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Montana Field Guide

Montana Field Guides

Smallmouth Bass - Micropterus dolomieu

Non-native Species

Global Rank: G5
State Rank: SNA

Agency Status


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General Description
The smallmouth bass has been called "pound for pound the best fighting game fish alive." Smallmouth are native to eastern central North America but were widely propagated in hatcheries and planted as early as the mid-1800s. They were first transplanted to Horseshoe Lake near Bigfork in 1914 and are still being introduced in selected locations by the Department of Fish, Wildlife and Parks. Smallmouth bass are primarily a stream fish but are also doing well in reservoirs like Fort Peck and Tongue River where specimens over 5 pounds have been taken. Smallmouth are spring, nest-building spawners. Due to erratic spring weather, nesting failure in Montana is not unusual. Smallmouth bass eat insects, frogs, crayfish, and fish.

Diagnostic Characteristics
Length of longest dorsal spine is less than twice the length of the longest dorsal spine at notch. Young have tricolored tail fin with yellow or orange innermost, a dark vertical band in center, and a whitish outer edge.

Species Range
Montana Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 1657

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Tongue River bass show two major movements: spawning migration in April-May & downstream migration in Sept.-Oct.

Prefers clear cool water and rocky substrates in both rivers and lakes. In streams, it prefers riffle areas with clean bottoms. In lakes, it prefers rocky shorelines, reefs, outcroppings, gravel bars, etc.

Food Habits
Feeds on most available item. Fry feed on zooplankton and small mayflies. Adults feed heavily on fish, frogs, and aquatic invertebrates. Seems to prefer crayfish, if available.

Young of year use backwaters as rearing areas. Backwaters and boulder substrates used for resting. 300 cfs recommended for spring migration in Tongue River.

Reproductive Characteristics
Sexually mature in 4 years. Spawns May-June. Tongue River bass spawn late May in average year when water temperatures exceed 60 degrees F. Spawn in backwater areas, usually over gravel Fry disperse about 2 weeks after hatching.

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Citation for data on this website:
Smallmouth Bass — Micropterus dolomieu.  Montana Field Guide.  .  Retrieved on , from