September 14, 1999

As a Species Vanishes, No One Can Say Why


On a plate, where most people encounter them, all Atlantic salmon are pretty much alike: orange-pink fillets or steaks that melt in the mouth when baked, broiled, grilled or poached, or when smoked and combined with an onion slice and cream cheese on a bagel.

But alive, in their North Atlantic habitat, salmon today come in two basic varieties, farm-bred and wild. The wild fish are sleek, silvery torpedoes that range from one side of the ocean to the other and whose beauty, heart and acrobatic grace have earned them a reputation as the aristocrat of aristocrats among game fish.

The farm fish spend cramped lives in ocean pens just off the shorelines of North America, Europe and Chile. Comparatively short and fat, often with fins frayed or eroded as a result of close confinement, they are a marine equivalent of domesticated cattle.

B. & C. Alexander/Photo Researchers
A wild Atlantic salmon on its journey upstream to spawn. Fewer are making the trip.
The odds are overwhelming that what a diner encounters is a farm fish, and that fact reflects a striking reversal: wild salmon, once abundant, are now outnumbered by their domesticated cousins at least 50 to 1, and probably more.

According to recent estimates, the wild salmon population is in what appears to be an accelerating downward spiral; the number that are returning to spawn in their native streams has plummeted to what some scientists say is an all-time low. "Something terrible is happening in the ocean," said Bill Taylor, the president of the Atlantic Salmon Federation.

Particularly worrisome is a plunge in key brood stocks.

These are the older, bigger, egg-rich fish on which the now-cloudy future of the species in the wild mostly depends.

Historically, it is estimated, there were 2.5 million to 5 million of these brood salmon migrating between ocean feeding grounds and North American spawning rivers.

By the mid-1970's, that figure had shrunk to 800,000; by 1991, to about 300,000; by 1996, to a little more than 125,000, and last year to about 80,000.

What is going on is far bigger than the familiar near-demise of wild Atlantic salmon in the northeastern United States.

Fewer than 300 of these prized fish return each year to the nine New England spawning streams that still attract them, all in Maine, and conservationists have recently sued to bring them under the protection of the Endangered Species Act.

But now the decline also appears to have accelerated throughout the North Atlantic basin at large.

Some experts, like Dr. Carl Safina, a marine biologist with the National Audubon Society, say that "tailspin" is not too strong a description of the situation.

Just three years ago, for instance, more than 200,000 salmon of varying ages returned to spawn in the Miramichi River of New Brunswick, a world-famous sport fishing stream that has been North America's biggest single salmon producer.

From 1992 through 1996, the Miramichi averaged about 112,000 returns a year.

Then, in 1997 and 1998, the number dropped to a little more than 40,000.

The count for 1999 is not yet in, since much of the spawning run takes place in the fall.

While some experts suspect there might be a relationship between the rise of farmed salmon and the decline of wild ones, others doubt that this is driving the decline in the wild.

And in fact, the general feeling among scientists is that the cause or causes of the wild salmon crash are unknown; it is as if they are disappearing into some ecological black hole.

The problem, scientists say, is not that too few salmon are being hatched in the wild. While many spawning rivers have been ruined by pollution, dams and silty runoff from farms and logged forests, experts say that there is still enough freshwater habitat on both sides of the Atlantic to produce reasonable numbers of young fish. But it appears that once in the ocean, proportionately fewer of these salmon are surviving to return to their natal rivers when it is their turn to reproduce.

Commercial fishing that began in the 1960's has commonly been blamed for the longer-term decline.

But fishing off North America and Greenland, in the area where salmon of North American origin congregate at sea, has been halted by international agreement, and yet North American salmon are still disappearing.

On the Miramichi, only about 1 percent of the young, first-year fish that go to sea return to spawn, according to the Atlantic Salmon Federation, an international nonprofit conservation group based in St. Andrews, New Brunswick.

Ten to 15 years ago, 6 percent to 12 percent returned -- at a time when large-scale commercial fisheries were taking wild salmon wholesale.

Many things, including natural factors, could bring on a population crash by breaking the salmon's classic life-cycle chain. Among possible causes being investigated are a changing climate that alters water temperature; competition, genetic weakening and disease transmission from escaped farm fish, and increased killing of salmon by seals and other predators.

The New York Times

But "we don't actually have an answer to what the problem is," said Dr. Malcolm Windsor, the executive secretary of the North Atlantic Salmon Conservation Organization, established in 1984 to execute a conservation treaty signed by the region's countries.

The organization is based in Edinburgh, Scotland.

The Atlantic salmon, Salmo salar, appeared in the seas tens of millions of years ago, and for about the last 10,000 years, since the end of the last ice age, their range has spanned the North Atlantic.

Young, six-inch-long first-year salmon, called by the old Anglo-Saxon name of smolts, migrate to two main oceanic feeding areas from their home streams in New England, eastern Canada and Iceland, and from rivers distributed along Europe's coast from Russia's Kola Peninsula through Scandinavia, and the British Isles to Spain.

Those from North America head for an open-ocean region between southwestern Greenland and northern Canada.

European fish make for waters around the Faroe Islands, north of Scotland (although many also swim all the way across the ocean to Greenland.)

In their feeding grounds, they fatten up on prey like sand eels and capelin, small smelt-like fish.

After a year of this, many return to the rivers of their birth to spawn.

These first-year returners, called grilse, typically weigh about five pounds.

They are predominantly male, and the females produce relatively few eggs.

Other fish avoid spawning as grilse, instead staying on the feeding grounds for two or three years and earning the full designation of salmon.

These grow to 10 to 20 pounds or more and include many more females, each of which carries many more eggs than grilse do.

They are the precious brood stock.

According to surveys taken by temporarily trapping fish as they ascend the rivers, fisheries scientists have been able to calculate present-day populations of breeders. The Miramichi is an important barometer. From 1991 through 1996, according to the salmon federation, an average of more than 31,000 brood fish ascended the river each year.

That number dropped to 18,442 in 1997 and to a mere 9,500 in 1998.

Biologists estimate that the total population of salmon of North American origin has dropped to fewer than 500,000 from about 1.5 million over the last 30 years.

Based on sparser and therefore more uncertain data, salmon of European origin are estimated to have decreased to about 3.5 million from about 6 million over the same period.

Estimates vary widely; these are in the mid-range.

But it seems clear, Mr. Taylor said, that apart from exceptions like the Kola Peninsula and Iceland, "there is not very much good news."

While the number of salmon returning to spawn in their native rivers is the lowest on record, Dr. Windsor said, it is not clear whether it is the lowest ever; records have been kept only since 1960.

"But," he said, "one has the feeling that things are not good for the salmon."

Fish populations, like those of almost all creatures, fluctuate naturally, but scientists say that several new factors might be having an impact on wild salmon.

One, conservationists say, might be the impact of farm fish on wild ones.

While no one has any solid numbers, estimates of the number of farmed Atlantic salmon off Europe, eastern Canada, Maine, the Pacific coast of North America and Chile run from 100 million to 200 million each year.

Atlantic Salmon Federation

The potential threat to wild salmon posed by farmed ones is said to be threefold.

First, it is argued, the farm fish are bred for selected characteristics like growth rate and tameness, and this could make them less genetically diverse and so less suited for survival in the wild.

The concern is that when they escape and breed with wild fish, they may reduce the ability of the offspring to survive.

Surveys on the Magaguadavic River in southern New Brunswick have found that fish escaped from offshore farm pens outnumbered wild ones by up to eight to one, and Dr. Windsor said large numbers had escaped in Europe.

Experts say they have no difficulty distinguishing the two varieties.

The farm fish "looks like a football as opposed to a sleek, well-tuned muscular fish," Mr. Taylor said.

Second, farm fish may compete with wild ones for habitat and food. Third, diseases and parasites are said to flourish in salmon farm pens, and these may be transmitted to wild fish.

Two parasites in particular, tiny brown sea lice and a microscopic organism called Gyrodactylus salaris, literally cover salmon and kill them by eating their flesh. Norway has had to poison all life in some of its salmon rivers to get rid of sea lice.

In North America, aquaculture interests say that while some farm fish may escape their pens, there is no evidence of any effect on wild salmon.

"There's no proven impact," said Dr. Brian Glebe, a salmon breeder for the aquaculture industry based in St. Andrews, whose enterprise is overseen jointly by conservationists, aquaculturists and the Government.

Moreover, he said, there are no pens anywhere near many important salmon rivers like the Miramichi.

Mr. Taylor of the salmon federation insisted, "We're not antiaquaculture." But, he said, the farm fish needed to be better contained.

He also said they could be neutered so they did not pass on their genes to wild fish, noting, "The technology exists." Salmon farming might also be relocated to land-based sites, Dr. Windsor said.

Despite the concern over aquaculture, some experts believe that climatic change may be a better candidate as the primary driver of the decline in wild salmon.

Over the period of the decline, the North Atlantic has been dominated by a natural climatic regime in which sea-surface temperatures have been unusually warm.

The North Atlantic seas alternate over decades between generally cooler and warmer states.

In the warmer phase, Dr. Windsor said, colder water from melting ice in Greenland may cause the temperature in the oceanic salmon feeding grounds to drop below levels that salmon can tolerate.

Some scientists believe that a general warming of the atmosphere may have brought about changes in atmospheric circulation that make the warmer phase of the North Atlantic temperature oscillation appear more frequently, but this has not been established.

Another possibility is that salmon predators like seabirds and seals have increased. Gray seals in the salmon region are indeed increasing by about 8 percent a year, Dr. Windsor said.

Why? "Brigitte Bardot," he answered.

Miss Bardot, a former actress from France, is a leading animal-rights advocate who has strongly opposed the hunting of seals.

In an effort to solve the salmon mystery, scientists have begun attaching tiny radio transmitters to smolts migrating out of their birth rivers.

By tracking them, they hope to learn their fate.

In the end, Dr. Windsor said, that fate may well turn out to have been shaped in one way or another by human activity.

With salmon and people, he said, "my guess is that the two of us don't go together awfully well."

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