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Shark nets

Shark nets have been protecting beach-goers for over 70 years but they catch more than just sharks. So should the nets be removed?

great white shark

A great white shark (Source: iStockphoto)

What are the intricacies of shark nets and is the recent push to remove shark nets more an issue of public liability than safety?

For over 70 years, shark nets have been protecting Australian swimmers from a death almost too awful to contemplate. Since their introduction in 1936, not one fatal shark attack has been recorded at beaches where nets have been installed.

But a growing body of scientific evidence suggests that shark nets remove more than just big-fanged predators from our beaches.

Protected species such as whales, dolphins and manta rays also get trapped in these nets. Ironically, another protected species, the majestic but terrifying Great White Shark is regularly caught in shark nets in significant numbers. No one really knows what removing such a high level predator from the marine food chain will do.

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Shark nets versus shark-proof enclosures

In Australia, we have shark nets and shark-proof enclosures, and the distinction is often confusing.

Shark nets are used on open ocean beaches, and are simply a straight, rectangular piece of net suspended in the water column between buoys. The mesh holes are 50cm wide, small enough to entangle sharks and other large marine species, while leaving smaller fish alone.

Shark net arrangements used on some Australian beaches entangle a variety of large marine species

Most shark nets stretch about 200 metres along the beach and down to a depth of six metres. Lines of torpedo floats at the top and sinkers at the bottom keep the net upright in the water. They are anchored at either end, usually about 200 metres from shore in roughly 10 metres of water. The nets are not intended to form a complete barrier, and sharks can still get through. The Queensland Shark Control Program uses another technique in addition to nets: hooks baited with fresh fish suspended from buoys to catch the sharks. In a typical 20km stretch of coastal surf beach, a strip of net will be set up every couple of kilometres along the beach.

With smaller mesh than Shark Nets, Shark Enclosures don't generally trap marine live

Shark enclosures, on the other hand, are more rigid constructions used on harbour beaches, and offer an unbroken barrier against incoming predators. The mesh in enclosures is much smaller than shark nets, and doesn't usually entangle any living creatures. These enclosures can't be easily built on open ocean beaches because experience has shown that the energy of the waves will eventually tear them to pieces. And like all beach constructions, they can also cause major sand erosion. When, for example, a temporary volleyball stadium was built on Bondi Beach for the Sydney Olympics a new surfing wave was created, dubbed the 'Olympic Lefts' by local surfers.

Now certain sections of the public and conservation groups such as the WWF (World Wide Fund for Nature) are calling for shark nets (the ones used at ocean beaches) to be completely removed. Not only do nets kill protected marine species, they argue, they don't guarantee protection for swimmers either. But how much more risk would we face without the nets? What if they were removed, would governments face big liability claims if a shark attack were to then occur on a previously protected beach?

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A brief history of nets

In 1935 one public submission to solve Australia's fear of sharks involved the use of machine guns

Invitations for public submissions on how to address the shark attack problem in 1935 resulted in some pretty outrageous suggestions, including the use of machine guns mounted on headlands, and explosives to kill sharks. Just imagine the brochures: little children frolicking happily in the surf, sea gulls and bullets flying overhead, great white plumes exploding on the blue horizon, and chunks of dead shark rolling in on the tide. Not ideal marketing material to sell your slice of paradise!

The theory behind the net is quite simple: fewer sharks equal less chance of shark attacks. The sharks are caught in the net by their fins and drown, reducing the risk of attacks. History suggests this works very well - prior to the introduction of shark nets in 1936, fatal attacks occurred about once a year on Sydney's popular ocean beaches. Since then, there have been no deaths associated with sharks. However how the nets are affecting shark populations is unknown. While theories about declining catch rates are yet to be confirmed much also remains to be learned about the territorial behaviour of sharks.

The four most potentially dangerous sharks
White SharkCarcharodon carchariasResponsible for most cool water attacks, particularly on divers
Bull SharkCarcharhinus leucasOmnivorous, aggressive, opportunistic feeder
Tiger SharkGaleocerdo cuvierOmnivorous, aggressive, opportunistic feeder
Oceanic Whitetip SharkCarcharhinus ongimanusNot normally found near land - probably responsible for most open-ocean attacks, particularly after air or shipping disasters
There are about 370 species of sharks world-wide. Nearly all fatal attacks on humans can be attributed to the above four species. Source: CSIRO

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To net or not to net?

Weighing the benefits of the reduced risk of shark attack against the relatively unknown environmental impact of shark meshing is complicated by several highly emotive issues. The impact on the marine ecology of removing large predatory sharks is not completely known, and protected species such as dolphins, turtles, and whales can also fall victim to the nets. For instance, in May 2001, a humpback whale calf became entangled in the nets off the Gold Coast and died while its 20 plus tonne mother looked on. As a result of this and other incidents, there is increasing pressure on the NSW and Queensland governments, which administer nets, to cease the practice.

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Our fear of sharks

Critics of nets argue that shark meshing is a hangover from a vastly different era, and that today's beach-goers know that the risk of being attacked is incredibly low. For example, about ten Australians are killed by lightning every year, versus an annual average of less than one for fatal shark attacks (although the relative risks are different: you can be struck by lightning almost anywhere, but you have to be in the water to risk a shark attack).

"Personally, after 17 years of surfing without even seeing as much as a dorsal fin, I admit the odd chill still runs down my back around sunset when I discover that I'm the last guy sitting out the back. Knowing the favourable odds provides little relief, and only dry sand can smooth my skin when those goosebumps set in. I have to confess that my reaction is disturbingly less urgent whenever I forget to put on my seatbelt!"
— Ruben Meerman

This issue is not simple. Our fear of being eaten alive by a huge shadow with razor-sharp teeth is probably deeply rooted in the most primitive part of our brains. We have known for years vivid images associated with 'high dread risks' can have a stronger influence on our perceptions than even the most convincing statistics.

In 1978, US researchers showed that we tend to overestimate how many people die from exotic or rare causes of death such as tornadoes, in comparison to common killers such as asthma. So it's not likely that being better informed today about the low probability of being attacked has had a significant impact on our fear of sharks!

It is true that shark meshing was introduced as a response to a perceived public demand almost seventy years ago. But a report submitted by the government appointed 'Shark Menace Advisory Committee' in 1935 is remarkably rational for its time. The document shows that the media's obsession with sharks probably dates back to well before the film 'Jaws', which has received much of the blame for sparking widespread white shark killings. In the absence of fatal attacks since meshing began, it is difficult to know whether the public reaction would be significantly different today if the nets were removed and fatalities returned.

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Risk versus litigation

Recorded catch in NSW
Shark Meshing Program
Total Sharks: 1972-904485
Dolphins & Porpoises: 1950-9394
Dugongs: 1950-935
Rays: 1950-932074
Killer Whale: 1950-931
Source: Biological Conservation Journal

The actual risk from attack may not be relevant to the decision of whether to remove the nets or not. It may be that any push to remove shark nets would be ultimately stifled by the risk of litigation. Although the United States has one of the highest rates of litigation in the world, it does not have shark nets. This is despite the fact that an average of more than 15 shark attacks per year occur on the Florida coast alone. It is not inconceivable in our modern blame culture that in the future, we could see a court ruling finding the liability for a shark attack at a previously meshed beach rests on the shoulders of the government.

Recorded catch in QLD
Shark Control Program
Total Sharks: 1962-8830,630
Dolphins: 1962-88520
Dugongs: 1962-88576
Turtles: 1962-883656
Rays: 1962-8813,765
Source: Biological Conservation Journal

Removing shark nets in Australia could expose the NSW and Queensland governments to a legal risk which doesn't even exist in the USA, where shark meshing has been considered but never practised. Until someone tries to sue a government for losing a limb, spouse, or child to a shark, we cannot be sure how the legal system would deal with this conundrum.

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Public opinion waivers

On the other hand, these governments who administer shark meshing are under increasing attack over the death of protected species such as whales in shark nets. Although efforts to reduce such fatalities and to release these animals alive have shown some success, the public and ecotourism industries are steadily becoming less tolerant of accidental deaths in the nets, resulting in increased pressure to end the practice.

Determining public opinion on the issue is also fraught with difficulties and would probably be strongly influenced by recent events. After a whale gets trapped in a shark net, for example, the public is likely to favour their removal. But when a fatal shark attack hits the media, no matter where it has occurred, it's more likely the public would want the nets to stay.

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The debate continues...

In the absence of reliable information about the legal implications of changing the status quo, or the true nature of public opinion the debate continues. So for now, whether you see shark nets as a waste of time and money, a danger to endangered species, or a bloody good idea, you'll just have to accept most people are justifiably terrified of being eaten alive.

How common are shark attacks in Australia?Australia's earliest recorded shark attack occurred in 1791 when an Aboriginal woman was taken off the north coast of New South Wales.Up until January 12, 2009, there have been 717 recorded attacks in Australia, of which 193 have been fatal.On average there have been 1.25 fatalities per year in Australia due to shark attack in the 20 years up until January 2008. To put this in perspective, 212 people died of accidental drowning and submersion in 2006.For the latest statistics visit the Australian Shark Attack File.Source: The Australian Shark Attack File and ABS

This story was last updated on 16 January 2009.

Tags: shark, safety

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Published 07 March 2002