In recent years, the search for an effective shark deterrent has intensified in the wake of highly publicized shark bite incidents around the globe. However, despite the increased attention given to these incidents, research suggests that shark interactions with humans have actually decreased. According to a recent study out of Stanford’s Hopkins Marine Station, shark bite risk on the California coast has dropped by more than 91 percent since 1950. The study, published in Frontiers in Ecology and the Environment, weighted the number of reported unprovoked bites in the last 60 years in the state against the number of people using the ocean for swimming, diving, surfing and other sports. While the number of statewide incidents has remained relatively steady (about one per year on average in the ’50s to one-to-two per year now) the number of people in the ocean has increased greatly. Therefore, the risk of being bitten by a shark today is much lower than it was in the 1950’s, which even then presented a very low risk.
Nevertheless, with increased media attention surrounding the few incidents that occur each year, there are repeated calls for action to be taken to reduce what is already a very low risk. Unfortunately, these situations can quickly get out of hand, which is what we saw in Western Australia (WA) in 2014 when the Government began culling sharks in a misguided attempt to reduce the risk to swimmers. A total of 172 sharks were caught (almost all tiger sharks), and eight other animals including stingrays, however not a single great white was caught, despite this species being identified as the one involved in the fatal incidents that sparked the cull in the first place.
Given the vital role that sharks play in the health of marine ecosystems, it is essential that we avoid destructive control measures, such as those undertaken in Western Australia. Instead, we must develop non-lethal methods to allow humans and sharks to coexist safely. As a result, our research scientists at SOS, in collaboration with partners at the University of Western Australia, have embarked on a mission to test and develop non-lethal shark deterrents to provide ocean users with an extra level of protection against negative interactions with sharks.
Previously, we reported the success we observed with an electric deterrent, the Shark Shield, which was able to effectively deter great white sharks from interacting with a baited canister. In our latest research, we focused our attention on the potential effect of auditory and visual signals on shark behavior. We were interested to see if by simply playing a sound or flashing a light, could we manipulate the behavior of an approaching shark?
The artificial sound that we created for this study was based on the work of Myrberg et al. (1978), which showed that a sound with a rapidly changing amplitude and frequency elicited a deterrent behavior in free-swimming sharks. In an attempt to increase the potential deterrent effect of the audio signal, we only activated the sound as white sharks approached within approximately 2m of the audio source. This was to reduce the chances of the sharks habituating to the sound as they approached from a distance. Nevertheless, we did not observe a significant deterrent response to the artificial sounds presented. Neither did we observe any significant deterrent response when the sharks were presented with a flashing strobe light. However, when the auditory and visual stimuli were presented in combination, white sharks spent significantly less time in close proximity to the bait. Furthermore, this effect was even more pronounced in smaller benthic shark species that we tested.
As the presentation of lights or sound alone did not show a significant deterrent effect on white sharks in this study, we do not advise their use as a strategy for mitigating shark–human interactions. However, due to their potential combined effectiveness, particularly with other species of sharks, there may be applications for this approach in deterring specific species from fishing hooks or nets to reduce fisheries bycatch.
We still have much to learn about how sharks utilize their senses to perceive and interact with their environment, but our hope is that our efforts will one day bring about practical solutions to help humans and sharks coexist peacefully.
This research involved scientists from Support Our Sharks, the University of Western Australia, Macquarie University, Flinders University, and Oceans Research in South Africa.
Please share your thoughts about this article below.
Other Interesting Articles:
Support Our Sharks posts articles and material prepared by other organisations and individuals not affiliated with Support Our Sharks for educational purposes. Support Our Sharks does not necessarily agree with the opinions expressed in such material. Support Our Sharks also provides links from this site to the websites of featured news articles above for informational purposes only. The links do not imply an endorsement by Support Our Sharks of these articles or the content of their respective web pages.