Jim Gilbert's Nature Notes: How do fish survive under the ice?

  • Article by: JIM GILBERT , Special to the Star Tribune
  • Updated: January 9, 2014 - 2:29 PM

We continue to hear lake ice cracking, groaning and booming. Why does this happen?

Once ice forms, it expands when warmed and contracts when cooled. Ice covers all Minnesota lakes except Lake Superior at this time of year. On most of the state’s 15,000 lakes, the ice is now from 1 foot to 2 feet thick. Under this concealment, fish and other animals are sealed off from their replenishing supply of oxygen. Without the mixing of air and water by waves, and with photosynthesis occurring at a much lower level, very little oxygen is introduced into the water.

To survive under all the ice and snow, fish moderate their eating, growth, movement and reproductive patterns. As winter progresses, oxygen first disappears from the bottom of lakes, because bacteria use it to decompose leaves and other organic matter in the sediment.

Consequently, sunfishes, northern pike and other species are forced to move up the water column. Lakes that are very shallow, quite small or that have high decomposition rates eventually run out of oxygen entirely. The result is what is known as “winterkill,” which may kill all the fish in a single lake.

Jim Gilbert’s Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.

  • get related content delivered to your inbox

  • manage my email subscriptions

Click here to send us your hunting or fishing photos – and to see what others are showing off from around the region.

ADVERTISEMENT

St. Louis 3 Bottom 2nd Inning
Chicago Cubs 3
Toronto - M. Buehrle 6:05 PM
NY Yankees - H. Kuroda
Arizona - W. Miley 6:05 PM
Philadelphia - K. Kendrick
Washington - T. Roark 6:10 PM
Cincinnati - A. Simon
Boston - J. Lester 6:10 PM
Tampa Bay - D. Price
San Diego - J. Hahn 6:35 PM
Atlanta - A. Wood
Oakland - J. Hammel 7:05 PM
Texas - J. Williams
NY Mets - Z. Wheeler 7:10 PM
Milwaukee - Y. Gallardo
Miami - B. Hand 7:10 PM
Houston - D. Keuchel
Chicago WSox - J. Danks 7:10 PM
Minnesota - K. Correia
Cleveland - J. Tomlin 7:10 PM
Kansas City - Y. Ventura
Pittsburgh - C. Morton 7:40 PM
Colorado - B. Anderson
Detroit - D. Smyly 9:05 PM
LA Angels - T. Skaggs
Baltimore - K. Gausman 9:10 PM
Seattle - F. Hernandez
Los Angeles - Z. Greinke 9:15 PM
San Francisco - T. Lincecum
Chivas USA 8:30 PM
Colorado
Calgary 26 FINAL
Edmonton 22
Winnipeg 9:00 PM
Brt Columbia
Ottawa 7/26/14 6:00 PM
Hamilton
Toronto 7/26/14 9:00 PM
Saskatchewan
Winnipeg 7/31/14 6:00 PM
Hamilton
Toronto 8/1/14 6:00 PM
Montreal
Brt Columbia 8/1/14 9:00 PM
Calgary
Saskatchewan 8/2/14 6:00 PM
Ottawa
Tulsa 6:00 PM
Washington
Chicago 6:30 PM
Atlanta
San Antonio 7:00 PM
Minnesota
Connect with twitterConnect with facebookConnect with Google+Connect with PinterestConnect with PinterestConnect with RssfeedConnect with email newsletters

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

question of the day

Poll: Should the lake where the albino muskie was caught remain a mystery?

Weekly Question

ADVERTISEMENT

 
Close