Beginning near Halloween, staff check fish for sexual maturity. For the next 5 months the crew will spawn fish as they become ripe. Fish are first moved into the spawning house where they are anesthetized for easier handling. Ripe fish are placed on the sorting table, where one by one they are air spawned. The air spawning method involves inserting a needle in the females's abdomen to create pressure, pushing the eggs out for fertilization with sperm (milt) collected from a male fish. Milt is collected separately and added to eggs collected in the hatchery building. After fertilization, eggs undergo the triploid (PDF) process and are then placed into vertical flow incubator stacks, where they will continue to develop into fish.
After roughly 35 days the egg will develop eyes. At this point most eggs are shipped, or moved into a hatching jar.
Thirty more days and fish will begin to hatch. These times vary with water temperature. Mount Shasta Hatchery has cold water and it takes longer for eggs to hatch into fish.
After hatch, fry develop in the hatchery troughs until they are large enough to either be stocked into approved backcountry waters by airplane or pack animal (horse or mule), or are raised to larger "catchable" size for truck stocking to local waters.
Rainbow trout (Shasta strain) and Eagle Lake trout are planted as fingerlings by air and mule, and as catchable-sized fish to roadside waters by truck.
Every year approved lakes are stocked by air to waters inaccessible by vehicle.
During the spring and summer months Mount Shasta Hatchery stocks catchable trout in approved local waters by truck.