Of all the major species anglers pursue in the wintertime, lake trout may be the most accommodating. Unlike walleye, sauger, crappies, bluegills, pike or perch, all of them sluggish and selective in winter, lake trout are the least affected by frigid water temperatures, reduced metabolisms, low oxygen levels and negative environmental conditions. In fact, winter represents a relative high point in the lake trout’s annual life cycle, a time of comparative ease, stability, and surprising plenty.
Unlike most other fish that spawn in the spring, lake trout lay their eggs in the fall. In many respects, their seasonal rhythms, recovery patterns and feeding habits are reversed, the Australians and New Zealanders, if you like, of the fish world.
Also, lake trout love cold water. It’s important for ice anglers to back up a few months and view trout in the mid- to late summer, when conditions for trout are at their stressful worst.
As cold-blooded creatures, fish are unable to regulate their internal body temperatures and seek water that most closely approximates their preferred temperature, generally 48°F to 52°F. In late summer, this zone of cool water is found in the middle to lower levels of most lake-trout lakes, often at depths of 60, 80, even 100 feet of water. But to prosper, lake trout need plenty of oxygen, and the deep basin of many lakes, where late-summer temperatures are most ideal, is also where decomposition of algae is most accelerated and where oxygen levels are low.
As a result, lake trout often are forced to navigate between two evils: Rise higher in the water column or swim into shallower portions of the lake—where oxygen levels are good, but where water temperatures are so warm as to approach lethal levels—or, stay down in cooler waters and suffocate.
Fall turnover brings relief to stressed lake trout. When the waters cool so that the entire column is 40°F, there’s no longer any thermal resistance to the mixing of the water layers. With the aid of wind and wave action, oxygen is restored throughout the water column and to all depths and levels of the lake. Surface water temperatures chill further, and soon ice forms along the shoreline to eventually stretch across the lake.
Now wintertime, the living is easy once again for lake trout, partly because their preferred water-temperature range is the lowest of the popular winter ice-fishing species, at 48° to 52°F, as mentioned. Compare that with the temperature preferences of walleyes at 67°to 72 °F, crappies at 68° to 73°F, and even pike at 66° to 70°F, and you’ll see why lake trout are much more active, mobile, and voracious during winter.
Most other species enter a state of near-hibernation, called torpor, during the frozen-water period. Their feeding is greatly reduced, their digestion rates are slow and their growth is limited. Biologists refer to the minimal winter eating-patterns of most fish as “maintenance feeding”—they eat just enough to survive. Even northern pike, fish that like cool water conditions, reduce their wintertime activity levels significantly, growing at a rate of only about 3.9 percent.
But the icy water temperatures play another important role for lake trout. They open up the entire lake for the trout to roam and search for food. During mid- to late summer, high water temperatures and negative oxygen levels combine to make as much as 90 percent of lakes inhospitable and totally out of bounds to lake trout.
