The Common Carp Threat
The Common Carp was introduced to North America by the U.S Fish Commission in the late 1800s as a cheap source of protein. Due to the culinary preference for this species by the immigrants of the time, the Fish Commission encouraged the cultivation of Carp. However, the Carp often escaped the fish farms during flood events. They prospered in the wild due to the lack of native predators and the abundance of suitable habitat.
The Carp population grew rapidly, dominating low gradient, soft bottom wetlands, lakes and streams. At one point, Carp represented 90 percent of the fish biomass in the Des Plaines River. Carp do significant harm to the native, aquatic ecosystems of North America (e.g., wetlands, lakes, streams, and rivers), affecting aquatic organisms. In their search for food, they stir up bottom sediments, and in the process, uproot the aquatic plants which provide numerous ecosystem services.
Aquatic plants slow flood waters and provide stable living conditions for the critical microbial communities which process pollutants such as excess nitrogen and phosphorous. The plants also trap carbon and sediment, provide habitat for a wide range of animals, and support biodiversity. Carp activities create an unsuitable environment for aquatic plant and animal species and their presence has negative impacts downstream. For example, carp are partly responsible for the dead zones forming in the Gulf of Mexico because they disrupt the growth of the microbial populations that remove upstream pollutants such as nitrogen.
Capture and Removal
It may be possible to install barriers to upstream migration in the spring and allow selective removal of Carp. Carp are known to migrate downstream in the late fall, seeking deep waters to avoid freezing during the winter. In the spring, at water temperatures above 60 degrees Fahrenheit, Carp migrate upstream, seeking grassy, inundated floodplains and wetlands in which to spawn. Two general methods can be used to impede upstream Carp migration in the spring.
Wetlands Research has spent some time and effort trying to understand how best to control the deleterious effects of the species. Traps, blocks, pesticides, and access to food supply are all methods of control that have all been tested in one form or the other.
One method involves the use of block nets around deep pools that act as winter traps which can be drained and seined. A second method uses block nets with female Carp emitting pheromones to attract male Carp. The attracted Carp are then removed. In the spring, the caged fertile females will be placed upstream of trap nets and the incoming fish directed by a fine meshed tube into a steel basket that can be lifted out of the water so that the native fish can be separated and returned to the river while the Carp are sold, buried, or left for scavengers. These proposed techniques and devices will be tested as possible means for controlling the Common Carp and its harmful effects on the physical environment, other aquatic organisms and humans.
The most effective control was the isolation of Carp from its food source using a wire mesh product called BenthoShieldTM. BenthoShieldTM prevented Carp from dredging, allowing other aquatic communities to flourish. Submerged and emergent plants grew, increasing light penetration, which allowed native site feeders to once again find their prey. In BenthoShieldTM treated aquatic environments, Carp activity and their deleterious effects are greatly reduced. For more information on or how to purchase BenthoShieldTM, please call or write Kathleen Paap at Wetlands Research (847-774-9118 or firstname.lastname@example.org).