When water temperatures begin to drop in early fall, the Postsummer Period has begun. Cooler nights cause the shift, which can signal the beginning of a peak in bass fishing. The Postsummer Period lasts until fall turnover, which typically occurs in deeper lakes and reservoirs when water temperatures have fallen into the low 60F or upper 50F range. This Turnover Period is short, lasting until water temperatures have stabilized in the low to mid-50F range. This disruption in the stability of summer typically means difficult fishing.

The Coldwater Period follows turnover, as water temperatures continue to fall to annual lows. In northern waters, this leads to freeze-up, sometimes just a month or so later. And the annual cycle completes itself.

WINTER PERIOD SPECIFICS
Bass are cold-blooded creatures, more properly called poikilothermic, as their body temperature closely corresponds to surrounding cold water temperature. Bass behavior is strongly affected by seasonal shifts as well as immediate weather patterns.

During the Frozen Water or Winter Period, largemouth and smallmouth bass display the least activity of the year. They typically hold in the deepest water they ever occupy. For at this time, the depths are slightly warmer and more stable than water near the icy surface. Precise depth depends on characteristics of the body of water.

In natural lakes, bass move to deep flats or basins of moderate depth in 15 to 30 feet of water, often roaming slowly throughout a wide area. Smallmouths hold more tightly, often in discrete wintering holes. In large reservoirs, largemouths, smallmouths, and spotted bass may move even deeper, beyond 50 feet in clear waters.

Bass in ice-bound waters often form large groups where they feed and move little to conserve their dwindling energy resources until spring arrives. Though not feeding, bass can be tempted with a small jig or livebait. Few ice anglers target bass, but incidental catches are common in many lakes and river backwaters.

Largemouths are more active during the first few weeks after lakes first freeze, and again seem to move and perhaps feed more toward the end of the ice-bound season. In shallow lakes, declining oxygen content in bottom waters may force fish closer to the surface in late winter. In severe conditions, fish kills may occur, with the largest fish affected first.

Bass in rivers that freeze seek backwaters with adequate oxygen and protection from current. In some cases, deteriorating water quality forces bass to shift location in midwinter. Because the number of good backwater habitats is limited in many rivers, large concentrations of bass can form.

Where waters don't freeze, bass metabolism is low and feeding is reduced. But the dense aggregations mean that a few fish often are active enough to bite, even at water temperatures below 40F, and good catches can be made. While smallmouths favor bluff areas, sharp drop-offs, or rocky crevices, largemouths often gather along deep creek channel ledges or deep timbered areas. Versatile spotted bass may hold among rock or wood, or off deep structure like main-lake points.

It's appropriate to note here that anglers who target bass in water deeper than 30 feet may find releasing their fish impossible, due to gas expansion in the air bladder, eyes, and other organs. This problem intensifies with each second a fish is held out of water or in a livewell. In extremely deep water, releasing bass can be considered wanton waste. In this regard, largemouths are most sensitive, followed by smallmouths, then spotted bass.

PRACTICAL APPLICATIONS
Understanding the In-Fisherman Calendar is one basis for learning the movement and activity patterns of bass. The calendar serves as a reference, a logical basis to discuss what's happening in the fish's world. Understanding that fish species progress through distinct periods of activity that vary only in their time of onset and duration from year to year based on weather conditions allows anglers to make valid predictions about bass location and appropriate presentations.

Intricacies of presentation have become a focus for bass fishing -- worm colors, crankbait diving depth, rattling lures, precision pitching, weight selection, and the like. Without a basic understanding of the seasons in the fish's world, this array of possibilities becomes baffling and then frustrating. Focus first on the nature of the beast, then presentation options will fall more clearly into place.