A federal recovery team monitored release of 75,000 white sturgeon larvae in northern Idaho's Kootenai River for clues to what undermines reproduction of the endangered species. The larvae, 1 to 4 days old at release June 12, were raised in the Kootenai Tribe's hatchery to boost sturgeon stocks, in decline since Libby (Mont.) Dam was built upstream in the mid-1970s. There are estimates of 1,400 adult sturgeon in the river in 1997, nearly all 25 years or older. The fish typically lives up to 100 years. For nine years, the Bonneville Power Administration increased water releases from the dam in spring to help improve spawning conditions - delayed this year for the larval release. Tribal and state fisheries biologists captured adult sturgeon to promote hatchery production before they are released. It has been difficult for researchers to find wild juvenile fish - only 15 have been captured since 1991, tribal fisheries biologist Sue Ireland said. "We don't know if eggs are being covered over by sediment and suffocating or potentially hatching but the productivity of the river has changed, and there may not be the right food items available for them." Experts also speculate natural predators have an advantage in the new river environment and gobble up all the larvae.