While many Wyoming fish hatcheries do their spawning in the spring, the Boulder Hatchery south of Pinedale spawns their rainbow trout in the fall. They are the only Wyoming hatchery to spawn rainbows in the fall and have been doing so since 1958. The benefit of the unique fall-spawning rainbows is simply to afford managers another option of fish that matures, and therefore can be stocked, at a different time of year. 

Every Tuesday morning at 7:00am, for several consecutive weeks this time of year, the Boulder Hatchery crew collect eggs from mature females and milt from male rainbows to fertilize hundreds of thousands of eggs. After about a year's growth (6-12 inches), the fish will be stocked in Wyoming waters statewide. Some of the fish may be traded to other states for other species of fish. 

After spawning, a portion of the brood fish are retired and stocked to various Wyoming waters. This year, the hefty mature rainbows were stocked in nearby Boulder Lake as well as Upper North Crow Reservoir and Sloan Lake near Cheyenne.