A shark cull in waters off of Western Australia, and authorized by local authorities, is now taking place in an attempt to make beaches safer there. George Burgess, director of the Florida Program for Shark Research at the Florida Museum of Natural History, told Discovery News that officials probably are hoping to target great white sharks, known as “white pointers” in Australia.
While a person’s chances of being bitten by another human, or dying in a car accident on the way to the beach, are far higher than an actual shark attack, experts have mulled over ways of preventing attacks without killing sharks.
Last month, researchers began testing some unlikely repellants -- including bubbles and underwater sounds and lights -- to see if they might be effective. "Sharks generally don't like anything that is unnatural and different, something that they're not familiar with," says Ryan Kempster, a shark biologist at the University of Western Australia.
Closing beaches to recreational water users from sunset to sunrise might be a more sure-fire way to prevent attacks. “This is when sharks are most active and have a competitive sensory advantage,” Burgess explained.
Sharks avoid metals that react with seawater to produce an electric field, reported NOAA scientists and colleagues in a study. “The alloy we used, palladium neodymium, appears to be a good alternative to more expensive metals,” said Richard Brill of NOAA’s Northeast Fisheries Science Center and the Virginia Institute of Marine Science. “It is also machinable and is reasonably resistant to corrosion in seawater.” Electric fields generated by such metals are thought to deter or repel sharks by overloading their sensory systems.
“The farther you are from shore, the farther you are from help,” Burgess explained. He added that beachgoers should also stay in groups, since isolated individuals are more likely to be attacked than large groups.
“There are big holes in our understanding of shark biology and behavior," Burgess said. “Researchers need to fill in the blanks to better identify places sharks go and when sharks will be at those locations.”
Marine biologist David Shiffman of the University of Miami suggests aerial patrols could help to determine when sharks are near beaches. He shares that the Australian Aerial Patrol has done this for many years. High-tech devices, such as drones (above), could be less expensive and noticeable.
Western Australia isn't the only place where sharks are killed in the name of public safety, Burgess and colleague Katelynd Sandusky told Discovery News. “Drum lines, nets or a combination of the two have also been used in Queensland, New South Wales and at KwaZulu-Natal in South Africa,” Burgess said. Both he and Sandusky added that shark culls occur off the waters of the Indian Ocean island of Reunion. In the past, sharks were also killed in an effort to prevent attacks off of Hawaii’s beaches.
Public pressure on leaders in Australia and South Africa could cause them to stop funding and supporting the culls, which Burgess said can indiscriminately take out dolphins, dugongs, sea turtles and other endangered marine life. “I hope that Australians exercise their democratic duty by pressuring local politicians involved in the culls to stop them.” These same politicians, in turn, could be encouraged to support non-invasive ways of protecting beach goers from shark attacks and promoting public education concerning attack prevention.
Both Shiffman and Burgess indicate that shark spotters have been effective in places such as South Africa. Shiffman wrote that monitoring sharks in this way can be “limited by clear water and suitable terrain.” He indicated that high ground close to the water can help spotters get a better view of sharks.
Waters shared by swimmers and surfers as well as sport and commercial fisherman, can lead to disaster. “Sharks can sense the smells emitted from bait at incredible distances,” Burgess said. "Designated swimming areas could be one solution," Shiffman suggested.
“People need to know the potential risks associated with their recreational activities, and how to effectively reduce them through their own choices and actions,” Shiffman told Discovery News. “Shark bites are extremely rare events to begin with: Hundreds of millions of people around the world go swimming in the ocean each year, and fewer than 100 on average are bitten by sharks.”
“I've interacted with over 3,000 sharks on three continents -- both in the water and from a research vessel -- and I've never had any kind of close call with a shark," Shiffman said. "I have dozens of pictures of sharks swimming away from me as fast as they can, because that's usually what sharks do when they see a person.”
“We can’t train sharks to do us the favor of not being sharks when we are invaders in their natural habitat,” Burgess said. “We pride ourselves on being smart animals, so why not use some of that intelligence to avoid shark attacks?” He offered these additional attack-prevention strategies: