Slender Madtom (Noturus exilis)

Status: State Endangered (1979).

Occurrence: The Rock and Pecatonica River systems, which is the northern limit of their range. A map outlining Pre-1977 and 1997 to Present Distribution is available.

Aid to ID: Distinguished from other catfish species by the combination of its slender body, subequal jaws and black margins on the fins. Blunt snout with two short, feeler-like barbels pointing upwards from nostrils. An additional four barbels protrude from the underside of chin. Dark gray or blackish with vague yellow blotches on the back. Adult size: 3-4 inches (76-102mm).

Habitat: Clear, moderately swift waters at depths of 4-12 inches (10-30cm) over gravel and boulder substrate interspersed with fine sand. Generally occurs in streams 29-36 feet (9-12m) wide, but may also be found in larger rivers with suitable current and substrate.

Food Habits: Eat caddisflies, midgeflies and other insects, and filamentous algae on the benthic (bottom) surface.

Natural History: Slender madtoms are mostly nocturnal. Spawning occurs in late May and June. From 150-200 eggs are laid in a large adherent mass under a flat rock where water can percolate between the developing eggs. Newly hatched young crowd together in a tight cluster.

Management Considerations: Slender madtom eludes most predatory fish and wading birds because of secretive daytime habits as well as maneuverability and quickness over short bursts. Populations have declined dramatically since the late 1970's. Reasons for declines appear related to siltation and turbidity in the farming areas over most of their range. Some of the declines can also be attributed to the improper operation of hydroelectric facilities resulting in the dewatering of habitat.

Information compiled from publication ER-091.