What's In a Name?
Mottled sculpin: sculpin comes from the Latin word for "sea scorpion" and mottled refers to the dark blotches on the body
Cottus (Kot´-tus) means "the bull's head" referring to an old name for freshwater European sculpins
bairdi (baird´-ee) named after the first U.S. Fish Commissioner, Spencer F. Baird

Where Do They Live?
Mottled sculpins occur primarily in the Rainy River, Lake Superior, St. Croix River, and Mississippi River (upper and lower) drainages. They also are known from the Otter Tail and Clearwater rivers in the Red River drainage. In streams they inhabit small, clear streams and large lakes that have rocky shores. They occupy both riffle and pools over sand, gravel, boulders, or limestone. Mottled sculpins favor clear water with some form of shelter (for example boulders or vegetation) to use as hiding spots. Common associates of mottled sculpins include white suckers, creek chubs, brook sticklebacks, and pearl dace, to name a few.

How Big Do They Get?
How Long Do They Live?
Minnesota mottled sculpins can get as big as 130 mm (about 5 in), but lengths of 75-90 mm (3-3.6 in) is more typical. Both sexes reach the age of 3 years. Very rarely one makes it to 4 years old.

What Do They Eat?
Since this fish is commonly a benthic (bottom dweller), they eat things that are found on the bottom. Diets vary from streams to lakes. In streams, aquatic insect larvae and sideswimmers are more common. In lakes, copepods, waterfleas, leeches, and algae are added. Occasionally, fish eggs and even small fish are found in mottled sculpin stomachs.

What Eats Them?
In trout streams, mottled sculpins are frequently eaten by large brook trout and brown trout. In other streams, they are eaten by young northern pike. They are eaten by smallmouth bass and walleye in northern lakes. American mergansers also prey on them. Humans do not eat them, but some anglers use them as bait.

How Do They Reproduce?
Mottled sculpins breed at water temperatures of 5-16° C (63-74° F), which is April and May depending on how far north the population is. Spawning takes place in cavities that males fan out beneath rocks, ledges, or logs. Males attract females through courtship displays of headshaking, headnodding, gillcover raising, and other body movements. The spawning pair turns upside down, and the female lays clusters of eggs on the underside of the rock or log. More than one female is likely to spawn with the male. The male protects the nest, keeps it clean, and eats dead, fungus-covered eggs (which are really embryos). A single female lays 100-600 eggs in a season, depending on her size. Embryos hatch in about 5-7 days.

Conservation and Management
Mottled sculpins are the most common (and probably abundant) sculpin in Minnesota. They have no special conservation status. Some biologist consider sculpin to be major predators of trout eggs, but their overall impact is probably small.