PAUL NELSON FISHING: Learn about the thermocline on the lakes

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The fall cool down continues as surface water temperatures in the lakes drop to the mid-60s. Fall fishing patterns can be slow to develop after a long hot summer, but by the time surface temperatures cool down to about 65 degrees, the fish have already started to move and get more active.

It is the same thing when fish get more active in the spring as the water warms as it is in the fall when fish get more active as temperatures cool in the fall going through the same temperature range.

The peak fishing usually occurs between 55 and 65 degrees as the temperatures warm in the spring and the same temperature range is also the peak fishing in the fall as water temperatures cool.

Anglers can see the thermocline on sonar when they drive over deep water in many lakes. It looks like a cloudy area on the screen that starts above the bottom and goes all the way to the bottom.

Anglers can learn a lot of important information from knowing if there is a thermocline in the lake and what depth the top of the thermocline is located.

The water below the thermocline in most lakes is stagnant and does not have enough oxygen to support fish unless the lake is very deep. Trout lakes are often two-story lakes with enough oxygen below the thermocline to support fish all summer.

Anglers can see when the thermocline disappears on sonar, so they know when the fish are able to go back into deep water.

Many fish are just starting to gather into larger schools. Crappies will move on to structures like brush piles or rock piles first, and then move into basin areas for the winter.

Walleyes gather together where the most food is located. Deep water access becomes more important to fish as fall progresses, but how deep is considered deep changes from lake to lake.

If the fish live in Upper Red Lake, deep water means 12 to 14 feet. On Cass Lake, deep water could mean 60 feet and beyond, depending on where the hard bottom turns to mud.

The edge between hard and soft bottom is often the most important edge in the lakes during the fall. The depth of the hard to soft breakline varies from lake to lake and spot to spot.

Anglers should also be able see when the bottom changes hardness on sonar. The signal is bright and wide over hard bottom and a weak darker color over soft bottom.

Once the lakes cool down, walleyes tend to be located on structures with direct access to one of the deep basin areas in the lake and don't frequent areas too far from deep water.

Jigs and minnows are the "go-to" walleye presentation for most anglers in the fall. Anglers should use a good sized minnow and a heavy enough jig to stay in good control of the jig .

Dragging anything on the bottom in lakes with zebra mussels will eventually result in damage to the line. Anglers should briefly test where the bottom is located and then swim the jig a measured distance off the bottom, depending on the level of the fish.

Crappie anglers can usually catch more crappies on artificial lures than live bait in the fall. Anglers don't have to reel up and check their lures unless it feels like the lure has fouled on the hook. There is no need to reel up lures to check or replace the bait, which keeps the lure in the strike zone of the fish longer.

Anglers also need to watch the level of the fish on sonar. Most fish are willing to come up to take a bait much more than they are willing to go down to take a bait.

Much of this is because of where the eyes are located on a fish. Fish eyes look up, in front and to the sides, but they don't look down.

Paul A. Nelson runs the Bemidji Area Lakes Guide Service. Guided trips for 2018 can be booked by calling or texting 218-760-7751 or via email at panelsonbemidji@gmail.com.