BOISE, Idaho (AP) — A utility's survey indicates the population of white sturgeon fish in the Snake River between a dam on the Idaho-Oregon border and another in western Washington state is holding steady from 14 years ago.

North America's largest freshwater fish, which dates to the dinosaurs, number about 4,000 in a 140-mile stretch of river between the dams. That tally counts fish measuring 2 ½ feet or longer. Idaho Power is required to monitor numbers of sturgeon as part of its federal license to operate three hydroelectric projects in Hells Canyon.

The utility's three-year survey ends in September. Experts say dams on the Snake River have isolated populations of sturgeon that historically moved up and down the river, reduced food sources and made water temperatures colder below Hells Canyon Dam.