The brook stickleback is found in streams and some natural lakes in the northern one-half of Iowa. It prefers streams with moderate currents that have sand and gravel bottoms and clean to slightly turbid water.

Brook stickleback are deep-bodied, compressed and scaleless fish. The mouth is small with swollen lips, and the lower jaw projects beyond the upper jaw. There are two to seven (usually five) unconnected spines followed by a dorsal fin that has 9 to ll rays. The anal fin has a single spine with 9 to l0 rays; the pelvic fin has one heavy spine with a single ray. The lateral line is complete, and there are 30 to 36 small, bony plates along its entire length. It is olive green in color on the back and sides with white or yellow spots and dark wavy lines scattered over the sides. The species attains a length of 2 to 3 inches.

Nest building by males begins in the spring at water temperatures of 59 to 66 degrees F. The nests are attached to a stem of vegetation by a whitish cement secreted by the male. A rounded nest is built from organic debris, filamentous algae and other materials. The male aggressively seeks a female that is gravid. The female enters the nest opening and is continuously prodded by the male until eggs are deposited. Immediately after leaving the nest the female is chased away by the male. The male then enters the nest and fertilizes the eggs. The eggs are incubated by the male, vigorously fanning a current of water through the nest. Eggs hatch in 7 to ll days, depending upon water temperature.

The male stickleback continues to guard the nest after the eggs hatch, retrieving fry that stray from the nest by catching them in his mouth one at a time and promptly spitting them back into the nest. After several days, young escape so fast that the male is unable to retrieve them, and he either abandons the paternal duty or consumes his own offspring. Brook stickleback feed principally on aquatic insects and live up to three years.

The brook stickleback is forage for numerous game fish. They make interesting aquarium fish, but because of their aggressive behavior it is difficult to keep other small fish.

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