Finding Fall’s Fish

Listen to the lake

     During summer, lakes are stratified into a warm upper layer and a cold lower layer, with an extremely important barrier separating the two - the "thermocline," a thin band of water where the temperature rapidly drops. If you turn up the power on your sonar, you can see the thermocline as a fuzzy, black band that's eight to 12 feet thick.

     For gamefish, this temperature barrier is virtually impassable. Warm water fish such as bass and walleye are restricted to the layer above the thermocline.

     The thermocline layer also has another interesting property - it's home to vast quantities of' phytoplankton and zooplankton, which attract important forage fish such as alewives, shiners, smelts and especially ciscoes. Because there are so many baitfish crammed into the narrow thermocline, warm-water fish living above it will swim down and dine along its upper edge.

     But in fall, nature mixes things up - literally. As autumn nights grow colder, the lake's surface water cools. At first, it's only the top few inches, but since cold water is heavier than warm water, this cooling water soon begins to sink and mix with the water below, chilling it, too. This process is enough to begin chipping away at the thermocline layer.

     The mixing is sped up even further by autumn breezes, which stir up the water, and ever-cooler evenings until the thermocline is completely dissipated. When that happens, the water temperature becomes consistent from the top to the bottom of the lake, creating the process we refer to as "fall turnover." It's also nature's way of bringing oxygen-depleted water up from the bottom of the lake, and replacing it with oxygen-rich water from the surface.

     As an angler, you need to appreciate that the fish are now free to roam and feed in every part of the lake, including those areas that were off limits to them all summer. The trick now is to figure out where the fish are likely to be feeding.

Follow the changing forage

     Since fall opens up so many new locations, you might think it's daunting to find the fish. But it doesn't have to be, as long as you remember that food is always the great equalizer. Find the food, and you will find the fish, too. However, fall turnover means the preferred food sources are also changing.

     During summer, crayfish are a vital source of protein for bass and walleye. Come September, however, crayfish begin to moult at the very same time turnover begins, shedding their hard, protective exoskeletons. Seemingly sensing they're now more vulnerable, the crayfish secret themselves beneath structure such as rocks and logs to avoid being eaten.

     This is Mother Nature at her miraculous best, because at the same time she's depriving shallow-water fish of this previously plentiful source of food, she serves up an entirely new menu item. In particular, as turnover progresses and the water continues to cool, baitfish
become more available and an increasingly important source of sustenance.

     Alewives, ciscoes, shiners and smelts spend the summer months in and around the thermocline because they favour its cool water temperatures. But since that layer has disappeared, these baitfish find the chilling shallow water more inviting with each passing day. So, as the likes of bass and walleye drift toward deeper structures and cover, they cross paths with hordes of ciscoes, shiners and smelt that are migrating toward the shallows. Talk about a fortuitous collision course.   

Search the deep structures

     By late October and early November, the temperature of the surface water has typically dipped beyond the chilly phase and is plummeting toward downright cold. When this happens,you can often count on the best fishing of the fall season. Why? This is the time that bass and walleye establish late-fall and winter home ranges. Find these locations, and the fish will be there from one year to the next, unless they end up in the frying pan, of course.

     In the fall, the fish are particularly attracted to deep structures, such as reefs, shoals and underwater points. And once turnover runs its course and the lake readies to freeze, the fish will move out to the very edge of those same structures. By then, the water in the deep basins below will be around 4°C, making it the warmest, most attractive water to the fish. To reach it, now all the fish have to do is go over the edge of the structure and slide down the steepest slope to the bottom.

     Find such edges and you're practically guaranteed success. Whether they're headed to deep or shallow water, fall fish tend to take the fastest, most direct routes.

Trolling trick

     When you’re trolling for fall walleye, it's important to first find the baitfish so you're not fishing aimlessly. The baitfish schools are typically balled up, and often suspended off the edges of deep-water structures. When I find these bait balls, I carefully mark them on my GPS unit. Then I troll my lures - typically crankbaits - around the pods at the same depth. I'll also employ snap weights and planer boards to spread out and precisely present my offerings.

 

By Gord Pyzer – Outdoor Canada