North America's largest freshwater fish population living between a dam on the Idaho-Oregon border and another in western Washington state was holding steady from 14 years ago, according to data from an Idaho utility's survey.

White sturgeon number about 4,000 in a 140-mile stretch of the Snake River between Hells Canyon Dam and Lower Granite Dam. That tally counts fish measuring 2 ½ feet or longer, according the Associated Press, citing the survey.

Idaho Power is required to monitor numbers of sturgeon there as part of its license to operate three hydroelectric projects in Hells Canyon, according to AP.

Preliminary information from the utility's three-year survey that ends in September shows the population is around the same as found by a study 14 years ago, Idaho Power fisheries biologist Brandon Bentz said in a statement.

Dams on the Snake River have isolated populations of sturgeon that historically moved up and down the river. They have even entered the Columbia River and reached the Pacific Ocean, according to AP.

The dams also reduced food sources like salmon, lamprey, and steelhead, and made water temperatures colder below Hells Canyon Dam.

The toothless, bottom-dwelling fish can weigh more than 1,500 pounds, and reach 12 feet. White sturgeon can be linked all the way back to the dinosaurs, and feature rows of armor projects along their bodies.

Sturgeon eat bottom-dwelling worms, clams, mussels and crayfish, according to AP.

The stretch of river from Hells Canyon Dam to Lower Granite Dam is a favorite among sturgeon anglers, said Jeff Dillon, fisheries manager for Idaho Fish and Game, according to AP.

"For one, it's just fascinating to catch a fish that's probably older and bigger than you are," he said. "And they're prehistoric fish. The other part of it, especially in Hells Canyon, is fishing for sturgeon takes you to really amazing places."

The Snake River has two self-sustaining populations of sturgeon. One is located in Hells Canyon and the other is the section of river between Bliss Dam and C.J. Strike Dam in southern Idaho, Bentz confirmed.

There isn't much known about sturgeon between Hells Canyon Dam and Lower Granite Dam. 

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