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Montana Field Guide

Montana Field Guides

Rainbow Smelt - Osmerus mordax

Non-native Species

Global Rank: G5
State Rank: SNA

Agency Status


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General Description
Montana has one member of the smelt family, courtesy of North Dakota. The rainbow smelt was introduced into Garrison Reservoir in 1971 as a forage fish for sport fishes. In 1979 it was first collected in eastern Montana below Fort Peck Dam. Its adipose fin and strong canine teeth make this species easy to identify. Rainbow smelt are spring broadcast spawners. They live in lake waters most of the time but run into streams to spawn. This species supports a commercial fishery in the Great Lakes, and a sport fishery in the tributaries when they make their spawning runs. Rainbow smelt eat insects, crustaceans and, as adults, fish. It is this latter feature that makes them undesirable as a forage fish. Their maximum size is about 10 inches in length. They are only occasional Montana residents.

Diagnostic Characteristics
Silvery with pink and purple iridescence, greenish or black. Smelts are small, slender fishes with an adipose fin and no pelvic axillary process. Scales thin and easily rubbed off. Spawning males feel like sandpaper due to numerous small nuptial tubercles on head, body and fins.

Species Range
Montana Range Range Descriptions


Observations in Montana Natural Heritage Program Database
Number of Observations: 12

(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)

Spawning runs up Missouri and Yellowstone River from Garrison reservoir North Dakota.

Found in cool-water lakes and associated tributary streams. Usually spawn in streams but also over shallow gravel deltas near shore.

Food Habits
Adults in Great Lakes eat mostly larger crustaceans. May consume many fish in inshore waters. Virtually stop feeding during spawning season. Cannibalistic.

It is probable the majority of smelt found in state occur as seasonal spawning runs from Garrison reservoir North Dakota though a few are collected all year long in dredge cuts below Ft. Peck dam.

Reproductive Characteristics
Spawns in 2 weeks from late March-early May when water temperatures reach 40 degrees F. or higher, shortly after ice-out. Broadcasts spawn. Incubation: 20-30 days at prevailing temperatures. Sexually mature in 2-3 years in Lake Superior.

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Citation for data on this website:
Rainbow Smelt — Osmerus mordax.  Montana Field Guide.  .  Retrieved on , from