Spawning operations underway at Ten Sleep Fish Hatchery Cody – The month of February marks the beginning of a busy time for Ten Sleep Fish Hatchery. The Wyoming Game and Fish facility located on the west slope of the Bighorn Mountains near Ten Sleep is home to one of only two captive broodstocks of Yellowstone cutthroat trout in the country. In late winter each year, spawning operations for this broodstock begin. Once a week over a two-month time frame, crews sort fish and select 3 and 4-year-olds that are ready to spawn. Eggs are then collected from female fish and milt from male fish. By early spring, approximately 1,100 adult female Yellowstone cutthroat trout will be spawned.