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Not Even An 'Extinction Vortex' Could Stop These Incredible Survivor Salmon

<p><a class="checked-link" href="http://commons.wikimedia.org/wiki/File:Adult_sockeye_salmon_encounter_a_waterfall_on_their_way_up_river_to_spawn.jpg" style="text-decoration: none;">Marvina Munch, U.S. Fish and Wildlife Service/Wikimedia</a></p>

Snake River sockeye salmon swim 900 miles - that's about 100 miles longer than the drive from Chicago to New York - in an annual migration to the sea. But in an equally remarkable journey, these endangered fish are one of the few animals to have escaped the downward pull of a so-called "extinction vortex," the point at which researchers believe a species' population has dipped so low extinction appears inevitable. (By definition, most species in such a vortex do not survive - the Hawaiian crow, for instance, is extinct in the wild.)

Though their immediate ancestors were fish raised in hatcheries, wild-born Snake River sockeye are once again completing their impressive voyages, the National Oceanic and Atmospheric Administration announced Monday. "This is a real American endangered species success story," said Will Stelle, an administrator of NOAA's fisheries, in a statement. "With only a handful of remaining fish, biologists brought the best genetic science to bear and the region lent its lasting support."

Sockeye and most other salmon species are born in freshwater, and then head to the salty ocean to grow fat. These fish make a return at the twilight of their lives to lay and fertilize the next generation in the same areas where they were born. How salmon - born either in hatcheries or in the wild - know how to make it to the ocean from their freshwater birthing grounds is one of nature's greatest mysteries. As ichthyologists at the U.S. Geological Survey write, "it must be a genetic clue," but how those genes guide the salmon to the sea is still anyone's guess.

By the early ‘90s, a gauntlet of dams made it nearly impossible for Snake River sockeye to complete their journey. In 1992, there was a single fish - affectionately named "Lonesome Larry" - who made it back to Redfish Lake. None of his other companions had completed the journey.

Around the same time, conservationists had captured 16 fish as part of a recovery program. From this salmon handful would spring 3.8 million hatchery-raised eggs; their children's survival rate would rise to 2,000 percent greater than what could have been achieved in the wild.

NOAA's new report found that wild-born salmon - the offspring of those fish raised by humans - have adopted the wanderlust ways of their forbears. These salmon are returning to spawn in Redfish Lake at three to 10 times the rate of their hatchery-born counterparts, exceeding expectations.

"We hoped we could get returns equivalent to what you'd expect to see from a hatchery," said Thomas Flagg, a researcher at NOAA's Northwest Fisheries Science Center. "We've seen the population respond even better than that, which bodes well for the idea that the lakes can produce the juveniles you'd want to see to get to recovery."

Considering the lackluster results of other salmon hatchery programs, the success of the Snake River sockeye is even more impressive. When Atlantic salmon failed to return to the Connecticut River, the U.S. Fish and Wildlife Service put the salmon hatchery program on hold after 40 years of effort in the northeast.

Salmon redds, or spawning nests, have shown a steady increase in Redfish Lake.

For the Snake River sockeye salmon, though, the long-distance future is a little brighter. "Now there is real potential that this species will be self-sustaining again," Stelle said. "The sockeye didn't give up hope and neither did we."

Salmon footage via the National Oceanic and Atmospheric Administration.