Paul Nelson: Surface water in Bemidji area lakes finally nears 70 degrees
Surface water temperatures in the Bemidji area lakes are finally getting close to 70 degrees because of the arrival of more “summer-like” weather. Summer fishing patterns will begin to develop in the lakes as long as the lakes continue to warm past 70 degrees.
Most lakes have been very clear so far this summer. The warming water temperatures will eventually cause an algae bloom in the lakes, which will tint the water green and significantly reduce the visibility.
Algae thrive in warming water temperatures once the lakes have reached 70 degrees. The unused fertility in the lakes fuels the algae blooms — the more nutrients are in the lake the larger the bloom will be.Some lakes, including Devils Lake in North Dakota, have so much agricultural runoff from the rising water table that the algae blooms can literally cover the lake with a thick layer of green slime during hot periods of calm weather.
Most lakes in the Bemidji area have considerably less fertility in the water so the algae blooms tint the water but seldom coat the lakes with algae.
Once an algae bloom causes a sudden loss in water clarity the fish have to make an adjustment and use all of their senses to locate their prey instead of just relying on vision to feed.
Fish are cold blooded creatures so the warmer water temperatures also have an impact on their metabolism. Warmer water means higher metabolism for the fish so they need to increase their calorie intake by feeding more frequently.
The first algae bloom of the summer is also one of the major contributing factors in triggering the summer fishing peak for muskies.
Muskies spend the first part of the summer feeding almost exclusively by sight. The clear water also gives the muskies a good look at anglers’ presentations, which theoretically makes them less likely to make a mistake.
The first algae bloom of the summer causes a sudden loss of visibility for the muskies. Until the muskies make the adjustment to feeding with significantly less visibility, the fish are more vulnerable and anglers have one of their best opportunities of the summer to fool a big muskie and get the fish to bite.
The deeper lakes will also begin to stratify by temperature and form a thermocline. The shallow lakes may start to stratify but they periodically get “turned-over” during heavy winds.
The water column in shallow lakes mixes from the surface to the bottom in heavy winds, which keeps the shallow lakes more uniform in temperature and oxygen content.
Many of the larger lakes in the Bemidji area qualify as shallow lakes and do not stratify and form a thermocline during the summer.
Examples of shallow lakes or shallow parts of larger lakes that do not establish a thermocline during the summer include Upper Red Lake, Big Traverse Bay of Lake of the Woods, Lake Winnibigoshish, Mille Lacs Lake and the shallow bays and main basin of Leech Lake.
Fish in shallow lakes act differently during the summer than fish in deep lakes. The differences are magnified as the water temperatures rise and decrease when water temperatures are cooler.
Summer fishing patterns also alter the presentations anglers should use. When the lakes are tinted with algae, the lowered visibility forces the fish to use their senses other than sight to locate their prey.
Among the big presentation changes for walleye anglers are using brighter colored lures, adding spinners to live-bait rigs and using other types of lures and presentations that elicit more of a reflex strike from the fish.
Bottom bouncers and spinners can combine to form one of the best rigs for deep-water walleyes during the heat of summer.
Safety pin spinners will also work for walleyes located in shallower water and they also allow anglers to fish for walleyes with a presentation that does not need to be in constant contact with the bottom to catch fish.
Anglers are not the only ones who will notice some changes in the lakes with the warming water temperatures.
Area swimmers will discover that swimmer’s itch is back in the lakes as the water warms past 70 degrees and the itch will just get worse as the water temperatures increase.