Northern Brook Lamprey (Ichthyomyzon fossor)
A poll on Favorite Fish of Illinois would presumably return zero votes for any lamprey. Granted, most of us do not consider the lamprey a fish at all, but rather an eel-y aquatic creature of unknown provenance. But eels are fish, too. You may have a vague notion that lampreys make you queasy. True enough, your average lamprey makes its living via parasitism, i.e. by attaching itself to other fish species. Parasitism will never win votes in a popularity contest.
Like many of us, the Northern Brook Lamprey suffers from an unfortunate family association. Note that it swims the Kankakee River without indulging in parasitic activity. An Atlas of Illinois Fishes suggests the species may have arrived in the state during the twentieth century, as a 1909 survey did not record it. The fish’s unappetizing physical traits—shared with other Illinois lampreys—include “lacks jaws and paired fins” and “oral disc with rasping teeth on the tongue.” Still, lampreys find mates. Their blind larvae, called Ammocoetes, favor debris in muddy pools and backwaters. Anglers also use Ammocoetes as bait.
An Atlas of Illinois Fishes: 150 Years of Change
Part nature guide and part natural history, An Atlas of Illinois Fishes is the authoritative resource on the topic. The 259 color photographs and 227 maps guide readers to up-to-date scientific information on Illinois’s 217 current and extirpated fish species.