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Montana Field Guide

Montana Field Guides

Mountain Sucker - Catostomus platyrhynchus

Native Species

Global Rank: G5
State Rank: S5

Agency Status


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General Description
The mountain sucker has a more limited habitat than other Montana suckers. It is virtually limited to running waters east of the Divide. It also is the smallest sucker in Montana with its largest specimens having a length of about 9 inches.

Diagnostic Characteristics
Back and upper sides are dusky or dark green with black specks; may have dark mottling shaped like saddles across the back; lower body whitish. Both sexes have a reddish orange band along sides during breeding season; band is brighter, longer, and wider in male. Mouth is so long it sometimes exceeds head width. See Snyder and Muth (1990) for a guide to the identification of larvae and early juveniles. No other Montana sucker has a notch in each corner of mouth.

Species Range
Montana Range


Western Hemisphere Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 626

(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)

Cold, clear streams with rubble, gravel or sand bottoms; sometimes turbid streams but seldom lakes. Found principally in riffle habitat in middle Missouri River study.

Food Habits
Mostly algae, aquatic plants and invertebrates obtain from the cobbles and pebbles from the stream bottom.

Young prefer slower side channels or weedy backwaters. Seldom exceed 6 inches in length as adults.

Reproductive Characteristics
Sexually mature : males in 2 -3 yrs., females in 4 years. Spawns June - July when water temperatures exceed 50 degrees F. Incubation period probably short.

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Citation for data on this website:
Mountain Sucker — Catostomus platyrhynchus.  Montana Field Guide.  .  Retrieved on , from