Biological control is a method of pest control and species management. It utilizes species of fish that prey on invasive species, trash fish, undesirable vegetation or fish whose population will boom without predators. This type of management is highly effective and if done properly

will lead to a well rounded and balanced fishery. It is important to use biological control strategically in line with a lake’s goals.

Carelessly dumping predator fish into a body of water can lead to unwanted results, so it’s best to have qualified experts in fisheries management and biology make recommendations in line with what the lake will be used for. If the goal is high yield fishing, the recommendations will be quite different from those of a trophy fishing lake, and so on.

Biological control has more applications than fisheries management. In areas where malaria is a constant public health concern, guppy fish are being strategically placed to control the mosquito population.

Below are some common species and families of fish commonly used for biological control.

Triploid Grass Carp

Triploid grass carp are widely used to control unwanted aquatic vegetation throughout the U.S. Grass carp have been so effective at aquatic weed control that they are now used in 35 different states

(Colle 2009). Their primary use is in aquaculture and closed public and private waterbodies, but they are also used in large lakes and reservoirs.

Piscivorous Fish

Stocking predatory fishes (e.g. northern pike, walleyes, and largemouth bass) has been used commonly by fisheries managers in the past to control early life stages of common carp. Several species of non-native salmonids were successfully introduced into the Great Lakes beginning in the mid-1960s to control invasive rainbow smelt (Osmerus mordax)

However, these fish control projects have highly variable effectiveness and have rarely included adequate monitoring to determine success (Meronek et al. 1996). A review of manipulative field studies showed that in about 75% of cases, generalist predators, whether single species or species assemblages, reduced pest numbers significantly (Symondson et al. 2002). Programs to stock predators as a means of reducing prey populations must consider the size and abundance of the predator, the size and abundance of the target prey, the size and abundance of alternative prey, and the physical-chemical characteristics of the habitat. Unfortunately, little is known about the susceptibility of bighead, black, grass, and silver carps, to native piscivores (Conover et al. 2007).

Molluscivorous Fish

Fishery hatchery managers have used molluscivorous fish to control snails in fish culture ponds (Carothers & Allison 1968). Computer simulation models have been used to estimate the effect of molluscivorous fish as a control for zebra mussels. Bioenergetics modeling suggested that there is a strong correlation between the effectiveness of molluscivorous fish and water temperature. Model results indicate that fishes in southern latitudes consumed up to 100 percent more food han those in northern systems because of increased metabolism. (Eggleton et al 2003).