Montana’s diverse landscapes host a rich array of aquatic life. Its varied aquatic environments, from pristine mountain streams to expansive prairie reservoirs, support remarkable fish biodiversity. Over 90 distinct fish species inhabit Montana’s waters, including 31 sought by anglers and 59 non-game species. This extensive range contributes to Montana’s reputation as a premier fishing destination, offering unique opportunities.
Coldwater Fish of Mountain Rivers and Streams
Montana’s cold, clear, oxygen-rich mountain rivers and streams provide ideal conditions for various coldwater fish species. Rainbow Trout, introduced to Montana in 1889, thrive in these waters and are known for their spirited fights. While most populations were introduced, a small native population exists in the Kootenai River drainage. These adaptable fish feed on plankton, aquatic insects, and sometimes smaller fish.
Brown Trout, originally from Europe, were introduced to Montana in the late 1800s. They can inhabit larger, slower-moving rivers, streams, and even reservoirs, showing a greater tolerance for warmer, murkier conditions than some other trout species. Larger brown trout are predatory, often feeding on other fish and crayfish, particularly at night.
Montana is home to two native Cutthroat Trout subspecies: the Westslope and Yellowstone Cutthroat. The Westslope Cutthroat, Montana’s official state fish, historically ranged across the state west of the Continental Divide and in the upper Missouri River drainage. Yellowstone Cutthroat Trout are indigenous to the Yellowstone River basin. Both subspecies require cold, clear water and utilize gravel substrates for spawning.
Brook Trout, introduced from eastern North America, favor small, cold, spring-fed headwater streams and ponds. These fish are identifiable by their distinctive vermiculated patterns on their backs and fins with white leading edges. While abundant in many areas, overpopulation can sometimes lead to stunted growth in certain high mountain lakes.
The Arctic Grayling is a unique native coldwater species, with Montana hosting the last remaining native fluvial, or river-dwelling, populations in the contiguous United States, primarily in the Big Hole River. These fish possess a prominent, sail-like dorsal fin and inhabit cool-water streams and pools. Lake-dwelling populations are also found in numerous lakes across western Montana.
Mountain Whitefish are native to Montana and commonly found in cold, clean rivers and some lakes, sharing habitats with trout. They are members of the salmon family, identified by their slightly larger, silvery scales and an overhanging snout used for rooting out aquatic insects from the riverbed. Mountain Whitefish are an indicator of healthy freestone fisheries.
Warmwater Fish of Prairies and Reservoirs
Montana’s eastern plains, larger reservoirs, and prairie rivers offer warmer, often slower-moving waters that support a different suite of fish species. Northern Pike are common predatory fish found in these warmer river sections and reservoirs.
Smallmouth Bass, though not native to Montana, have established populations in various waters. They are often found in reservoirs like Fort Peck and Tongue River, preferring clear, cool water with rocky substrates. Smallmouth bass are adaptable, predatory, and have expanded their range into some of Montana’s major rivers.
Largemouth Bass are warmwater fish, thriving in temperatures up to 90 degrees Fahrenheit. They typically inhabit clear, vegetated lakes, ponds, and quiet backwaters. These aggressive feeders are found in areas like Flathead Lake, Tongue River Reservoir, and Fort Peck.
Channel Catfish are native to Montana and significant for recreational anglers. They are primarily found in the Yellowstone and Missouri River drainages. These catfish reproduce during spring or early summer, with specimens weighing 2-4 pounds being common catches.
Unique and Lesser-Known Species
Beyond popular game fish, Montana’s aquatic ecosystems are home to several unique and lesser-known species that play important ecological roles. The Paddlefish, with its distinctive long, paddle-shaped snout, is notable for its prehistoric appearance and filter-feeding behavior.
Native suckers, such as the Longnose Sucker, are prevalent throughout Montana’s waters. While not typically targeted by anglers, these fish are important forage for larger predatory fish and indicate overall ecosystem health. Their feeding habits often involve consuming detritus and small invertebrates from the river bottom.
Various native minnow species, including the Creek Chub and Fathead Minnow, are found across the state. These small fish are crucial components of the food web, providing a primary food source for many larger fish. They are often found in prairie streams and other shallow water habitats.
The Pygmy Whitefish is a rare native species discovered in deep, cold-water glacial lakes in Northwest Montana, including Tally Lake and Big Salmon Lake. These small salmonids are considered a “Species of Concern” in Montana, serving as an important food source for native bull trout and westslope cutthroat trout. Their presence helps biologists understand coldwater food web dynamics.