The lampreys are primitive eel-like fish which differ from the more familiar fishes by the absence of jaws, paired fins, and the presence of gill pockets in place of gill covers and arches. These fishes, together with the marine hagfishes, are frequently called cyclostomes, meaning animals with round mouths. Most of the lampreys are parasitic, attaching themselves to fishes and other aquatic animals. They also feed, to a certain extent, upon dead organic material. Body size ranges from the small brook lamprey, which rarely exceeds 6 to 7 inches, to the sea lamprey which attains a length of nearly 3 feet.

Four lamprey species, silver, chestnut, northern and brook, are native to Iowa streams. The silver and chestnut lampreys, both parasitic fishes, occur in the Mississippi River. Fishermen, both sport and commercial, occasionally find them attached to fish, and as many as three or four have been observed on a single host. The brook and northern lamprey, are non-parasitic form. They are most common in the smaller and medium size streams of northeastern Iowa. It seems to prefer rocky riffles, is quite secretive and is seldom observed by anglers.

Lampreys ascend small clear-water tributaries of the large rivers to spawn in the spring of the year. They construct depressions in the sand and gravel bottom, in swift water, to deposit their eggs. Young lamprey larvae are called ammocoetes, and the various species are difficult to tell apart.

The American brook lamprey and silver lamprey are classified as threatened species in Iowa and are protected.

*Mayhew, J. (editor). 1987. Iowa Fish and Fishing. Iowa Department of Natural Resources, Des Moines, Iowa. 323 pp.