Mottled Sculpin are a small fish with adults reaching only about 3 inches (7.5 cm) in length. They have large fan-like pectoral fins and large second dorsal and anal fins. They vary from light to dark brown in colour and have darker mottling on the back and sides. Pigment in the fins forms dark bands with a broad orange distal edge in breeding males (Scott and Crossman, 1973).

Columbia Basin: Columbia and Kootenay rivers below the Arrow Lakes, and the Flathead River and its lower tributaries.

British Columbia: Outside the Columbia Basin* they are restricted to the Similkameen River and its tributaries, and the Kettle River below Cascade Falls.

*Please note that the Similkameen and Kettle rivers are part of the Columbia system (flow into the Columbia River), but they are outside the "Columbia Basin" as defined in this report.

Global: Ranges widely, but discontinuously across North America from Tennessee to the Great Lakes to northern Labrador, and in western North America from parts of the Missouri and Columbia River systems.

Mottled Sculpin are found in flowing water ranging from small creeks to large rivers, and in montane lakes. They tend to occur in the main stem of the Columbia River, whereas the closely related Shorthead Sculpin preferred the smaller tributaries> In the Flathead River they are most abundant where the bottom is not heavily sedimented and there is a slow current. (Cannings and Ptolemy, 1998).

This species faces potential threats from coal mining in the Flathead valley and by hydroelectric developments in the Columbia and Similkameen rivers (Cannings and Ptolemy, 1998).