http://en.wikipedia.org/wiki/Rainbow_smelt
This species is both Landlocked and sea-run. It provides an excellent source of food for many species of fish. Smelt inhabit deep, cold lakes and seek cool depths during the summer. Their diet consists mainly of shrimp and other small crustaceans, small fish and occasionally insects. They are cannibalistic and larger Smelt may subsist almost entirely on smaller smelt. They may be taken through the ice with small tackle and cut bait. Spawning runs occur at night in streams and along lake shores in early spring, and may be dipped with nets in a few waters. Smelt are highly valued for human consumption. The average size is about 5 inches, but they occasionally attain sizes of 8 inches or better. Smelt ascend many of the freshwater streams and rivers during the winter and are readily taken there, as well as in Great Bay, by fishing through the ice. The Exeter and Lamprey Rivers are popular sites for groups of bob houses and fisherman take sizeable fish in good numbers.