Shark management: Can anything be done to keep people safe in the water?


Posted

November 06, 2018 20:10:07

A cluster of shark attacks in North Queensland’s Cid Harbour has raised questions about the measures being taken to protect people in the water.

Key points:

  • Shark management methods include drumlines, surveillance, shark nets, tagging, and public education
  • No method is failsafe, and it is hard to say which ones are effective
  • Experts say our best bet is to learn more about shark behaviour

A man died after being attacked by a shark there on Monday and two others were attacked and injured by sharks in the same area in September.

After the first two attacks, shark control drumlines were temporarily installed, killing six sharks.

What works? It’s hard to know

There are various shark management methods in use around the country.

But none of them are failsafe, according to Professor Colin Simpfendorfer, who is the director of the Centre for Sustainable Tropical Fisheries and Aquaculture at James Cook University.

“While drumlines provide some short-term protection, or at least make people feel better about the situation, they don’t necessarily do very much at all,” he told The World Today.

“Here in Queensland we’ve got the very long-term, well established shark control program, which is a program essentially that removes large, dangerous sharks.”

Methods in use around the country include things like shark nets, drone and helicopter surveillance; tagging and tracking of dangerous sharks; and educating the public.

But Professor Simpfendorfer said it is hard for scientists to determine which measures work.

“We actually don’t have any good scientific data to evaluate how effective these things are,” he said.

“So, we’re mostly going on how successful they seem to be, rather than actually being able to measure the success, because we don’t know what would have happened if the control measure wasn’t in place.”

He said that makes it challenging when trying to help policy makers decide on the appropriate approach.

“We can’t actually give them a really hard and fast answer,” Professor Simpfendorfer said.

He said what we do know is that shark attacks have been relatively rare, particularly at beaches that are protected.

He said the key thing is to educate people about the risks.

“Are there any indicators of increased risk? So, dirty water, fish in the area, people fishing in the area — all these things can increase risk,” he said.

“And also the time of day — early in the morning or late in the day as the sun is going up or down we know are riskier times.”

‘Far more effective to understand sharks’

Shark researcher Dr Blake Chapman believes trying to understand the behaviour of sharks, rather than drumlines, is the best way to keep people safe.

“Their whole purpose is to kill sharks, to remove them from the population, on the premise that a smaller shark population will result in fewer bites on humans, and so far, that’s been proven equivocal,” she said.

Dr Chapman said there is no evidence that measures like that are effective, particularly in the long term.

She said the migratory nature of sharks means that culling populations must be done very consistently in order to have any effect.

“If you put in a lethal culling method, like these drumlines, then you might catch the sharks that are in the vicinity then and there,” she explained.

“But a month down the track, if others move into the area — which they will if there’s something else that’s bringing them into the area — those lethal measures that were put in a month ago and removed aren’t going to be doing anything.

“It’s been shown through the research that it’s far more effective to understand sharks, and to get a sense of their movement patterns, what’s drawing them into an area, what might have changed in that environment to be bringing these sharks in, and then to educate humans, as opposed to just going out and randomly killing sharks.”

Dr Chapman said we will never be able to predict where sharks are going to be with total certainty.

“They’re quite mysterious to us, especially tiger sharks unfortunately, but we can do a lot better if we start to understand and really take note of what’s happening,” he said.

Professor Simpfendorfer said it is very difficult to work out what is causing the cluster of events.

“The ocean is a very complex place and we have a lot of different impacts in that sort of space,” he said.

“It would take a lot of work to understand what is really happening in this situation.”

Feeling in control

Associate Professor Culum Brown, from Macquarie University’s Department of Biological Sciences, agrees there are many gaps in our understanding of the animals’ behaviour.

He said having three incidents so close to one another at Cid Harbour is unusual and suggests there is something odd happening there, and it would be nice to know why.

“Animal behaviour is hard to predict and tiger sharks in particular … [are] really unusual in terms of shark behaviour, because they tend to rely on strength and surprise, and they’re extremely mobile, so they don’t usually hang around in any one place for any length of time,” he said.

“[This] highlights the fact that we have a lot more to learn about shark behaviour and what motivates sharks to move, or even in this case perhaps hang around in one place.”

Professor Brown has been working for 10 years to understand shark behaviour, but he said there is a still a long way to go.

“There are lots of different species of sharks and lots of potential things that might drive their behaviour, including things like climate change,” he said.

He thinks it is likely that an environmental factor is driving shark behaviour, such as temperature or an unusual number of bait fish in the area.

Tiger sharks are not territorial, so the idea that sharks can be exterminated locally “is just a ridiculous idea”, he said.

“Using drumlines or any method of catching and moving, or killing sharks is a bit like trying to dig a hole in dry sand, because sharks are extremely mobile,” Professor Brown said.

“So, if you catch a shark and move it … you might move it maybe 50 kilometres away or something like that, but a tiger shark will cover that distance in a couple of hours, so there’s absolutely no point in doing that.

“And similarly, if you capture them and kill them, some other shark is just going to move in.”

He believes continuing to use this method, despite lack of evidence recommending it, is largely about feeling in control.

“It doesn’t work, the science has proven time and time again that it doesn’t work, but men just continue to do this kind of thing because they think they need to be seen to be doing something,” he said.

He supports the NSW Government’s decision to stop shark net trials, because they are ineffective and kill marine life including dolphins and turtles.

“There’s a public misconception about how shark nets work — they’re not a barrier, they’re just a net that hangs in the water colon,” he said.

“Deploying shark nets is certainly not the way forward.”

Queensland’s Fisheries Minister Mark Furner said no-one should swim in Cid Harbour at anytime.

“Drumlines or not, no-one should swim in Cid Harbour,” he said in a statement.

“As local charter operators have advised, Cid Harbour is primarily a site for mooring.”

Queensland’s Tourism Minister Kate Jones added: “Neither the local mayor, Andrew Willcox, marine authorities, nor local tourism operators want to see drumlines redeployed.”

Topics:

shark,

marine-biology,

states-and-territories,

safety,

fishing-aquaculture,

travel-health-and-safety,

whitsundays-4802,

perth-6000,

sydney-2000



Source link

Leave a Reply

Your email address will not be published. Required fields are marked *