I have a County Agent friend that told me a story about the County Extension Agent that preceded him in the county he was in; he told me the county agent had a boat named “The County.” I told him that was an unusual name for a boat. His reply was that the prior County Agent would leave out of the office and tell the secretary that he would be out in “The County.” The man must have been a genius. He could be out in” The County” enjoying one of life’s best pastimes. I think if I had a boat I would name it “The Yard;” that way I could tell my wife I’ll be out in “the yard.” We are more than half through spring and temperatures are already creeping up to summer-like highs; it will not be long before summer is upon us.
Summer! What a great season to enjoy many outdoor activities, especially fishing. There are many good fishing ponds in our area, and what better way to spend an afternoon than casting for that big fish? The unofficial start for summer is just around the corner, May 28, Memorial Day. Summer and fishing go hand in hand, but there are some things to be on the lookout for regarding your pond. Fish kills are common this time of year, and can be caused by several factors, but by far the most common would be oxygen depletion. Oxygen depletion can result from a number of situations: too many fish, decomposition of organic matter, and failure to produce enough oxygen through photosynthesis. Unfortunately, when oxygen levels reach crucial levels, oxygen marks don’t automatically drop down to supply needed oxygen. Most of the time oxygen depletions aren’t noticed until the fish are belly up.
So, how do you tell you may have an oxygen problem? Fish will swim to the surface and gulp air. If disturbed, they dive but quickly return to the surface. Early morning is the best time to check. Fish may surface early in the morning, but return to deeper water as dissolved oxygen builds up during the day. Some County Extension Offices have water test kits that can monitor oxygen levels during critical times.
Pond water generally has three levels during warm months. The top layer is the productive layer. It contains most of the oxygen-producing phytoplankton. The middle layer is a thin, mixing layer characterized by sudden drops in temperature and dissolved oxygen concentrations. The bottom layer is made up of the coldest and heaviest water, which contains very little oxygen. When the top and bottom layer mix during a “turnover,” oxygen in the top layer of the pond is often not enough to meet oxygen demand, and oxygen depletion results.
There are several weather-related mechanisms which cause ponds to “turnover.” But, by far, the most common weather-related condition causing oxygen depletion is cloudy, overcast days. Aquatic plants must have high levels of sunlight to produce enough oxygen to meet the demand of respiration and decomposition. Several consecutive days without sunlight can cause aquatic plants to produce less oxygen than fish consume. This can lead to a fish kill. There are emergency treatments available for ponds with oxygen problems, if you suspect you have problems. Most of these are band-aid fixes to another problem. Contact your local County Extension Agent. Prevention through proper management is the only permanent solution. Your pond may need aeration or simply a reduction of the number of fish. Watch your pond carefully for oxygen problems, from now to October, and remember the old saying “an ounce of prevention is worth a pound of cure.” If you think you have an oxygen problem in you pond, please be sure to call your local County Extension Office for further information.

Bill Starr is Sumter County Extension agent, University of Georgia Cooperative Extension Service. Contact him at 229-924-4476.