"It was one of the most beautiful reefs in the world and believe me I've seen them all. It was a pearl and it's really very painful to see it dying," said Professor Yossi Loya, an internationally renowned coral ecologist.

He and other experts say Eilat's reefs will soon be wiped out unless the government swiftly closes companies that breed some five million fish a year in cages and are operating without permits.

"We are in the 11th hour, the very last moment to save them," said Loya, who has studied Eilat's reefs for decades.

The fish firms deny any direct link with the coral decline.

The reefs had sustained damage for years as Eilat and the neighboring Jordanian Red Sea resort of Aqaba grew from isolated desert outposts into tourist boom towns.

Loya and other experts say the most severe damage began in 1993 after fish companies started mass production.

At the time, the reefs should have regenerated as a sewage plant began to treat Eilat's waste. Instead, coral degradation accelerated and new coral growth dropped to near zero.

"What happened between 1993 and 2000 is there was an exponential increase in the yield of fish cages from 300 tons per year to something like 2,000 tons per year," Loya said.

These fish excrete nitrates that develop plankton, the enemy of corals as they make the sea water murky and block sunlight which is an essential ingredient for coral survival.

"The key point is that the Gulf of Eilat is an oligotrophic sea, a sea that does not have nitrogen at all," Loya explained.

"Coral reefs thrive in seas that are poor in nitrogen. If you increase nitrogen you are changing the environment and in such a sensitive environment like coral reefs it is mainly affecting the reproductive system of corals."

"ECOLOGICAL TIME BOMB"

Experts say the nitrates excreted by the fish numbers amounts to 250 tons annually. A governmental report by international scientists found the fish cages contributed around 90 percent of nitrates entering the sea around Eilat.

"If you calculate how many nitrates are going into the water, it is equivalent to a town of 30,000 people," said oceanographer Dr Amatzia Genin. "It is an ecological time bomb."

The fish companies and their supporters say the industry should not be shut down unless there is incontrovertible proof that it is killing the corals.

"There is no research that shows any direct correlation between the fish cages and the Eilat reefs' deterioration," said Dr Baruch Rinkevich from the state-owned Israel Oceanographic and Limnological Research Institute, whose mariculture wing developed the fish cage industry and earns royalties from it.

Loya and other marine biologists say it will take years to complete studies that prove definitively that the fish cages are responsible for the destruction of Eilat's corals. By the time they have it, the corals will have long disappeared, they say.

The connection between a high concentration of nitrates and the decline of corals is widely accepted by marine scientists, and there is plenty of anecdotal evidence, the biologists say.

The reefs in Aqaba or along Egypt's adjacent Sinai Peninsula are in far better shape than those off Eilat despite thriving tourist industries, a major port in Aqaba and the Jordanian city's release of sewage into the sea after basic treatment.

Several reefs in Eilat kept off-limits to scuba divers are also in deep decline, so the problem is not tourism, said David Zakai, a ranger at Eilat's underwater reserve.

Environment Ministry officials say spillage of phosphates, crude oil and other materials at the Eilat port almost never happen and sewage leaks are rare and minor.