Just like on land, production in a pond starts with sunlight driving photosynthesis. Anything that reduces the sunlight reaching a pond or otherwise interferes with photosynthesis will reduce productivity. Conversely, anything that increases photosynthesis increases the pond productivity. There are several factors that affect photosynthesis, alone or in combination, and determine the basic productivity of a pond.

The primary factor in pond production is the quality of the water. If a pond has not been limed, the hardness and alkalinity may be too low to make phosphorus available to the phytoplankton (one- celled, microscopic plants that are the start of the food chain). Also, the pH can vary enough to keep the fish stressed and reduce growth rates. Ponds that are not fertilized usually lack enough phosphorus for maximum production of phytoplankton. Dissolved oxygen levels need to be above 5 ppm (parts per million) for fish to grow. They will start dying at levels below 3 ppm, large fish first. This is usually not a problem in the winter, but warm summer waters may be saturated at only 5 ppm dissolved oxygen.

Turbidity, or how muddy the water is, will affect production if it is to the point that it prevents sunlight from penetrating water. For the same reason, trees around a pond will shade the water, reducing productivity. Turbidity is usually caused by run-off into the pond. Also, if there is too much watershed draining into the pond causing the water to be completely exchanged every 30 days or less, your fertilizer and lime will be washed out. In this case, you may need to dig a diversion ditch for some of the water.

Livestock watering at a pond can cause muddy water and sloughing of the banks. If possible, it is best to fence off the pond and water the animals from a tank connected to the pond. The Natural Resources Conservation Service, part of the U.S. Department of Agriculture, in your area can help with a design.

Aquatic weeds can affect production. You want up to 20% to 30% weed coverage to give small fish some cover. More than that and the pond will be hard, if not impossible, to fish. Not only that, but weeds use up nutrients that would otherwise be available to the phytoplankton. Maintaining a “bloom” of phytoplankton will shade out weeds, helping to keep them under control. Also, water deeper than 3 feet is too deep for most weeds, so the faster a pond reaches this depth, the better. Steep banks can be stabilized with riprap, which also provides cover for small fish.

The length of the growing season will also have an affect on production. Essentially, the sun is more intense the closer you get to the equator. This translates into higher levels of photosynthesis, and therefore primary production in a pond.

Also, since fish are cold blooded, their metabolism is higher and so they grow faster in warm water – up to about 85�F. Bluegill in the southern states with longer summers may spawn 4-5 times a year. In colder, northern states they may only reproduce once a year. Obviously, ponds with longer growing seasons will be more productive.

When looking for ways to improve the fish production in your pond, keep the basics in mind. Phytoplankton undergoing photosynthesis is the start of the food chain. Anything that favors this will increase the productivity.