During the fall months, landowners may notice more dead fish in their ponds. Officials said there is usually nothing to be concerned about, as it’s a sign of pond turnover.
The natural process takes place in deep bodies of stagnant water and is caused by poor oxygen circulation. When sunlight does not fully penetrate the pondwater, it forms layers that are not mixed until temperatures later cool.
This lack of oxygen throughout the pond causes algae blooms and kills fish, usually in late summer and early fall. Officials said the process is completely natural and does not mean any harmful chemicals or diseases have seeped into the water.
Rebecca Konopka is the Carter County Agriculture and Natural Resources Extension Agent. She said the fish deaths usually do not signify a deeper problem.
“A lot of times, people will think maybe a chemical’s gotten in there, maybe something’s gotten in there or somebody’s done something to kill the fish, and that’s usually not the case. It’s usually just the natural occurrence of that water mixing,” said Konopka. “So unfortunately, about the only thing you can do to prevent it is to make sure that water is mixing throughout the hot seasons.”
Konopka said this is only truly possible through mechanical methods.
“That’s why, typically, if you’re building a pond for fish production, they’ll be shallower, and that kind of prevents that stratification of the water level. But if you do have a deep one, having some kind of mechanical aeration is the best way to prevent pond turnover,” said Konopka.
Konopka said it is completely fine to leave dead fish in the ponds, and they will emit less odor when in water rather than on land. Once the fish fully decompose, the pond goes back to normal. Anyone concerned about their pond water quality can bring samples to several labs statewide for testing.