Shark attack prevention
There are a range of shark attack prevention techniques employed to reduce the risk of shark attack and keep people safe. They include removing sharks by various fishing methods, separating people and sharks, as well as observation, education and various technology-based solutions.
Techniques that involve culling sharks are contentious. Environmental groups have voiced concern over the impact of reduced shark numbers on ocean ecosystems and the problem of by-catch of other marine life, particularly endangered species. Because sharks are important to the ecosystem, removing them harms the ecosystem.
Nets
Shark net
The majority of shark nets used are gillnets, which is a wall of netting that hangs in the water and captures the targeted sharks by entanglement. The nets may be as much as long, set at a depth of, have a mesh size of and are designed to catch sharks longer than in length.Shark nets do not offer complete protection but work on the principle of "fewer sharks, fewer attacks". They reduce occurrence via shark mortality. Shark nets such as those in New South Wales are designed to entangle and capture sharks that pass near them. Historical shark attack figures suggest that the use of shark nets does markedly reduce the incidence of shark attack when implemented on a regular and consistent basis.
A downside with shark nets is that they do result in bycatch, including threatened and endangered species. Between September 2017 and April 2018, 403 animals perished in the nets in New South Wales, including 10 critically endangered grey nurse sharks, 7 dolphins, 7 green turtles and 14 great white sharks. However note that bycatch from shark nets is minor compared to bycatch from commercial fishing with estimates of 50 million sharks caught unintentionally each year.
Total cost for the shark netting program in New South Wales for the 2009/10 year was approximately, which included the cost of the nets, contractors, observers and shark technicians, shark meshing equipment, and compliance audit activities. For the 51 beaches protected, this represents a financial cost of approximately per beach per year.
Shark nets have been criticized by environmentalists and conservationists; they say shark nets damage the marine ecosystem. The current net program in New South Wales has been described as being "extremely destructive" to marine life; it has also been called "outdated and ineffective". The New South Wales government prohibits people from rescuing entangled animals — this prohibition has been called "heartless and cruel".
Shark barrier
A shark barrier is seabed-to-surface protective barrier that is placed around a beach to separate people from sharks. Shark barriers form a fully enclosed swimming area that prevents sharks from entering. Shark barrier design has evolved from rudimentary fencing materials to netted structures held in place with buoys and anchors. Recent designs have used plastics to increase strength and versatility.When deployed in sheltered areas shark barriers offer complete protection and are seen as a more environmentally friendly option as they largely avoid bycatch. However barriers are not effective on surf beaches because they usually disintegrate in the swell and so are normally constructed only around sheltered areas such as harbour beaches.
A shark barrier installed at Middleton beach in Albany, Western Australia cost to install, with annual maintenance budgeted at per annum. On Réunion Island in 2015 two shark proof enclosures cost €2 million to install and €1 million a year to maintain.
Drum lines
A drum line is an unmanned aquatic trap used to lure and capture large sharks using baited hooks. They are typically deployed near popular swimming beaches with the intention of reducing the number of sharks in the vicinity and therefore the probability of shark attack. Drum lines were first deployed to protect users of the marine environment from sharks in Queensland, Australia in 1962. During this time, they were just as successful in reducing the frequency of shark attacks as the shark nets. More recently, drumlines have also been used with great success in Recife, Brazil where the number of attacks has been shown to have reduced by 97% when the drumlines are deployed. While shark nets and drum lines share the same purpose, drum lines are more effective at targeting the three sharks that are considered most dangerous to swimmers: the bull shark, tiger shark and great white shark. SMART drumlines can also be utilised to move sharks, which greatly reduces mortality of sharks and bycatch to less than 2%.In 2014 a three-month trial utilising up to 60 drum lines in Western Australia cost.
Drum line programs that involve culling have been criticized for being environmentally destructive and speciesist, and have sparked public demonstrations and vocal opposition, particularly from environmentalists, animal welfare advocates and ocean activists. Conservationists say the death of sharks on drum lines harms the marine ecosystem. The current drum line program in Queensland has been called "outdated, cruel and ineffective". However environmental damage from drumlines is minor compared to commercial fishing with estimates of 50 million sharks caught unintentionally each year.
Other protection methods
Moving sharks
Moving sharks is a way of reducing shark attacks and reducing shark mortality, by capturing, transporting and releasing the sharks further shore. In Recife, Brazil, sharks that were near shore were captured and physically moved offshore with 70% of potentially aggressive sharks and 78% of other animals caught released alive. Sharks that were moved did not return to the same location. This technique has also been successfully demonstrated in the NSW North Coast SMART drumline trial where 99% of targeted sharks and 98% of other animals caught were released alive.Electronic shark deterrents
Electronic devices create an electromagnetic field to deter shark attacks and are used by surfers, scuba divers, snorkelers, spearfishers, ocean kayak fishers, swimming areas off boats and for ocean fishing. The Ocean Guardian devices, marketed with the Shark Shield brand name, are considered one of the few electrical devices on the market that has performed independent trials to determine the effectiveness at deterring shark attacks. Whilst it is noted the Shark Shield technology does not work in all situations and divers have been attacked whilst wearing Shark Shield, modelling research from Flinders University in 2021 indicated that the proper use of personal electronic deterrents is an effective way to prevent future deaths and injuries. It was estimated that these devices could save up to 1063 Australian lives along the coastline over 50 years.The West Australian government in 2017 announced that they are supporting the Ocean Guardian FREEDOM7 and the Ocean Guardian FREEDOM+ Surf via a $200 subsidiary.
Shark tagging and tracking
Across the world a sample of sharks have been tagged with electronic devices that transmit their location. Acoustic tags transmit pulses which are detected by underwater listening stations when the sharks swim close by, typically within 500 metres. Fin-mounted satellite tags are also commonly used. These tags allow shark movements and behaviour to be monitored and studied and swimmers and surfers can be warned if a shark is detected close to shore.However a limitation with the system is the tagging will only highlight a very small portion of the dangerous sharks present. It also may lead people into a false sense of security.
Shark spotting
Shark-spotting programs using drones, fixed-wing aircraft, helicopters, patrol boats, beach patrols, observation towers and even blimps, are being used and trialled in various locations across the globe. However visibility issues with water clarity can be a problem particularly with aerial patrols, which have been found to identify less than 20% of sharks present. There is also the financial cost of hiring aircraft and/or personnel to conduct the surveillance.Personal shark repellents
A shark repellent is any method of driving sharks away from an area and includes magnetic shark repellent, electropositive shark repellents, electrical repellents and semiochemicals. One example is a product called Anti-Shark 100 which is an aerosol can that contains an extract of dead shark tissue. There is a range of evidence that supports the effectiveness of this product. Chemical repellents have been researched since before the 1940s, some of which have raised concerns as to their effectiveness. The semiochemical used in the Anti-shark 100 product have been independently tested & verified on Caribbean reef sharks, however there are concerns it may attract Tiger and White sharks.Other examples of personal shark protection technologies include wearing interruption patterned or camouflage wetsuits, magnetic repellents incorporating a small magnet in a band worn on the wrist or ankle, acoustic repellents that mimic the sound of orcas and changing surf board colours. However, either the products associated with these technologies have not been independently tested, or independent tests highlighted that they did not work.
In 2018 independent tests were carried out on five Shark Repellent technologies using Great white sharks. Only Shark Shield's Ocean Guardian Freedom+ Surf showed measureable results, with encounters reduced from 96% to 40%. Rpela, SharkBanz bracelet & SharkBanz surf leash and Chillax Wax showed no measureable effect on reducing shark attacks.