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Minnesota Sea Grant
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The mottled sculpin is the most common of the four species of this unusual fish that inhabit Lake Superior’s watershed and is being studied by scientists to understand the operation of the lateral line along the side of the fish, which senses water movement.2 of 2
Minnesota Sea Grant
203sculpin2
Blending into its background nicely, the mottled sculpin depends on camouflage as one of its best defenses from predators like lake trout and burbot.By David D. Lonsdale
Large fish, glitzy fish and bizarre fish attract the attention of the human animal. Lake Superior and its watershed contain their share of all three types of fish.
Perhaps the most bizarre - the ones that catch people’s attention quickly when removed from their watery home - are the sculpin. Sculpin are members of the fish family Cottidae, which has more than 300 living species. Most are found in marine habitats, with a few found in fresh water. Four commonly occur in Lake Superior.
All sculpins are similar in shape. Their large heads appear to be squashed or depressed, as through someone has stepped on their foreheads. Their bodies taper back from head to tail. A wide mouth, protruding eyes, cheek spines and large rounded pectoral fins all add distinctive and charismatic embellishments to our vision of the standard fish shape. Lower mouth location and a flattened ventral (bottom) side are adaptations important to the sculpin’s life on the bottom. They are also protected from predators by their drab mottled appearance, which provides a pattern of disruptive coloration that serves as camouflage.
The Deepwater Sculpin (Myoxoephalus thompsoni) is one of the four species found in the Lake Superior watershed. The genus name (first name) can be translated as “a head resembling a dormouse.” This five-inch-long sculpin plays an important role in the Lake Superior food chain and has been found in the stomachs of lake trout and burbot. Deepwater sculpin feed on small shrimp-like invertebrate creatures, fish eggs and small fish that live in the sediments and water column of Lake Superior.
The Mottled Sculpin (Lottus bairdi) is the most common sculpin along Lake Superior, living mostly in streams among riffles and rocky debris. The male sculpin constructs nest sites and entices females to enter and spawn batches of sticky yellow eggs that adhere to the roof of the nest. Two or three females will deposit eggs in the nest and are then chased away by the male, who tends the nest until the eggs hatch.
The mottled sculpin are being studied to understand the operation of the lateral line along the side of the fish. The lateral line is the organ used by the fish to sense the movement of water and is made up of sensory cells similar to the human auditory system cells.
The Slimy Sculpin (Cottus cognatus) is commonly found in the the lake’s shallows and in shoreline streams. Difficult to discern from the mottled sculpin, the slimy sculpin lives at a stream’s headwaters, while the mottled sculpin prefers life further downstream.
The smallest of Lake Superior’s sculpins is the Spoonhead Sculpin (Cottus ricei), which does not normally exceed four inches in length. The spoonhead lives in shallower water and, like all sculpins, has no scales. Instead, its skin has prickles that can be readily felt.
The best way to find a mottled, slimy or spoonhead sculpin is to explore the shallow waters of a shoreline stream. Find a gravel or rocky bed and look carefully. With a bit of luck you might find a bizarre and cleverly camouflaged neighbor from the Lake Superior watershed.
David Lonsdale is the former executive director of the Great Lakes Aquarium at Lake Superior Center, coming to that position from Chicago’s Shedd Aquarium. He will regularly contribute a column on the science of Lake Superior in future issues of this magazine.