Dealing with Wildlife: Sharks

Oceans
Photo: national geographic.com.au

October 31, 2003: 13-year-old Bethany Hamilton hits the water for a morning surf at Tunnels Beach, Kauai, with her best friend Alana Blanchard, blissfully unaware that an encounter with a 4.3-metre tiger shark would alter her life instantly and forever.

“I felt a tug on my arm and right away I knew what was happening,” she recalled. “A shark had taken my arm.” By the time she reached the hospital, she had lost over 60 percent of her blood and was in hypovolemic shock.

Hamilton made a full recovery, albeit without her left arm, and eventually joined the Women’s World Professional Surfing Tour, along with Blanchard. Her story is depicted in the movie Soul Surfer.

Soul Surfer Bethany Hamilton. Photo: surfer.com

On July 19, 2015, Australian surfer Mick Fanning was competing in the final of the J-Bay Open World Surf League event at Jeffries Bay, South Africa when he was attacked by a great white shark.

Fanning had a lucky escape. “All of a sudden, I just had this instinct that something was behind me,” Fanning said. “I started getting pulled under water. The shark came up, and I was on my board and it was like right there, and I saw the whole thing thrashing around.”

A great white shark attacks Mick Fanning. Photo: WSL/WSL

“I just saw the fin, I didn’t see the teeth. I was waiting for the teeth to come at me as I was swimming…I punched it in the back,” he recalled. Unlike Hamilton, Fanning escaped unscathed and returned to compete at Jeffries Bay the next year.

There is probably no other creature on earth the instills more fear in humans than sharks. These prehistoric monsters of the ocean have inhabited the earth for 420 million years and their telltale fin slicing through the water can instantly strike terror in the minds of swimmers, surfers, fishermen and divers. Most people who have swum in the ocean have felt the fear brought on by the mere possibility of a shark nearby.

There are 440 species of sharks globally. The smallest shark, the dwarf lantern shark, is only 17 centimeters in length, while the whale shark is the largest, growing up to 12m. Some sharks are aggressive, some are docile, but all have the potential to terrify an innocent victim when it becomes apparent that they are sharing their patch of water with a potential killer. A shark is a shark, after all! Yet most species pose no threat to human life. Even the whale shark feeds exclusively on minute plankton.

The dwarf lantern shark — the world’s smallest shark. Photo: abc.net.au

While media reports suggest that shark attacks are on the rise, assaults on humans are exceedingly rare and are even more rarely fatal. While the number of recorded shark attacks has risen in recent years, the rate per capita has not. As more people spend time in the water, more are exposed to the risk of an attack. More effective methods of reporting may also be adding to the statistics.

Until recently, the prevailing wisdom attributed shark attacks on humans to misdirected feeding attempts. That is, sharks took a bite or two out of humans because they looked like food. In most cases, the sharks determined that their victims weren’t prey and swam off, leaving the victim severely injured or worse.

Recent intensive studies of shark behavior have suggested other factors at play in these attacks. The theory that surfers like Hamilton and Fanning, arms dangling off their boards, may be perceived as seals from below by sharks has largely been discarded. Sharks have extremely powerful vision and are unlikely to mistake a surfer for a seal. However, it is true that the erratic motion of humans and the contrast between their skin and their attire can confuse sharks, especially in turbid waters.

In shallower waters near shore, where schools of smaller fish are common, shark encounters likewise occur from confusion. The shark is hardwired to snap at anything that looks remotely like a thrashing fish, such as a foot with a tanned top and paler bottom, and may bite a human playing in the surf.

Photo: smartertravel.com

While sharks do not necessarily have territories like some terrestrial predators do, sharks do exhibit a dominance hierarchy  — a pecking order. Some encounters may spring from the shark’s instinct to defend its food or domain against all comers.

Sometimes sharks are simply curious, and because they are the dominant predators in most ocean ecosystems, they aren’t afraid. Their mouths function as finely tuned sensory organs, leading them to “mouth” unfamiliar objects to examine them and determine their possible food value.

The shark has the greatest electrical sensitivity of any animal, with thousands of electroreceptor organs known as the ampullae of Lorenzini, which detect the electromagnetic fields that all living things produce. This enables sharks to be extremely efficient in finding prey.  

According to the Florida Museum, there were 66 unprovoked attacks on humans and 34 provoked attacks worldwide in 2018. A provoked attack is where a human initiated the interaction. The unprovoked number was lower than the most recent five-year (2013-2017) average of 84 incidents annually.

Of these 100 attacks in 2018, five were fatal. Of these, four were unprovoked. These numbers are in line with the annual global average of six fatalities per year.

2018 Shark attacks. Diagram: floridamuseum.ufl.edu

Coastal U.S.A. and Australia have the most sharks in the world. The United States experienced the most unprovoked shark attacks in 2018, with 32 confirmed cases, representing 48 percent of the worldwide total. This is a decline from 2017, which saw 60 percent of the worldwide unprovoked attacks in U.S. Only one shark attack in the United States was fatal.

In Australia, home to 170 species of shark, there was a total of 20 unprovoked incidents, slightly higher than the recent five-year annual average of 14 incidents for the country.

The odds of being killed by a shark in Australia are one in 8 million, the same as the odds of being killed by a kangaroo. One is adored as a national emblem, the other is feared. In the U.S., the odds of being attacked are 1 in 11,500,000 and the odds of being killed are 1 in 264,000,000 — only slightly less than the odds of winning the Powerball lottery.

In 2017, nearly two-thirds of victims, or 59 percent, were surfing or engaged in water sports. Another 22 percent were swimmers and beachgoers, 9 percent were snorkelers and divers and 2 percent were body surfers.

Only 12 species of shark are potentially dangerous to humans, and only three are responsible for double-digit unprovoked fatal attacks: the great white, the tiger shark and the bull shark.

Great White Shark

The great white is the largest predatory fish in the world. Of all sharks, it is responsible for the most unprovoked attacks and deaths. Great whites live in the coastal surface waters of all major oceans where the water temperature is between 12° and 24°C.

Range of the great white shark. Diagram: Wikipedia

The highest concentrations of great whites occur in the United States (northeast and California), South Africa, Japan, Oceania, Chile and the Mediterranean. One of the densest known populations is found around Dyer Island, South Africa.

The female great white grows up to 6 metres long and weighs up to 1,905 kilos, while the males are slightly smaller. They can swim at 56kph and dive to as astonishing depth of 12,000m. Great white sharks typically attack their prey from below with great speed, delivering a single devastating bite.

The great white shark. Photo: news.harvard.edu

They can travel enormous distances. Scientists managed to tag a great white off the South African coast that swam 20,000km to Australia’s northwestern coast and back in under nine months.

Tiger Shark

A solitary, mostly nocturnal hunter with excellent sight and smell, the tiger shark has the most flexible diet of all sharks. Its prey includes crustaceans, fish, seals, birds, squid, turtles, sea snakes, dolphins and even smaller sharks. It is also an effective scavenger, and unfortunately also consumes inedible, man-made objects such as bottles, tires, nails, balls, clothing, license plates and even explosives.

Tiger shark. Photo: whitesharkdivers.co.za

Second only to to the great white in recorded fatal attacks on humans, tiger sharks grow up to 5m long and weigh 650kg. They live in many tropical and temperate waters, especially around the central Pacific islands. Its name derives from the dark stripes down its body. As the shark matures, the lines begin to fade and almost disappear.

The range of the tiger shark. Diagram: Wikipedia

Tiger shark teeth have distinctively sharp, pronounced serrations and an unmistakable sideways-pointing tip that developed to slice through flesh, bone and other tough substances such as turtle shells. The teeth are considerably shorter than those of a great white shark but better for slicing through hard-surfaced prey.

A tiger shark’s uniquely shaped teeth. Photo: barrierreef.org

Bull Shark

The bull shark lives worldwide along warm coastlines, including shallow, brackish waters and freshwater estuaries. They thrive in both salt and fresh water and may travel far up rivers. They have been recorded up the Mississippi River as far as Alton, Illinois, about 1,100km from the ocean.

The bull shark’s aggressive nature and presence in recreational waters make it potentially dangerous. Larger bull sharks are probably responsible for most near-shore shark attacks, including many bites attributed to other species.

The range of bull sharks. Diagram: Wikipedia

The Brisbane River and the canals of the Gold Coast in Queensland, Australia have very high concentrations of bull sharks, and it is not uncommon for floods to wash them onto the streets. A  local golf course is now home to a number of bull sharks that became trapped in a lake on the course during such a flood. The golf club has capitalized on the novelty and now hosts a monthly tournament called the Shark Lake Challenge. It’s no coincidence that golfer Greg Norman, known as the Great White Shark, hails from Queensland.

Bull sharks are large and stout, with females larger than males. Adult female bull sharks average 2.4m long and typically weigh 130kg, whereas the slightly smaller adult male averages 2.25m and 95kg.

The bull shark’s diet consists mainly of bony fish and small sharks, including other bull sharks, and stingrays. They also eat turtles, birds, dolphins, terrestrial mammals, crustaceans, and echinoderms. They prefer to hunt in murky waters, where it is harder for the prey to see them coming. Bull sharks sometimes use the bump-and-bite technique to attack their prey. After the first initial contact, they continue to bite until the prey is unable to flee.

As part of their survival strategy, bull sharks may regurgitate food in order to escape from a predator. This is a distraction tactic; if the predator moves to eat the regurgitated food, the bull shark uses the opportunity to escape.

Shark Deterrents and Repellents

The shark repellent industry has grown significantly in the last 20 years. Today, a number of smart devices and gadgets can keep sharks away from humans. Although repellents and deterrents will never be 100 percent effective, they definitely provide peace of mind.

The market offers five main types of shark deterrent: magnetic, electrical, sound, semiochemical and visual.

They reach consumers in the form of surf leashes, rubber bands, spray cans and wetsuits. Some are more appropriate for surfers; others are more comfortable for divers and swimmers. Some of the most popular devices are:

SharkBanz 2 uses no batteries, chemicals or electricity. The technology relies on magnetic waves emitted by the band that disrupt the shark’s electroreceptors.

Shark Shield is a removable power module that is installed in a tail pad kicker of a surf board.

Modom Shark Leash is a surf leash that incorporates a magnetic technology that repels sharks. It doesn’t lose its deterrent powers over time and it requires no charging.

Anti Shark 100 is a repellent spray that deters 15 species. It does not harm sharks or wildlife and it does not affect fish. Once it is released, sharks won’t go near for approximately 30 to 45 minutes.

NoShark is an electronic shark deterrent. The device emits a high voltage signal which reacts with the electroreceptors in the shark’s nose, causing the shark to stay away. This small unit is worn on the ankle and lasts hours on one charge. The device activates in salt water and has been tested on more than 40 sharks.

NoShark Deterrent ankle band. Photo: diversworld.com.au

SharkStopper emits an acoustic signal that repels sharks. The device automatically powers itself in the water and works for four hours.

Shark Shocker is an ankle or wrist band using a rare-earth neodymium-iron-boride magnet. It activates in the water and emits a magnetic field that disrupts the shark’s ampullae of Lorenzini.

Radiator Diverter is a wetsuit that, used in conjunction with a shark deterrent surfboard sticker, disrupts the shark’s visual perception and presents the wetsuit user as potentially dangerous and not pleasant to taste.

SAMS Radiator wetsuit. Photo: radiator.net

How to avoid shark attacks

Besides these devices, the Taronga Conservation Society advises the following to reduce the likelihood of a shark attack:

  • Swim at beaches that are patrolled by Surf Life Savers and/or aerial shark patrols.
  • Swim, dive or surf with others, as their presence may deter a potential encounter and they can help if you get into trouble.
  • Avoid swimming at dusk, dawn or at night.
  • Avoid swimming near a river mouth, especially after a rainstorm, when heavy rain washes food into the sea and attracts fish and sharks.
  • Don’t enter the water near large schools of fish, which attract sharks.
  • If you’re kayaking and see a large shark, join up together with other kayakers to make a bigger object.
  • Don’t wear shiny jewellery, as the reflected light resembles the sheen of fish scales.

A hammerhead shark. Photo: bbc.com

Many Australian beaches have been protected since the 1930s by drum lines or shark nets. Shark nets are a mesh approximately 200m long and 6m high and usually anchored at a depth of 10 to 14m.  A drum line is a series of fishing lines anchored to buoys with large fishing hooks that are lowered into the oceans. The drum line was introduced to reduce the amount of marine life, other than sharks, that were getting caught in the nets.

Both methods are not foolproof and attract significant ire from shark conservationists. They claim that there is no evidence that these make ocean-goers safe, and only serve to kill sharks and give a false sense of security. The nets and lines also kill other marine life, such as whales, dolphins and rays.

Source: Queensland Department of Fisheries and Agriculture

The political debate around the use of drum lines has been fiercely fought for a number of years in Australia. Up until this year, the Queensland government was responsible for killing sharks in the Great Barrier Reef, using 173 lethal drum lines. Last year, the Humane Society International Australia filed a lawsuit requesting that the drum lines be removed there. In April 2019, the Administrative Appeals Tribunal ordered that sharks no longer be culled in the Great Barrier Reef, based on evidence that killing sharks makes no difference to swimmer safety.

Shark Conservation

Whatever the ultimate cause of shark attacks, humans are a far greater threat to them than they are to us. We have decimated their populations, with some 100 million taken each year both on purpose and as bycatch.

Shark Drone Patrols in New South Wales Australia. Photo: particle.scitech.org.au

The International Union for Conservation of Nature Shark Specialist Group determined that 16 percent of the world’s shark species face extinction. They identified 465 species of shark, and rated that 74 species are either critically endangered, endangered or vulnerable.

The SSG is currently active in the protection of angel sharks, which were once widespread throughout Europe’s seas but have now vanished from much of their former rangeThe Canary Islands are the last stronghold of the angel shark.

Angel sharks are a critically endangered species. Photo: oceana.org

In 1991, South Africa was the first country to legally protect great white sharks. However, the KwaZulu-Natal Sharks Board is allowed to kill great white sharks in its “shark control” program in eastern South Africa. The great white shark was declared vulnerable by the Australian Government in 1999 and is currently protected by legislation.

Shark finning bans have also been implemented in the United States and the European Union. China, by far the world’s largest shark market, and Japan, which battles all attempts to extend the convention to marine species, continue to oppose all regulation of trade in sharks. Despite this, in 2013, three endangered commercially valuable sharks, the hammerhead, the oceanic whitetip and porbeagle were added to Appendix 2 of CITES, bringing shark fishing and commerce of these species under licensing and regulation.

Sharkfin soup is regarded as a delicacy in parts of the world. Photo: eenews.net

Several regions now have shark sanctuaries or have banned shark fishing, including American Samoa, the Bahamas, the Cook Islands, French Polynesia, Guam, the Maldives, the Marshall Islands, Micronesia, the Northern Mariana Islands, and Palau.

About the Author

Peter Winsor

Peter is a journalist, travel writer and photographer based on the Gold Coast, Australia.

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3 Comments on "Dealing with Wildlife: Sharks"

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Karissa
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Nicely written. Thanks for the info!

Mark
Guest

Fantastic article Peter! Plenty of great informations and resources too. Might try to tee off at Carbrook this Chrissy break…

RlR
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Extremely interesting and informative article!