Types of attacks

Shark attack indices use different criteria to determine if an attack was “provoked” or “unprovoked.” When considered from the shark’s point of view, attacks on humans who are perceived as a threat to the shark or a competitor to its food source are all “provoked” attacks. Neither the International Shark Attack File (ISAF) nor the Global Shark Attack File (GSAF) accord casualties of air/sea disasters “provoked” or “unprovoked” status; these incidents are considered to be a separate category. Postmortem scavenging of human remains (typically drowning victims) are also not accorded “provoked” or “unprovoked” status. The GSAF categorizes scavenging bites on humans as “questionable incidents. “The most common criteria for determining “provoked” and “unprovoked” attacks are discussed below:

Provoked attack

Provoked attacks occur when a human touches, hooks, nets, or otherwise aggravates the animal. Incidents that occur outside a shark’s natural habitat, such as aquariums and research holding-pens, are considered provoked, as are all incidents involving captured sharks. Sometimes humans inadvertently provoke an attack, such as when a surfer accidentally hits a shark with a surf board.

Unprovoked attack

Unprovoked attacks are initiated by the shark—they occur in a shark’s natural habitat on a live human and without human provocation. There are three subcategories of unprovoked attack:

Hit-and-run attack – usually non-fatal, the shark bites and then leaves; most victims do not see the shark. This is the most common type of attack and typically occurs in the surf zone or in murky water. Most hit-and-run attacks are believed to be the result of mistaken identity.
Sneak attack – the victim will not usually see the shark, and may sustain multiple deep bites. This kind of attack is predatory in nature and is often carried out with the intention of consuming the victim. It is extraordinarily rare for this to occur.
Bump-and-bite attack – the shark circles and bumps the victim before biting. Great whites are known to do this on occasion, referred to as a “test bite”, in which the great white is attempting to identify what is being bitten. Repeated bites, depending on the reaction of the victim (thrashing or panicking may lead the shark to believe the victim is prey), are not uncommon and can be severe or fatal. Bump-and-bite attacks are not believed to be the result of mistaken identity.

An incident occurred in 2011 when a 3-meter long (~500 kg) great white shark jumped onto a 7-person research vessel off Seal Island, South Africa. The crew were undertaking a population study using sardines as bait and initially retreated to safety in the bow of the ship while the shark thrashed about, damaging equipment and fuel lines. To keep the shark alive while a rescue ship towed the research vessel to shore, the crew poured water over its gills and eventually used a pump for mechanical ventilation. The shark was ultimately lifted back into the water by crane and, after becoming disoriented and beaching itself in the harbor, was successfully towed out to sea, swimming away. The incident was judged to be an accident.

Reasons for attacks

Large sharks species are apex predators in their environment, and thus have little fear of any creature (other than orcas) with which they cross paths. Like most sophisticated hunters, they are curious when they encounter something unusual in their territories. Lacking any limbs with sensitive digits such as hands or feet, the only way they can explore an object or organism is to bite it; these bites are known as test bites. Generally, shark bites are exploratory, and the animal will swim away after one bite. For example, exploratory bites on surfers are thought to be caused by the shark mistaking the surfer and surfboard for the shape of prey. Nonetheless, a single bite can grievously injure a human if the animal involved is a powerful predator such as a great white or tiger shark.

A shark will normally make one swift attack and then retreat to wait for the victim to die or weaken from shock and blood loss, before returning to feed. This protects the shark from injury from a wounded and aggressive target; however, it also allows humans time to get out of the water and survive. Shark attacks may also occur due to territorial reasons or as dominance over another shark species, resulting in an attack.

Sharks are equipped with sensory organs called the Ampullae of Lorenzini that detect the electricity generated by muscle movement. The shark’s electrical receptors, which pick up movement, detect signals like those emitted from fish wounded, for example, by someone who is spearfishing, leading the shark to attack the person by mistake. George H. Burgess, director of the International Shark Attack File, said the following regarding why people are attacked: “Attacks are basically an odds game based on how many hours you are in the water”.

Prevention

Reducing the risks

General advice to reduce risks of being bitten by a shark include:

Staying in groups as solitary individuals are more at risk of being bitten
Only going in the water during the day
Avoiding areas with a lot of fish or fishers
Not wearing jewelry, which can create reflections like fish scale
Avoiding splashs at the surface, because it makes sound which attracts sharks

Shark barrier

A shark barrier (otherwise known as a “shark-proof enclosure” or “beach enclosure”) is a 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.

Shark nets

In Australia and South Africa, shark nets are used to reduce the risk of shark attack. Since 1936 sharks nets have been utilised off Sydney beaches. Shark nets are currently installed at beaches in New South Wales and Queensland; 83 beaches are meshed in Queensland, compared with 51 in New South Wales. Since 1952, nets have been installed at numerous beaches in South Africa by the KwaZulu-Natal Sharks Board.

Shark nets do not offer complete protection but work on the principle of “fewer sharks, fewer attacks”. They reduce occurrence via shark mortality. Reducing the local shark populations is believed to reduce the chance of an attack. Historical shark attack figures suggest that the use of shark nets and drumlines does markedly reduce the incidence of shark attack when implemented on a regular and consistent basis.

The downside with shark nets is that they do result in bycatch, including threatened and endangered species. Between September 2017 and April 2018, 403 animals were killed in the nets in New South Wales, including 10 critically endangered grey nurse sharks, 7 dolphins, 7 green sea turtles and 14 great white sharks. Between 1950 and 2008, 352 tiger sharks and 577 great white sharks were killed in the nets in New South Wales—also during this period, a total of 15,135 marine animals were killed in the nets, including whales, turtles, rays, dolphins, and dugongs. KwaZulu-Natal’s net program, operated by the KwaZulu-Natal Sharks Board, has killed more than 33,000 sharks in a 30-year period—during the same 30-year period, 2,211 turtles, 8,448 rays, and 2,310 dolphins were killed in KwaZulu-Natal.

Shark nets have been criticized by environmentalists, scientists, and conservationists; they say shark nets harm the marine ecosystem. In particular, the current net program in New South Wales has been described as being “extremely destructive” to marine life. Sharks are important to the ecosystem, and killing them harms the ecosystem.

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 utilized to move sharks, which greatly reduces mortality of sharks and bycatch to less than 2%.

Drum lines result in bycatch; for example, in 2015 the following was said about Queensland’s “shark control” program (which uses drum lines):

“[Data] reveals the ecological carnage of [Queensland’s] shark control regime. In total, more than 8,000 marine species with some level of protection status have been caught by the Queensland Shark Control Program, including 719 loggerhead turtles, 442 manta rays and 33 critically endangered hawksbill turtles. More than 84,000 marine animals have been ensnared by drum-lines and shark nets since the program began in 1962 […] Nearly 27,000 marine mammals have been snared. The state’s shark control policy has captured over 5,000 turtles, 1,014 dolphins, nearly 700 dugongs and 120 whales.”

Drum lines have been criticized by environmentalists, conservationists and animal welfare activists—they say drum lines are unethical, non-scientific, and environmentally destructive; they also say drum lines harm the marine ecosystem.

Other protection methods

Beach patrols and spotter aircraft are commonly used to protect popular swimming beaches. However, aerial patrols have limited effectiveness in reducing shark attacks. Other methods include shark tagging efforts and associated tracking and notification systems, capture and translocation of sharks to offshore waters, research into shark feeding and foraging behaviour, public shark threat education programs and encouraging higher risk user groups (surfers, spear-fishers and divers) to use personal shark protection technology.

Shark attack is

According to the International Shark Attack File (ISAF), between 1958 and 2016 there were 2,785 confirmed unprovoked shark attacks around the world, of which 439 were fatal. Between 2001 and 2010, an average of 4.3 people a year died as a result of shark attacks.

Only a few species of shark are dangerous to humans. Out of more than 480 shark species, only three are responsible for two-digit numbers of fatal unprovoked attacks on humans: the great white, tiger, and bull; however, the oceanic white tip has probably killed many more castaways which have not been recorded in the statistics. These sharks, being large, powerful predators, may sometimes attack and kill people, notwithstanding the fact that all have been filmed in open water by unprotected divers. The 2010 French film Oceans shows footage of humans swimming next to sharks in the ocean. It is possible that the sharks are able to sense the presence of unnatural elements on or about the divers, such as polyurethane diving suits and air tanks, which may lead them to accept temporary outsiders as more of a curiosity than prey. Uncostumed humans, however, such as those surfboarding, light snorkeling or swimming, present a much greater area of exposed skin surface to sharks. In addition, the presence of even small traces of blood, recent minor abrasions, cuts, scrapes or bruises, may lead sharks to attack a human in their environment. Sharks seek out prey through electroreception, sensing the electric fields that are generated by all animals due to the activity of their nerves and muscles.