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Fall pond maintenance protects against turnovers, helps ensure healthy fish

PINE BLUFF — In the fall, farm pond owners can take some steps to ensure the health of their ponds, Scott Jones, small impoundment Extension specialist at the University of Arkansas at Pine Bluff, said in a news release.

Smart pond management in the fall will help ensure the health of fish populations.

“Fall can provide some of the best fishing of the year, so pond owners should be sure to take advantage of the nice weather and enjoy their ponds a few more times before things get really cold,” he said. “It is also the right time to protect your pond against the danger of turnovers and take measures to ensure your sport fish are in good condition for the winter.”

Protecting a pond from a turnover

Substantial fish kills can occur during fall turnovers. The event occurs when surface and bottom layers of water in a pond mix, which results in changes in water properties, Jones said. Water that is suddenly murky, muddy or chalky-looking may be a sign of a turnover.

“Ponds with heavy organic loads, such as dead aquatic plants, leaf litter, limbs, grass clippings, uneaten fish feed or runoff from nutrient-rich drainages are at higher risk of fish kills,” he said. “What ultimately kills fish is oxygen depletion from a combination of algae blooms dying off and rapid decomposition of organics.”

Farm pond owners can help reduce the severity of turnovers by:

• Minimizing fertilization to what is necessary to create an algae bloom.

• Only feeding fish the amount of feed they can eat in 5 to 10 minutes.

• Minimizing organic and nutrient inputs from runoff.

While ponds and lakes are naturally good at processing organic debris, it is best to minimize the amount of leaf litter, dead plant material and nutrient-rich runoff that enters the water, Jones said. That does not mean a pond owner has to rake all the leaves out of the pond every fall, but any measure that reduces organic input to the pond will help prolong its effective life. Nutrient loading is one of the most difficult issues to deal with in ponds and lakes, so it is best to slow this process down as much as possible.

“Also, keep in mind that an expensive, but excellent insurance policy against turnovers and fish kills is a pond aeration system,” Jones said.

Adding agricultural lime

For ponds with low alkalinity and hardness, adding agricultural lime can provide water quality benefits. Potential signs of low alkalinity include clear water and failure of fertilizer to create algae blooms. Low hardness can cause water to stay muddy indefinitely.

The Arkansas Cooperative Extension Service can test the water for alkalinity and hardness. If alkalinity and/or hardness are below 20 mg/L of calcium carbonate (CaCO3), applying 1-2 tons of agricultural lime per surface acre can help increase the health and productivity of the pond. It is best to apply agricultural lime in the fall so that it has time to fully dissolve before spring and so that it does not clear the water during a time of year when aquatic weeds could become problematic.

Stocking forage fish

If a pond’s sport fish looked a bit skinny during the summer months, the fall is a good time to stock forage fish, Jones said. These smaller baitfish will provide sport fish with a nice boost of energy to help them make it through the cold months ahead. Bluegill are one of the best all-around forage fish for ponds and small lakes, but fathead minnows and golden shiners can also provide a short-term boost for sport fish growth and condition.

And if a pond owner has noticed that small forage fish are overly abundant, they can perform partial water level drawdowns in the fall and winter months, he said. A water level drawdown is the practice of partially draining the pond, reducing the depth of the water and exposing some of the shoreline to drying.

Drawdowns are especially important in ponds where there is a lot of shallow cover where small forage fish can hide indefinitely from sport fish. A water level drawdown can draw these fish out of their cover and expose them to predators. It also provides control of some aquatic plants by exposing the stems and roots to drying and freezing, and it is useful if a landowner needs to install shallow cover or make repairs to piers, docks, bulkheads, shorelines or water control structures.

Thanks to drawdowns, forage fish numbers will be thinned, allowing the remaining forage fish to grow larger due to less competition for food. This will provide sport fish with larger meals, which will potentially increase their growth as well. Fall is generally the best time to perform drawdowns because water temperatures are cooler, which is less stressful on the fish. Spring rains will naturally restore water levels.

For ponds with built-in water control structures, landowners can simply open the drain and allow water to exit the pond. When water control structures are not available or have malfunctioned, gasoline powered trash pumps can be used to drain the pond.

“A much cheaper, albeit slower, option is a temporary siphon drain built from PVC plumbing materials,” Jones said. “Diagrams and demonstrations of how to build and use pond siphon drains are readily available online. Dropping the water level 2 to 3 feet usually achieves the objectives most owners are seeking. Just try to avoid draining more than 50% of the pond’s volume during a drawdown. Shallower water provides less insulation from temperature changes and exposes fish to increased predation.”

Optimizing feed and fertilization

Fish may not understand that winter is approaching, but their coldblooded metabolism and behavior is directly tied to water temperatures, Jones said. When the summer heat starts to break and fall winds help mix and cool water further, fish tend to become more active and feed more often. This period of increased activity can last for several weeks before water temperatures start dropping below 60 degrees.

“Generally, feeding should stop around 60 degrees,” he said. “However, this is not a hard-and-fast rule because some fish will continue eating feed well into the mid 50s. If your fish are still eating feed well, continue feeding them until they stop responding. Fish usually will not eat much feed over the winter, but you might get some response to feed after a few consecutive days of warm, sunny weather.”

Pond owners should also stop applying fertilizer when water temperatures drop below about 60 degrees, Jones said. Desirable algae do not grow much below this temperature, so fertilization will just be adding nutrients to the system with no immediate payoff.

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