head and anterior flattened dorso-ventrally; terminal mouth with numerous teeth in narrow bands on the upper and lower jaws; two lobed, narrowly connected dorsal fins; head, back, and sides olive brown with dark mottling; lower region of head and belly lighter to whitish
coldwater streams in northeast Iowa
larval aquatic insects, invertebrates
The slimy sculpin is a common inhabitant of many coldwater streams in northeast Iowa. With only one exception, collections made in Iowa before 1969 reported only slimy sculpin. Noting the difficulty in distinguishing between the two species, it seems likely that past surveys probably contained both slimy and mottled sculpins.
The head and anterior body are flattened dorso-ventrally with the posterior body and caudal peduncle compressed laterally. The mouth is terminal with numerous teeth in narrow bands on the upper and lower jaws. It has two-lobed, narrowly-connected dorsal fins. The frontal dorsal fin has 7 to 9 soft spines and the second lobe has 16 to 18 rays. The anal fin has 11 to 13 rays; the pelvic fins are thoracic with a single spine and 3 pelvic rays. The pectoral fin contains 13 to 14 rays. Scales are absent and the lateral line is incomplete, ending under the second dorsal fin. The head, back and sides are olive-brown with dark mottling. The lower region of the head and belly are lighter to whitish. Specimens rarely exceed 4 inches in length.
The slimy sculpin lives on the stream bottom. Movements are darter-like in their rapidity and often resemble hopping. Activity is mostly nocturnal. When the fish lies motionless in one place for long periods of time, its coloration so perfectly blends into the surroundings that it is difficult to observe. Its diet consists mainly of larval aquatic insects and other invertebrates. Spawning takes place in late April and May. A nest cavity is cleaned by the male; eggs are deposited by the female in clusters on the undersides of stones. The male guards the nest 3 to 4 weeks, until the fry leave. Records indicate slimy sculpin living at least 5 years.
Sculpins have long been accused of trout egg and fry predation and even for direct competition for benthic invertebrates. Most of the trout eggs consumed are probably loose eggs that were not buried in the redd. Little evidence is available which shows sculpin limit trout numbers. It has even been speculated that sculpin predation on predaceous stoneflies may increase the numbers of drifting herbivorous insects for trout and reduce stonefly predation on trout eggs and young.