In a stunning display that marks a swelling comeback of the sockeye salmon population, at least 41,000 of the fish swam over a dam in the northwest United States’ Columbia River Basin on Wednesday.
That was just in one day.
Since 1938, when the Bonneville Dam was built just outside Portland, many years went by when the total number of salmon to swim over the fish ladders never reached 38,000. In 1995, the area saw fewer than 9,000 salmon over the whole year.
Wednesday’s record number of 41,000 salmon adds to the number of salmon that have returned so far this year, bringing the current total to 290,000. Experts predict the total number of the once-fading salmon will reach a record run of 400,000 this year.
“Right now those fish are utilizing maybe a quarter of their historic habitat,” said Joe Peone, fish and wildlife director for the Confederated Tribes of the Colville Indian Reservation in an interview with CBS News. “If more habitat is restored, you could see a million fish coming back here.”
Most of these salmon are wild fish bred in rivers and not hatcheries. The sockeye salmon is the Columbia Basin’s farthest-swimming salmon. They cross nine dams before they reach spawning grounds in northern Washington and Canada.
Biologists believe that improved dams, favorable ocean conditions and restored habitat in the Okanagan River Basin are the cause for the sockeye salmon resurgence. The Okanagan River Basin drains into the Columbia River.
Okanagan sockeye salmon were never listed as endangered, but Snake River sockeye in Idaho were listed. In the early 1980s and 1990s the future was looking especially bleak for Okanagan salmon, when only 9,000 of them returned to the Columbia Basin.
Hydroelectric dams would regularly wash out sockeye eggs after the fish laid them in the water, otherwise they were left high and dry before they hatched. This species was especially difficult to raise in hatcheries, which decimated the population.
Tribes on both sides of the Canadian-American border recognized this problem and teamed up with the local utilities that owned the dams to solidify rules for maintaining a viable flow of water for the fish. The improved dam operations have benefited not only sockeye salmon, but chinook, coho, chums, pinks and steelhead, according to Ritchie Graves, NOAA Fisheries Service biologist.
Combined, the six species had 1.8 million salmon swim over the Bonneville dam in 2010, compared to 1938′s number of 471,144.
Image from KSI Photography on the flickr Creative Commons