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slender madtom

slender madtom (Noturus exilis)
Photo © Isaac Szabo/Engbretson Underwater Photography

Features and Behaviors


The slender madtom is a small, thin fish, averaging three to five inches in length. The rear edge of the tail fin may be round or square. Its adipose fin forms a ridge rather than a flap. The spine in the pectoral fins has saw-like teeth along the rear margin. The dorsal, tail and anal fins are dark-edged or darker along their outer margins. The upper and lower jaws are nearly equal in length. The body is yellow-brown on the back and sides and white or yellow on the belly.


The slender madtom lives in small streams to large rivers which have permanent flow and silt-free areas of gravel, rubble or large rocks. It is tolerant of moderate turbidity. This fish hides under rocks during the day and feeds on the bottom from dusk to dawn. It attains maturity at age three years. Spawning occurs April through May in a nest constructed by the male near or under large rocks. The female deposits 30 to 75 eggs in a cluster. The male guards the eggs and the newly hatched fry until the yolk sac is absorbed. This fish eats insects and small crustaceans.

Illinois Range


Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Ictaluridae

Illinois Status: common, native