Until the early 1970's, it was believed the best way to maintain good fishing in rivers and streams was to stock trout. Consequently, most major rivers and streams were stocked by the Montana Department of Fish, Wildlife and Parks every year, usually with 5-10 inch rainbow trout. This practice was halted in the early 1970's after studies on the Madison River and elsewhere showed that stocking hatchery trout in rivers and streams usually made fishing worse because the hatchery fish did not survive very long, but in the meantime they chased out the wild trout. As a result, Montana adopted a management policy that emphasizes naturally reproducing wild trout and very few rivers or streams are stocked nowadays. On the other hand, it is well known that trout do not reproduce well in many lakes and reservoirs. Therefore, stocking of hatchery trout became more focused on these waters and annual stocking of many lakes and reservoirs continues to this day.
