Lake habitat can be simply defined as the environments that aquatic organisms (primarily your fish) live in and around. It’s a simple definition that has many important implications for your lake management program. A lake’s habitat encompasses a broad list of chemical, biological, and physical categories such as water depth, temperature, and oxygen content; pond-bottom substrate and contours; live floating, submerged, and emergent vegetation; dead standing or fallen timber; and artificial “cover” such as sunken concrete blocks, rocks, and “trees” or “reefs” constructed out of plastic, PVC pipe, and other structures.
Learning the habitat requirements and preferences of common fishes will help pond owners to not only manage the needs of various life stages of those fishes, but also provide habitat that improves angler success.
Water depth, temperature, and chemistry will affect decisions about species to stock, water aeration, and placement of artificial structure. For example, in most southern ponds, warm season water temperatures are too high and oxygen too low for nonnative rainbow trout, but cold winters decrease stocking success of Florida strain largemouth bass as compared to the native northern strain. Introduced hybrid striped bass do not reproduce, so they do not need spawning habitat, but they do need deep, open water and adequate forage production in those habitats (unless you plan on supplemental feeding).
During summer months, especially if winds do not regularly agitate the water’s surface, ponds can stratify into sharply defined layers. Stratified ponds become uncomfortably warm for fish nearer the surface, but the cooler bottom layer can become depleted of oxygen. To ensure that fish make good use of added structure, place it in water that will be less than six feet deep when allowing for water level changes, or install air diffuser systems designed to oxygenate and mix the layers (see Aeration section).
A firm, gravel substrate is ideal for nest spawners such as largemouth bass and sunfish. A 10 x 10 foot area of gravel three to six inches thick can be added where water will be three to four feet deep during the spring. Gravel should be placed either on plastic sheeting or some other bottom barrier to avoid sinking into the bottom sediments over time.
Nesting largemouth bass prefer sites near large simple structure natural log or pressure treated lumber held in place above the bottom by concrete blocks). This provides adults with cover, especially from bird predators in clear water. However, it should be located 10 to 20 feet away from complex structure (e.g., sunken brush) that early in the season harbors small fishes that eat eggs.
As ponds age, organic silt is naturally deposited on the pond bottom, covering and “filling in” the crevices between substrate particles. For a balanced pond system, this process is slow, but erosion of soil from an unprotected watershed, or frequent nuisance algae or vegetation growth and die off, can increase sediment buildup. Dredging can be accomplished in old ponds to remove silt deposits, but can be expensive.
Non-breeding, adult fish often prefer areas that offer rapid change in water depth and irregular bottom contours. Many ponds that were built to accommodate livestock watering are “bowl-shaped”, offering little habitat complexity. The Pond Construction section of this manual offers ways to effectively address these issues early in the planning stage.