Most of Mississippi has enjoyed a relatively cool summer, but its waters still got “summer hot.” With August and September gone, nights are cooler, days are shorter and the sun is far less intense. The water cools; that is predictable. What fish do is not so predictable, but if you can follow the changes they face and how they might respond, better days on the water could be the result.

Change 1. The water cools from the surface. If the lake or a large embayment lacks water flowing through it during the summer, it was stratified and had a thermocline. When the surface water cools to the temperature of the lower water, the water will mix. Many anglers refer to this as the lake “turning over.” In lakes with occasional current, the water will cool slowly. The cooling and the changing length of daylight will trigger a variety of changes in the lake’s plants and animals.

Fish metabolism increases with warming water and slows with cooling water. Metabolism dictates food intake: warmer water, faster metabolism, greater food intake. Catfish appear to follow this simple rule. 

Bass also follow this general relationship, but their preferred temperature and temperature for peak food consumption is in the low- to mid-80s. So bass may actually increase their food intake when the water cools. Exactly what happens to the rate at which bass feed in Mississippi’s warm waters is unknown, but savvy anglers know to fish in cooler water if available. Feeding by crappie is probably more like bass than catfish, but again, these questions await answers.

Change 2. Aquatic vegetation starts to die back. Emergent vegetation in shallow water may remain healthy for a month or more, but it soon begins to deteriorate. Submerged aquatic vegetation, too, stops growing and begins to deteriorate. Hydrilla may seem to be an exception, because surface mats may be at their thickest in October and November, but that doesn’t mean the parts of the plant below the mat are vigorous. Anglers need to be aware that any pattern based on aquatic vegetation is going to be very dynamic as summer turns to winter.

Change 3. The forage changes. Several important changes are happening at the same time, and the changes have different effects on different fish.

Insect larvae are a big part of sunfish’s diet. Many insects started their life cycle in summer. The young insect larvae are plentiful but small. Remember the big mayfly emergence this summer? Yes, those larvae were big when they emerged, but they will spend a year growing from a larva just a few millimeters long to the adults that will emerge next summer. 

Aquatic plants are home to a lot of aquatic invertebrates that bluegill relish. This resource vanishes when plants die. Sunfish will change habitats, looking for food. Think brush or any healthy vegetation that’s left.

Shad are the mainstay of crappie and bass diets in most Mississippi waters. When shad move in the fall, bass and crappie follow. A very accomplished pro bass angler told me that “In the fall and winter, the forage are the structure.” What makes shad move is another unknown, but the known part of that equation is that bass and crappie find the shad.

Shad spawned in the spring and summer are growing, and their numbers are declining. Sometime in the fall — maybe early winter — small crappie and bass run low on food. Plenty of shad remain. They are just right for large crappie and small keeper-size bass, but too big for small crappie and bass and too small for big bass. For big bass, find the much-more elusive large shad.

With the shad growing, becoming less abundant and moving around, some bass and crappie may switch to other forage, like sunfish and minnows. For bass, add crappie and crayfish as well as a variety of other finfish to their menus. Fall is a good time for an angler to think like a shad, but it is also a season to be thinking like a bream, crayfish or the prevalent open-water minnow in the water body.