The great white shark is one of South Africa’s most impressive predators, but new research reveals that their numbers are falling. By Olivia Wickstrom
When researcher and Shark Diving Unlimited owner Michael Rutzen led excursions in the ’90s, his boat would be enveloped in South Africa’s great white sharks. With 20 to 40 great whites circling the boat, his cage divers were promised a thrilling experience. This week Rutzen’s divers were greeted by only three sharks, and a lifeless sea. Not only was it a duller excursion, but a warning sign from the changing environment.
Rutzen was a part of the research team and study released 20 July 2016 by Stellenbosch University, bringing to light the South African great white shark’s current threat of extinction. Dr Sara Andreotti’s six-year study was conducted to count the number of great whites still remaining in South African waters, and her findings were startling. Only 353 to 522 South African great whites remain.
The researchers discovered this through two techniques: photo identification and genetic sampling. Each shark’s dorsal fin has a unique pattern, similar to a human fingerprint, which allows them to be identified from one another at an eye level. Andreotti was able to create a database of photographs featuring dorsal fins, each photograph showcasing a different shark. By dragging fish chum behind the moving boat, photographed sharks were lured closer for a biopsy, providing researchers with genetic information as well. They shot almost 5,000 photographs of the animals but could identify only 400 individuals in the photographs, realising the great white population was smaller than expected.
Where are the sharks disappearing to?
South Africa’s great whites are distinct from the white sharks found elsewhere in the world. Research done by Stellenbosch University compared genetic material from local sharks with different global populations and found the South African sharks possess a low genetic diversity – a defining yet problematic trait. Just under 90 percent of these white sharks share the same lineage. With such a narrow genetic makeup the species is less able to adapt to changes in their surroundings. Combine that with the number of sharks killed through nets, poaching and baited hooks, and you’ll see there’s a problem: more sharks are disappearing than emerging, and the population is fading.
Without conservation South Africa’s great whites will soon be extinct. The problem is, there are few conservation efforts concerning the great whites. Professor Conrad A. Matthee from Stellenbosch University noted that shark conservation is rare, because sharks are seen as the enemy – whereas an elephant is admired, a shark is feared. But sharks play a crucial role in the marine environment, and extinction of South Africa’s great whites would put the stability of our oceans in flux. Take Cape fur seals as an example. With no sharks to eat the seals their population will increase, resulting in a decrease in the number in fish. The effects would continue to spiral on.
Our unique white shark needs our help. We need to get the nets out of the ocean and take a stand against illegal poaching. Without protection, the South African great white shark could quickly disappear.