Pacific lampreys, an eel-like fish species, are passing the Bonneville Dam in droves this year.
The U.S. Army Corps of Engineers reported Monday that lamprey returns are 170 percent higher than averages from the past decade.
On Sept. 18, 63,863 lampreys were tallied during the day compared with the 10-year average of 41,414. Biologists estimate total daily returns are likely soaring upwards of 165,000, as lampreys remain active at night.
Fish managers credit ongoing modifications to fishways as a contributor to the increasing populations, though many factors are involved.
“Although we’re encouraged by this year’s numbers, we know a lot of this is driven by ocean conditions and food availability in the Pacific Ocean,” said Sean Tackley, regional fish policy and program manager, in a statement Monday. “These kinds of years motivate us all to continue to do what we can to help these important fish.”
The species is more than 450 million years old — predating the evolution of trees and dinosaurs.
Similar to other Columbia River fish, its population has been in decline from habitat degradation, passage barriers and rising water temperatures.
The State Wildlife Action Plan identifies Pacific lamprey as a species of greatest conservation need, and the Washington Department of Fish and Wildlife considers the fish a priority species.
