Find “Air Conditioned” Water To Catch Summertime Fish

Upstate Outdoors
June 14, 2018 - 9:26 am
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Phillip Gentry

When it gets hot during the summer, people prefer to spend time somewhere it’s cooler. That could mean up in the mountains, near the water at the beach, or inside where the air conditioner is running. Fish are really not that different.

To find cooler water, fish also have several choices, they can go upriver where cooler water is flowing in, they can find an area that stays shady throughout the day, or they can go deep, where nature provides it’s own form of air conditioning 

During the summer months when fishing can become more difficult, much of that “air-conditioned” water that anglers are looking to find fish in is related to a thermocline.

A thermocline is a layer of water more often found in a large body of water, where the temperature gradient is greater than that of the warmer layer above and the colder layer below. To understand the concept, a quick physical science lesson is in order.

A typical reservoir may have uniform temperatures throughout the lake, from top to bottom, for only a short time in the spring and again in the fall. In the summer, most lakes with sufficient depth (usually 30 -40 feet) are stratified into distinct, non-mixing layers of different temperatures. The top warmer layer is referred to as the epilimnion and the colder bottom layer is known as the hypolimnion. These two layers are separated by the metalimnion layer. The metalimnion, better known as the thermocline, is a zone of rapidly changing temperature.

You’ll understand the concept better if you have ever dove down into a lake while swimming and found substantially colder water several feet below the surface. Fish thrive in this cooler layer because it has the best balance of dissolved oxygen. The colder water below, the hypolimnion layer, is actually devoid of oxygen. Because little sunlight reaches the hypolimnion, photosynthetic oxygen production is negligible and decomposition of dead plant and animal matter on the lake floor leads to declining oxygen levels as the summer progresses. 

As water temperatures rise during the summer, any lake that can and will develop a thermocline is in the process of stratifying. This means that 90% of the fish will most certainly be holding at specific depths in stratified reservoirs to take advantage of the cooler water that provides the highest dissolved oxygen. 

To understand the seasonal movements of fish in our local reservoirs – striped bass, largemouth and spotted bass, and even larger catfish species, during the expansive summer months, you have to be constantly on the water monitoring them. As the temperatures and water inflows change, so do fish movements.

The best way to determine the level of the thermocline is by adjusting the sensitivity on most of today’s modern sonar units. The cooler, denser water will rebound the signal and chart a slight line across the graph, marking the depth level. If fish are present in that area of the thermocline, it will also be the level where most of them are residing. 

The next step to finding fish is locating where the thermocline layer meets suitable fish cover.

Anglers often confuse the terms “structure” and “cover”. Simply stated, structure is any terrain feature that crappie, bass, stripers, or other fish will find favorable given the time of year. Cover is a physical object, a stump, tree, rock pile, bridge piling or boat dock, that usually rises vertically in the water column to either break current or provide a hiding place. 

Many successful anglers understand the concept of fishing break lines – an underwater ridge where the bottom drops away to deeper water. As a method of locating fish at a particular depth, get on a specific break line and just follow it all over the lake. Since we already know that fish are more inclined to suspend at the level of the thermocline, the key is to put your baits right in the top of the thermocline and then follow the break line until you come across the fish holding on or above some kind of structure.

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Phillip Gentry is the host of "Upstate Outdoors," noon to 2 p.m. Saturdays on 106.3 WORD FM. This week's guest is Capt. Chip Michalove, the Shark Whisperer, from Hilton Head Island.

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Anglers who understand how fish relate to the rapidly changing temperature zone known as the thermocline, will have a much better chance at catching fish during the summer. Photo by Phillip Gentry.

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