Shock and flaw: Dr Charlie Huveneers on shark repellents and other research
As well as being a keen surfer, Dr Charlie Huveneers is one of Australia’s leading researchers working on sharks and rays. He is an Associate Professor at Flinders University, Research Leader of the Southern Shark Ecology Group, and Co-director of the Centre for Animal Behaviour. His latest research was into the effectiveness of a variety of shark repellents.
Swellnet: So what's your background in surfing?
Dr Charlie Huveneers: I started surfing when I moved to Australia about fifteen years ago and have had the opportunity to surf in many locations around the world including South Africa, Indonesia, France, England, Brazil, Nicaragua, USA, Australia, New Zealand, French Polynesia, and Palau.
Is that what led to your interest in sharks?
I got interested in sharks at around twelve-years-old when I did a presentation about sharks for school. The book I read to do my presentation emphasised how little we knew about sharks, which sparked my interest. We now know a lot more about sharks and there is a large number of students, junior and senior researchers working on sharks worldwide.
However, there is still a lot we don't know. For example, while we increasingly know where sharks are going, the factors driving some of the small and large-scale movements are less understood - and are more complex than 'where food is'.
Out of the 500-plus sharks species, there are also many about which we barely know anything and new species are regularly being discovered or described.
What is your academic background? How do you get to be a shark researcher?
Following an undergraduate degree at the University of Southampton in England, I did a PhD on wobbegong sharks in NSW at Macquarie University. I moved to South Australia in 2009, for a joint position between the South Australia Research and Development Institute [SARDI] and Flinders University. I'm now working full-time at Flinders University with the College of Science and Engineering where I teach Marine Biology and Animal Behaviour and lead a research group focused on the ecology and biology of sharks and rays.
Are there many researchers working in this area in Australia? Globally..?
While there were not many people focusing on sharks and rays when I first started, scientific interest in sharks has been continuously increasing and there is now a growing number of scientists and students working on sharks in Australia and around the world.
Can you briefly explain the research you have done on shark repellents? And the results..?
I've worked on three major studies testing the efficacy of personal shark deterrents. Across those studies, we tested seven products in a range of situations including breaching, which involves sharks rising out of the water in pursuit of a prey. This ensured that testing occurred when white sharks were in a predatory mode. We also tested deterrents using bait ensuring a certain level of motivation.
Our studies show that white sharks can be deterred by some shark deterrents, including in situations when sharks are attempting to feed on a natural prey. One of the devices tested also affected and effectively stopped the breaching behaviour of white sharks. However, none of the devices tested provided a guaranteed protection with white sharks.
For example, the Freedom+ Surf reduced the percentage of times the shark obtained the bait from 96% to 40%. It also kept white sharks further away on average - although sharks were still capable of being within close proximity. The other shark repellents, however, had little or no measurable effect on white shark behaviour.
Of course, testing is required in different locations, for different shark species, and in different circumstances, before the universal effectiveness of any proclaimed shark deterrent can be quantified completely. Nonetheless, our study identified one product that reduced the likelihood of an interaction with white sharks by more than 50% - and identified others that did not.
Given the results for the Freedom+ surf, can you explain how it works?
Sharks, rays, and skates are capable of sensing weak electromagnetic fields detected by ampullae of Lorenzini in the head of sharks and in the head and pectoral fins of skates and rays. Although electro-reception detection threshold of sharks and rays is species-specific, studies have shown that sharks and rays can show a behavioural response at levels as low as <1nV/cm. This led to the concept of using electrical fields to create repellents to reduce the probability of an attack.
Electric shark deterrents therefore aim to overwhelm the electro-sensory organs of sharks by applying a strong localised electric field. Some people have suggested that sharks might be attracted to electric repellents from a distance prior to being deterred. However, electric fields dissipate quickly in saltwater, hence why sharks were still able to come in close proximity to the deterrents, and sharks use other senses to detect preys from a distance - for example, olfaction and hearing - not electro-reception.
We also previously tested whether sharks were attracted to electric deterrents prior to being deterred and found no detectable attraction effect.
What other research on sharks have you done?
My research group works on a broad range of topics related to sharks and rays including assessments of their vulnerability to fishing pressure and other human, environmental, and climatic impacts, and investigations of their movement dynamics and residency patterns. Recently, a lot of my research has focused on the effects of wildlife tourism, shark bite mitigation measures, and public perception of sharks.
Why is shark conservation important?
Broadly, sharks and rays are more vulnerable than most other vertebrates, with one in four shark and ray species being threatened with extinction, mainly as a result of overfishing. However, this is the overall conservation status of sharks and rays, and some populations are stable and have been commercially fished sustainably for decades, while the extinction status of some species is improving.
Other species are considered critically endangered and many regions in the world have documented sharp declines in shark populations.
Is there any evidence for an increase in the population of white sharks around the Australian coast?
Although many people will say that they've never seen so many sharks when surfing and that the number of shark bites in recent years has to be related to an increase in the number of sharks, there is no scientific evidence that the number of white sharks in Australia has increased - or that it is increasing.
However, there is also no evidence that the Australian white shark population is currently decreasing or stable. There is unfortunately no robust scientific data available on white shark population trends.
This lack of empirical information is due to the challenges of accurately estimating the number of individuals in a population that undertake large-scale migrations. A recent genetic study has estimated the Australian population size of white sharks, but could not reliably determined whether it was going up or down. One modelling study has, however, suggested that under zero fishing mortality - that is: no white sharks are caught through bycatch or in the beach meshing program - the annual increase in population abundance likely varies between 2 and 6% per year.
Several studies are also underway to hopefully shed more light on whether white shark numbers are increasing.