Myoxocephalus thompsoniiDeepwater sculpin

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Geographic Range

Although there are similar Nearctic and Palearctic species, as well as similar European freshwater species, deepwater sculpin, Myoxocephalus thompsonii are limited to North America. 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), the geographic range of deepwater sculpin is rapidly shrinking.

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

Habitat

During their first year, deepwater sculpin are pelagic, rather than benthic organisms. They live in the water column feeding on pelagic phytoplankton and small invertebrates. As they age they undergo physiological changes and become benthic organisms.

Adult deepwater sculpin are generally found in waters deeper than 20 meters and are particularly abundant between 70 and 90 meters. In Lake Superior they have been found at depths of 407 meters. Although all adults are benthic, the largest fish of a population are found in the deepest waters. Deepwater sculpin live only in cold water, 40 degrees Celsius or less.

Due to their benthic habitat, deepwater sculpin spend their adult lives in complete darkness where the temperature ranges between 3 and 6 degrees Celsius. At this depth, the bottom substrate is fine particulate matter, mud and clays of a uniform size. When they were much more plentiful, they could also be found on substrates consisting of combinations of sand, silt, clay and mud intermixed with rocks, coal and cinders. During one study in 1952, they were found in the waters off Munising, Michigan, on thick beds of aquatic vegetation (Jacoby 1953).

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

Physical Description

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. Eyes are set close together on top of the flattened head. There are four preopercular spines, the two upper ones so close together as to be mistaken as one (Brandt, 1986). There are two dorsal fins, the second significantly larger than the first. In mature males, this second dorsal fin often overlaps the base of the caudal fin, and is one of the distinguishing characteristics of deepwater sculpin (Page et al., 1991). Although deepwater sculpin have no scales, they do have prickles on top of the body.

Coloration is largely characteristic of what one would expect in a habitat with very little if any light. The dorsal region is gray-brown, while the ventral is several shades lighter. The top and sides are speckled and there are thin oval shaped-marks dotting the back (Page et al., 1991).

Sexual dimorphism is apparent only in sexually mature individuals. The largest fish tend to be the most sexually dimorphic in the development of the fins. “In order of decreasing magnitude, it is most pronounced in the second dorsal, pelvic, anal, first dorsal, pectoral, and caudal fins” (Jacoby, 1953). (Jacoby, 1953; Page and Burr, 1991)

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

Development

Although research is ongoing, due to the deepwater sculpin’s inaccessible habitat, there is little concrete documentation of their developmental stages.

Ontogenetic changes occur during the deepwater sculpin’s first year of life, transforming them from pelagic larva to benthic organisms as juveniles, and eventually as adults (Bruch, 1986).

Size increase is greatest in the first year. During the second and third years of life, size increase is typically three-fifths that of the first year. In successive years, the length increase was less than two-fifths that of the first year. On the other hand, weight gain is inversely related to length increase. Deepwater sculpin put on the least weight in the first year, despite the greatest gain in length. In successive years, as elongation slows, weight gain increases (Selgeby, 1988). The largest fish tend to be the oldest.

Reproduction

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

Sexual maturity does not occur during the first growing season. Instead, after becoming benthic organisms, gonads begin to develop during the second half of the second growing season. Even at this rate, less than half of this age group is fully mature by fall of their second year. The remainder of the fish become fully sexually mature by the fall of their third year (Selgeby, 1988).

Deepwater sculpin spawn during late fall and winter in the Great Lakes and during summer and early fall in Canada (Black et al., 1981). The average number of eggs found in the ovaries of ripe females (females who are just about to lay eggs) is 481. As in other aspects of sculpin life, size does matter and the largest females have the greatest numbers of eggs. Eggs range in size from 1.5 to 2.2 mm (Jacoby, 1953). In the Great Lakes the eggs hatch at the same time that the ice on the lakes begins to break up. (Black and Lankester, 1981; Selgeby, 1988)

  • Breeding interval
    Breeding is likely to occur each year.
  • Breeding season
    Breeding occurs in late fall and winter.
  • Average number of offspring
    481
  • 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

Lifespan/Longevity

The general method for determining age has been to count the annual ‘rings’ on the otolith. According to data collected in the summer of 1973, the maximum age for deepwater sculpin in the Great Lakes was seven years. More recent research suggests that alternating clear and dark bands on the otolith reflect rapid growth during the summer and much slower growth during the winter. (Selgeby, 1988)

  • Typical lifespan
    Status: wild
    7 (high) years

Behavior

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

Communication and Perception

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.

Food Habits

Data on food preference is based on stomach contents of captured fish. The most prominent food item in all specimens examined was the amphipod Pontoporeia hoyi. Also often consumed were opossum shrimp, Mysis relicta (Black et al., 1981). An overwhelming proportion of the diet of large deepwater sculpins is made up of P. hoyi compared to the diet of smaller sculpins which feed fairly equally on P. hoyi and M. relicta (Brandt, 1986 and Wojcik et al., 1986). (Brandt, 1986)

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

Predation

Predators of deepwater sculpin include lake trout (Salvelinus namaycush) and burbot (Lota lota) (McAllister et al., 1979). By the early 1950s, lake trout and burbot were nearly extirpated from Lake Ontario after falling victim to over-fishing and sea-lamprey parasitism. Shortly after the population declines of these two keystone predators, deepwater sculpin disappeared from Lake Ontario for almost the next 50 years. It is believed that the loss of these keystone predators resulted in huge disruptions to this freshwater fish community and deep population declines of sculpin.

Anti-predation mechanisms have barely been studied in deepwater sculpin. The prickles on the top of the body and the four spines on top of the head may serve as deterrents to predators. In addition, the fact that deepwater sculpin spend most of their time under conditions few other species can withstand, limits their interaction with potential predators.

Ecosystem Roles

Deepwater sculpin are the number one prey item for lake trout (Salvelinus namaycush), a once widely available, commercially harvested fish found in all the Great Lakes. Although a concerted effort has been made since 1950 to restore lake trout populations to the Great Lakes, success has been spotty and limited. Natural reproduction of lake trout is currently occurring on a widespread basis only in Lake Superior. In Lakes Huron, Michigan and Ontario, only limited natural reproduction has occurred. Of these three, only in Lake Huron do the larval fish survive into adulthood (USGS, 2001).

Due to their role as key forage items for lake trout and burbot and because M. relicta and P. hoyi are their main food sources, deepwater sculpin are thought to be responsible for facilitating the majority of the energy movement from benthic organisms to higher trophic levels. This obscure but critical role is likely to have far ranging influences on the overall productivity of the entire Great Lakes ecosystem.

It may be that competition between sculpin species contributed to a decline in deepwater sculpin. Data on competitive feeding habits of various sculpin species are limited, however, juvenile deepwater sculpin and slimy sculpin (Cottus cognatus) have over-lapping food preferences and habitat use, creating the potential for competition. There is also evidence that slimy sculpin prey on the eggs and larvae of deepwater sculpin. (Brandt, 1986)

Economic Importance for Humans: Positive

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.

Economic Importance for Humans: Negative

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

Conservation Status

From 1942 to 1972, no deepwater sculpin were captured in Lake Ontario so far as is known. Between 1972 and 2002, only six have been caught there, despite continued government mandated trawls aimed at determining the extent of their extirpation from the Great Lakes. All six were caught in Canadian waters, three in 1972 and three in 1996 (Black et al. 1981).

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 even being a species of concern for the Great Lakes region (NYSDEC, 2002). They are however, listed by the New York State Department of Environmental Conservation and the Canadian government as being threatened and monitored (NYSDEC, 2002, COSEWIC, 2001). Research efforts are underway to determine how many deepwater sculpin are left in the Great Lakes and the other deep water lakes of 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 the amphipod Pontoporeia from the majority of the bottom of Lake Michigan. As one of their main food sources, the loss of this important food source will substantially impact the recruitment of deepwater sculpin. The second threat is the presence of invasive round gobies in off-shore waters that overlap the distribution of spawning sites for deepwater sculpin. Round gobies are fierce fighters, and often out-compete sculpin species in the same area (Jude et al., 2002).

Contributors

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

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

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

References

"New York State Department of Environmental Conservation" (On-line). Accessed November 19, 2002 at http://www.dec.state.ny.us/website/dfwmr/fish/fishspecs/endgtext.html#deepwatersculpin.

"Scientific Committee on the Status of Endangered Wildlife in Canada (COSEWIC)" (On-line). Accessed November 19, 2002 at http://www.speciesatrisk.gc.ca/media/back3_e.cfm.

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.