Surface water temperatures are still hovering around the 70-degree mark on most lakes in the Bemidji area. The mayfly hatch is virtually done and there is a moderate algae bloom beginning on some of the more fertile lakes in the area.
The potential for hot weather continues to fade as we enter the last week in July. Lake water temperatures are close to the average of the daily high and low temperatures, so it takes highs in the 80s and lows in the 60s to produce water temperatures in the 70s.
The Bemidji area has had only a handful of days in the 80s this summer. Temperatures are typically on the decline by mid-August, so there is not much time left for a drastic warmup in water temperatures.
Fish are cold blooded creatures. Much of what they do is directly related to the temperature of the water. Summer fishing patterns are created by warm water temperatures.
Warm water speeds up metabolism in fish, so they must eat more to keep up with the extra calories they are burning.
Warm water increases algae blooms in lakes that have enough fertility in the water to support the algae. Algae cuts down the amount of sunlight that is able to penetrate through the water and limits visibility in the lake.
The loss of water clarity from algae blooms eventually cuts off the oxygen supply below the thermocline and forces fish above the thermocline to have enough oxygen to survive.
Hot weather has a cumulative effect on the fish and will cause many of the larger fish in the lake to stack up on the edge of the thermocline, where they try to stay in the coldest water that still has enough oxygen to breathe.
The only other choice for fish during hot weather is to bury themselves in the weeds during the heat of day and only come out during low-light conditions.
Cold summers like this summer allow fish to use more of the lake, because there is nowhere in the lake that is too hot or has too little oxygen to limit their movements.
Fish metabolism doesn't rise as much in cool water, algae doesn't bloom as heavily, lake water stays clearer, oxygen stays higher below the thermocline and fish can go anywhere in the lake, as long as they can find enough food to eat.
There are still a lot of walleyes in the area using water less than 15 feet deep, much like they would be earlier in the season.
Lakes with a shallow walleye bite typically have more sediment in the water, or they are stained lakes or they are more fertile lakes with some algae bloom to green up the water.
Many lakes are developing a good walleye bite on top of structure. More fish will move shallow if lake water temperatures hold above 70 degrees, so the algae blooms continue.
Anglers fishing shallow may have trouble keep their presentations free of weeds. Presentations need to be kept off the bottom to be more productive in shallow water.
Bobber rigs control the depth of the bait and can be used to target fish in weeds or can be slowly retrieved with a cast and pause presentation.
Plastics can be another good option for shallow water. They can be rigged weedless and will catch a mixed bag of fish, including bass, northern pike, walleyes, panfish and even an occasional muskie.
Spinner rigs are also effective for keeping baits off the bottom, whether anglers use a light sinker and a night crawler harness or a safety-pin style spinner bait with a jig and plastic or a jig and live bait.
Casting or trolling crankbaits is another presentation that can target a specific depth, with casting working better in the weeds and trolling working better over clean bottom or in deep water.
Anglers have a lot of options for lakes and species to fish in the summer. Switching species or taking multi-species trips can help anglers stay on an active bite, which usually translates to having more fun on the water.
Paul A. Nelson runs the Bemidji Area Lakes Guide Service. He can be contacted by calling 218-759-2235.