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brook stickleback

brook stickleback (Culaea inconstans)
Photo © Uland Thomas

Features and Behaviors

The brook stickleback may attain a maximum length of three and one-half inches. It lacks scales. There are four to six spines along the back and one spine in the pelvic fin. The body is green to brown on the back, silver on the sides and silver to light green on the belly. The sides may have yellow spots. The breeding male is dark green to black.

The brook stickleback lives in creeks and rivers. It prefers areas with plants and a mud or sand bottom. This fish spawns in late spring and early summer. The male builds a nest from vegetation that is held together by sticky secretions from his kidney. There is an opening on one side of the nest only. The male courts the female to get her to enter the nest and deposit eggs. When egg-laying is completed, the male enters the nest and releases sperm. The male guards the eggs and young. The brook stickleback eats invertebrates and algae.

Illinois Range


​Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Gasterosteiformes
Family: Gasterosteidae

Illinois Status: common, native