Divers have found at least 18 coelacanths on KwaZulu-Natal’s north coast — indicating that these ancient fish, which have been linked to human evolution, may be permanent residents along the African mainland.
Coelacanths are nicknamed “old four legs” because they date back about 400-million years. They are believed to have used their limb-like fins to crawl out of the oceans and evolve into reptiles, mammals and eventually humankind. They were thought to be extinct until the curator of the East London Museum spotted one in a trawler’s catch in 1938.
South Africans have been intimately involved in the development of that discovery into one of the greatest scientific finds of the 20th century. Ichthyologist JLB Smith persuaded the then-prime minister, DF Malan, to charter an airforce plane in the early 1950s so that he could claim a coelacanth found on the Comoros archipelago.
The legacy lives on in research along the south-east African coastline since two fish were spotted by divers near Sodwana Bay in 2000. South Africa’s new Coelacanth Programme is actively supported by the Cabinet and is punted as a flagship for the New Partnership for African Development, linking various countries along the south-east African coastline in research and training.
“The coelacanth is an icon for conservation. It provides both a window into the past and door to the future,” says Tony Ribbink, coordinator of the programme.
After his return last month from the 2003 research expedition in the submersible Jago, Ribbink enthusiastically reported that “there are at least 18 coelacanths in Jesser and Wright Canyons” near Sodwana Bay.
The researchers have repeatedly identified four individual coelacanths during expeditions over the past three years, and report that three of the coelacanths appear to be pregnant.
Though it is too early to state categorically that the Sodwana population is self-sustaining, the scientists say the conditions under which the South African coelacanths live are dramatically different from those in the Comoros. The local coelacanths live and hunt in shallower waters — at depths of about 100m, as against up to 700m recorded in the Comoros.
The distinction is important because, if it can be proved that the south-east African population is stable, this could show that “old four legs” originated along the African mainland.
“Coelacanths roamed the oceans long before the Comoros Islands existed. The Comoros, therefore, are unlikely to be the ancestral home of coelacanths. Continental Africa is old enough to provide an ancestral home,” says a report by the South African Institute for Aquatic Biodiversity.
The latest research indicates the coelacanths at Sodwana are not an ephemeral colony carried down by currents from the Comoros.
“It is now clear that the strong currents are primarily in the surface waters; within the canyons, calmer conditions prevail and coelacanths find shelter in caves,” says the report.
Tests are being done to establish the genetic make-up of the South African population, how coelacanths mate and whether the individuals found in Sodwana are all members of one family.