The mottled sculpin, Cottus bairdii, is a small fish native to areas in both eastern and western North America. The species is native to Utah and common in the state; mottled sculpin can be found in many of Utah's coldwater streams. The mottled sculpin is a bottom-dwelling species that is important as a forage fish for stream-dwelling trout. Because trout predation can devastate mottled sculpin populations if sculpin do not have adequate hiding places, the species does best in areas where plenty of cover exists.
Mottled sculpin feed primarily on aquatic insect larvae, although small fishes, crayfishes, fish eggs, and plant matter are also consumed. The species prefers rock, gravel, or sand substrate.
The mottled sculpin spawns from late winter through the spring. Male sculpin spawn with multiple females, and then guard the eggs until they hatch, which usually occurs in two weeks.