Montana’s aquatic ecosystems, ranging from high-mountain alpine lakes to vast prairie reservoirs and famed freestone rivers, support a wide array of fish species. The fish found here represent a mix of native species that have lived in these waters for millennia and introduced species that have successfully established thriving populations. This variety provides angling opportunities across environments, from cold-water streams to warmer, slower-moving impoundments.
The Iconic Trout Species of Montana
Montana’s global reputation as a premier fishing destination is built largely on its robust populations of cold-water trout. These species thrive in the state’s clear, oxygen-rich rivers and streams, each exhibiting distinct preferences for habitat and feeding behavior.
Rainbow Trout are celebrated for their strong, acrobatic fight, making them a favorite among fly anglers across the state. They are recognized by the broad, pink-to-red stripe running along their sides and are widely distributed, flourishing particularly well in the nutrient-rich tailwater sections of large rivers, such as the Missouri River. These fish are generally insectivores, but larger specimens will consume smaller fish and crustaceans, contributing to their impressive growth potential.
Brown Trout, introduced from Europe, are prized for their size and elusive nature. They prefer slower, deeper water with ample cover, such as undercut banks and submerged logs, and frequently feed nocturnally. They have a characteristic olive-brown back and yellowish sides with dark spots, some of which are surrounded by light halos.
Brook Trout are smaller on average but display striking coloration, featuring a dark green back with worm-like markings and bright red spots surrounded by blue halos. These fish are typically found in cold, small, high-elevation streams and mountain ponds, often near the headwaters. Brook Trout tend to overpopulate in confined environments, which can result in stunted growth, though trophy-sized fish are found in larger, productive lakes.
Cutthroat Trout are the state’s only native trout, identifiable by the distinctive red or orange slash mark beneath their lower jaw. They are highly sought after by anglers for their willingness to rise to a dry fly, especially in the state’s remote, pristine wilderness waters. Though they do not typically reach the size of Rainbow or Brown Trout, their presence signifies a healthy, undisturbed stream environment.
Major Warm Water and Reservoir Game Fish
Moving away from the cold, fast-flowing rivers of western Montana, the state’s large reservoirs and eastern prairie waters host a different suite of popular game fish. These species thrive in the warmer, more turbid conditions of these vast impoundments, providing a different type of fishing experience.
Walleye are one of the most highly targeted fish in these eastern waters and are known for their delicate white flesh. These fish are primarily found in large reservoirs like Fort Peck, Canyon Ferry, and Tiber Reservoir, where they often congregate around underwater structure and rocky points. Walleye are visually adapted to low light, making them most active at dawn, dusk, or in deeper, turbid waters.
Northern Pike are apex predators recognizable by their long, torpedo-like bodies and sharp teeth. They are widespread across Montana’s lakes and reservoirs, where they are ambush hunters, lurking in dense vegetation and slow-moving backwaters. Pike are non-native in most of the state and are often managed with liberal harvest regulations due to their predatory impact on other species.
Smallmouth and Largemouth Bass are non-native species that have established strong populations in the warmer, lower-elevation lakes and reservoirs in the western and central parts of the state. Smallmouth Bass, known for their powerful fight, are common in the Clark Fork River and Noxon Reservoir, preferring rocky shorelines and clear water. Largemouth Bass are more often found in the weed-choked bays of lakes like Echo Lake and the Tongue River Reservoir, using the aquatic vegetation for cover.
Kokanee Salmon, the landlocked form of sockeye salmon, are popular game fish found in many of the state’s large, cold-water lakes and reservoirs. These plankton-feeding fish are a schooling species and are commonly targeted in places like Flathead Lake and Lake Koocanusa. Kokanee typically average around one pound but offer fast-paced action, with their size being heavily dependent on the available food supply.
Native, Threatened, and Unique Aquatic Species
Montana’s aquatic life includes several unique native species that hold significant conservation status due to habitat loss and competition from introduced fish. These species are indicators of the health of the state’s most pristine waters.
The Bull Trout, a native char, is listed as a threatened species under the Endangered Species Act and is found west of the Continental Divide in the Flathead and Clark Fork drainages. This fish requires the coldest, cleanest water of any trout species in the state, with complex habitats featuring deep pools and large woody debris. Conservation efforts focus on suppressing non-native competitors and restoring habitat connectivity to allow for their long-distance spawning migrations.
The Westslope Cutthroat Trout, the state fish, has seen its genetically pure populations reduced to less than 10% of their historic range. The primary threats are hybridization with non-native Rainbow Trout and habitat degradation. Efforts to protect them involve establishing populations in isolated headwater streams above barriers to prevent mixing with non-native species.
The Arctic Grayling has the last remaining river-dwelling (fluvial) population in the contiguous United States located in a restricted stretch of the Big Hole River. Grayling are easily identified by their strikingly large, sail-like dorsal fin, which is often edged with red and iridescent spots. While the river population is rare, the lake-dwelling (lacustrine) form has been successfully introduced into several alpine lakes.
The Paddlefish, sometimes called a “living fossil,” is an ancient, cartilaginous filter feeder that can weigh over 100 pounds. This unique species is native to the Missouri and Yellowstone River systems, with a significant population in Fort Peck Reservoir. They use their long, paddle-shaped snout, or rostrum, to detect zooplankton, which they filter from the water with specialized gill rakers.
Non-game fish like Suckers, including the Longnose and White Sucker, play an important role in the ecosystem. These bottom-feeding fish convert detritus, algae, and insects into fish protein. Their massive spring spawning runs produce millions of eggs that become a primary food source for game fish and other aquatic life, contributing significantly to the overall health of Montana’s rivers.