In Lake Superior the largest catches of slimy sculpin were at 300 - 345 feet. Detailed food studies for the slimy sculpin indicate that the primary food is invertebrate benthic insects. The more important insect groups were mayflies, caddis flies, dipterous larvae, stone flies, and dragonflies. Large fish tend to eat the larger larvae species. A number of predatious fish, such as lake trout, brook trout, salmon, speckled trout, northern pike, and burbot feed upon this sculpin.
Streams inhabited by the slimy sculpin are invariably good brook trout waters.
The slimy sculpin is a common associate of both lake trout and brook trout and forms part of the food supply of both. Perdition by slimy sculpins on trout eggs were studied, but there was virtually no evidence that sculpins feed upon the eggs and only rare instances of predation on young brook trout. The difference is that the eye may be a little larger, a slightly different teeth arrangement, the numbers of spiny and soft rays on the fins, and a slight color variation. There are two and sometimes three dark saddle marks under the second dorsal fin. The dorsal fin of the mottled sculpin is pigmented with a spot fore and aft, which becomes continuous in breeding males to form a dark band with a broad orange distal edge.