Cold temperatures andstrong winds this past week kept most anglers off the lakes and made fishing tough for those willing to brave the elements.
Wind gusts in excess of 30 miles per hour are strong enough to cause the upper portion of the water column to mix down past 30 feet, which is deep enough to completely turn over many of the large shallow lakes.
Big waves make the water swirl sideways in a big spiral, mixing the water as the waves roll toward the windward shore.
When the waves finally crash into shore they create an undertow that forces the water on the bottom back in the opposite direction of the waves.
The turbulence caused by waves stirs the bottom, breaks off the tops of the standing weeds and evens out the temperature and oxygen content in the water.
Some big shallow lakes like Winnibigoshish, Upper Red Lake, Mille Lacs and shallow bays of Leech Lake and Lake of the Woods can have the whole water column turned upside down in a strong wind.
This week the shifting strong winds resulted in the shallow lakes experiencing turnover several times.
Lakes with a significant amount of water deeper than 35 feet will only have the upper portion of the water column turned over by the wind, which is usually most of the water above the thermocline.
The thermocline is the thin layer in the water column that separates the warm surface water from the cold stagnant water on the bottom.
Most deep lakes will form a thermocline somewhere between 20 and 35 feet deep in early summer as water temperatures increase. The thermocline, however, will break down in the fall,as water temperatures decline.
Water temperatures in the Bemidji area dropped from the low 70s to the low 60s in less than a week, which is fast enough to disrupt fishing patterns and change fish locations in the lakes.
It usually takes at least a couple of days after the winds subside for the lakes to settle and productive fishing patterns to redevelop.
Many of the aggressive presentations anglers used all summer have suddenly stopped working and many of the locations where anglers have been catching fish have changed because of the drastic drop in water temperatures.
Most fish will begin migrating toward their early-winter locations as water temperatures drop into the 50s, so the lakes went from summer to fall from one weekend to the next.
Fish migrations can be very different, depending on the size of the lake. Small isolated lakes will have fish moving only a short distance to some portion of the lake where they will begin the winter.
Larger, more complex lakes or lakes in chains of lakes may have fish moving much greater distances in the fall, with fish moving because of food or to a specific section of the lake because of the food and/or habitat it provides.
Good examples are the walleye migrations into river systems like in the Rainy River, Winnipeg River, Red River of the North, Saskatchewan River and many other large rivers connected to larger lakes across Canada and the ice belt of the United States.
Most walleye anglers like to slow their presentations in the fall. They will try to locate schools of fish with their electronics and then hold their boats over the top of the fish while they fish vertically below the boat.
There is also a shallow bite in lakes like Winnibigoshish, Leech and Upper Red Lake in the fall. Anglers will find walleyes relating to shallow rocks or on shoreline breaks that have plentiful amounts of baitfish in the area.
The competition for time is a big issue in the fall for those who like to participate in all aspects of the outdoors. The shorter days make it harder to work, attend school-related activities and still have enough time left over to hunt and fish.
The choices are about to get even more complicated this weekend as the game (including grouse) and archery deer seasons open Saturday.
Paul A Nelson runs the Bemidji Area Lakes Guide Service. He can be contacted at email@example.com.