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CENSUS PUTS ANCIENT FISH ON VERGE OF EXTINCTION

Unless decisive steps are swiftly taken to curb human predation, the coelacanth, a very rare fish once thought to have accompanied the dinosaurs into extinction, will truly die out, a team of German zoologists reports.

This gloomy assessment by Dr. Hans Fricke and his colleagues at the Max Planck Institute for Behavioral Physiology in Seewiesen follows their latest annual census of coelacanths living off the coast of Grande Comore, the largest of the islands making up the Federal Islamic Republic of Comoros.Along a five-mile stretch of coast where the fish concentrate - about one-tenth of the island's coastline - the coelacanth population remained steady from 1989 to 1991, Fricke reported recently in the journal Nature. But from 1991 through 1994, the average number of coelacanths living in their deep Indian Ocean lava caves fell from 20.5 fish per cave to 6.5.

It is possible, Fricke says, that this alarming decline is the result of a natural population fluctuation or an emigration of coelacanths away from the survey area, but it seems much likelier that human predation is responsible.

Coelacanths are nocturnal animals, hunting at night for bottom-dwelling prey at depths up to 2,300 feet and resting during the day in their caves. Since individual coelacanths have distinctive markings, scientists can identify and track them year after year.

Although a handful of the big fish have been found in waters off the coast of South Africa and elsewhere in the Indian Ocean, the only known community of substantial size lives along the Grande Comore coast.

Fricke believes there are about 200 coelacanths in this area, barely enough to stave off extinction.

The main problem threatening the survival of the coelacanth (Latimeria chalumnae) is that it lives in a coastal area heavily fished by Comorians for other species of fish used as food and sources of oil.

Although the 5-foot coelacanths have little or no commercial value, they occasionally grab the hooks intended for other fish and are hauled to the surface.

Under a new Comoros conservation law, the landing of coelacanths is forbidden, so local fishermen usually kill them and throw them away after retrieving valuable fishhooks from their mouths.

Both European government agen-cies and the Comorian government have tried to halt the accidental landing of coelacanths. One measure was the mooring of "fish attractors," long, brightly colored plastic streamers, from buoys anchored farther from shore than the coelacanth habitats. The attractors only lure ordinary fish and apparently do not appeal to coleacanths.

But the attractors were anchored so far from shore that fishermen found it inconvenient to paddle their canoes to the designated area. To rectify this, international agencies helped local fishermen buy outboard motors for their canoes.

But by last December, Fricke said, most of the motors had broken down and the fishermen were again working the coelacanth zone.

In their Nature paper, the scientists from the Max Planck Institute group propose a new approach. They suggest mooring attractors close to shore but at a depth well above the coelacanth habitat.

Coelacanths are members of a very ancient suborder of fishes called crossopterygians, or "fringe-finned" fish. Although fossil crossopterygian fishes are common in sedimentary rock dated between 350 million and 60 million years old, they were long thought to have died out shortly after the end of the Mesozoic era, the age of dinosaurs.

But in 1938, paleontologists were stunned to learn that fishermen off the coast of South Africa had landed a coelacanth, which captured world attention as a "living fossil."

Naturalists, biologists and paleontologists agree that every effort should be made to save the only species of crossopterygian known to have survived to the present day, the coelacanth.

"Everybody feels sorry about extinctions," Fricke said, "but they have become so common a lot of us just don't pay much attention anymore. The coelacanth is something special, however. It is a remarkable fish, a window into the distant past and a treasure of nature. If we let him die out it will be a tragedy."