The rainbow smelt (Osmerus mordax) is a species of fish of the family Osmeridae. Its distribution is circumpolar, and it has been introduced to the Great Lakes, and from there has made its way to various other places. Walleye, trout, and other larger fish prey on these smelt. The rainbow smelt prefer juvenile ciscoes, zooplankton such as calanoid copepods (Leptodiaptomus ashlandi, L. minutus, L. sicilis), and other small organisms, but are aggressive and will ea