A new shark has been making waves in Kleinbaai, the shark capital of South Africa.
There has been increased sightings of bronze whaler sharks (Carcharhinus brachyurus), otherwise known as the copper shark, because of its distinctive colouration.
It is not known if the bronze whaler shark is predatory to humans. It does however face pressures from the fishing industry and is considered near threatened by International Union for Conservation of Nature (IUCN).
Shark cage diving operators in Gansbaai are working towards a no-catch policy in the Kleinbaai area.
“We first noticed bronze whalers at the shark boats in 2013 and it has been amazing to see how they have adapted to the area in the absence of white sharks,” says Wilfred Chivell, owner of Marine Dynamics and founder of the Dyer Island Conservation Trust.
The decline of white sharks are largely attributed to the presence of orcas (Orcinus orca).
Shark biologist Alison Towner and the team from Marine Dynamics and Dyer Island Conservation Trust dealt with the washed-up great white sharks (Carcharodon carcharias) in 2017 and conducted necropsies on site to confirm orca predation.
Towner says great white shark sightings have since been unpredictable, causing much consternation among shark cage diving operators, who employ hundreds of people and have many directly and indirectly dependent on this tourism venture. This industry attracts up to 85 000 visitors to Gansbaai.
Towner and the team were called out in May and June of 2017 to retrieve the carcasses of four white sharks, a female of 4,9 m and three males at 3,6 m, 4,5 m and 4,1 m.
All four sharks had related open wounds, and their livers were found to be missing. This indicated orca predation. The liver is the only part that the orcas appear interested in, although the one male shark was also missing a heart.
The orca, also known as the killer whale, belongs to the dolphin family, and is the only known natural predator of the very legendary apex predator, the great white shark. In the last two years there have been more frequent sightings of orca in Gansbaai.
There is speculation about how the orcas affect shark behaviour, and according to Towner it is confirmed that some orcas do indeed pose a serious threat to the already vulnerable population of great white sharks on the South African coastline.
Chivell says the Dyer Island ecosystem is complex and delicate, and white sharks are an important apex predator for keeping the abundant Cape fur seal population in check.
“The shark cage diving industry has a limited permitted area in which to operate, and sightings have been incredibly variable over the last two years,” says Chivell. “There were some good patches of white shark sightings, such as in May 2018, and then absences for weeks at a time.”
Marine Dynamics conducts daily observation data and studies the sharks and water temperatures closely. “Marine Dynamics places a lot of emphasis on protecting and looking after sharks and all animals of the sea,” explained Brenda du Toit, Public Relations officer for Marine Dynamics.
Chivell explains the region’s ecosystem is faced with interesting and challenging times.
“Just a couple of years ago we were wondering where our southern right whales were, and then we unexpectedly had the highest count ever in 2018.”
He said: “While some white sharks have travelled eastward, we also know that two longliners are sitting off our coast, and white sharks could be a bycatch. Right now, the shark cage diving industry is the only protection white sharks have.
“We can only hope the white sharks return as quickly as they left.”
Retrieval and necropsy of one shark costs around R20 000. Should you wish to support the work of the Dyer Island Conservation Trust, please see their website www.dict.org.za.
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