Facts & Guide to Rainbow Smelt (Osmerus mordax)

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Rainbow smelt in hand
Rainbow smelt are relatively small fish, reaching an average length of 7 – 9 inches, and are native to North America. Cassidy Best / CC BY 4.0

Rainbow smelt are small fish found in cold freshwater and marine environments at northern latitudes. They are known for their silvery-pink appearance and are typically between 7 to 9 inches (18 to 23 cm) in length. They have a slender, elongated body with a silver-blue to greenish-blue coloration on their upper sides and a silver-white underside. Additionally, they have large eyes and a pointed snout.

Overall, rainbow smelt are small fish with a pink hue on their bellies. This pink hue can come in many shades, sometimes presenting as an iridescent purple or blue in addition to the pink color.

Rainbow smelt are native to North America and can be found in various lakes, rivers, and coastal areas in the northern United States and Canada. Within their native range, they play a significant ecological role in the food web, serving as prey for various fish species, birds, and mammals. They are also crucial in recreational and commercial fisheries in some regions, where they are caught for their tasty flesh, usually fried and eaten whole.

Rainbow smelt, American smelt, Atlantic smelt, freshwater smelt, leefish, Maine smelt, smelt
Osmerus mordax
Marine and freshwater, found in the northern waters of North America
Aquatic invertebrates, worms, and small fish
28.8 to 68°F (-2 to 20°C)
7 years
7 – 9 inches (18 – 23 cm)
Least concern

Where Do Rainbow Smelt Live?

Missouri River
The introduction of rainbow smelt to non-native waters in North America has had a negative impact, especially in the Missouri River (pictured) and Great Lakes. Cmichel67, CC BY-SA 4.0, via Wikimedia Commons

The rainbow smelt can be found in freshwater, brackish, and marine habitats from open lakes and rivers to coastal waters. In North America, the rainbow smelt is only native to some parts of coastal New England, and it has been introduced intentionally and unintentionally to new waters across the country. The water bodies that are most notably impacted by the introduction of the rainbow smelt are the Great Lakes and the Missouri River.

The rainbow smelt is invasive outside of its native range. For instance, where it has been introduced to novel North American lakes, it competes directly with native fish species for food, resulting in the decline of native species. Additionally, O. mordax is associated with various parasites, diseases, and viruses, which may spread with the rainbow smelt and pose an additional threat to native species.

Do Rainbow Smelt Migrate?

School of rainbow smelt
Rainbow smelt can be anadromous just like salmon, meaning that they can migrate from freshwater to seawater to reproduce. Ian Manning / CC BY 4.0

This species is highly migratory. Like salmon, the rainbow smelt can be anadromous, migrating from freshwater to seawater to reproduce. In their landlocked form, they can reproduce without migrating to the ocean and establish sustainable populations in large lakes and reservoirs.

How Do Rainbow Smelt Reproduce?

Rainbow smelt eggs
During the breeding season, female rainbow smelt can produce up to 80,000 eggs! Bex Goreham / CC BY 4.0

Adults spawn at night in trios or larger groups. Usually, one female is accompanied by many males. During the breeding season, males can be identified by pronounced tubercles. Spawning occurs when water temperatures achieve 40 to 50 °F (4.4 to 10 °C) after iced-over sections of a lake or river have thawed. This usually occurs in the spring or late in the winter.

Females can produce as many as 80,000 eggs during the breeding season. Once laid, their eggs sink into the substrate and stick to it for 10 to 30 days. Free swimming larvae will mature between 1 and 4 years of age and live up to 7 years. Females are typically larger than males and have a longer lifespan. Young rainbow smelt consume zooplankton, like copepods, and transition to larger prey items like small crustaceans and fish larvae as they mature.

Due to their small size and relative abundance, the rainbow smelt is a vital forage fish for predatory fish species. As a result, most smelt larvae will be eaten by predators like sizeable predatory fish, birds, and marine mammals.

Do Humans Eat Rainbow Smelt?

Rainbow smelt are caught and eaten by humans. This fish is usually caught, gutted, frozen, or sold fresh in markets. Recipes for rainbow smelt usually involve sautéing or frying it.

How Do Rainbow Smelt Survive in Sub-Freezing Temperatures?

The rainbow smelt is incredibly resistant to freezing temperatures. When water temperatures drop below freezing, this smelt survives by producing glycerol. This antifreeze protein improves its ability to move through cold water and prevents tissues from becoming damaged by frigid temperatures. They also resist changes in nutrient density, pH, salinity, and oxygen.

What Is the Best Way to Catch Rainbow Smelt?

Before fishing for rainbow smelt, consult local fishing regulations for any restrictions regarding this species. Some areas limit the amount of rainbow smelt, and an angler may have to protect the species where it is native and prevent it from spreading where it is non-native.

Rainbow smelt are typically found in cold, clear waters and are often more active during the colder months. They are known to spawn in the early spring, making this an excellent time to target them. Anglers should look for locations where rainbow smelt are known to gather, such as deep, calm waters near the mouths of rivers or inlets. It is best to fish for this species at night using a light to attract them to the shore or a boat. Then, using a specialized smelt net, anglers can scoop up large quantities of smelt from the water.

Keyla P
About the author

Keyla P

I have a bachelor’s degree in Natural Resources focusing on Wildlife Ecology and a minor in Entomology. I am also an award-winning student researcher with five years of experience with wildlife-related research.

Read more about Pond Informer.

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