Quality habitat is essential for healthy fish populations. Habitat includes all of the physical, chemical, and biological characteristics that affect the pond environment. Water quality, depth, bottom type (mud, gravel, etc.), vegetation, watershed type (forest, grass, etc.), and climate are all habitat characteristics. The pond owner has control over most of these and can manipulate them to benefit fish populations.
Fish need quality water to survive, grow, and reproduce. Quality water has no pollutants, is high in dissolved oxygen, and does not have excessive organic matter or silt. Fencing a pond to prevent access by livestock is extremely important for maintaining good water quality (see Aquatic Vegetation section). Livestock trampling erodes pond banks, which causes pond shallowing, muddy water, and loss of fish habitat. Livestock wastes promote algae and other plant growth, increase organic content, and increase the chances for fish kills. Livestock fences should be 50 to 100 feet from the pond bank and completely enclose the pond, including the dam and spillway.
Every pond should have a vegetated border. Forested or grassy areas at least 50 feet wide will reduce soil erosion and reduce the amount of fertilizer and pesticides entering the pond with runoff. Trees along the shoreline (not the dam) are desirable for shading and nutrient uptake.
Oxygen in water is produced by microscopic plants (phytoplankton) and other larger plants during photosynthesis, and by wind and wave action mixing the air and water. Most fish need at least 5 parts per million (ppm) of dissolved oxygen for good health. Oxygen levels below 3 ppmstress fish, and most will die when dissolved oxygen levels fall below 2 ppm. Mechanical aeration may increase dissolved oxygen levels in ponds with poor water quality.
Some fish have strict habitat requirements. For example, trout are very sensitive to temperature and dissolved oxygen levels. To survive, trout typically need water less than 70° F, and dissolved oxygen levels greater than 5 parts per million.
Muddy water directly influences the health of a pond. Sight feeding fish like largemouth bass and bluegill need reasonably clear water to find their food. Water clarity is necessary for plankton production, the basic component of the food chain. Water clarity should be at least 18 inches throughout the year. Clarity can be measured using a Secchi disk, which is an 8 inch disk made of wood, metal, or plastic. The disk is marked into quarters alternately painted black and white. Attach the disk to the end of a yardstick or pole (right). Ponds that receive excessive sediments from heavy rains may need a diversion ditch to channel water away from the pond. Ponds that stay muddy may need lime to reduce acidity and to settle suspended clay. Contact your local county extension office or any DWR office for help with muddy water problems.
The primary purpose of fish attractors is to congregate fish for the angler. Bluegills, minnows, and other prey fish use the attractors to hide from predators. Larger fish seeking an easy meal gather at these attractors. Brush piles, Christmas trees, stake beds, and rock piles all make good fish attractors. In ponds 1 acre or less, one attractor is enough. In larger ponds, one shelter for every 2 to 3 acres is appropriate. Attractors should be placed at depths exceeding 2 feet, and within casting distance of the shoreline. Do not place fish attractors in your pond if sunfish or crappie are overabundant and stunted, because you will provide more hiding places for them to escape from bass.
In Virginia, most warmwater species such as largemouth bass and bluegill are generalists and will spawn on practically any bottom material. Channel catfish spawn in hollow tree stumps, root wads, or holes in the bank. In catfish-only ponds, reproduction is undesirable because the catfish tend to overpopulate and stunt when no predators are present. Therefore, nesting structures should not be provided.
Most (not all) minnows spawn on rocky substrate, and a gravel bed (½ to 1 inch diameter, 4 to 6 inches deep) makes a good spawning area. Bluegill are attracted to these areas as well. Gravel beds can be added anytime, although locating potential sites before pond construction or during drawdowns is preferred. Do not locate gravel beds in sites prone to heavy erosion. Floating boards (1×6, 1×8, etc.) and cinderblocks make good spawning substrate for minnows that don’t spawn on rocky substrate.
Because they require flowing water to keep their eggs oxygenated, trout do not typically spawn in ponds.