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Montana Field Guide

Montana Field Guides

Peamouth - Mylocheilus caurinus

Global Rank: G5
State Rank: S5

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General Description
The peamouth is a native minnow that is found in lakes and the slow waters of rivers west of the Continental Divide in Montana. Its common name probably refers to its small mouth. Specimens can get quite large, up to 14 inches. Unfortunately, at this size they are not likely to be preyed upon and so do not contribute to the food base of predatory sport fishes. Peamouth are unusual in that they can tolerate diluted sea water. This feature has allowed them to colonize some inshore islands off the coast of western North America. Peamouth are schooling fish that feed on aquatic insects and bottom organisms. They can be caught readily on small bait.

Diagnostic Characteristics
Dark on back and silvery below; two dusky stripes along side; reddish at corners of mouth. Breeding fish have red midside stripe. Small barbel at each corner of mouth.

Species Range
Montana Range

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Western Hemisphere Range


Summary of Observations Submitted for Montana
Number of Observations: 4996

(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)

Shallow weedy zones of lakes or rivers.

Food Habits
Young feed mainly on micro-crustaceans. Adults eat micro-crustaceans, snails, adult aquatic and terrestrial insects. Occasionally small fish.

Peamouth x Northern Pikeminnow and Peamouth x Redside Shiner hybrids have both been found in Montana. Increased from rare to abundant upstream from Libby dam with damming of the Kootenai River.

Reproductive Characteristics
Sexually mature in 3 yrs. (mostly males) or 4 yrs. Spawns May - June at water temps. of 54-64 degrees F. Eggs stick to rocks or other substrates.

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Citation for data on this website:
Peamouth — Mylocheilus caurinus.  Montana Field Guide.  .  Retrieved on , from