The kokanee operation here is one of many. Across Colorado, state biologists introduce 76 million fish a year into rivers and reservoirs.

Most of the fish in Colorado lakes and reservoirs, said Division of Wildlife spokesman Randy Hampton, are non-natives that require human management to survive.

Artificial spawning and stocking "is an important tool, but it is not a substitute for having healthy habitats and healthy trout," said David Nickum, director of Colorado Trout Unlimited, an ecosystem advocacy group.

Colorado River, greenback and Rio Grande cutthroat trout are the only native game fish in the state. Other native fish include razorback suckers, the humpback chub and the Colorado pikeminnow, bottom-feeders that need the warmer pools that form along free-flowing rivers.

"We want to make sure there are good, healthy native populations, especially of those cutthroats," Nickum said.