In the past eight months a study has shown 10 000 movements by sharks in False Bay, the site of this week’s fatal shark attack.
Researchers tagged up to 50 sharks with radio acoustic positioning gear and set up several monitoring devices on the sea bottom at False Bay. The tags relayed a signal — called a ”hit” — whenever a shark swam past a device. Similar research was conducted at Mossel Bay and Gansbaai on the Cape south coast.
That research has now been expanded into a broad survey of False Bay ecology and the sharks’ role therein — a joint project by Iziko Museum’s shark research unit, the University of Cape Town and Marine and Coastal Management (MCM), a division of the national Department of Environmental Affairs and Tourism.
Another survey, run by MCM and the Cape Town city council, has posted a monitor to record the number of people in the water at any one time and to track whether sharks’ routes correspond with the areas where people are swimming and enjoying water sports.
Marine biologists maintain sharks have always been around, particularly in areas close to seal populations. Seal Island in False Bay is home to a 50 000-strong seal colony. But the increased number of people in the water because of a ready availability of wetsuits and the increased popularity of water sports has heightened the likelihood of attack.
”There is simply greater exposure [of people] to sharks that have always been there,” says marine biologist Dr Sheldon Dudley of the Natal Sharks Board. ”Sharks are not really out to get people. If they were there would be many more attacks.”
The shark attack that killed retired teacher Tyna Webb (77) on Monday was the third incident in the peninsula, and the second fatal attack, in the past 14 months. In April JP Andrews lost his right leg after a shark attack while surfing at Muizenberg. In September 2003 another surfer, Dave Bornman (19), died at Noordhoek.
Attacks are not confined to the Peninsula, however. Nkosinathi Mayaba lost his life in June at Gansbaai on the Cape south coast.
Still, marine officials say this did not necessarily reflect an increase in attacks. Since 2000 three or four attacks have been recorded annually along the Cape coast, which stretches from the Peninsula to the northern reaches of the Eastern Cape, according to Natal Sharks Board statistics.
In comparison there were 15 attacks in 1998 and eight the following year, and one each year was fatal.
”If you look at the figures, there’s really not been an increase [of attacks]. We need to get a handle on water users,” said MCM principal oceanographer Herman Oosthuizen.
While the heated debate around chumming flared up again this week, marine experts remain sceptical about possible links. Instead, some say, a shark attack is used by some elements to push their personal agendas.
Chumming, the use of a slick of fish oil and parts and bait on rope, started in 1998 as shark watching and cage diving were developed as lucrative tourist attractions. However, it is restricted to the vicinity of seal colonies, where sharks can be seen moving on prey dozens of times a day. Sharks find the food rewards in chumming limited.
And MCM is keeping a sharp eye on illegal operators. Earlier this year it shut down one illegal operator in False Bay; two legal operations remain. It is investigating another in Gansbaai for possible contraventions after the operator was bitten in the foot last week.
Shark nets are not a solution: the gill nets are expensive to maintain and kill dolphins and other marine animals, while the often rough Cape waters pose additional challenges.
Shark attacks are ”a bolt out of the blue. It can happen tomorrow or in five years’ time”, said Dr Leonard Compagno, head of the shark research unit at Iziko Museum, where a new exhibit on sharks opened this month.
The new research is expected to tell more about sharks’ behaviour, he said: ”It may help a bit to make people aware of them — not to dive in places where they congregate — [but] by their very nature sharks are not focused on humans.”