Fish population management is an important practice when goals include trophy pond management or general fishing. Within any ecosystem, a balance must be maintained to support the overall condition of said ecosystem. Straying too far to either side of balance often negatively impacts the ecosystem. This is extremely evident in species populations as imbalances can occur between individual fish species and even within the same fish species. Methods for managing fish populations within a given body of water can depend on target species, available habitat, water access, lake size, and available equipment.
Within privately owned lakes and ponds, management is most often focused on predator prey relationships. More specifically, largemouth bass (Micropterus salmoides) vs. bluegill (Lepomis macrochirus), golden shiner (Notemigonus crysoleucas), or shad (D. petenense or D. cepedianum). Most commonly an imbalance occurs as a result of an overabundance of predators (largemouth bass) and results in limited recruitment and survivorship of forage species present. Limited forage increases intraspecific competition within predator species and reduces the individual condition of predators.
Maintaining a balanced largemouth bass population is best done through the practice of an annual harvest. An annual harvest removes predators from the fish population with the goal of maintaining a predation rate that allows sufficient recruitment for a sustainable forage population. Depending on the lake fertility and carrying capacity, harvesting 10-20 lbs. per acre of bass less than 14 inches in total length is generally recommended as a good starting point, adjusting in accordance to the needs of the individual lake. Correcting an already overabundant bass population often requires an increased selective harvest of the overabundant size classes in order to restructure the fish population. Common methods of harvesting include hook and line (just go out and go fishing!) or electrofishing.
In smaller lakes and ponds, hook and line can be effective as fewer fish need to be removed each year. In larger lakes where a few hundred fish may need to be harvested, electrofishing is recommended as it is more efficient and effective at collecting large numbers of individuals.
While extremely rare, it is possible for an overabundance of forage species to negatively affect predator abundance. This can occur through the interspecific competition between forage species and juvenile and larval predators. During the early life stages predator diets consist primarily of zooplankton and insects until they are large enough to switch over to a more piscivorous diet (other fish). Extremely high densities of forage can actually out-compete these juvenile/larval predators and result in reduced survivorship of predator species. This occurrence is typically only possible in the absence or low density of adult predator species.
With that being said, the most effective way to get the lake back on track is to stock larger predators into the fish population that can consume the average size forage species and begin harvesting any large forage bycatch.
If you suspect this type of occurrence in your lake, contacting a fisheries professional is strongly recommended to determine the causation and path to a solution.
If you have any questions about annual or selective harvests, feel free to contact me at email@example.com and I will be happy to help you determine the best approach for your lake or pond.