The water temperatures are not high enough to cause most fish problems, but they are high enough to keep metabolism levels elevated for the fish. Everything has to eat more to keep up with the calories they are burning.
The water in most lakes has some color from algae, but lakes infested with zebra mussels are still on the clear side, especially for August.
One the first changes in the lakes infested with zebra mussels is the edge of the deep weedline begins to move deeper as the sun is able to penetrate further into the depths of the lakes.
The weeds will grow as deep as sunlight is able to reach all the way to the bottom. Turbid lakes have a shallow deep weed edge that may be only 6 to 8 feet deep, while lakes with zebra mussels may have vegetation growing deeper than 20 feet because of extremely clear water.
This does not necessarily mean zebra mussels are good for weeds. The zebra mussels will cover everything in the lakes as the population expands. Anglers catching weeds in infested lakes often find pieces of weeds that are covered with zebra mussels.
The deep weed edge may be the most desirable location in the lakes for most species of fish. When water temperatures are near their peak like they are right now, the coolest place in the lake with the most oxygen and the most food is the deep weed edge.
There are places in most lakes where walleyes, northern pike, largemouth bass, smallmouth bass, crappies, sunfish, perch and muskies are all using the deep weed edge as their primary feeding location.
Anglers can find areas where they can troll the deep edge of the weeds with bottom bouncers and spinners. Anglers need to have good boat control to stay on the edge of the weeds and not get into the weeds, where their spinner rigs will get snagged.
The fish can be located all the way down to the upper edge of the thermocline in most lakes. Anglers can see the thermocline on their sonar as a band of clutter that happens at a similar depth over any areas of deep water.
The depth of the thermocline varies between lakes. Long narrow lakes don’t get as much wave action to mix the water, so the thermocline can be as shallow as the low to mid-20s.
Round deep lakes are much more windswept than narrow lakes, which keeps the water mixed down past 30 feet, so some lakes may have a thermocline down past 40 feet.
The deeper the thermocline, the deeper the suitable oxygen levels go in the lake. A few lakes can have significant spring action on the bottom, so they may be capable of supporting trout.
These lakes are considered “two-story” lakes, which means they are capable of supporting warm water species in the upper portions of the lake and cold water species below the thermocline near the bottom.
Many of the “two-story” lakes are stocked with rainbow trout in the Bemidji area. These trout lakes may also have warm water species living in the shallows, with trout occupying the lower depths of the lakes.
Trout can be caught on things like leeches, night crawlers and even corn. Anglers can also use downriggers or leadcore line to troll smaller crankbaits and spoons.
There is also a spinner rig for trout called “cowbells” which have to be seen to be believed. Anglers usually fish cowbells with night crawlers or a small crankbait.
Anglers need to purchase a trout stamp along with their regular Minnesota Fishing License to fish trout in designated trout lakes. There may also be live bait restrictions in these lakes, so be sure to check the regulations.
Paul A. Nelson runs the Bemidji Area Lakes Guide Service. Guided trips for the 2018 season can be booked at firstname.lastname@example.org.