The Fall Turnover

During the summer, lake water stratifies into three zones. The epilimnion, or upper layer, is the warmest and contains the greatest amount of dissolved oxygen. The thermocline, or middle layer, is lower in temperature and dissolved oxygen. The hypolimnion, or lower layer, has the coolest temperature and least (perhaps little or no) dissolved oxygen. Because of the low oxygen levels and the decaying matter at the bottom of many lakes, most gamefish avoid the lower layer or at least the deeper parts of it. In the fall, when the average air temperature is lower than the water's surface, the temperature in the upper zone declines and mixing takes place. Cold water is denser than warm water, so newly cooled surface water sinks to deeper levels. This causes a mixing of the water throughout the zones, and eventually the zones disappear. When the water column mixes completely, the temperature is virtually the same from top to bottom. This phenomenon is the actual turnover. Complete mixing may take several weeks to occur, or it may occur very quickly. A severe cold front can drop surface temperature dramatically, perhaps even 10 degrees in virtually a day's time; this hastens turnover. There is a disagreement as to whether wind plays a role in turnover. Although wind doesn't cause turnover, some biologists say that wind aids the mixing. In any case, the mixing often causes new turbidity in the water for a while. You may also notice suspended leaves and other matter in the water, the result of decaying bottom matter that was in the lower zone being dispersed through all levels.

FISH ON THE MOVE: Once a lake has stabilized after the turnover, fishing improves markedly. With the water now cooling down, bass move out of deeper water and into the shallows where they are more accessible to anglers. This is especially noticeable in large southern lakes and warm summer surface temperatures. Nutrient or plankton dispersal caused by turnover stimulates baitfish activity, and all fish will be feeding actively to build energy reserves for the approaching winter. Also, bass are more likely to be active throughout the day due to less potent sunlight. With all these factors working in the angler's favor, the post turnover can be an excellent time to catch bass. But you must do more than simply rush into the shallows and start fishing any available cover. Shallow cover near deep water is particularly worthwhile, especially if it is abundant or thick. Various types of plants, like reeds, milfoil, lily pads, and hydrilla, provide good places to fish and will hold bass until they start to decay and turn brown. You should also fish creeks and coves, since bass often follow bait there. Start at the mouth and fish your way farther in. Points at the edge of, or leading into, these places are often very productive, as they serve to funnel bait. Main lake points also see the passage of many fish, and they're even better if they're near deep water. If the lake has not yet fully stabilized, don't overlook deeper water since fish may be roaming. Trolling is an effective technique if fish are scattered, so don't be afraid to give it a shot.

LARGE LURES: Often water becomes clearer after the fall turnover, so when selecting lures, go for a natural looking appearance. Plug patterns that resemble shad (or alewife or shiner), bluegills, yellow perch, or crayfish, depending on the environment, are good bets instead of more exotic lures. These patterns are especially productive if they have a sparkling or glittering appearance to produce flash that suggests a moving baitfish. Baitfish are generally big this time of year, so this is a good opportunity to fish larger lures. Try plugs that weigh 1/3 to1/2 ounce and minnow plugs that are 4 to 6 inches long. Minnow bodied plugs that float and dive work well as surface lures, especially for morning fishing, and suspending models are good for subsurface stop and go twitching, Popping or chugging surface plugs are likewise effective, especially in lakes with lots of baitfish activity. If bass are active, you can use fast moving lures. Crankbaits are great for fall fishing; midrange divers are standard, though some places and situations will call for deep runners. But if bass aren't active, or when the action slows, turn to slower and more careful presentations. Soft jerkbaits (single or twin tailed soft bodies) fished in a slow, subsurface twitching motion work well around submerged like grass, brush, and stumps, often catching fish that ignore faster retrieved lures. While spinnerbaits that are slow rolled over objects or dropped along deeper edges of cover may be productive at this time, another good choice would be crankbaits and jigs. Try a jig and pig where the bank is steep, especially if lined with rocks or logs or treetops near deeper water. If bass are shallow but in thick cover, a flipped or pitched jig is prime. Fish it around docks, pilings, and blinds.

SPRING TURNOVER: Turnover is sometimes a spring phenomenon, although only in northern lakes. Calling what happens in spring a turnover is a bit of a stretch; it often does not have the same water disturbing effect as fall turnover. In frozen lakes, water directly beneath the ice is nearly 32 degrees and dense. When longer days and warmer air temperature melt the ice, the densest water sinks, the wind helps mix the water, and the water column becomes a uniform temperature. Soon surface water and shallow areas warm quickly and become very attractive to fish.