/ 30 October 1997

The fossil fish may soon be dead again

The centuries-old coelacanth may soon come to the end of its life, writes Ellen Bartlett

It probably wasn’t pleasant being foreign minister of a pariah state like South Africa, but no doubt one of the minor perks of Pik Botha’s job in the bad old days was getting presents from the few heads of state willing to receive him.

Those attending one of his last state visits, in April 1991 to the Islamic Federal Republic of the Comores, recall the look of keen anticipation on the minister’s face as he waited to see what the president had for him. They recall how it fell when he was presented with a dead fish. The fish weighed 80kg, was 1,64m long, and, having been dead for some time, was starting to smell.

Luckily for the minister, someone from the JLB Smith Institute of Ichthyology stepped in and said he’d be happy to take the fish off his hands. There is a model of it in the Two Oceans Aquarium in Cape Town, christened, appropriately, the “Pik Botha coelacanth”.

It was, of course, no ordinary fish. Like the minister, the coelacanth was once one of the world’s great survivors. Assumed to have died out with the dinosaurs, in the great end-Cretaceous extinction of 60-million years ago, it surfaced in 1938 in the net of a fishing trawler off East London, the marine equivalent of a living dinosaur.

But as the 60th anniversary of its discovery nears, the venerable fish is in danger of extinction, this time for real. Highly successful in its heyday – there are 125 species of coelacanth in the fossil record – only one species remains. Latimeria chalumnae, having survived 400-million years, exists in a single, tiny, relic population off Grande Comore. It is the last living example of the crossopterygians – or lobe-finned fishes, the end of the ancient line that many scientists believe gave rise to the first tetrapods, or four-legged land- dwelling vertebrates.

Pale mauve-blue with iridescent white markings, growing to an average adult length of 1,6m, with its peculiar paired limb-like fins, the last of the coelacanths lives in the deep water off the western shore of Grande Comore, at depths of 200 to below 700m.

Other individuals have been caught, off South Africa, Mozambique and Madagascar, but all are believed to be strays from the Comoran population. And the population is in severe decline.

Marine biologist Hans Fricke and his colleagues from the Max Planck Institute in Germany have been following the Comoran population for 10 years, conducting surveys from a submersible vessel. They have identified 100 fish individually, and tagged more than a dozen. Their early surveys, from 1987 to 1991, showed a stable population of as many as 650 fish. But by 1994, the number of fish in their census area had dropped by 30%.

Further surveys found that the coelacanths’ range was more limited than previously believed, forcing population estimates even lower. In a paper to be published early next year in the journal Conservation Biology, Fricke and colleague Karen Hissman estimate the population at less than 300 individuals, in a range of less than 60km. They warn that overfishing in the area is reducing the population at such a rapid rate that the species is now “critically endangered”.

“We think there is not very much time left to do something effective,” Hissman says. If the coelacanth does die out, those who study it say it will be one of the most tragic of modern extinctions.

“Here we have got one of the most significant back-boned animals that ever evolved and it’s going extinct. It could disappear within the next 15 to 20 years and there is no effective conservation measure in place,” says Professor Mike Bruton of the Two Oceans Aquarium in Cape Town, and a leading authority on coelacanths.

What is perhaps worse is that the coelacanths’s demise is unintentional. It is dying out because it keeps getting caught by fishermen who don’t even want it. What Comoran fishermen are looking for when they cast their long lines off Grande Comore is Ruvettus pretiosus, more commonly known as the oilfish. The oilfish and the coelacanth share the same habitat, swim at the same depths, take the same bait. Catching a coelacanth, Bruton says, “is regarded as a bit of a nuisance”. At best, the fishermen let it go. But the coelacanth has impressive jaws and rows of small sharp teeth – and hooks are expensive and hard to replace – and so the more typical response has been to beat it to death, and retrieve the hook before throwing it back.

There was a flurry of local interest in the coelacanth after its discovery. JLBSmith, the biologist who was the first to describe the fish in 1939, posted notices all over the islands, offering 100 pounds for a specimen. His efforts were finally rewarded in 1952, when a second coelacanth was caught off Grande Comore.

There were no commercial flights to the islands, so Smith flew up to fetch the fish in a South African military Dakota. The French, who claimed the Comores as a colony at the time, were so incensed they closed the islands to scientists for the next decade.

Coelacanths were caught in increasing numbers until the 1980s; most were sent to museums and aquaria for study. Even then there was concern that in collecting specimens for research, scientists were endangering the species. When the annual catch declined in the 1980s it was not due to conservation, but to the development of offshore fishing. In an effort to help the impoverished Comorans expand their fisheries, the European Community and the Japanese funded the placement of “fish aggregation devices,” or FADs, offshore. Because the fishing areas were beyond the reach of the traditional galawas or hand- paddled outrigger canoes, the funders also paid for new boats with outboard engines.

But the project ended. The engines broke down, and there was no one to fix them. The fishermen went back to their old dugouts, and back to fishing the inshore waters. They started hooking coelacanths again, and the population went on the sharp decline that continues today.

If the coelacanth were to die out, it will do so leaving many questions unanswered, among them its place in prehistory. It has long been debated whether it was the coelacanth, with its primitive limbs, or the lungfish, capable of breathing air as well as obtaining oxygen from water, that was closer to the evolutionary line that led to amphibians and other tetrapods, and ultimately to us.

Those in favour of the coelacanth argue that its blood haemoglobin is similar to that of tadpoles – though not to that of adult frogs. But tests of the mitochondrial DNA of lungfish indicate it is a more favourable candidate. Five species of lungfish, which emerged 460-million years ago, also survive in Australia, South America and equatorial Africa.

At the time the coelacanth was rediscovered, the thinking was that it would be a window into the past, a modern model of how a primitive animal works. But that has not been the case. The living coelacanth may look like its fossil precedessors, but it does not operate like them.

“The coelacanth is a highly specialised, extremely sophisticated animal, which almost certainly is not operating now the way it did 400-million years ago,” Bruton says. “It is by no means ancient and primitive.” The coelacanth borrowed from both the cartilagenous and the bony fishes, and remains somewhere between the two.

The coelacanth is the only vertebrate to have an intracranial joint, a feature once common among frogs, enabling it to raise its top jaw as it lowers its bottom jaw, to increase its gape. Perhaps most intriguingly, the coelacanth gives birth to live young, and did so long before the mammals came along. They lay a number of eggs, the size of oranges, which hatch in utero; the young consume the yolk sac, and the eggs of lagging siblings.

But most of what coelacanths do is beyond human reach. By day they rest in caves formed by underwater lava flows, in social groups as large as 15 fish per cave. They hunt at night, moving down to depths below 700m, beyond the scope of the submersibles and the range of the transmitters.

Coelacanths operate like the big gliding birds of the air, circling on the ocean currents and gyres. They compensate for their inefficiency at procuring oxygen from the water with a slow metabolism. Their fin movements are slow. “Almost balletic,” Bruton says, “except when they ambush, and then they have a very fast acceleration.

“It’s very difficult to get money to conserve an animal that you can’t see, and which tourists can’t pay to go and look at,” says Bruton. “It’s a campaign I have been on all my life: people love conserving the hot and furries, but they don’t like conserving the wet and slimies.”

ENDS