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Montana Field Guide

Montana Field Guides

Fathead Minnow - Pimephales promelas

Native Species

Global Rank: G5
State Rank: S4S5
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
Currently ranked a S5 because it is common, widespread, and abundant (although it may be rare in parts of its range). Not vulnerable in most of its range.
General Description
The fathead minnow is another native inhabitant in both ponds and streams of the prairie ecoregions of Montana. They are an indicator species of the core prairie fish assemblage found in the Intermittent and Perennial Prairie Stream Aquatic Ecological Systems. This fish also has a limited distribution west of the Divide in Montana, but it is not native to that drainage. This species has been reared throughout the U.S. for use as a forage and bait fish. The reproductive behavior of the fathead minnow is unlike that of most of the minnows which broadcast their eggs and give them no parental care. Fatheads deposit adhesive eggs on the undersides of rocks and logs, and males guard the eggs during their incubation period. The breeding males form small, bony bumps called tubercles on their snouts. These serve no apparent purpose but may be a sign of beauty or prestige in the fish world. The largest fatheads are about 4 inches long. Fatheads can tolerate very low oxygen levels and a wide variety of temperatures. They utilize a wide variety of foods.

Diagnostic Characteristics
Back dark olive or brown, sides dusky, pale below. Young are lighter and have a dark midside band. Breeding males nearly black with two light blotches. Body of adult is stout. Lateral line usually incomplete. Scales ahead of dorsal fin are small and crowded. First ray of dorsal fin is short, thick and blunt - not easily seen on females and young.

Species Range
Montana Range

All Ranges
(Click legend blocks to view individual ranges)

Western Hemisphere Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 2284

(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)

Habitat is highly variable but found mostly in small turbid creeks and shallow ponds of flatlands. Very tolerant of extreme conditions found in a prairie environment (turbid water, high temperature, and low dissolved oxygen).

Food Habits
Food consists of a variety of minute aquatic plants and animals.

Two years is the usual longevity for this species.

Reproductive Characteristics
May reach sexual maturity during 1st growing season. All are mature after 1 yr. Spawns May - Aug. when water temperatures exceed 60 degrees F. Incubation: 4-6 days.

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Citation for data on this website:
Fathead Minnow — Pimephales promelas.  Montana Field Guide.  .  Retrieved on , from