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Montana Field Guide

Montana Field Guides

Peamouth - Mylocheilus caurinus

Native Species

Global Rank: G5
State Rank: S5

Agency Status
USFWS:
USFS:
BLM:


 

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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

Year-round

Western Hemisphere Range

 


Observations in Montana Natural Heritage Program Database
Number of Observations: 567

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

Recency

 

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



Habitat
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.

Ecology
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.

References
  • Additional ReferencesLegend:   View Online Publication
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    • Craig, V.E. 1952. A story of fish production as it applies to Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 92 p.
    • Hill, C.W. 1958. Observations on the life histories of the Columbia River chub and Columbia squawfish in western Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 29 p.
    • Nelson, M.L. 1999. Evaluation of the potential for resident bull trout to reestablish the migratory life-form. M.Sc. Thesis. Bozeman, MT: Montana State University. 72 p.
    • Rahrer, J.F. 1963. Age and growth of four species of fish, Flathead Lake, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 16 p.
    • Sylvester, R. and B. Marotz. 2006. Evaluation of the Biological Effects of the Northwest Power Conservation Council's Mainstem Amendment on the Fisheries Upstream and Downstream of Hungry Horse and Libby Dams, Montana. Montana Fish, Wildlife, and Parks Annual Report prepared for U.S. Department of EnergyBonneville Power Administration. Bonneville Power Administration Project No. 2006-008-00 Contract No. 28350. 124 p.Contract No. 28350
    • Sylvester, R. and B. Stephens. 2011. Evaluation of the physical and biological effects of the Northwest Power Conservation Council's Mainstem Amendment upstream and downstream of Libby Dam, Montana. Libby, MT: Montana Fish, Wildlife, and Parks Annual Report prepared for U.S. Department of Energy Bonneville Power Administration. Bonneville Power Administration Project No. 2006-008-00, Contract Nos. 43309 and 48555. 282 p.
    • Sylvester, R., A. Steed, J. Tohtz, and B. Marotz. 2008. Evaluation of the Biological Effects of the Northwest Power Conservation Council's Mainstem Amendment on the Fisheries Upstream and Downstream of Hungry Horse and Libby Dams, Montana. Montana Fish, Wildlife, and Parks Annual Report prepared for U.S. Department of EnergyBonneville Power Administration. Bonneville Power Administration Project No. 2006-008-00 Contract No. 28350. 124 p.Contract No. 28350
    • Sylvester, R.M., B.C. Stephens, and J.T. Frye. 2014. Mainstem Columbia Amendments Research at Libby Dam - Evaluation of the Physical and Biological Effects of the Northwest Power Conservation Council's Mainstem Amendment Upstream and Downstream of Libby Dam, Montana. Libby, MT: Montana Fish, Wildlife, and Parks Annual Report prepared for U.S. Department of Energy Bonneville Power Administration. Bonneville Power Administration Project No. 2006-008-00. 461 p.
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Citation for data on this website:
Peamouth — Mylocheilus caurinus.  Montana Field Guide.  .  Retrieved on , from