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Deepwater sculpin

Myoxocephalus thompsonii

What do they look like?

Deepwater sculpin have been known to reach 9 inches (23 cm) in length, although the average is between 2 and 5 inches (5 to 10 cm). The body is slender, with a large flattened head and blunt snout with a large mouth. The eyes are set close together on top of the flattened head. There are two dorsal (back) fins, the second much larger than the first. In large males, this second dorsal fin often overlaps the base of the caudal (tail) fin. Although deepwater sculpin do not have scaled skin, they do have prickles on top of the body. Deepwater sculpin are grayish brown with a slightly lighter belly. The back and sides are speckled with thin oval-shaped marks.

  • Sexual Dimorphism
  • sexes alike
  • Range length
    23 (high) cm
    9.06 (high) in

Where do they live?

Deepwater sculpin are found in the deep, cool lakes of northern North America. They were once abundant in the Great Lakes and most deep lakes of Canada (especially Nipigon in Ontario, Great Slave in Manitoba, Waterton in Alberta, and Great Bear in the Northwest Territories), but the range of deepwater sculpin is rapidly shrinking.

Currently, deepwater sculpin are plentiful in lakes Huron, Michigan and Superior, and rare in Ontario and Erie. Despite their deepwater habitat requirements, they are also sometimes found in the inland waterways that connect the Great Lakes, such as the St. Claire River.

What kind of habitat do they need?

During their first year of life, deepwater sculpin are found in the open water feeding on plankton and small invertebrates. As they age their body shape and physiology changes and they become bottom-dwelling fish.

Adult deepwater sculpin are generally found in waters deeper than 20 meters and are especially abundant between 70 and 90 meters deep. In Lake Superior they have been found at depths of 407 meters. The largest deepwater sculpin individuals are found in the deepest waters. Deepwater sculpin live only in cold water, 40 degrees Celsius or less.

  • Range depth
    20 to 407 m
    65.62 to 1335.30 ft
  • Average depth
    70-90 m

How do they grow?

There isn't much known about development in deepwater sculpin because they are difficult to study. Deepwater sculpin undergo changes from egg to open-water larvae to bottom-dwelling juvenile (young) within their first year of life. This first year is a time of rapid growth in length, after which the growth in length slows and deepwater sculpin grow both in length and weight.

How do they reproduce?

Because it is so difficult to study deepwater sculpin, little is known about their mating systems.

Deepwater sculpin can begin to reproduce when they reach 3 years old. It is thought that they breed throughout the year, with breeding in late fall and winter in the Great Lakes and in summer and early fall in Canadian lakes. Females lay an average of 481 eggs each time they breed, with the largest females laying the most eggs. In the Great Lakes the eggs hatch at the same time that the ice on the lakes begins to break up.

  • How often does reproduction occur?
    Breeding is likely to occur each year.
  • Breeding season
    Breeding occurs in late fall and winter.
  • Average number of offspring
  • Range age at sexual or reproductive maturity (female)
    2 (low) years
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Range age at sexual or reproductive maturity (male)
    2 (low) years
  • Average age at sexual or reproductive maturity (male)
    3 years

Like other sculpin species, male deepwater sculpin build nests and guard the eggs.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male

How long do they live?

Fish ages are determined by counting the "rings" on bones in their ears (otoliths). Like tree rings, these rings represent years of growth. According to data collected in the summer of 1973, deepwater sculpin in the Great Lakes live as long as seven years.

  • Typical lifespan
    Status: wild
    7 (high) years

How do they behave?

These fish live in cold, deep waters and very little is known about their behavior.

How do they communicate with each other?

Deepwater sculpin live in very dark environments. Little is known about their modes of perception and how they might communicate, but it is likely that they use tactile and chemical perception in their dark habitat.

What do they eat?

Data on food preference is based on stomach contents of captured fish. Deepwater sculpin eat mainly crustaceans, especially deepwater amphipods and opossum shrimp. Larger sculpins prefer deepwater amphipods.

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • aquatic crustaceans

What eats them and how do they avoid being eaten?

Predators of deepwater sculpin include lake trout and burbot. By the early 1950s, over-fishing and sea lamprey parasitism of lake trout and burbot resulted in their near disappearance from Lake Ontario and severe declines in other Great Lakes. Shortly after the population declines of these two keystone predators, deepwater sculpin disappeared from Lake Ontario for almost the next 50 years. It is thought that the loss of these keystone predators resulted in huge disruptions to the Great Lakes freshwater fish community.

The prickles on the top of the body and the four spines on top of the head may make it difficult for predators to eat deepwater sculpin. Also, deepwater sculpin spend most of their time in very cold and deep places, where there are few predators.

What roles do they have in the ecosystem?

Deepwater sculpin are the number one prey item for lake trout, which was once one of the most important fish in the Great Lakes. They were fished on a large scale and were very important economically. Overfishing and the introduction of non-native sea lampreys caused a huge decline in lake trout populations. Since 1950 many agencies have been trying to restore lake trout populations to the Great Lakes, but without much success. Lake trout are currently only doing well in Lake Superior. They are reproducing in the other Great Lakes but only in Lake Superior and Lake Huron are young lake trout surviving into adulthood.

It may be that competition between sculpin species led to a decline in deepwater sculpin. Young deepwater sculpin and slimy sculpin eat the same foods and use the same habitats. Slimy sculpin may also prey on the eggs and larvae of deepwater sculpin. Competition with slimy sculpin might have contributed to the decline in deepwater sculpin.

Do they cause problems?

There are no known negative affects of deepwater sculpin on humans.

How do they interact with us?

Deepwater sculpin currently are not seen as having any commercial value or economic importance on a local, national or international scale. They are important members of the native Great Lakes and northern lakes ecosystem.

Are they endangered?

From 1942 to 1972, no deepwater sculpin were captured in Lake Ontario. Between 1972 and 2002, only six were caught. Despite their disappearance from Lake Ontario and steady decline in the other Great Lakes, the United States Fish and Wildlife Service (USFWS) does not list deepwater sculpin as being a species of concern for the Great Lakes region. The New York State Department of Environmental Conservation and the Canadian government list deepwater sculpin as being threatened and monitored. Current research focuses on figuring out how many deepwater sculpin are left in the Great Lakes and other deep water lakes in Canada. The decline of deepwater sculpin may have been linked to the introduction of two non-native species in the Great Lakes: alewives and rainbow smelt. Both of those fish species eat deepwater sculpin eggs and compete with them for food.

There are currently two known threats to the continued survival of deepwater sculpin. The first is the loss of their main prey, deepwater amphipods. The second threat is the presence of an introduced species: round gobies. Round gobies are fierce fighters, and often push deepwater sculpin out of foraging and breeding areas.


William Fink (editor), University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.

Alexandra Belinky (author), University of Michigan-Ann Arbor.


"New York State Department of Environmental Conservation" (On-line). Accessed November 19, 2002 at

"Scientific Committee on the Status of Endangered Wildlife in Canada (COSEWIC)" (On-line). Accessed November 19, 2002 at

Black, G., M. Lankester. 1981. The biology and parasites of deepwater sculpin, *Myoxocephalus quadricornis thompsonii* (Girard), in Burchell Lake, Ontario. Canadian Journal of Zoology,, vol. 59 (7): 1454-1456.

Brandt, S. 1986. Disappearance of the deepwater sculpin (*Myoxocephalus thompsonii*) from Lake Ontario: the keystone predator hypothesis. Journal of Great Lakes Research,, vol. 12 (11): 18-24.

Bruch, R. 1986. Age and Growth, Mortality, Reproductive Cycle and Fecundity of the Deepwater Sculpin, Myoxocephalus thompsonii (Girard), in Lake Michigan. Milwaukee, Wisconsin: University of Wisconsin - Milwaukee.

Crossman, E., H. Van Meter. 1979. Annotated List of the Fishes of the Lake Onatario Watershed. Ann Arbor, MI: Great Lakes Fisheries Commision.

Jacoby, C. 1953. Notes on the Life History of the Deepwater Sculpin, Myoxocephalus quadricornis L., in Lake Superior. Ann Arbor, Michigan: Department of Fisheries, School of Natural Resources, University of Michigan.

Momot, W., S. Stephenson. 1996. Atlas of the Distribution of the Fish within th Canadian Tributaries of Western Lake Superior. Toronto, Ontario, Canada: University of Toronto.

Page, L., B. Burr. 1991. A field guide to freshwater fishes of North America. Boston, Massachusetts: Houghton Mifflin Company.

Selgeby, J. 1988. Comparative biology of the sculpins of Lake Superior. Journal of Great Lakes Research,, vol. 14 (1): 45-51.

Wojcik, J., M. Evans, D. Jude. 1986. Food of deepwater sculpin, *Myoxocephalus thompsonii*, from Southeastern Lake Michigan. Journal of Great Lakes Research, vol. 12 (3): 225-231.

University of Michigan Museum of ZoologyNational Science Foundation

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Belinky, A. 2003. "Myoxocephalus thompsonii" (On-line), Animal Diversity Web. Accessed February 26, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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