Fish
Deepwater Sculpin
Myoxocephalus thompsonii · also called deepwater sculpins
Far below the surface of a large northern lake, in water cold enough that few other fish species can tolerate it, a deepwater sculpin rests on the lake bottom, a living remnant of a population isolated there since the glaciers that once covered the region retreated for good.
Overview
The deepwater sculpin, Myoxocephalus thompsonii, is a cold-water fish native to the deep waters of a small number of large lakes across northern North America, including several of the Great Lakes. Its status as a glacial relict species, near-total restriction to the coldest, deepest lake zones, and daily vertical migration tied to light levels make it one of the more ecologically distinctive freshwater fish in North America.
A survivor left behind by the ice
Each isolated population of deepwater sculpin has been quietly persisting in its own cold lake depths since the ice age ended, cut off from every other population by warmer water it simply cannot cross.
Status
Least Concern — present and stable within the cold, deep lake habitat it depends on across northern North America, though naturally fragmented on a lake-by-lake basis as a glacial relict species.
Deepwater Sculpin: common questions
Why is the deepwater sculpin called a glacial relict?
This species survives today as a population left behind in cold, deep lake habitat after glaciers retreated at the end of the last ice age, and because it cannot tolerate the warmer, shallower water separating one deep lake from another, its populations have remained isolated from each other for thousands of years, a pattern typical of what scientists call a glacial relict species.
Why does the deepwater sculpin stay so deep in lakes?
This species is adapted specifically to cold water temperatures found only in the deepest portions of the large lakes it inhabits, and because it cannot tolerate the warmer conditions typical of shallower water, it remains almost entirely restricted to these cold, deep zones rather than venturing into the shallows most other freshwater fish use.
Does the deepwater sculpin move around much during the day?
This species does undertake a vertical migration within the water column tied to light levels, generally staying deeper during daylight hours and moving somewhat shallower under the cover of darkness, a pattern thought to help balance feeding opportunities against the risk of predation.
Where is the deepwater sculpin found?
This species is native to the cold, deep waters of a small number of large lakes across northern North America, including several of the Great Lakes, with each lake population remaining largely isolated from the others due to the warmer, unsuitable water separating them.