Conservation of the shark population along South Africa’s coastline has come under the spotlight, following extensive research into the movements of white sharks that revealed worrying numbers.
Tourism Update spoke to Alison Towner, a Marine Biologist who has studied white sharks in South Africa for 12 years, in conjunction with Marine Dynamics and the Dyer Island Conservation Trust in Gansbaai, South Africa. She says: “Without white sharks in the area we would see shifts in ecological composition. Top predators have key roles in the transfer of nutrients in the system, keeping trophic levels at bay, maintaining the delicate balance of the ocean. It is the same as in a land ecosystem; the only thing is in the ocean you can’t always see when things go out of balance.”
Towner emphasises the role that the shark cage-diving industry plays in this system. As a researcher, she has a trade-off with Marine Dynamics, a shark-cage operator in Gansbaai. “I can go on their boat and give their clients information on sharks and at the same time, collect my data and samples.”
In South Africa, there are shark cage-diving operators around False Bay, Gansbaai and Dyer Island, Mossel Bay’s Seal Island and, the newest, at Bird Island, 60km off the coast of Port Elizabeth.
Tom Slough, Marine Biologist at White Shark Projects in Gansbaai says: “In the winter months, sharks typically move to our island network where the well-known shark alley is located. During these months is generally when we observe the highest concentration of white sharks in the area and it is possible to see upwards of ten sharks in a three hour trip. In the summer months there are normally fewer sharks in the area.”
Towner’s research on the movement of sharks in the area has examined the interaction between sharks and the cage-diving boats. “We’ve spent over 500 hours tracking tagged sharks between 2010 and 2016. We track all different sizes of sharks, which helps understand the different energy consumptions amongst age and size. We found with each shark that we tracked that all of them visited shark cage-diving boats at some point, but there was no extended effect. A shark would come to the boat, spend a couple of hours, and then resume its natural hunting patterns at the island.”
A recent study published by Charlie Huveneers argued that interaction with boats changes the immediate energy consumption of the animals. Towner reiterates that this is for short periods of time: “We are finding that they spend more energy at the boats but they lose interest over time. Being a mobile predator that is very efficient at hunting, they can leave when they want. They aren’t trapped at the boat; most of the animals we observe head off to Seal Island to hunt.”
Towner believes there is a misconception of the industry’s role on the sharks. She says: “I don’t think it’s transparent enough how quick the visits are to the area. The residency time of animals in the area is quite short. It’s not long enough for a shark to become conditioned to a boat.”
Both Slough and Towner stress that, in addition to the scientific benefit of cage diving, the activity is crucial to changing these misconceptions. Slough says: “Cage diving offers a unique perspective on sharks; we help show how different they are from their reputation.”
He goes on to add that cage diving offers practitioners and those passionate about sharks the opportunity to change opinions. “We are given a chance to highlight how vulnerable sharks are, how endangered they are, and we can spread a different message.”
As evidence of this, Slough explained the observations made last year when a pair of orcas – nicknamed Port and Starboard – moved into the area and “that on the occasions the two orcas had been spotted in the area, there was an immediate drop in shark sightings for an average of two to three weeks. We wouldn’t have been able to observe this if we were not out on the boats as much as we are.”