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Montana Field Guide

Montana Field Guides

Largescale Sucker - Catostomus macrocheilus

Native Species

Global Rank: G5
State Rank: S5

Agency Status


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General Description
The largescale sucker is native to Montanas western drainage. Like the previously mentioned suckers, it is present in both rivers and lakes. In Montana, the maximum size in this species is usually less than 5 pounds. The food habits of largescale suckers are similar to those of other suckers.

Diagnostic Characteristics
Back and sides dark olive gray, changing abruptly to white or yellowish on underside. Dorsal fin usually has 13 to 15 rays, its base is long. Scales are medium sized, 62 to 80 in lateral line.

Species Range
Montana Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 1333

(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)

Upstream migration accompanies spawning.

Found in both streams and lakes. Spawns in gravel riffles with strong current or along lake margins (Brown 1971, Huston et al. 1984, Weisel 1957).

Food Habits
Eats almost any available organism found on the substrate (Brown 1971).

Have decreased in abundance below Libby dam due to colder water temperatures delaying spawning (May and Huston 1979). Young rear in quiet backwaters or lakes.

Reproductive Characteristics
Sexually mature in 4-5 years - some males in 3 years. Spawns April - May. No parental care. Eggs stick to bottom and hatch in 2 weeks (Brown 1971).

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