The hot weather in the Bemidji area eased a bit this past week, especially at night. Overnight temperatures in the low 50s with highs in the 70s for several days were enough to drop the surface water temperatures in the lakes from the high 70s into the low to mid 70s.
Algae are short lived and extremely sensitive to quick changes in water temperature. A hot spell can cause an algae bloom, just like a cold spell can quickly kill off some of the algae.
The cool overnight temperatures were enough to knock down some of the algae in the lakes, which almost immediately increased visibility in the water by half a foot or more in some lakes.
Many walleyes have been feeding in shallow water in lakes with a heavy algae bloom but some walleyes were quick to drop off the sides of structure into deeper water as soon as the water temperatures dropped several degrees.
There is still a thermocline in the deep lakes that is acting as a barrier to the fish, with virtually no oxygen left in the water below the thermocline.
Anglers may notice large schools of tulibees suspending off the sides of structure, holding just above the thermocline in the coolest water they can find that still has enough oxygen to breathe.
The bite for most species of fish has been spread out during the day. Smaller groups of walleyes have been moving onto structure at almost any time of day where they will feed and then drop back into deeper water or suspend off the sides of structure.
There was a night bite this past week during the full moon phase. Walleyes and other species were able to feed more effectively after dark and avoid feeding as much during daylight hours.
Walleye anglers have been catching some fish on most of the larger lakes but it has been a slow grind most days. Anglers usually have to fish multiple spots and keep moving to pick off a few of the more active fish.
The extended forecast predicts moderating temperatures this coming week but there is still time for another warm-up in August before the fall cool-down begins. Most years the lakes begin to cool at some point towards the end of August.
Anglers fishing for all species should benefit from the cooler water and increase in the visibility in the lakes. Fish will be able to see anglers' presentations from a greater distance, which should help anglers get more bites without having to put their baits right in front of the fish to be seen.
Anglers on many lakes have been noticing that many of the fish they catch and clean have had full stomachs so the fish are eating - anglers just have to be at the right place at the right time.
Lake Winnibigoshish and Leech Lake have been slow for walleyes recently, in part because of the huge hatch of perch in both lakes this spring.
Anglers cruising across the lakes are seeing the surface of the water dimpling as they go by. Those dimples are caused by schools of small perch spooking from the wake of the boat.
The young-of-the-year perch are getting big enough to become a viable food source for many species of fish. The small perch will begin to shy away from the surface of the lakes and move into deeper water once the algae blooms diminish and the lakes become clearer.
The clear water makes the small perch easy targets for birds. The loss of algae also reduces the amount of zooplankton on the surface, which is what the small perch have been feeding on.
Walleye anglers are still having success with spinner rigs on bottom bouncers when working the sides of structure. Anglers can also fish spinner rigs with a bullet or egg sinker in shallower water to keep the rigs from digging into the bottom.
Anglers will be able to switch back to jigs and live bait rigs for walleyes once the walleyes move out of the shallows and begin to feed in tighter schools.
PAUL A. NELSON runs the Bemidji Area Lakes Guide Service. He can be contacted at firstname.lastname@example.org