Rainbow Smelt

Osmerus mordax - scientific name

Smelts (Osmeridae) Family

During their spawning period in April, people typically use dip-nets to capture them from streams and the Great Lakes.
Smelt populations in the Great Lakes are no longer as large as they once were and smelt dipping has suffered accordingly. The best smelt dipping these days is in Upper Peninsula streams.

Rainbow smelt are native to the Atlantic Coast and Lake Champlain in Canada. Rainbow smelt are invasive to the Great Lakes watershed through an introduction of eggs to Crystal Lake in Michigan in 1912. This lake drains into Lake Michigan, and the rainbow smelt escaped into Lake Michigan and spread quickly throughout the Great Lakes and their tributaries.

Rainbow Smelt may be confused with fish in the minnow family Lake Whitefish, and Cisco.
Whitefish and Cisco, Unlike Rainbow Smelt fish in the minnow family, do not have an adipose fin, nor large teeth.
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.

Growing up in the 70's and 80's I remember big populations of smelt dipping fishermen on the jetties drinking all night and fishing for smelt.  It was a custom to bite the head of the first smelt you caught, but I always felt it was something they only did to new comers.