Islands in Ice: Lake Huron Fish Spawning Habitat Created by Ancient Streams of Ice

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Paleo-ice streams, or corridors within ice sheets that move more quickly than surrounding ice, may have formed much of the egg-laying habitat for critical fish species in Lake Huron during the last glacial period.

Paleo-ice streams, or corridors within ice sheets that move more quickly than surrounding ice, may have formed much of the egg-laying habitat for critical fish species in Lake Huron during the last glacial period, according to a new U.S. Geological Survey study.

Scientists with the USGS and partners compared lake trout, lake whitefish and cisco spawning sites to surface sediments and to the estimated locations of ancient ice streams in what is now Lake Huron. They found that spawning habitats likely formed within the beds of these ice streams like small rocky islands by the erosion and movement of rocky material about 22,000 to 13,000 years ago.

“Our findings could help resource managers identify and protect spawning habitats for these valuable, native fish species, some of which are now rare or non-existent in areas of the Great Lakes,” said Stephen Riley, a USGS scientist and the lead author of the report.

The new study also suggests that similar processes may have created spawning habitats for fish species throughout the Great Lakes and in glaciated landscapes worldwide, including marine fishes. 

The Great Lakes were formed during the last glacial period, when most of Canada and much of the northern United States were covered by a massive sheet of ice called the Laurentide Ice Sheet, or LIS.

“Like arteries within the LIS, large ice streams cut, ground and dislodged rock as they flowed,” said Riley. “This displaced material likely formed most of the spawning habitat that is critical to lake trout, lake whitefish and cisco in Lake Huron today.”

Paleo-ice streams also existed in lakes Michigan, Ontario, Erie and western Lake Superior, and may have created spawning habitats in these lakes.

Lake trout, lake whitefish and cisco spawn, or lay their eggs, on rocky substrate. These species historically supported the most valuable freshwater commercial fisheries in North America, but their populations crashed in parts of the Great Lakes during the 1950s and 1960s due to overfishing and invasive species.

The USGS partnered with the Great Lakes Fishery Commission on the new study, which was recently published in the journal Fish and Fisheries.

For more information about fish habitat in the Great Lakes, please visit the USGS Great Lakes Science Center website.