RESEARCHERS who have studied decades of catch records from Japanese fishing fleets, and data collected by American and Australian agencies in the 1990s, have concluded that populations of large ocean fish have fallen by as much as 90 per cent.

Jack Ward, Director of Conservation Services, said the reduction in numbers was entirely realistic, and conformed to Bermuda's experience when considered in light of early records of the "pristine" environment found by Bermuda's settlers.

The scientists, who reported their findings in the current issue of Science, say their study is the first broad look at diversity across open oceans, and the reduction of species leaves ocean ecosystems less resilient against environmental changes like global warming.

"I think that there a number of realities there that should concern us," said Mr. Ward. "A leading researcher, Daniel Pauly, said that unless we are comfortable with the idea that our successors will be eating plankton, we should all be concerned.

"Some people may find the 90 per cent number difficult to swallow, but it's reasonable in the light of the concept of shifting baselines, which holds that what we have come to think of as the 'normal' state of an environment was already substantially degraded.

"There was probably a loss of 50 per cent a very long time ago, and the early records make it clear that before man was out there heavily exploiting the oceans, there was a huge abundance. It was reported that Sir George Somers could catch enough fish to feed the whole complement of the Sea Venture in half an hour."

The Japanese data record the catches in 50 years of fishing for 15 species of tuna and billfish like marlin and swordfish. But the researchers cross-referenced this information with data collected about more than 140 species by American and Australian government agencies, and the results suggest their conclusions apply more widely.

Boris Worm, a biologist at Dalhousie University in Canada and a lead author of the paper, said: "The oceans have been drained of species, basically", and suggested that more must be done to protect areas where diversity persists.

One of the five sizeable diversity "hot-spots" recognised by the scientists is close to Bermuda: an area of the east coast of Florida, and the others are south of the Hawaiian Islands, off the Great Barrier Reef in Australia, in the central South Pacific north of Easter Island, and in the Indian Ocean near Sri Lanka.

The researchers said fishing records show how areas with high diversity in the 1950s have been shrinking in the years since. The area between Australia and Indonesia used to be one of those "hot spots", but Dr. Worm told the New York Times that the area of robust diversity "just got smaller and smaller until it was indistinguishable from the rest of the ocean".

He said global warming was worrisome because warmer waters were very bad for strong swimmers like tuna and billfish, which generate enormous quantities of internal heat as they swim.

"The world's tuna fishery today is largely a matter of yellowfin and skipjack tuna, because bluefin, albacore and other species rarely appear on fishermen's lines."

The topic is important to Bermuda, because just last month the island's Big Game Fishing Classic was estimated to have generated $3 million of revenue in four days, and that tournament was the highlight of the newly-introduced Bermuda Triple Crown Billfish Championship.

Tourism Minister Dr. Ewart Brown said: "Attendees of the event continue to be pleased with the abundance of blue marlin in Bermuda's waters."

A Bermudian fishing expert said Bermuda would be well served by the creation of a sanctuary within the 200-mile limit which would preclude any industrial fishing.

"We have size limits in place, in terms of what fish can be landed, and tag and release rules, and fines for those who don't comply. I don't know if Government will restrict game fishing further, because it's still important for tourism."

Mr. Ward said Bermuda should be careful about the possibility of over-exploiting billfish species.

"I think that the big prize has been won in Bermuda the last three years, and we're going to be an extremely popular destination for those game fishermen.

"To date, it certainly benefits tourism to a great extent, and puts us on the map for that activity, but if you win globally three years in a row, more boats will certainly show up next year.

"There are size limits, but the fishermen are allowed to take the larger ones, and there is a concern that some of them are reproductively-active female fish. I believe that these 1,000-pound fish are not inconsequential to that population, and perhaps the angling fraternity could be leaned on to develop some form of technology which allows them to document the size of the fish without pulling it out of the water.

"I am not an expert on these aspects, and I know that the billfish population around Bermuda has considerable economic value, so we need to find a way to allow the recreational and tourism value to be maintained without destroying the fish."

In many areas, the researchers say, species diversity has fallen by half since the 1950s, meaning that boats now catch only half the number of tuna and billfish species they did then.

Another author of the new study, Dr. Ransom Myers, also of Dalhousie, said: "It doesn't mean that all of those species are extinct, but the fact they are not being caught is pretty dramatic."