The mayfly hatch is finally winding down in the Bemidji area. The mayfly hatch is usually done by the middle of June, so summer fishing patterns have been slow to develop this year.
Surface water temperatures are inching their way back above 70 degrees again, after dipping into the upper 60s for most of the past week.
Big winds last weekend broke down any thermocline that had developed in large shallow lakes like Winnibigoshish, the main portion of Leech Lake, Upper Red Lake, Traverse Bay of Lake of the Woods and Mille Lacs Lake.
It may be hard to imagine the wind being strong enough to turn over the water these big lakes, but it does. Upper Red Lake is less than 15 feet deep, so it turns over quite easily in a big wind.
The rest of the lakes on the list have less than 10 percent of their acreage deeper than 40 feet, which is less than twice the length of the average big water walleye boat. These lakes usually take waves larger than five feet and sustained winds in excess of 30 miles per hour to turn over the water column.
The periodic mixing of water in these big shallow lakes keeps oxygen levels and water temperatures fairly constant from the surface to the bottom of the lake. These are also some of the most consistent and productive walleye waters in the state, with nearly all of the lakes' acreage useable for walleyes.
Summer patterns for big walleyes in these lakes often involve direct access to the deepest water in the lake.
There are small trenches of deep water in Leech Lake and Lake of the Woods that get a significant amount of pressure during the heat of summer from anglers trolling artificial lures with downriggers, lead core line of some other system of presenting shallow running lures in deep water for walleyes.
These deep water trolling patterns improve as water temperatures increase. In a cool summer like this one, deep water trolling patterns for walleyes are not nearly as effective as they are in a hot summer, because most of the walleyes are not concentrated in deep water.
Water clarity is another issue for walleye anglers. The algae bloom this summer has been limited because of cool water temperatures. This can change quickly if temperatures would suddenly become more seasonal and the water temperatures in the lakes would rise into the mid to upper 70s.
The potential for hot weather this summer is fading fast. July is usually the hottest month of the summer, with temperatures already beginning to cool down by August.
The effects of cool water temperatures on walleyes is it keeps them scattered, using a wide range of depths in most lakes. There are walleyes anywhere from the inside edge of the cabbage weeds to the edge of the basin in deep water in most lakes.
Shallow walleyes get pushed around by northern pike and muskies, which makes patterning walleyes in shallow water difficult. One day the walleyes will be active in the weeds, the next day the same weed bed may be infested with pike and a muskie or two.
Deep water walleyes can roam around the basin between structures, following the schools of baitfish they are keying on. These nomadic walleyes are also hard to pattern because they keep moving with their food source.
Fishing pressure is greatest on walleyes relating directly to structure. Many lakes have only a limited number of mid-lake humps and sunken islands, so the same areas get hit by anglers on a daily basis, especially with many anglers having GPS units with map chips.
The best lakes are often the ones with the most structure or the least structure, because it can confuse anglers and they give the walleyes more places to hide.
Lakes with a large amount of structure like Cass Lake, Winnibigoshish and Mille Lacs tend to spread out the anglers because of the shear volume of spots.
Lakes like Upper Red Lake and Traverse Bay of Lake of the Woods have very little structure, so anglers can have trouble patterning walleyes because everything looks the same.
Paul A. Nelson runs the Bemidji Area Lakes Guide Service. He can be contacted by calling 218-759-2235.