dollars.

Our current research focuses on the new generation of magnetic and electrical deterrents, especially those designed to be used or worn by surfers and swimmers. We will test these devices in the field with white sharks to assess their efficacy. In the case of the electrical devices, we will map the electrical fields they emit to assess the strength and shape of these fields.

Importantly, by combining these approaches, we can correlate electric field strength with actual deterrent efficiency. This will help to streamline the development and testing of such devices by weeding out prototypes that do not work because their electrical fields are too weak to repel a motivated shark.

Fundamental shark research is essential

Our research will also focus on the physiological response of the shark’s electroreceptive system to the devices’ electrical and magnetic fields. This information will provide an improved biological understanding of the effect of these different stimuli on the sharks’ senses.

History shows that developing shark deterrents based on what we know about shark sensory biology is far more efficient than a trial-and-error approach. This research will also assist in adapting some of the personal deterrent technologies or concepts for use at a larger scale, such as the electric shark barrier being trialled in South Africa.

Any shark attack can be traumatising to the people directly or indirectly involved, and it is critical to reduce risks as much as possible. However, it is also important that scientists and governmental agencies do not overstate their ability to reduce risks of a shark attack.

The general public should be aware that there is no magic bullet when it comes to preventing attacks. No deterrent will prevent every shark attack in every situation.

The only way to remove all risk of an attack is to swim within a well-maintained enclosure that excludes sharks by means of an impervious barrier, or to stay out of the water altogether.

For those determined to venture further into the ocean, we encourage responsible SharkSmart behaviour. This includes staying close to shore, swimming in groups and avoiding large schools of bait fish.

Authors: Nathan Hart, Associate Professor of Biological Sciences, Macquarie University

Read more http://theconversation.com/not-just-nets-how-to-stop-shark-attacks-without-killing-sharks-69400

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