In an attempt to deter attacks on surfers and bathers, the government of Western Australia last month began implementing its controversial plan, dubbed "catch and kill", to cull sharks.
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As part of the tough measures, professional fisherman are being contracted to use hooks on baited drum lines to snare any great white, tiger or bull shark that is longer than three metres.
A series of baited lines has been placed one kilometre from the shore in the state's south-west and more will soon be installed off Perth beaches.
Despite numerous protests, the government and its advisers pressed ahead, with federal Environment Minister Greg Hunt exempting the shark cull from national environment laws.
The cull is in the "national interest" and will protect the public and tourism, Mr Hunt informed West Australian Premier Colin Barnett.
What is the justification for this? Importantly, is there any scientific basis for a shark cull?
No, insists shark expert William Winram. "In fact, in most places that have practised culling there is zero change in the number of incidents with sharks."
All the information, he says, "leads one to believe that culling is simply a response to a situation that politicians are uncomfortable with. I am of the opinion that they just want to be perceived as doing something ... it's sad really."
Sharks are apex predators, says Mr Winram, a diver who swims freely with great whites without the protection of a cage. "We have seen when you remove sharks from an ecosystem there are dire consequences. They play many important roles in keeping an ecosystem in balance and healthy."
Another reason to preserve sharks is their value to eco-tourism, he says. "People love sharks and will pay money to travel to destinations where they can dive with them. In most places that have done assessments of the 'live value' versus 'dead value', the live value always comes out on top. In addition, 'sharks alive' is a sustainable and healthy approach."
Sue Sargent, a marine scientist with Fauna & Flora International Australia in Queensland, agrees. "I think the shark cull is an ill-thought-through and poorly conceived idea that will have a non-determined benefit for visitors or tourists," she says. "It will almost certainly have an impact on the ecology of top-level marine predators."
Ms Sargent has worked on a project researching the critically endangered grey nurse shark. Hunted almost to the point of extinction in the 1950s and 1960s by well-meaning, although misdirected, fishers and spearfishers, Australia's east coast population of grey nurses is now estimated to be between 1000 and 1500.
Research
The argument to protect rather than cull sharks is backed by a recent study published in the international online journal, PLOS ONE. "The loss of sharks can have an impact that propagates down the food chain," the researchers write. "Simultaneously ... the effects of bottom-up processes of bleaching and cyclones appear to propagate up the food chain through herbivores ... but do not affect carnivores."
The scientists conclude: "Because their presence may promote the abundance of herbivores, the removal of sharks by fishing has implications for both natural and anthropogenic disturbances involving the loss of corals, as herbivores are critical to the progress and outcome of coral recovery."
Other victims
One of the target species in the WA cull plan, the great white shark, is a threatened species under Australian legislation.
"It is also likely that other threatened species will get caught on the drum lines, such as the grey nurse shark, shortfin mako shark, fur seals, sea lions, turtles, whales and dolphins," says marine biologist Pam Allen of the Australian Marine Conservation Society.
She agrees with other experts that there is no scientific evidence for baited drum lines reducing the incidence of shark bites. "In fact, the measures may actually draw sharks into the area as they smell the bait on the hooks," Ms Allen says.
Also, she adds, such measures could create a false sense of security for beachgoers. "There are many alternatives to the plan that will keep beachgoers and surfers safe, such as increased monitoring and education by surf lifesavers and findings from research into non-lethal methods of shark deterrents."
The latter includes a Twitter program, where tagged sharks "tweet" their location as they swim past underwater detectors. "It's a good way of detecting sharks and studying their movement patterns across the WA coast," Ms Allen says.
Researchers funded by the WA government are also studying ways of predicting shark movements through environmental patterns, using strobe lights, bubble curtains and sonar.
"Many of these methods improve our knowledge of sharks, and since so many of these beautiful creatures are under threat, findings aid in conservation efforts as well," Ms Allen notes.
Under attack
With an estimated 100 million killed every year, about one-third of all open-water species of sharks are facing the prospect of extinction, an international report reveals. The at-risk list includes great white and hammerhead sharks.
The report is based on a survey conducted by 174 researchers from 38 countries who analysed the International Union for Conservation of Nature's Red List, which categorises a range of animals based on how likely they are to become extinct.
The reason the sharks are facing extinction is in part because of the increasing popularity of shark fin soup.
"This is an international problem, driven by the high value of shark fin in the Asian market," says Melbourne oceanographer and marine biologist Tooni Mahto, from the Australian Marine Conservation Society. "Fins are also imported and can be found on restaurant menus around Australia."
The legal situation regarding shark finning here is complicated, she says, because it differs between states and territories. "As it stands, it's illegal to return to port without the fins and at least the body of the shark – although they don't have to be connected in all jurisdictions."
Sanctuaries
Internationally, important advances have been made in shark conservation, with Pacific Island nations leading the way.
For example, Palau, in Micronesia, and the Maldives have established shark sanctuaries; Mexico, Honduras and the Bahamas have introduced shark fishing moratoriums, and Hawaii, the Northern Mariana Islands and Guam have banned the trade in shark products.
The Marshall Islands, meanwhile, has the world's largest sanctuary to protect sharks across nearly 2 million square kilometres of ocean. In addition, the US has signed the Shark Conservation Act, with California implementing a ban on the sale of shark fins.
"Australia is lagging," Ms Mahto laments. "This is because sharks are caught in a number of fisheries managed by Australia's states and territories," she says.
Two fisheries are of note. First, the East Coast Inshore Fin Fish Fishery has an annual quota of 600 tonnes of tropical sharks from around the Great Barrier Reef. "The quota could be considered a stab in the dark as there are no assessments of how many sharks there are," she explains.
The other one is the Gulf of Carpentaria Inshore Fin Fish Fishery. "In this fishery, there is no quota assigned to the take of sharks – it's managed by controlling fishing effort, for example. So there is no understanding of whether the fishery is depleting sharks in our northern waters," Ms Mahto says.
Net effects
Beach nets designed to protect bathers are also of concern. A report on NSW's beach meshing program concludes that the number of sharks caught in nets has decreased, probably reflecting a general population decline.
Beach nets are listed under the NSW Fisheries Management Act as a key threatening process for sharks. The purpose of these nets is to catch and kill sharks, similar to the drum lines, Ms Allen adds. "The nets are not selective, and catch a wide range of other marine animals," she says.
For example, between 1992 and 2008, the Queensland shark netting program reported catching 74 common dolphins, 26 humpback whales, nine dugongs, 82 manta rays, 99 tuna and more than 100 turtles. Many of these animals do not survive in nets following capture.
"Netting programs don't keep our beaches safer, but they do kill our precious wildlife," Ms Allen says.
Surveys
Internationally, surveys suggest that roughly 90 per cent of the ocean's big fish have been lost since the 1950s. "About 100 million sharks get killed every year," Ms Mahto says. "This means the structure and function of the food web associated with sharks will be disrupted in some way."
One documented case attributed the collapse of a US east coast scallop fishery to overfishing of sharks. "When sharks were removed from the ecosystem, it created an artificial build-up of their natural food source, the cow-nose ray, which in turn ate the local scallops. With no sharks present to keep the rays in check, the natural balance was lost."
Links
Learn more about the shark-saving work of William Winram at: http://williamwinram.com/
Watch William in action in IMAX Melbourne Museum's gripping movie Great White Shark 3D. Details: www.imaxmelbourne.com.au/movie/great-white-shark-3d
Read about research by the WA Fisheries Department at: www.fish.wa.gov.au/Education-and-Partnerships/Shark-Hazard/Shark%20research/Pages/default.aspx
Check out shark reports, including having tagged sharks Tweet their location, at: www.fish.wa.gov.au/Education-and-Partnerships/Shark-Hazard/Pages/Shark-sightings-and-response.aspx
Learn about government-funded research into shark mitigation at: www.fish.wa.gov.au/About-Us/Media-releases/Pages/-archive/$900,000-awarded-to-shark-mitigation.aspx and at: www.fish.wa.gov.au/About-Us/Media-releases/Pages/$967,000-awarded-to-shark-mitigation-research.aspx
Read the PLOS ONE report on the effectiveness of shark culling at: www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0074648
Collect data on sharks as by-catch in Commonwealth-managed fisheries, provided by the Australian Fisheries Management Authority (refer to the bottom box) at: www.afma.gov.au/managing-our-fisheries/environment-and sustainability/Protected-Species/
Cross-reference the species noted in the reports with the International Union for Conservation of Nature's Red List at: www.iucnredlist.org/
For example, short fin mako is listed as being vulnerable, as shown at: www.iucnredlist.org/apps/redlist/details/39341/0
Visit the hammerheads and other sharks at Melbourne Aquarium. Details: www.melbourneaquarium.com.au/experiences/shark-walker
Follow the latest work and projects of the Australian Marine Conversation Society at: www.marineconservation.org.au
VCAA links
AusVELS Science: Biological sciences: http://ausvels.vcaa.vic.edu.au/Science/Curriculum/F-10
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