Beluga Thrives Again in St. Lawrence

The beluga whale, the gentle giant of the St. Lawrence River in Quebec, teetered on the brink of extinction 20 years ago, its numbers depleted first by commercial hunting, then by industrial pollution.

At one point, the beluga's blubber was so saturated with toxins that its carcass could not legally be transported in Canada without a hazardous waste permit.

But the playful beluga, with its huge bulbous head and song so sweet that it is called ''canary of the sea,'' is now thriving in the St. Lawrence, a vast saltwater estuary that links the Great Lakes with the Atlantic. There are nearly 1,000 belugas there today, up from barely 300 two decades ago.

The story of the belugas, told here last week to a Marine Mammal Science Conference of more than 1,000 experts from 60 countries, is one of modern ecology's great successes.

The beluga, the size of a great white shark but gentle as a puppy, was a prime source of oil and leather for early Canadian settlers. Over the years a simple but deadly efficient technique was developed for taking them in numbers. Strings of long poles, driven into the river bottom, guided the whales toward shore, where they were penned in like cattle, beached by the outgoing tide and slaughtered.

Michael Kingsley of the Maurice Lamontagne Institute in Mont-Joli, Quebec, a branch of the Canadian Department of Fisheries and Oceans, said the beluga, which in the last century numbered 20,000 in the St. Lawrence, was on the verge of extinction by the late 1970's.

An alarmed Canadian Government banned beluga hunting entirely in 1979. But by then, industrial pollution had become an even more sinister enemy.

''The belugas remaining were not in good shape,'' Mr. Kingsley said in an interview. ''We were finding as many as 24 chemical toxins in them.''

Pollution controls were enacted, but belugas were already suffering degenerative disease and sterility.

''We may not know the extent of the damage to the beluga for decades,'' Mr. Kingsley said.