Heavy snow cover could impact oxygen levels on area lakes

There are many small lakes that have received very little fishing pressure this winter because of the deep snow and poor ice conditions. Anglers fishing larger lakes have also been limited to areas that are plowed by resorts or individual anglers.

There is a good chance that lakes prone to winter-kill will be having some fish die-off this winter.

Shallow lakes usually have heavy weed growth in most of the lake because of the limited amount of deep water. These lakes may not have enough water volume to provide enough oxygen to sustain a fish population all winter if there is too much snow and cold weather.

When heavy snow blocks much of the sunlight penetrating through the ice, the weeds stop growing and begin to decay. Eventually this consumes the available oxygen in the lake and fish begin to die from lack of oxygen.

DNR officials use shallow natural ponds to raise fish for their stocking programs, especially walleyes and muskies. Most of the natural ponds have less than 10 feet of water and are subject to periodic winter-kill, which makes them perfect for raising fingerlings.

If the shallow ponds don't winter-kill, the carry-over fish from past stockings will prey on the fry that are put in the ponds. This lowers the yield of fingerlings harvested for stocking in the fall.

Insects and minnows in the ponds are not as susceptible to winter-kill as the larger fish, so the carry over fish can all die but the food source for the next year's fingerlings will survive.

Deer, birds and other animals may also be having difficulties with the deep snow and cold temperatures this winter. Once the snow gets too deep for deer to move around freely, the deer can "yard-up", which means they will stay where they have the snow packed down, eventually eating all of the available food in the limited area.

The deer herd in Minnesota may suffer some losses this winter if the current weather trend continues. The effects are cumulative, with snow depth and the duration of the cold weather the key factors.

There was a brief break in the cold weather this week. It wasn't enough to melt much snow but it was enough to have a positive effect on the fishing.

Walleyes have been moving shallower and getting more active on many of the larger lakes. There has been a good bite for walleyes in 16 to 24 feet of water in the evenings, with the bite lasting into the night. There has also been a brief flurry in the mornings on most lakes.

The best areas for walleyes usually have hard bottom with some scattered rock and direct access to deep water.

When walleyes are actively feeding they often make a feeding movement towards structure. They will feed on top of a hump if it is in the right depth range or they will concentrate on the points and turns on larger structures that are too shallow on top.

Anglers can drill a series of holes on structure with a power auger and then move from hole to hole with sonar, looking for fish. This approach works best for panfish, which usually travel in larger schools and may be suspended off the bottom, which makes them easier to see on sonar.

Gamefish tend to travel in smaller schools so they are harder to see on sonar, which makes it more difficult to qualify a hole just by looking at it with sonar.

A better approach is to make a quick drop down the hole with a jigging lure. Active gamefish within sight of the hole are going to take it quickly so it only takes a minute or two to check each hole for active fish.

Underwater cameras can also be very useful when searching for walleyes. Anglers only have to see one walleye to know they are there. Anglers should also watch the bottom for rocks or other unique structure which can help locate the best place to set-up a fish house.

Paul A. Nelson runs the Bemidji Area Lakes Guide Service. He can be e-mailed at panelson@paulbunyan.net.