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Rainbow Smelt

Osmerus mordax
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Rainbow Smelt is a predatory fish native to the north Atlantic coastal regions of North America as well as a few lakes in the Ottawa Valley in the St. Lawrence River watershed. Deliberate stocking in Michigan in the early 20th century led to established Rainbow Smelt populations in Lake Erie, Lake Michigan, Lake Huron, and Lake Superior. The fish likely invaded Lake Ontario from Atlantic coastal areas through the Erie Canal, New York. More recently, people have illegally introduced Rainbow Smelt to inland lakes.

In their native habitat, Rainbow Smelt spend most of their lives at sea and migrate into freshwater to spawn. Rainbow Smelt that have invaded Ontario waters cannot return to the sea, but they still follow old behaviour patterns. In the spring, they move in large schools from lakes into streams and along shorelines to spawn. Rainbow Smelt eat plankton – small animals and plants found in the water – as well as juvenile native fish.


Outside its native range, the Rainbow Smelt can be found in the St. Lawrence River watershed, each of the Great Lakes, other inland lakes, such as Lake Simcoe, Lake Nipissing, and Lake Nipigon, as well as many smaller inland lakes. The fish has also been introduced to the Hudson Bay watershed, lakes in northwestern Ontario and Manitoba, including Lake Winnipeg and many American states.

For an up to date distribution map of Rainbow Smelt in Ontario, visit

Impacts of Rainbow Smelt

By competing with other fish for food and predating on juvenile fish, Rainbow Smelt have had a serious impact on their invaded ecosystems.


  • The Rainbow Smelt’s eating habits may disrupt food webs and lead to declines of the small animals, known as zooplankton that are eaten by other fish.
  • The introduction of Rainbow Smelt has led to reduced populations of native fish species, such as Yellow Perch (Perca flavescens), Walleye (Sander vitreus), Lake Herring (Coregonus artedi), Whitefish (clupeaformis), and Lake Trout (Salvelinus namaycush).

How to Identify Rainbow Smelt

  • Adult Rainbow Smelt have long, slim bodies averaging 19 cm (7.5 in) in length.
  • Their bodies are olive-green on the back, with purple, pink, and blue iridescence on the sides, with a silvery belly.
  • The mouth is large, relative to the fish, with a protruding lower jaw and large canine teeth on the roof of the mouth and the tongue.
  • Rainbow Smelt have a single dorsal fin in the middle of its back and a small fleshy fin near the tail, known as an adipose fin.
  • Scales are small and easily detach during handling of the fish, much like our native shiners.

Rainbow Smelt may be confused with fish in the minnow family (Cyprinidae sp.), Lake Whitefish (Coregonus clupeaformis), and Cisco (C. artedi). Unlike Rainbow Smelt, fish in the minnow family do not have an adipose fin, nor large teeth. Whereas, Lake Whitefish and Cisco are silvery fish with an adipose fin, much like a Rainbow Smelt, but their bodies are deeper than the Rainbow Smelt and they do not have teeth on the tongue and roof of the mouth.

What You Can Do

  • Learn how to identify Rainbow Smelt and how to prevent the spread of this unwanted species.
  • Never buy or use live Rainbow Smelt as bait; it’s against the law. Dead Rainbow Smelt may be used as bait in Ontario, with exceptions in Fisheries Management Zones 2, 4, 5, and 6 (see, where it is illegal to use them or possess them as bait.
  • Don’t put any live fish into Ontario lakes, rivers, or streams.
  • When cleaning Rainbow Smelt, be careful not to dump entrails into a lake or river.
  • If you have any information about the illegal importation, distribution, or sale of Rainbow Smelt, report it immediately to the MNRF at 1-877-847-7667, toll-free any time. You can also call Crime Stoppers anonymously at 1-800-222-TIPS (8477).
  • If you’ve seen a Rainbow Smelt or another invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, visit EDDMapS, or search for the ‘Invasive Species in Ontario’ project on to report a sighting.

Resource Files


OFAH/OMNRF Invading Species Awareness Program. (2021). Rainbow Smelt. Retrieved from:
This factsheet may be reproduced for non-commercial purposes.

Header photo by Great Lakes Fish Company

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