Sarah Waries
Sharks inhabit all five of the Earth’s oceans and can even be found in some freshwater rivers and lakes too.
While this may be alarming to some people, it is important to remember that not all sharks pose a potential threat to people. There is an incredibly diverse range of shark species worldwide, and they all play an essential role in ecosystem function and resilience and help keep our oceans healthy.
Of the more than 400 shark and ray species worldwide, with around 200 of those in South Africa’s waters, only a small percentage are implicated in unprovoked bites on humans.
However, no matter how small the risk, there is no doubt that shark-bite incidents are traumatic events that have wide-ranging impacts on communities, local economies, and the environment.
For nearly 100 years, governments across the world have been looking for ways to manage shark-human conflict, to reduce shark bites and protect people. Historically, shark-bite mitigation has involved lethal control of sharks including sporadic shark hunts immediately after a shark bite, or long-term shark culls using methods such as shark nets and drumlines.
Thankfully, following public pressure and improved knowledge of the importance of sharks in the oceans, there has been a shift in recent years to look towards sustainable, non-lethal shark mitigation measures, that protect both people and our marine environment.
What are the measures, and how effective are they?
Several places across the world have shark-detection programmes in place to prevent human-shark interactions. The programme work as proactive early warning systems, alerting water users to the presence of sharks nearby and asking them to exit the water until the shark has left the area.
In Cape Town, for example, trained observers (shark spotters) are positioned at elevated vantage points scanning the ocean for sharks. The use of shark spotters has proved to be effective in Cape Town since 2004. However, they are also subject to some limitations, including the need for mountains or similar elevation close to the sea, the impact of weather on spotting ability, and the potential for human error.
There are also several emerging technologies being investigated in the field of shark detection, including the use of drones for aerial surveys, as well as inshore sonar detection systems.
Perhaps the oldest forms of sustainable beach-wide safety measures in existence are those of exclusion barriers. These work on the principle of creating an exclusion zone that prevents sharks from entering a “safe bathing area”. Shark exclusion barriers are primarily non-lethal and are therefore different from traditional shark nets.
Unfortunately, they are suitable for relatively calm and sheltered bays only, as strong winds and swells easily damage them, and their repair and maintenance costs tend to be high.
Recently, several new concepts in the development and testing phase for deterring sharks from an area have been explored. The KZN Sharks Board in South Africa is developing an electronic repellent cable that uses a low frequency pulsed electronic signal to disrupt the electroreceptors of sharks and deter them from an area.
It is hoped that this non-lethal exclusion system will eventually replace the shark nets and drumlines in place along the KwaZulu-Natal coastline. Another South African product in development and testing is the SharkSafe barrier, which uses fake kelp containing rare earth magnets to create a visual and magnetic deterrence for sharks entering an area.
For those wanting to reduce their individual risk of encountering a shark, several personal protective devices have been developed over the years, but how effective are they?
A 2018 study from Flinders University in Australia compared the effectiveness of five of the most popular personal shark deterrents commercially available for surfers including the Freedom+Surf, Rpela, SharkBanz bracelet, SharkBanz surf leash and Chillax wax.
The repellents use a range of methods to deter sharks including electrical currents, magnetic fields and olfactory stimulants, and were subjected to rigorous scientific testing on great white sharks at the Neptune Islands, South Australia.
The results were worrying, with only one device, the Freedom+ Surf, seen to have a significant effect on white shark behaviour, and even then, it was only effective 40% of the time. This study highlights the need for water users to search for peer-reviewed scientific research that supports a company’s claims about its products.
There are a plethora of possible sustainable alternatives to the lethal shark control measures governments have been using across the world for decades. However, there is no silver bullet – each beach, and each situation needs a tailored solution, and no strategy, whether lethal or sustainable, can ever guarantee 100% effectiveness.
Ultimately, there is one thing that all of us can do to reduce our risk of a shark bite when entering the ocean, and that is #BeSharkSmart.
Being “Shark Smart” means learning safety tips on how to avoid encountering a shark, taking responsibility for our own safety and making informed decisions around shark risk when entering the water, changing our behaviour accordingly.
| Waries is the chief executive of Shark Spotters
To read the full version of this piece go to http://wildtrust.co.za/shark-safety-strategies-feasible-or-far-fetched/
