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northern brook lamprey

​northern brook lamprey (Ichthyomyzon fossor) [state endangered]
Photo © Konrad P. Schmidt, University of Minnesota

Features and Behaviors


The northern brook lamprey is about seven inches in length. Its larvae are gray-brown on the back and sides and yellow on the belly and fins. The adults are dark brown, becoming nearly black when spawning is done. The small oral disc has weakly developed teeth, and the digestive tract is degenerate. When expanded, the oral disc is narrower than the head. The dorsal fin has a shallow notch, but the fin is not divided into two separate parts.


The northern brook lamprey may be found in the Kankakee River in Illinois. After transforming to the adult, this nonparasitic lamprey travels a short distance upstream into gravel-bottomed creeks to spawn and die. Its nest is constructed in a gravel-bottomed riffle. The larval, or ammocoete, stage exists for about four years. It burrows tail-first into the bottom substrate with only the head sticking out. The ammocoete feeds on plankton near the mouth of its burrow. Transformation to the adult form begins in late summer and is completed by December. During this time the body length decreases by about 10 percent. The adult does not feed and dies soon after spawning.

Illinois Range


​Kingdom: Animalia
Phylum: Chordata
Class: Cephalaspidomorphi
Order: Petromyzontiformes
Family: Petromyzontidae

Illinois Status: ​state endangered, native

The northern brook lamprey is endangered in Illinois. It has a very small range in the state, only existing in the Kankakee River. Its habitat is threatened by declining water quality. To ensure this species’ survival in the state, measures must be taken to protect the Kankakee River from degradation.