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People fishing in a boat on a pond

Pond Construction and Watershed Management is part one of seven in the Management of Recreational Fish Ponds series.

Alabama has about 250,000 small ponds covering more than 134,000 acres. Ponds are usually built for several purposes: irrigation, livestock watering, and recreation. Recreation is probably the most important reason for building a pond in Alabama.

Unfortunately, most ponds are poorly managed for recreation, even though as much as 25 percent of all fishing takes place in private ponds.Properly managed ponds provide excellent recreational opportunities. A good fishing pond must be managed like a vegetable garden: It must be seeded (or stocked) properly, limed and fertilized correctly, weeded now and then, and harvested in the correct numbers and on an appropriate timetable.

The purpose of this series is to provide the owner or manager with keys to success–guidelines for correct pond management. The first step in recreational pond management is to decide what kind of recreation is desired. Ponds can be managed for fishing, swimming, wildlife attraction, and esthetics. It is difficult to manage for all of these recreational activities equally well, but the most important can be emphasized. This publication will target fishing and attracting wildlife.

Pond Dynamics

No two ponds are ever exactly alike. Even ponds in the same watershed and built very close to each other can be very different in appearance, and differences in watershed and soil characteristics are particular to each pond. Differences affecting management are those associated with water quality, plankton, and fish populations.

Water Quality

Water quality factors of temperature, pH, alkalinity, hardness, and dissolved oxygen affect fish health and production. These factors are rarely constant in a pond. Temperature, dissolved oxygen, and pH will change or cycle each day, and alkalinity can change over longer periods of time.

Oxygen Cycle

Oxygen is dissolved in water from two sources–air and photosynthesis. Oxygen dissolves into the pond water from the air as the two are mixed together through wind and wave action. Mechanical aeration using pumps, sprayers, and paddle wheels can be used to increase dissolved oxygen levels during periods of low oxygen.

Photosynthesis is the other source of dissolved oxygen. In this process, plants produce oxygen while making food from carbon dioxide and water in the presence of sunlight. Algae release this oxygen directly into the water during photosynthesis. Since photosynthesis is driven by the energy of sunlight, oxygen production occurs during daylight. Therefore, dissolved oxygen concentrations in ponds tend to rise throughout the day. At night dissolved oxygen slowly declines as fish, insects, zooplankton, bacteria, and algae consume oxygen through respiration. Under normal conditions dissolved oxygen concentrations should not fall below 3 or 4 parts per million (ppm). Oxygen concentrations below 3 ppm stress fish, and many fish will suffocate at concentrations below 2 ppm.

Alkalinity, Hardness, and pH

Alkalinity and hardness are important in providing adequate natural food and in maintaining a healthy fish population. The pH of the pond cycles daily because of respiration and photosynthesis. Carbon dioxide released from respiration reacts with water, producing carbonic acid. The pH scale measures the acidity; therefore, as carbonic acid is formed the pH is lowered or the pond becomes temporarily more acidic. Algae use carbon dioxide for photosynthesis during daylight hours and the pond water becomes less acidic with the decline of carbonic acid. Because of this, a pond pH normally fluctuates between 6.5 and 9. If the pH drops below 5, as it does in ponds that receive acid runoff, or rises above 10, as in low alkalinity ponds with excessive algae blooms, fish will be stressed and can die. The only practical method to manage for abnormal pH changes is to increase the alkalinity of the pond.

Alkalinity is a measure of bases in the water. Bases react to neutralize acids and, therefore, directly influence pH. As bases react with the hydrogen ions present, they buffer or suppress pH changes. Some alkalinity is necessary for good algae production. An alkalinity of 20 ppm or more is necessary for proper algae growth and, therefore, good fish production.

Hardness is a measure of calcium and magnesium ions. Hardness concentrations are usually similar to alkalinity (if derived from limestone) but can be different, especially in coastal areas. A lack of hardness can reduce plankton production and increase the likelihood of muddiness.

Blooms and Pond Color

Plankton is a term used for all microscopic and near microscopic living things that float in the water. Plankton includes both tiny aquatic plants called phytoplankton or algae and animals called zooplankton. Planktonic algae serve as the base of the food chain. Zooplankton and aquatic insects feed on algae, and they in turn are eaten by small fish (fry). Small fish are then eaten by larger fish.

 

Pond food chain from fertilizer to fishing

Pond food chain from fertilizer to fishing

Directly or indirectly, algae provide almost all the basic food for the pond except for a small quantity of insects and worms that fall or wash into the pond. Managing planktonic algae is essential in providing the food to produce an abundant and healthy fish population.

Changes in pond water color can be related to planktonic algae concentrations, called “blooms,” or to suspended sediments and organic matter. Water that is good for fish production is green water; the green color comes from billions of suspended microscopic algae. Water color changes if these algae blooms “die-off” rapidly, turning the water brown, black, milky, or clear. When this happens, decomposition of the dead algae consumes oxygen, leading to possible stress, suffocation, or disease. Algae die-offs are common in deep hill-type ponds or in fish ponds receiving too many nutrients. Mechanical aeration may be necessary after algae die-offs to keep fish alive.

Sediments washed into ponds after heavy rains will also change pond color. Color should return to normal within a few days as settling occurs. Heavy sediment loads can stress fish by irritating the gills and reducing oxygen production. Ponds that receive sediments from surrounding fields may need a wide sod strip around the pond to help trap the sediments before they enter the pond (see Pond Construction). A pond that receives sediment only during heavy rains may need a diversion ditch built around it to channel excess water away from the pond. Many chronically muddy ponds need lime to reduce acidity and to settle suspended clay. If your pond is always muddy, contact your county Extension office for help. Visit www.aces.edu/directory.

Essential Ingredients of Pond Management

Even though ponds are never exactly alike, all can be managed for fishing. The basic guidelines for good pond management will increase pond productivity and decrease problems. The guidelines are discussed in the following:

  1. Pond Construction and Watershed Management
  2. Species Selection and Stocking
  3. Removal of Unwanted and Overpopulated Species of Fish
  4. Liming and Fertilization
  5. Harvesting and Record Keeping
  6. Pond Balance Management
  7. Weed Control

Pond Construction and Watershed Management

Poorly constructed ponds are always difficult to manage. Water levels may fluctuate radically because of pond seepage or inadequate watershed (area that drains rainfall into the pond), or both of these conditions. Aquatic weeds may grow rapidly in shallow areas. Erosion and contamination from the watershed may make good management impossible. For assistance in pond construction or renovation, contact your local USDA Natural Resources Conservation Service (NRCS) Office. The NRCS can provide assistance in design, layout, and monitoring construction of ponds.

All ponds should be designed and maintained with the following guidelines:

  • The dam should have a compacted clay core.
  • Soil lining the pond should be a minimum of 30 percent clay.
  • Pond size should be closely matched to watershed area.
  • Banks should slope rapidly to a depth of at least 2.5 feet.
  • Drains and overflow pipes should be built through the dam.
  • An emergency spillway should be constructed for periods of heavy run-off.
  • Livestock should have limited access to the pond.

Pond leaks because of poor construction are common. Pond dams must be constructed with a compacted clay core that is trenched into impervious soil or rock layer below the pond bottom. Trees or other woody vegetation should never be allowed to grow on the dam, because roots will eventually penetrate the core and cause the pond to leak. Drains allow water levels to be regulated for better control of weeds, fish populations, and for easy access to repair or renovate the pond.

Alabama ponds generally need 4 to 30 acres of watershed per acre-foot of pond storage. Soil types, slope, and vegetation covering the watershed will affect runoff. Generally, more area is needed if the watershed is wooded than for open watersheds. If the watershed is too large, a diversion ditch around the pond may be needed to keep the pond from flushing too rapidly.

Aquatic weed growth occurs most easily in shallow water. Pond banks should slope rapidly (2:1 or 3:1 ratio) to a depth of 2.5 feet or more. Aquatic plants do not easily establish themselves at this depth, especially if a good algae bloom is maintained (see Fertilization and Liming).

Livestock should be kept away from the pond. Livestock erode pond banks, which creates shallow areas that can become infested with aquatic weeds. Cattle also cause damage to dams. Livestock watering troughs should be built below the dam and livestock should not be allowed to loaf in the watershed near the pond.

Fields next to ponds should have a sod border. Sod or grass strips 50 to 100 feet wide between the field and the pond reduce soil erosion and pesticide contamination that can cause fish kills.

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Cutting a trench for the clay core of the pond

Cutting a trench for the clay core of the pond

 

Management of Recreational Fish Ponds Series

 

 

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