Big Springs Trout Hatchery is the largest coldwater production hatchery in Montana, capable of producing up to two million fish annually weighing 160,000 pounds. These fish are planted in about 100 different waters throughout the state. Species of trout and salmon raised at the hatchery vary year to year but may include different strains of Rainbow, Yellowstone Cutthroat, Grayling, Brown Trout, Chinook salmon and Kokanee salmon. No fish are spawned at this hatchery. Instead, eggs are received from other Montana state and federal hatcheries and from some wild sources.
The upper unit has egg incubation and indoor raceways where eggs are hatched. Typically, fish are raised inside to about two inches and then moved into outdoor raceways at the upper or lower unit for more growth. The size of fish stocked ranges from one to twelve inches but averages between four and eight inches depending on what the biologists want. Stocking starts in April and continues through July, then again in September through October.
The hatchery grounds are open to the public every day of the week, dawn to dusk. The public can view fish in the raceways but are encouraged not to feed or bother the fish. There is a circular display pond at the upper unit where people can buy a handful of fish food and feed these fish. The City of Lewistown maintains a park adjacent to the upper unit. This park has a baseball field, shaded picnic area and the beautiful spring area. Wildlife viewing includes deer and other small mammals and a variety of birds.