Australia shark attacks
February 28, 2013
It's a gorgeous summer morning at Scarborough, one of Perth's most popular surf beaches. It's thirty degrees and a solid swell is rolling in. It's early, but numerous surfers are already riding the waves and groups of ocean swimmers are kicking rhythmically beyond the surf break.
As a dozen of kids jump into the water for a surf lesson, a shark patrol helicopter starts to hover overhead. It's an ominous sign. A few minutes later, the wails of the shark alarm echo along the beach. The helicopter has spotted two tiger sharks - one of them is 3.5 meters long.
"We have had a confirmed shark sighting this morning, please stay out of the water," a lifesaver yells into her megaphone as she runs down to the water's edge.
With five fatal shark attacks off Western Australian waters in the past 18 months, everyone is quick to get out. But shark alarms were once "a novelty," according to surfer John De Carlo, who has been coming to Scarborough for more than forty years.
"Back then, they would go off once or twice a year," he said. "Now it's like three times a week."
Little science, many myths
There are a number of theories for the increasing numbers of big sharks such as great whites and tiger sharks being spotted off the Western Australian coast.
One theory says that there are more great whites around now because they are a protected species. Another popular theory is that the rebounding seal and whale populations are luring sharks closer to land than before. On the other hand, it could be that the media is reporting more shark sightings. The problem is that there is no hard data. Scientists don't know if shark numbers in the region are really on the rise, and they don't understand their beahvior much.
Studies, however, have shown that there is an increase in the number of shark attacks. According to statistics kept by the Australian Shark Attack File at Taronga Zoo, the average number of shark attacks has nearly doubled in Australia in the past decade. With swimmers, surfers and divers demanding to know why the attacks are increasing and what they can do about them, scientists are now trying to find out more. And the state government has recently released several million dollars to fund shark research, following headlines trumpeting Western Australia as the shark attack capital of the world.
Attack any time of day
One of the major beneficiaries of the funding for shark research is Western Australia's Department of Fisheries. The department has already released findings of a study examining correlations between great white shark attacks and factors such as the time of day, the time of year and weather conditions.
According to popular belief, white sharks are more likely to attack at dawn and dusk, and in cloudy conditions. However, this is absolutely not true, according to Dr Rick Fletcher, the executive director of research at the department.
"There is no shark weather," he said. "And the number of attacks was during the middle of the day but that is probably when the greatest number of people are in the water."
What the attack analysis showed is that the further people are away from the shoreline, the higher the risk of being bitten by a great white. Over the past two decades, only one person has been attacked within 30 meters of the shore.
Western Australia's Department of Fisheries has also expanded its great white shark monitoring project to try to find out more about the predator in the region. So far, researchers have tagged 110 animals and taken their genetic samples. It's hoped this will help the scientists come up with a population estimate, but the results are "likely to be five to ten years, not one or two years," Fletcher said.
The tagging project will also map the great white's movements and find out whether they favor certain locations or conditions.
"What we are looking for is how does behavior change between years," Fletcher explained. "Is that then correlated with some type of oceanographic conditions, for example? If we can get an understanding of if it is correlated, then we might get some understanding of whether the risk (of attack) in different areas is going got be higher or lower."
Shoo shark
University of Western Australia's Oceans Institute also has received money from the state government for shark-related research. It is looking into potential deterrents, such as certain underwater sounds, smells or chemicals that could be used to scare off sharks. Studies by the US Navy already showed that rotting shark flesh is a deterrent, according to Dr Nathan Hart, a neurobiologist at Oceans Institute.
"The trick is to find out what is in that and if you can purify that and release it in a controlled fashion," Hart said.
They'll also take a look at things like bubble curtains, which are already used to guide fish away from intakes at power stations.
Hart and his research colleagues are particularly partial to the idea of strobe lights as a potential shark deterrent because they could be deployed with no lasting ecological effect. In addition, strobe lights can potentially be used in different ways, such as on a surfboard, attached to a swimmer, or put on buoys strung along the beach.
Some of the ideas sound simple but the research is complex - involving studies of shark physiology and their reactions in the institute's aquarium. Also, the researchers have to test if a particular deterrent works for a range of shark species.
"Take the bull shark and the white shark for example," Hart explained. "They have very different life histories, feed on different things. So they have a different biology and their sensory systems are designed in different ways subtly. There are important differences that may influence behavior so we need to make sure we are covering all bases."