Poor salmon runs along British Columbia's central coast rainforest since 2003 have spurred scientists to gauge the fish's nutritional impact on grizzly bears
?| August 8, 2011
Editor's note: This story is part of a four-part series that Anne Casselman, a freelance writer and regular contributor to Scientific American, reported in early June during a rare opportunity to conduct field reporting on grizzly bears in Heiltsuk First Nation traditional territory in British Columbia. For a first-person acocunt of her experience there, click here.
HEILTSUK TRADITIONAL TERRITORY, British Columbia?"Remember, if she charges, don't run," Doug Brown, researcher and field station manager for Raincoast Conservation Foundation and member of the Heiltsuk First Nation, who tells me as we climb out of the boat at the head of one of the countless inlets found in the of the Heiltsuk Traditional Territory along British Columbia's central coast. It's June and the early morning summer sun rapidly scales over the steep slopes flanking the inlet. Several hundred meters away a grizzly mother is grazing along the edge of the estuary with her two and a half-year old cubs. "Cub," however, is a misnomer in this instance. These are three-year-olds, large beasts in their own right. Through my binoculars I see the mother lift her broad head to sniff the wind. The muscles powering her lumbering 135-kilogram-plus body ripples still. "So how far away does the bear need to be for the bear spray to work?" I ask Doug. "Ten feet," he replies. I picture just how large this grizzly would be that close?and how fast she would close that distance. "Wow," I mutter. Doug replies: "Yeah, that's why I carry two canisters."
This mother's triplets are likely the fruit of a banner salmon run four years ago, a rarity, given the poor runs seen here since 2003. Like so many marine and terrestrial animals of the Great Bear Rainforest?roughly defined as the north-central coast of British Columbia?the grizzlies here rely on salmon in their diet to sustain their life cycles, which may be a problem because the salmon aren't doing so well. "All of us are governed by the same ecological currencies, and the currency here is salmon," Chris Darimont, chief scientist with the Raincoast Conservation Foundation (RCF) and conservation ecologist at University of California, Santa Cruz, says. "When the wealth of salmon goes away there's poverty for the people here, and also ecological poverty."
The Heiltsuk First Nation is well aware of the ecological toll that a diminishing salmon biomass will exact on terrestrial and marine systems alike. "The land and the bears and the sea, our people have always said it goes hand in hand," says William Gladstone, chief negotiator of the Gladstone Reconciliation and community elder. "We've been really fortunate that we do have enough salmon going up our [river] systems but there is a point where the balance is going to be upset, where you're going to start losing them, too." With salmon on the decline, the animals supported by the system are endangered, Gladstone says. "We're very concerned about that."
Anecdotes of grizzlies starving to death or becoming scarce are increasingly common along the central coast, but just how big a threat diminishing salmon stocks are to grizzlies remains unknown. Research has shown that salmon availability determines how big a bear will grow as well as the reproductive output of a female bear. Beyond that, the details of the relationship between grizzlies and the fish are unclear. "It would be nice to have a mechanistic and quantitative understanding of how bear populations respond to the variation in salmon population," Darimont explains. Such research could forecast grizzly populations into the future and help fisheries managers optimize the salmon needs of the bears with those of fisheries. For example, Darimont has recently co-authored a study (recently submitted for publication) that models and estimates how reducing salmon catch by fisheries would boost flagging grizzly numbers in interior British Columbian watersheds.
Source: http://rss.sciam.com/click.phdo?i=716d9e08d3cc3e2c7262457b5a77fab4
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