By Norman A. Latona, Jr
Southeastern Pond Management

The summer months in the Deep South are brutally hot and generally lacking in rainfall. In the months of July, August and September, ponds may lose several feet of storage capacity, the result of severe heat and lack of rainfall.

As the water level drops the water temperature, particularly the surface temperature, rises to near 100 degrees. How do fish, largemouth bass, bluegill and shellcracker, deal with these extreme conditions?

Fish are cold-blooded. Their body temperature is strictly regulated by their surroundings. Most of us are familiar with this concept when it comes to fishing. To catch fish in the wintertime, when water temperatures are low, lure presentations must be slow and methodical as cold-blooded fish are slow moving in these conditions.

Likewise, springtime brings increased air and water temperatures and increased fish activity. During these months fishing action may be fast and furious as warm-water fish species such as largemouth bass, bluegill and shellcracker thrive at their "ideal" body temperature and metabolic rate
But what about when water temperatures exceed the ideal? What are fish, bass and bream alike, doing to deal with the heat? And how can they be enticed to bite a hook during the "dog days" of summer

In order to understand the summertime patterns of fish in static waters like ponds, we must first understand a little bit about water chemistry. As water temperature rises, water becomes less dense. This phenomenon, as the sunlight and intense heat constantly warm the surface of a pond, causes a layering effect, called thermal stratification.

In some ponds, stratification may occur in the early summer, resulting in a dramatic decrease in water temperature just a few feet below the surface. In this case, fish simply move to the deeper, cooler water, right?

Well, not really. Along with thermal stratification comes chemical stratification. In effect, as surface temperatures rise and the layering effect occurs, oxygen becomes concentrated near the top. Typically, the point in the water column where temperature begins to fall dramatically also represents the point where dissolved oxygen becomes scarce. Naturally, fish, which must "breath" oxygen to live, are forced to spend the majority of their time in the upper warmer water zone
So, how exactly do fish behave when the water temperature becomes unbearable but the lack of oxygen in the deeper, cooler areas prevent them from spending significant time there? They do several things, and understanding the fish's response to the heat may help you catch more fish
Shade and cover are a fish's ally in the hot summer months.

We have all experienced the drop in temperature when entering a shady spot on a hot summer day. The effect underwater is just as dramatic. Cold-blooded fish, always looking for ideal water and body temperature, take advantage of the shade provided by cover. Once situated in these thermal refuges, fish may be enticed to bite, but likely only by putting the bait right on top of them. Otherwise, fish in heavy cover may be content to wait for cooler temperatures or less sunlight before making the effort to feed

Moving water, even the slightest of movement, may result in noticeably lower water temperature and can prompt heavy summer feeding activity. Some individuals have installed small underwater pumps, designed simply to move water beneath the surface, as an effort to provide hot weather feeding zones for fish.

More extreme approaches to creating water movement include the installation of compressor-driven aerators which are capable of constantly moving tremendous volumes of water; these systems are often referred to as "summertime fish reefs," a result of their ability to lure active fish during even the hottest times of the day.

Wind action may actually help to block sunlight from the bodies of fish living in shallow water. A ripple on the surface may be sufficient to break up intense sun rays and decrease the amount of heat radiating below the surface.

Periods of high wind may actually cool the surface water. In any case, aside from being a fisherman's friend in the hot summer, a slight breeze may actually stimulate fish feeding activity
Finally, fish make a serious adjustment in their moving and feeding times. In the spring and fall, when water temperatures are ideal, fish may feed most actively during daylight hours, taking advantage of the sunlight to help silhouette their prey for easier capture.

In the summertime, however, fish may feed more actively at night. Large predators, in particular, are known to be far more active after nightfall.

Nighttime fishing is often a great deal more productive than fishing the same waters during the daylight.

Summertime temperatures can exceed the level of tolerance of largemouth bass, bluegill and shellcracker.

Although rare, heat-stress mortality is occasionally observed in Deep South ponds. Typically, these fish kills are mild; a few adult individuals may succumb to prolonged periods of unusually high temperature without relief from clouds and/or rainfall.

No mechanism is presently known to reverse the effects of acute heat-stress on fish. Fortunately, these cases are few and far between.