Fall fishing patterns are slowly developing on lakes in the Bemidji area. Surface water temperatures are in the mid-60s in most lakes, so water temperatures have stalled a bit in the past week.
The thermocline on the deep lakes will start to break down as soon as the water temperatures above that line get close to water temperatures below.
Anglers can see a thermocline on sonar in the deepest parts of a lake if one exists. Parts of a lake where the water is not deep enough won’t have a thermocline.
Once the thermocline is gone, the fish will be able to return to the deepest parts of the lakes, if that’s where they want to be.
Water becomes more dense as it gets cooler until it reaches about 40 degrees. The coldest water in the lake eventually sinks to the bottom.
Once the surface water becomes cooler than the water on the bottom, it will sink. When this happens in the fall it is called “turn-over”, which oxygenates the entire water column and gets it ready for winter with the maximum amount of oxygen in the water
Turnover also makes water temperatures uniform from the surface to the bottom, so the lake can continue to cool and eventually freeze.
The fall patterns really don’t start to kick in until the thermocline disappears in the deep lakes. Shallow lakes and shallow bays of larger lakes don’t have a thermocline, with the walleye bite usually improving as the lakes cool.
Walleyes and other species are able to feed for longer periods of time as the water cools and will be able to expand the depth range where they are able to search for food.
There will still be fish in the weeds as long as they are green and healthy, but more of the fish are starting to push off the sides of structures.
Water in many lakes are clearing quickly. Algae (phytoplankton) dies off fast when water temperatures start to drop. Many of the best walleye lakes also have zebra mussels, so the algae is starting from a lesser point in those lakes and clears even more quickly.
The spring hatches of minnows have been living in the shallowest cover in the lakes all summer. Once the algae begins to die, the minnows lose the cover provided by the algae bloom in the water, which makes them more vulnerable to gulls, terns and other birds.
The minnows gather into larger schools when they leave the shallows and head for deeper water, where many new predators are awaiting their arrival.
Anglers can see the big schools of minnows on sonar and know that in a “healthy lake,” there should be predators there to feed on the minnows at some point during the day.
Getting the right presentation is always important to catching fish. The better the fish are biting, the more ways there will be to catch fish.
Anglers are free to try different approaches and make tweaks in their presentations to try to find combinations that catch fish best.
It doesn’t have to be big changes, sometimes several little details can make the difference between getting a few bites and finding something the fish will inhale to the back of their throat.
It can be as simple as changing the color or size of the hook. Adding a bead or changing the color of the bead, changing the pound test or the length of the leader. Switching baits from minnows to leeches to night crawlers will also often result in a few more fish getting caught.
Anglers can change from live bait rigs, to jigs, to artificials, to give the fish different looks. Many of the lures anglers use for walleyes during the winter for ice fishing will also work during the fall.
These lures include different types of jigging spoons, several styles of jigging minnows and even blade baits that can be used for vertical fishing walleyes and other species like crappies.
Paul A. Nelson runs the Bemidji Area Lakes Guide Service. He can be contacted by calling or texting 218-760-7751 or by email at firstname.lastname@example.org