Rainbow Smelt

  • Rainbow Smelt

    (Osmerus mordax)

    The Rainbow Smelt is well known on the Great Lakes but is native to the north Atlantic coastal region of North America and the lower St. Lawrence River watershed. They were stocked in a Michigan lake in 1912 and spread throughout the four upper Great Lakes. They likely spread into Lake Ontario from the Erie Canal, which connected New York to Buffalo in the 1920s. They have also been illegally released in smaller, inland water bodies.

    Within their native range, most Rainbow Smelt spend most of their lives at sea before migrating into freshwater streams to spawn, although there are some landlocked, freshwater populations. Those in the Great Lakes migrate in large schools into streams and along shorelines to spawn during the spring ice breakup. Females release up to 50,000 eggs.

    Rainbow Smelt eat plankton (small animals and plants in the water) and the eggs and young of native fish species.


    Rainbow Smelt are established in the Great Lakes, the St. Lawrence River, the lower Ottawa River watershed and many inland lakes. It has also been introduced to the Hudson Bay watershed, Lake Winnipeg and lakes in northwestern Ontario and Manitoba.

  • Identification

    • Adult Rainbow Smelt average 19 cm in length with a single dorsal fin and a small fleshly fin (adipose fin) near the tail.
    • Their long slim bodies are covered with small and easily detached scales, which are olive green on the back, iridescent purple, pink and blue on the sides and silver on the belly.
    • The mouth is large with a protruding jaw and large teeth on the roof of the mouth and tongue.
    • Although Rainbow Smelt look like fish in the minnow family (Cyprinidae), Whitefish (Coregonus clupeaformis) and Cisco (C. artedi), minnows do not have adipose fins or large teeth and Whitefish and Cisco have deeper bodies and do not have teeth on the roof of their mouth and tongue.


    • Rainbow Smelt compete with native species for plankton, disrupting food webs.
    • Smelt predation on the eggs and young of native fish species has contributed to reductions of populations of native fish species.
    • Great Lakes smelt have tested positive for the enzyme thiaminase, which destroys one type of Vitamin B and causes mortality in the eggs and young of some native fish species.

    How can you help?

    • Learn to identify Rainbow Smelt and how to prevent their spread.
    • Do not use live Rainbow Smelt as bait; it is against the law.
    • Do not put any live fish into Ontario’s water bodies.
    • Do not dump Rainbow Smelt guts into water bodies when cleaning fish, as fertilized eggs can introduce new populations.
    • Report any information about the illegal distribution or sale of Rainbow Smelt to the toll-free Ministry of Natural Resources TIPS line at 1-877-TIPS-MNR (847-7667) or contact your local Ministry of Natural Resources office (www.ontario.ca/mnroffices) during regular business hours. You can also call Crime Stoppers anonymously at 1-800-222-TIPS (8477).
    • You can also report invasive species sightings to the toll-free Turtle Island Invaders hotline at 1-844-872-2348 (1-844-TRACE-IT) or to your local Lands or Natural Resources officer.
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