Basic Biology

Rainbow smelt

  • Averaging 6 to 8 inches long, rainbow smelt are slender with a pointed head and a large mouth. They are green on top with slightly paler sides and a silver belly. They have a conspicuous silvery streak running lengthwise along each side.
  • Rainbow smelt can live as long as 6 years, but more typically they live 3 or 4 years.
  • Both sexes become sexually mature at about 2 years of age, although some 1-year-olds may participate in spawning. The number of eggs produced by a female per spawning season ranges from 33,400 eggs for a 6-1/2 inch fish to 75,600 for a 9-inch fish.
  • Smelt usually travel in schools less than 2 kilometers from shore and in water less than 6 meters deep. Their travels are associated with seasonal changes in water temperatures. In summer, they seek out cooler areas in coastal waters, sometimes moving offshore if the coastal water temperature is high. During fall and winter, they live in estuaries, harbors, and coastal waters.
  • Beginning in late winter (Massachusetts) to late spring (eastern Maine), rainbow smelt migrate into rivers and streams to spawn.
  • The species is native to coastal waters from Virginia to the Canadian Maritimes.
  • Rainbow smelt eat shrimp, marine worms, amphipods, euphausiids, mysids, and smaller fish.
  • They serve as prey for striped bass, Atlantic salmon, Atlantic cod, grey seals, and many birds such as herons, cormorants, and osprey.
Map of rainbow smelt spawning grounds in the U.S. Gulf of Maine

Click on map to view it larger.

Rainbow smelt deposit their eggs on rocks and some other substrates in stream beds.

Rainbow smelt spawn in rivers and streams that have the habitat characteristics and water quality that they require. Land development, pollution, and other factors are making good spawning places scarce.

Scientists from Maine, Massachusetts, and New Hampshire are studying the rainbow smelt in order to understand its ecology and to develop a conservation plan for the species.