Yet, even in northern Minnesota, shallow panfish bites can occur in shallow water. Stange says: “We have a few large lakes near the office (in Brainerd, Minnesota) that have little bays or basins connected to the main lake by small channels. These often hold panfish all winter. In one case, panfish have to squeeze through a little channel that’s only 4 to 5 feet deep. They might have only a foot of water under the ice to travel through.

“Nobody was fishing these bays through the ice until about 12 years ago,” he says, “and now it’s a popular spot. One small bay beyond the channel has a 20-foot hole, but no inlet. Somebody has to investigate before most of these shallow patterns are found throughout the country, because factors that can’t be registered with the naked eye play a role in determining where panfish might hold in winter.”

Genz directs the Trap Attack circuit of ice-fishing tournaments each winter. “In southern Michigan, during the first weekend in January, fish are caught in 6 to 15 feet of water, inside the weeds. In Illinois, during the Trap Attack in mid-January last year, participants were catching Chain of Lakes panfish inside the weedline in 5 to 7 feet of water, because the oxygen content was high in the shallows. Some of the weeds were green, but a lot were brown, too. The oxygen counts remained high, possibly because of plankton counts. What we can’t tell by looking at the water is the plankton count.”

Zooplankton requires oxygen, too, and it’s provided not only by green weeds, but also by phytoplankton—plants of the microscopic world. Biologists studying plankton counts throughout the year have noted that populations can crash during winter, especially in the Far North, and especially during harsh winters with thick ice and heavy snowfall. The more snow and ice a lake has over its surface, the harder it becomes for sunlight to penetrate. Sunlight is, of course, the key to photosynthesis—the process by which green plants create food, giving off oxygen as a by-product.

Dying weeds not only stop producing oxygen but also create an oxygen deficit. The bacteria and other organisms that aid in the process of decay increasingly consume oxygen as death rates and decay increase. Normally, larger fish can’t be found around brown, decayed weeds. But in the presence of unusually high counts of phytoplankton, panfish sometimes remain. The only way to find out is to look. Traditional thought patterns are hard to break—something any fisherman can turn into an advantage over the locust-like swarms of winter panfishermen we find out on the ice.

“On the Finger Lakes, in New York, we caught nice bluegills in the weeds during late January last year,” Genz says. “We don’t catch panfish deep in those lakes during winter. The water is exceptionally clear, and the weeds stay green all winter. And it doesn’t freeze until Christmas, giving wave action an extra month or so to mix oxygen into the water, compared to lakes in Minnesota, Canada, or northern Wisconsin. In cloudier lakes near the Finger Lakes, however, deep panfish patterns exist. The thing to keep in mind isn’t what panfish generally do, but what they generally do in your area. In all the mid-latitude areas we’ve mentioned—southern Michigan, Illinois, and Iowa—deep patterns for panfish persist all winter. It’s just a matter of knowing the environment where you’re fishing.”