OUTDOOR CORNER: PERRY CO. LAKE BREATHES NEW LIFE

The Missouri Department of Conservation has installed an aeration system at Perry County Lake near Perryville. This lake is a part of a statewide study to determine why crappie populations in many small impoundments are in poor shape.

Perry County Lake supports about 27,000 white crappie longer than 5 inches, but only 5 percent are longer than 9 inches. There is plenty of food in the lake, but crappie are not eating it. The theory is that during the summer months, crappie stop growing because they are stressed by a combination of low oxygen concentrations and high water temperatures.

As water temperatures rise in the summer, a lake will form two distinct layers, a process called stratification. The warm surface layer has plenty of oxygen due to wind and the oxygen produced by aquatic plants. In Perry County Lake, this layer extends about 10 feet down.

In the cold deep layer, all of the oxygen is gradually consumed by decomposition of organic matter. Aquatic plants can't live in this layer because there is not sufficient sunlight. As oxygen levels drop, crappie are forced to move from the cool water they prefer into the warm upper layer. There they find enough oxygen to survive, but don't eat enough to grow. This condition persists until fall, when the upper layer cools and the two layers mix and restore oxygen throughout the lake, a process called turnover.

The Perry County Lake aeration system consists of two pumphouses which will pump air to 10 air stones located throughout the lake. Besides adding oxygen to the lake, this will create upwellings which should break the stratification, allowing fish to use the deeper and cooler water. On calm days, anglers can easily see the upwellings.

Another part of the study at Perry County Lake is the introduction of aquatic vegetation. In the 1980s, anglers complained about excessive aquatic vegetation. Grass carp were stocked and they did the job too well; there has been very little vegetation present since 1990.

Square stem spikerush has been planted at seven locations around the lake. This plant will stabilize the shoreline and provide habitat for small fish and insects. Spikerush shouldn't hinder bank anglers because it only grows in shallow water and anglers can easily fish over it.

While improving the crappie population is the primary goal of this project, the channel catfish, largemouth bass and sunfish populations should also benefit.

Hopefully by next year anglers will notice an improvement in the fish populations. However, it may take several years for the fish populations to improve, so fisheries personnel will continue monitoring the fish populations. In addition, anglers are being interviewed to determine use and fishing success.

Paul Cieslewicz is a fisheries management biologist with the Missouri Department of Conservation.