So far this year there have been over 700 car fatalities on Australian roads. That’s about 115 per month and works out to be 5 deaths per 100,000 people. Recently there has been considerable media attention to the attacks on humans by sharks which when you put it into perspective works out to be 0.1 per 100,000 people. This rate becomes even less if you live inland and never go near the oceans.
Public perception of sharks took a hit post the release of the 1975 movie “Jaws”, but this also inspired some our greatest conservationist, biologist and shark lovers.
Today though, whilst our understanding of the sharks themselves has improved from scientific study we are still in fear of them and contact between humans and sharks continues. Sometimes in a random one-off incident and other times a period of activity around certain beaches. The Australian Shark Attack File Annual Report Summary for 2017 currently reports that so far that year to date there has been 1 fatality in all States and Territories, with a further 9 people injured. So what we can do to protect ourselves from shark attacks? Vincent Raoult, a post-doctoral fellow, from the University of Newcastle who has trained in fisheries shark behavior and biology says there are a number of different shark deterrent systems in operation across beaches in NSW designed to limit encounters between sharks and humans.
Shark Nets
Vincent describes shark nets as being in place for over 50 years without a fatality on a beach with them installed. They consist of netting deployed in 10 metres of water, stretching over 150 metres in length with a height of 6m. They act as means to entangle sharks that approach the beach but provide a partial barrier and not a total prevention system.
“The nets are a complex issue because it’s not just about the science. If a politician were to remove the shark nets and someone was to get bit and die then there would be hell to pay for the government.” he said
Compared to other techniques, nets are very cheap to maintain but indiscriminate with significant amount by-catch. The recent expansion of seasonal shark nets deployed at 5 beaches between Lennox Head and Evans Head were in response to the rise in human / shark encounters in 2016/17 in this area. In the initial 5 month period 133 animals were entangled and died, with 120 being caught but released alive.
“Target species as well as by-catch do not go to waste, like a lot of people may think, they are used for science purposes” he said. “The numbers of animals actually killed by nets is insignificant, its not causing any of the species caught to be threatened.”
Drumlines
In 2014 the WA government hit the headlines with their catch-and-kill policy using baited drumlines, following a spate of attacks along the state’s coastline. It was subsequently abandoned after recommendations from the Environmental Protection Authority (EPA) due to the potential adverse impact it could have on shark populations.
Drumlines and SMART drumlines, are generally weighted barrels with baited hooks on long lines. Animals bite the bait, become hooked and die from exhaustion. SMART drumlines have one, or two functional hooks, so when the shark bites down on the hook it pulls one of the buoy’s down and starts a mechanism that alerts fisheries management that there is something on that drum line”.
The issue with traditional drumlines is they have a lot of by-catch where they are left in the water for long periods of time and there is no way of knowing when something has taken the bait. They have been very effective at catching large sharks and were developed in the French territory of Reunion, in the Indian ocean to harvest sharks.
Instead of killing the shark, the main focus of the SMART drumline is to release the animal if it is by-catch like a dolphin, ray or turtle, or other non-targeted species of sharks like hammerheads that are not a threat to humans. If they are targeted species of shark, like tiger sharks, bull sharks and white sharks, they get tagged with an acoustic transmitter, pulled out to sea and released.
“The cool thing about the smart drumlines in Australia is it that it is good at protecting surfers as the key group of people at risk from shark bites, but also it has good scientific and conservation benefit as there is no by-catch and you release the tagged sharks to learn more about their movements patterns” he said.
Vincent described the ongoing white shark tagging program led by shark researcher, Barry Bruce. “He’s been tagging white sharks for a while, so the SMART drumlines are a huge supplement to that project. There is already an acoustic receiver array across Australia and so makes sense to continue this project on a larger scale. You have to be able to predict what an animal will do in an given situation. At this stage our understand of white shark behavior and patterns is very limited”
Future of shark deterrent systems
There are other deterrent systems that have been used across the globe that range from magnetic field devices, helicopter surveillance, human spotters overlooking beaches and the use of drones.
Vincent stated that magnets do have an effect of shark behavior, but it is unclear as to whether it will be a deterrent from a curious or hungry shark. If you sell to people a system that will prevent them from getting bit, and that system that fails then the whole technology comes into question. They work in South Africa with less exposed beaches but NSW is more exposed and they are less effective. The strength of the field reduces based on the range of the device, is that going to be possible as you would need extremely powerful magnets and is that practical on devices like surfboards.
The NSW fisheries have conducted a study on how effective helicopters are at spotting sharks in the water. This was undertaken using shark silhouettes placed at different depths to understand how effective the helicopters were at spotting them.
“They had a 30% detection rate due to surface clutter, waves, water clarity , the substrate being light or dark so it makes it hard to see something from the surface as to what’s below it” he said.
With drone footage people will realise that sharks are more prevalent than they used to be aware of which may create concern that shark numbers are increasing, when in fact they are given more information on what has been out there all the time. “There are always sharks at beaches but we need to manage the negative effects, educate people to the dangers, know that there are deterrent systems”.
Traditionally surfers have been anti-shark cull and with the water being the sharks domain, but in the last year or so, some surfers have become more concerned. “One of the bastions of shark conservation has been surfer groups. The fact that they feel threatened by something that has a very low risk is a worry, and its time to have that conversation with those groups to discuss the risk of shark bites and their responsibilities as people and users of the sea and acknowledge that there is some level of risk. Whether they want to balance that level of risk through their enjoyment of surfing is for them to decide, and not necessarily something that justifies the killing of large numbers of innocent until proved guilty animals.”
A few weeks ago a juvenile male white shark named “Fluffy” was washed up on the shoreline in Manly, placed in the ocean pool and finally released offshore. This allowed many people who would not normally get to see a shark up close the chance to remove some of the fear and get excited to learn more about them.
The only way we truly avoid a shark attack is to not get in the water in the first place. We manage our risks every day when we drive a car or cross the road and likewise we need to balance our risks of the ocean accordingly.