Deepwater sculpin

Deepwater sculpin
Conservation status
Special Concern in Canada
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Scorpaeniformes
Family:	Cottidae
Genus:	Myoxocephalus
Species:	M. thompsonii
Binomial name
Myoxocephalus thompsonii Girard, 1851

The deepwater sculpin (Myoxocephalus thompsonii) is a freshwater sculpin that inhabits the bottoms of cold, deep freshwater lakes of northern North America. Its distribution ranges from the Great Bear Lake of Canada to the Great Lakes. It is a designated at-risk fish species in Canada, protected as a species of Special Concern under Canada's Species at Risk Act.^[1][2]

The deepwater sculpin is generally gray-brown with mottling on its head, back, and sides with a whitish underside. When full-grown, they are usually between 4 and 6 inches (10–15 cm), but they can reach to 9 inches (23 cm). They weigh less than an ounce (<25 g). They are a bottom-feeding species, which makes them vulnerable to a build-up in contaminants in polluted lakes. They were considered extinct in Lake Erie and Lake Ontario, but have recently been rediscovered there. They mostly eat tiny crustaceans and aquatic insects and are eaten by lake trout and other predatory fish.^[1]

Distribution

The distribution of the Deepwater Sculpin is almost entirely limited to Canada with the exception of the American Great Lakes and a few inland lakes in Michigan, Minnesota and Montana.^[1] A September 2007 study by the Waterton Lakes National Park and the University of Lethbridge found that the Deepwater Sculpin is the third most common fish in Upper Waterton Lake in extreme northwestern Montana and Canada.

"In Canada, its distribution is patchy and limited to cold, deep lakes in areas that were formerly glaciated or with proglacial lake connections. This includes the Gatineau region through the Laurentian Great Lakes, Manitoba and Saskatchewan and northward to Great Bear and Great Slave lakes in the Northwest Territories. An isolated population also exists in Waterton Lake, Alberta. Designated at risk (Special Concern) are the Great Lakes-Western St. Lawrence populations, which are found in only 10 lakes in eastern Canada. In Ontario, this fish occurs in lakes Nipigon, Ontario, Superior, Fairbank, Huron and Erie. In Lake Erie, only larvae (young-of-the-year) have been observed. In Quebec, it occurs in Lac des Îles and in Roddick, Thirty-one-Mile and Heney lakes. Populations in Heney Lake and Lac des Îles are in decline or may even no longer exist."^[1]

Habitat and Life History

"The Deepwater Sculpin is a bottom-dwelling fish that is found in cold (< 5 °C), well oxygenated, deep lakes. In the Great Lakes, adults usually live between 60 and 150 m in depth. For this reason, not much is known about the biology of this fish. The reproductive cycle is not well understood and the time of spawning is not known. Age of maturity has been estimated at three years for females and two for males. It appears that individuals from the Great Lakes, especially Lake Ontario, are generally larger compared to other populations. The Deepwater Sculpin is also likely preyed upon by deepwater Lake Trout (Salvelinus namaycush)."^[1]

Diet

"The diet of Deepwater Sculpin consists largely of the crustaceans Mysis and Diporeia and chironomid larvae. Zooplankton likely comprise the diet of the larval stage, which is pelagic (open water). Often found to survive on spineless type Manson bugs that frequent the deep water of the cold deep lakes."^[1]

Threats

"The Deepwater Sculpin is likely impacted by changes in zooplankton species composition and abundance. For example, a decline in Diporeia spp. in the lower Great Lakes may pose a threat to this fish since it is an important food source. In addition, the enrichment of lakes with nutrients (eutrophication) and the resulting low oxygen levels in bottom waters likely contributed to the decline of the Deepwater Sculpin in Heney Lake and Lac des Îles."^[1]

Similar Species

The marine and freshwater forms of the fourhorn sculpin (M. quadricornis) are closely related to the deepwater sculpin. However, the marine four-horn sculpin has four horn-like spines on top of the head, which are lacking in the deepwater sculpin.^[1] The freshwater fourhorn sculpin is only found in arctic regions of Canada.

References

1. ^ ^{a b c d e f g h} The Deepwater Sculpin (Great Lakes-Western St. Lawrence)... a Species at Risk Department of Fisheries and Oceans fact sheet (accessed 12 Feb 2011).
2. ^ Assessment and Update Status Report on the Deepwater Sculpin Myoxocephalus thompsonii in Canada COSEWIC Status Report 2006.

• Deepwater sculpin Royal Ontario Museum fact sheet