So what is turnover and why does it happen?
In the summer, the days are longer, the sun shines and the warmest water rises to the surface. Sunlight warms the water, and it contains enough oxygen for fish to thrive. As you descend down into the water column, you’ll hit what is called the thermocline. This is the line where water becomes significantly cooler than the surface water. Oxygen levels also drop as dip beneath this invisible line.
Above the thermocline is a warmer water layer that is called the epilimnion. Fish like walleye can survive comfortably in the oxygen-rich water. Below the thermocline – in an area called the hypolimnion -the water has low oxygen and this discourages fish from spending much time there. Decomposing weeds and dead fish that lay on the lake bottom also contributes to the low oxygen level.
Turnover is aptly named. Water is at its heaviest at 39 degrees F, so as the surface temperature of a lake drops to around 50 degrees that top layer of water becomes heavier. Because of this that surface water wants to sink. Lakes can take a couple of days to turnover or it can happen in a day. A cold front, cold rain, or a heavy north wind can increase how fast the turnover occurs.
When a lake turns over, the surface water descends and the warm water from the bottom rises to the top. At times, the bottom water can carry mud and rotting weeds, and it can create murky looking water. This will clear in time. At the same time, the highly-oxygenated surface water falls to the bottom, and spreads oxygen throughout the lake.
How does turnover affect fishing?
Finding fish right after turnover can be a trick. The whole lake basically becomes oxygen rich and an even temperature. The spots you normally find walleye in the spring and summer, like at river mouths, points or along shoreline reefs, may not have fish. Walleye tend to drop into deeper water after turnover and are often found at specific depths. However, find the fish at a certain depth, and you will find them at that depth pretty much everywhere else you look.
Locating walleye after turnover
The reality of fall walleye location is it can be like finding a needle in a haystack. So you have to put the odds in your favour. The easiest way to do that is to mark fish with a depth finder or look for underwater spots that are promising like humps, rockpiles or drop offs. If you are flying into a lake, I would highly recommend bringing a portable depth finder that runs off a rechargeable 12 volt battery. If you already have an ice fishing depth finder, that will work too. You can put the ice transducer in a little pool of water in the bottom of your boat and it will shoot the signal right through the floor. I used a Humminbird Ice 55 flasher last year on a moose hunting trip and it worked splendidly.
Locate deeper structure with your depth finder and even if you don’t mark fish, drop a jig down and work if for 5 to 10 minutes. Generally, fall walleye are 15 feet or deeper. If you don’t get bit move shallower or deeper, depending on what structure you are on. For instance, if you are fishing the top of an underwater hump, you may want let the jig drop off the side into the deeper water. If walleye are around they should hit fairly quickly. If after 15 minutes you have not boated a fish, move to another spot. It may take a little searching but be patient. Once you find them – and that magical depth they are living at – the rest will be easy.
Fall Walleye Tactics
Normally, when I fish for fall walleye, it is all about live bait. Big minnows in particular. Yet in remote fly in lakes, I almost never use live bait. These fish are less fussy and will crush a rubber minnow on a jig head in short order. My go to is a 3/8 ounce lead head with a 4 inch Berkley power minnow. You can use twisters and other rubber bodies as well but the power minnow is a proven killer. Another option, especially if you are trying to locate fish, is a deep diving crankbait. There are a number of cranks that will run down to 15 feet or deeper. The Rapala DT15 is a good choice, but there are others. Another good trick is to run a floating crankbait like the classic Rapala minnow or a Smithwick on a three foot leader behind a lead bottom bouncer. A bottom bouncer of two or three ounces will do the trick. Very few walleye can resist a crankbait and the big ones really like them.
Turnover is a tricky time to fish, but with a little effort you can crack the code. A few walleye fillets popping in oil will make all the effort worthwhile.