Published March 13, 2012, 11:15 PM

Temperature changes impact fish behavior

Winter began Dec. 21 and ends March 21. Or so says the calendar, if you prefer a specific date – rather than a change in weather to note the arrival and departure of seasons. For many, winter didn’t really feel like winter until the snow and storms of late February, at least in the eastern part of the state. While that late-winter blanket of white quickly snuffed out memories of January temperatures that felt more like October or April, it didn’t last long. Personally, I acclimated quite well to the winter-like conditions and the reflex of warming up the truck, and making sure it still had sandbags and shovels and various other winter survival gear. Plus, it’s a little easier to take a Sunday nap when you can refer to it as hibernating, or pretending winter will disappear just by closing your eyes.

By: Doug Leier, INFORUM

Winter began Dec. 21 and ends March 21. Or so says the calendar, if you prefer a specific date – rather than a change in weather to note the arrival and departure of seasons.

For many, winter didn’t really feel like winter until the snow and storms of late February, at least in the eastern part of the state. While that late-winter blanket of white quickly snuffed out memories of January temperatures that felt more like October or April, it didn’t last long.

Personally, I acclimated quite well to the winter-like conditions and the reflex of warming up the truck, and making sure it still had sandbags and shovels and various other winter survival gear. Plus, it’s a little easier to take a Sunday nap when you can refer to it as hibernating, or pretending winter will disappear just by closing your eyes.

Fish are kind of like that. While they don’t necessarily hibernate away the winter, they do change their routine a little bit beneath the ice, and seasoned ice anglers have adapted as well.

An article in the January 2008 issue of the North Dakota State Game and Fish Department’s magazine, North Dakota Outdoors, provides some insight into winter fish behavior.

In winter, ice anglers mostly target the state’s cold-water fish species, including yellow perch, walleye and northern pike. Like trout, a cold-water species, these fish remain active even under two or three feet of ice and snow.

Conversely, warm-water species such largemouth bass, smallmouth bass, white bass and catfish slow way down, doing as little as necessary to make it through the winter months. “You could say their internal furnaces are not running on high in winter,” said Randy Hiltner, Game and Fish Department northeast district fisheries supervisor, Devils Lake. “Their metabolism slows down and they just don’t feed as much.”

White bass in Devils Lake, for instance, likely aren’t wasting energy by chasing minnows, but rather eating from the incredible – and easier to catch – freshwater shrimp buffet for which the lake is noted.

Biologists can see this period of lethargy by looking at fish scales, which read like growth rings on a tree. In winter, white bass scale rings are packed closely together, indicating little growth.

Fish are adapted to optimums, said Scott Gangl, Department fisheries management section leader. In summer, for instance, when waters warm, trout become stressed while bass thrive. In winter, the opposite is true. “We don’t know a lot about fish behavior under the ice, other than warm-water species slow way down and likely don’t go actively searching for food,” Gangl said. “So by not being very active, they can reduce their stress level.”

Every winter, though, ice anglers catch the occasional white bass, largemouth or other warm-water species. “Likely what’s going on is the angler just happens to put the bait right in front of the fish, and the fish could be biting more out of natural reaction than because it’s hungry,” Gangl said.

These chance encounters with warm-water species may also have something to do with winter fishing techniques and where fish are hanging out under the ice. “The majority of ice fishermen are putting their bait on or near the bottom, and it just may be that many of these warm-water species are suspended somewhere in the water column,” Gangl said.

Then again, who knows for certain?

“It’s difficult enough to study fish during the open water months, let alone trying to figure out fish behavior when lakes are frozen,” Gangl added.

As the seasons turn in March, I’ll gradually move into my spring pattern. So will the fish and fowl, maybe even a little earlier than normal this year.


Leier, a biologist for the North Dakota Game and Fish Department in West Fargo, can be reached at dleier@nd.gov

Leier’s blog can be found online

at www.areavoices.com

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