The building of Madison Dam on the Madison River formed Ennis Lake. This 4800-acre lake is quite shallow and often gets very warm during the height of summer, which limits trout populations and can hinder fishing.
The lake itself essentially divides the Madison River. Downstream from the dam is the Beartrap Canyon stretch of whitewater on the Lower Madison River. Upstream from the lake is the prime trout waters of the Upper Madison River.
Despite that, Ennis Lake has some large rainbow and brown trout. The larger fish inhabit the lakes deeper holes. Unfortunately, locating these holes on the moderate sized lake can be a challenge without a depth finder or someone knowledgeable about the lake. Large streamers on sinking lines are the best choice for catching these larger trout.
Other fish species in the lake include brook trout, mountain whitefish and grayling.
Ennis Lake receives a surprising amount of fishing pressure. To avoid the crowds, plan to fish during the off-season or during weekdays. On weekends, many pleasure boaters make their way to the lake.
Access to the lake is adequate, with a decent fishing access site and boat ramp available on the western side of the lake near the town of Ennis.
Although Ennis Lake is not a massive reservoir, it is still fairly sizable and often gets windy. As such, a motorized powerboat is the boat of choice for fishing the lake. However, if wind conditions allow, good paddling boats such as inflatable kayaks for lake paddling, inflatable canoes and pontoon boats work well.