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A brown bear is chased high up a tree by one of Kim Robinson's hunting dogs near Merritt, B.C., on Sept. 17, 2009. (JOHN LEHMANN/JOHN LEHMANN/GLOBE AND MAIL)
A brown bear is chased high up a tree by one of Kim Robinson's hunting dogs near Merritt, B.C., on Sept. 17, 2009. (JOHN LEHMANN/JOHN LEHMANN/GLOBE AND MAIL)

An ecosystem in turmoil puts its predators at risk Add to ...

When the team of scientists returned from the dripping, primordial rain forest on Vancouver Island, they carefully prepared their specimens, drying, then grinding to a fine powder samples of tree trunks, plant leaves, soil, flies and beetles.

There, in the core of ancient Hemlock and spruce, in the traces of crushed insects and in the residue of berry bush foliage, tests found something remarkable - the isotopic signature of salmon.

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How did the salmon get into the forest?

The bears did it, according to the research which illuminates the intricate connection between the biggest land predators in British Columbia - coastal black and grizzly bears - and their prime source of protein, salmon.

The importance of the bear-salmon nexus came into focus when conservationists and ecotourism operators raised fears last week that a wide-spread die-off of bears may be occurring because of a lack of chum.

Chum, a species of big salmon, is the number one target of fish-eating bears.

If there is a collapse of bears, it will have wider ecological implications because of the role they, and salmon, play in a healthy, functioning rain forest.

Fred Seiler, who runs Silvertip Ecotours, in Terrace, and who, for the past three months, has been swimming rivers to do salmon counts for government and first nation fisheries departments, was the first to sound the alarm about missing bears.

Mr. Seiler, who has kept records of bear sightings for 20 years, said in a peak year he'll see 45 to 55 grizzlies, and in a low year 35.

"I've got a crash I can't understand. … I'm really scared because a typical watershed where I count up to 45 bears, I've got a couple [of bear sightings] I've got no science. This is all anecdotal … but the bears are just not there," he said.

"I'm not going at this because I want to shut the grizzly hunt down. I'm going at this because something is wrong and as a society we've got to quickly grab hold of this before it becomes a [total]collapse. Having our largest predator die off would be, like, wow."

Mr. Seiler said on one river he swims, the chum salmon run has declined from 40,000 fish a few years ago to 1,000 this year. In another he swam 12 kilometres without seeing a single chum.

Ian McAllister, conservation director of the non-profit conservation group, Pacific Wild, said he's convinced bears are starving because of a multiyear collapse of salmon stocks.

That claim, now under investigation by government biologists, has been disputed by hunting guides, who say the bears have simply shifted away from salmon streams to feed elsewhere.

"Talking with the outfitters that operate on the central coast, on a 10-day hunt, they are seeing 80 bears, 80 different grizzly bears," said Scott Ellis, spokesman for the Guide Outfitters Association of B.C.

"So, what we believe is that - we are very concerned about the low salmon returns - but what we believe is that there is a shift [to berry crops]"

While the debate is raging about whether the bears died, or simply moved into the rain forest to feed on berries, everyone agrees the loss of salmon could be catastrophic - not only affecting bears, but cascading down through the food chain, all the way to the forest floor.

Tracking isotopes

Few know more about that than Thomas Reimchen, of the University of Victoria, who worked with colleagues on the research that tracked salmon isotopes into the streamside ecosystem.

Dr. Reimchen found bears were dragging so many salmon carcasses up riverbanks that they were fertilizing the surrounding forest and feeding a myriad of other species. He calculated up to 4,000 kilograms of fish carcasses can be found per hectare along streams where salmon and bears proliferate.

In another research project, he sat in the middle of a small stream on the Queen Charlotte Islands, while bears feasted nearby.

"The stream was only four meters across and … I'm sitting in the stream, as the bears would be foraging," he said.

And the bears never threatened him?

"No, absolutely not. Certainly in the night they were aware of my presence but they essentially ignored me … they ignore each other pretty much as well."

This lack of aggressiveness, common in bears when they are feeding on salmon, allowed Dr. Reimchen to make close observations and gain some remarkable insights.

The eight black bears that shared the stream with him captured 4,281 salmon over a 45-day spawning period. They would eat about 12 salmon a day, taking prime pieces, rich in fat.

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