Introduction

In part 1 of this blog series, you will note that most shark attack prevention techniques were physical barriers and/or catch mechanisms, usually resultant in the killing of sharks (not necessarily target species) furthermore resulting in collateral deaths of other large marine species e.g. dolphins, whales and turtles.

Image result for great white shark
Attribution: Terry Goss- The Great White shark “Carcharodon carcharias”)

The contemporary scene still features older physical barrier type methods but now made slightly more sophisticated, aimed to reduce unintended deaths of marine organisms including the targeted shark species. Added to these are some chemical, electro-magnetic and other researched methods which have come into use from some further understanding of shark physiology, with varying degrees of success.

Shark nets of New South Wales, Australia

In Australia shark nets have been used since 1937 under the Shark Meshing Program. over the 80 years that the shark nets have been deployed, only one fatal shark attack has happened inside a netted zone. The shark nets are deployed across 51 popular beaches from Wollongong to Newcastle, from the 1st of September to the 30th of April. Deployed as “sunk net” just below the water surface between depths of 10-12 m, the nets are 150 m long and 6 metres deep with 60cm sized mesh. These shark nets are designed not to completely enclose a beach, but limit non-target marine species capture. Whale alarms and Dolphin pingers are used to deter cetaceans (Dolphins, Whales etc) from the area. This of course does not deter other marine organisms e.g. marine turtle species from being trapped in the netting.

Tagging

The tagging of sharks has been a method for shark research since the 1940’s, initially developed to assist scientists in understanding shark behaviour and other information, rather than preventing shark attacks. This has changed over recent years with tagging being implemented with, for example sonar buoys. As a tagged shark passes within range of the sonar buoy an alert is sent to scientists or private contractors. This again does not actively prevent shark-human interaction, but warns locals to shark activity in the area, which should reduce the amount of people swimming or surfing in the area. Tagging of sharks allows for other vital information to be taken suck as length, DNA profiles and unique descriptors for future observations like dorsal fin shape, unique scars, and possibly migration patterns.

There are several varieties of shark tags available: (see  http://www.dutchsharksociety.org/tagging/ )

SMART drumlines (Shark-Management-Alert-in-Real-Time)

Using an anchored buoy, attached to a trigging magnet and a drumline buoy which is attached to a large baited hook. “Smart” drumlines are seen as the successor to earlier models. Early drumlines were effective but left little hope for survival to any marine organism curious enough to take the hooked bait. Modern day “Smart” drumlines inform researchers that the bait has been consumed, who then go and try to free the creature before it dies.  “Smart” drumlines are a valuable resource in tagging sharks, allowing the shark to be set free alive and its data collected and recorded. In Australia’s New South Wales there are 35 Smart drumlines deployed daily from Evan’s Head and Lennox Head, with 10 more being trialled at other locations including Kiama and Shall cove.   https://www.dpi.nsw.gov.au/fishing/sharks/management/smart-drumlines

Drones

(Credit; Little Ripper)

 

Drones are increasingly being used to identify sharks from the air: much cheaper than using planes to patrol off beaches. Recently, drones are also deployed with artificial intelligence, which can likely identify sharks and other large marine organisms. This artificial intelligence is likely to be a more successful approach to identifying sharks aerially, without the risks of human error in successively identifying known problem shark species from other marine organisms or even boats.

There is an interesting development with drones and they have been referred to as “Life Saver” drones (produced by the “Little Ripper ” company) this means that the drones are equipped with items that can be dropped to a person in distress offshore whether that be due to a shark attack or potential drownings. Items can include inflatable lifesavers, anchors, whistles and even electro-magnetic shark deterring/ repelling devices.   https://newatlas.com/shark-spotter-drone-little-rippers/52006/

Shark repellent electro-magnetic devices

These are devices that can attach to a person or object, i.e. surf board, to deter potential shark attacks. one of the most well-known of these devices is the “Shark Shield” which attaches to a surfer’s board: other types include wrist or ankle device. The devices release a powerful magnetic field that is many times stronger than a shark will experience from it’s usual prey items

Shark repellent

Necromones, thus far, are showing themselves to be an effective form of shark attack prevention. When a shark dies, and begins to decompose, it releases chemical signals in the water which cause alarm in the nearby shark population. Harvested from dead sharks is obviously a concern as we try to protect both humans and sharks, so a synthesised product should be developed. Typically, the necromones are released in a “gas” or “smoke” grenade-like setup, releasing the cloud into the water were it disperses, causing a “flight” response by sharks in the immediate location.

Shark Repellent Spray
Credit; Shark Tec “Shark Repellent”

 

Bubble net

Bubble nets have been an interesting proposed method of shark deterrent for a while now. http://www.abc.net.au/news/2012-12-07/lights2c-sounds-and-bubble-curtains-to-deter-sharks/4415756  The idea behind the bubble net is to use long pipes which have many holes to released air under pressure into the water, in order to hopefully distract/deter sharks from entering the area through an apparent barrier. This has had limited success as many shark species including the Tiger shark have been known to ignore the wall of bubbles and once acclimatized to the bubble net, the sharks were not deterred from passing into protected areas.

 

Conclusion

So, in terms of outlining the above methods and diverse picture, the likelihood is that a mixture of methods will continue into the future. The bases of the research efforts mentioned in this blog will likely continue along the dual lines of area protection and individual protection, such as the electro-magnetic devices. Many of the above methods are still in their infancy and will over time become more refined and accessible.

As time has passed the efforts to conserve the lives of both humans and organisms has become a high priority. Instead of killing the sharks in nets, tagging and protection have become a priority in many communities across the globe.

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