Montana Field Guide

Slimy Sculpin - Cottus cognatus

The slimy sculpin is native west of the Continental Divide. Like the mottled sculpin, it prefers clear, cold, rocky streams but will also be found along cobbly shorelines of lakes. All freshwater sculpins are spring spawners. The males select spawning sites on the undersides of rocks. The female is courted, enters the nest, and deposits a mass of adhesive eggs upside down on the ceiling of the nest. The male then guards the nest and newly-hatched young sculpins with vigilance.

The back and sides are brown to black with mottling; dark bands are often present. The underside is white. The first dorsal fin is fringed with orange on breeding males. No palatine teeth are present. Pelvic fins have 3 or 4 soft rays; if a fourth (inner) ray is present, it is usually two-thirds or less the length of the longest. Other Montana sculpins have four fully developed soft rays. Note: sculpin pelvic fins have one spine in addition to the soft rays. It is encased in a fleshy membrane with the first (outer) ray and is not distinct.

Montana Range

Its usual habitat is in the rocky riffles of cold, clear streams, but it is sometimes found along the rubble beaches of lakes, especially near the mouths of inlet streams (Brown 1971).

Food is comprised of mostly immature aquatic insects and invertebrates, but also includes any small fish available (Brown 1971).

Construction of the Libby Dam wiped out populations in a stretch of river now occupied by Lake Koocanusa (Huston 1984).

Spawning occurs in spring (Brown 1971). Incubation is in 30-40 days at 48-50 degrees F. They may become sexually mature at 2 years (Weisel 1957). Populations in northern Saskatchewan spawned in early May at 46 degrees F. with eggs hatching in 4 weeks (Scott 1973).