Fascinating and controversial story by Matthew Preusch in today's print editon of The Oregonian titled, Can salmon evolve to survive among fish-killing dams?
I'm sure salmon can evolve to survive dams, given enough time. The question really is, are they?
Dams hurt salmon, robbing them of free-flowing rivers and confusing them on their celebrated, circuitous life journey.
But maybe the fish can take it.
In the Northwest, more than a billion dollars a year is spent to repair the damage done to salmon by massive hydroelectric dams on the Columbia and Snake rivers. For at least a decade, a debate has raged over whether four of the massive concrete plugs on the Snake should be torn down to help fish protected by the Endangered Species Act. At one point, President George W. Bush even stood atop one of those dams to pledge that wouldn't happen. In the meantime, some salmon appear to have changed in a way that could turn that debate on its head.
The story notes that some fall chinook salmon in the Snake River are delaying their trip to the ocean for up to a year. During that time they grow larger, presumably to better survive the rigors of being a salmon.
The Pacific Northwest's salmon restoration program is one of the world's largest stewardship programs. So could the salmon be saving themselves? Are they truly evolving? Maybe we don't have to spend $1B per year to save them.
Preusch's' story broaches the evolution issue:
But whether that adaptation is merely a response to rapidly changing conditions without any genetic change or true evolution remains an open question, said Robin Waples, senior scientist at NOAA's Northwest Fisheries Science Center in Seattle.
"Both factors are probably involved," Waples said. "That would be my guess."
Waples co-wrote a study last year that examined whether the fall chinook were evolving. In part, he said, they are.
It appears that fish that migrate as yearlings and return to spawn pass along that trait to their offspring.
"There's a possibility that there's strong selection now that favors this life history," he said.
The 50 or so years since the first dams were built on the Snake means about 12 generations of fish, enough time for natural selection -- the engine of evolution -- to take its course, Waples said.
Some prominent fish experts disagree with that conclusion, including Howard Schaller, head of the U.S. Fish and Wildlife Service's Columbia River Fisheries Program Office.
"We have to wait and see over a longer period time," Schaller said. "It's an interesting piece of information, but there's a lot of uncertainty."
If the salmon are truly adapting and transmitting these traits to their offspring, then that begs the question: what happens to them if and when the dams are removed?
That could be the $1B question.
"If that system becomes natural again, they may not react well to that." -- William Connor, U.S. Fish and Wildlife Service biologist (quoted in the story)