Durban - Providing better information to the public about the risk of shark attacks is a better safety solution than culling sharks, according to a group of US researchers who found that the risk of great white shark attacks off California had dropped by 91 percent since 1950.
“Just like we check the weather before going boating, or the surf forecast before going surfing, getting information about the risk of encountering large predators can become a normal precaution we take before going into the ocean,” says Stanford University shark researcher Francesco Ferretti.
Ferretti, the main author of a new study published in the journal Frontiers in the Ecology, acknowledged that there had been an increased number of attacks on humans off California in recent decades, but this masked the actual risk factors.
The authors said many more people were enjoying the ocean, and so although the number of shark bites per year had increased over the past six decades, these numbers were hiding a much reduced risk to individuals because three times as many people now lived in coastal California compared with 1950.
The popularity of ocean sports had also expanded dramatically.
The 7 000 surfers hitting the waves in California in 1950 became 872 000 by 2013, while certified scuba divers grew from about 2 000 at the beginning of the 1960s to about 408 000 in 2013.
Ferretti said there was a higher chance of finding big white sharks off the California coast in the autumn compared with spring, when they migrated to Hawaii.
Overall, they had recorded a total of 86 “injurious attacks” by great white sharks between 1950 and 2013 off California, 13 of which were fatal.
Fellow Stanford University researcher Fiorenza Micheli said while every shark attack was a tragedy, such attacks were “extremely rare – of the order of 10 per year worldwide”.
By contrast, almost 100 million sharks of various species were killed globally each year as a result of fishing, habitat degradation and growing demand for shark fins.
Commenting on the research, the KZN Sharks Board said sharks were more active in the late afternoon off the KwaZulu-Natal coast, which was why the board warned the public to avoid swimming at dawn, dusk or at night.
While bathers were advised to stay close inshore, some attacks had happened where the victim was standing.
“The difficulty lies in staying out of the water on a sweltering hot summer afternoon, even if a nearby river has come down in flood and the sea is discoloured, particularly if you have come down to the coast for your two-week holiday and you know the risk of an attack is very low,” said Geremy Cliff, the board’s head of research.
“Our situation is complicated by the fact that we have three problem species (Zambezi, great white and tiger – in that order). So while Zambezi sharks are more common in summer, white sharks are more common in winter,” he said.
Length reduced
Since 1992, the total length of shark nets along the KZN coastline had been reduced from 45km to 27km in an effort to reduce shark deaths, without compromising the safety of bathers.
From a risk perspective, there had been 103 shark attacks/incidents off the South African coastline between 1960 and 1990.
Of these 41 percent were swimmers, 41 percent board riders and 17 percent divers. Since 1987 the majority of attacks had happened in Cape waters.
The vast majority of attacks on divers involved spearfishermen, almost half of whom had shot a fish just before the attack,
Off the KZN coast, 50 percent of all shark attacks since 1960 happened in the late afternoon and 30 percent in the early afternoon.
It was also calculated that 73 percent of all attacks happened in turbid water conditions (less than 3m visibility).
Of the 11 fatal attacks on humans between 1960 and 1990, six were in KwaZulu-Natal (all before 1980) and five were in the Cape.
Off the Cape south coast there had been a “disproportionally high number of incidents involving spearfishermen compared with swimmers and board riders”.
Research also suggested that sharks might have been attracted to attack several surfers and board riders wearing brightly coloured leashes or ankle bands.
The Mercury