The mystery and eco-importance of Pacific salmon
Scientists still know little about how salmon navigate the open ocean, identify
their native river or stream, find their way to within feet of their birth, and
change color from a brackish green at sea to a deep crimson in fresh water.
We do know that these enigmatic fish are responsible for the gigantism associated
with the towering coastal rainforests of Alaska and British Columbia.
Salmon are the reason the region’s grizzly bears, who gorge on the fatty fish ahead
of their long, winter nap, often top 1,000 lb.
The creatures that feed on dying salmon carry nitrogen into the forests, fertilizing the
surrounding trees and allowing Sitka spruce to reach more than 20 stories into the sky.
Salmon’s effect on trees is so dramatic that scientists can tell how well a salmon run is
doing simply by looking at the surrounding forest.
It's hard to overstate the importance of this keystone species to trees and wildlife, including
birds, bears, and wolves ... and to coastal peoples for whom the fish are a vital food and cultural touchstone.
Over a few weeks in fall, the Adams turns a deep crimson, in one of the world’s greatest
natural wonders, as the fish flood the river and its tributaries—where they hatched four
years earlier—to spawn, then die.
The 4,000-km journey may be the most extraordinary migration in the natural world.
When they begin migrating upstream, sockeye stop eating and drinking, and grow weak.
Still, the fish somehow power their way against strong currents, leaping up waterfalls and
man made obstacles like dams and fish ladders.
By the time salmon near their journey’s end, they can barely move. Yet even then, the females
hold out, inching their way forward, searching for the perfect patch of gravel, where their eggs
will be protected, and will have a better chance at not being washed downstream.
Of the 5,000 fish who begin this near-impossible journey, just 2,000 will survive.