Silver (Hypopthalmichthys molitrix), bighead (Hypopthalmichthys nobilis), black (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella) are invasive fish native to Asia. They were introduced to the United States back in the 1970s as a method to control algal blooms in wastewater treatment plants and aquaculture ponds, as well as a food source for humans. They have since become established in the natural waters of the Mississippi River basin and other large river systems in Missouri and Illinois.
Sterile or triploid grass carp are permitted by the NYS DEC as a biocontrol for aquatic plant management in privately owned ponds in New York State.
Although the impacts of silver, black, bighead, and grass carp may not be direct, the presence of these species can reverberate through the food chain and impact both native species and local economies. This is due mostly to the food sources they consume. These include plankton which is also a major food source for native mussels, larval fish, and several species of adult fishes. In this way, carp can disturb food web interactions and negatively impact native species and their associated energy flows.
The disturbance of native food webs by invasive carp can also impact local commercial fisheries as their presence results in declines of native species. In addition, there is not yet a large market for invasive carp. Without the establishment of such markets, local fisheries could be compromised. In addition, silver carp (Hypophthalmichthys molitrix) jump out of the water when startled and can injure boaters.
Control and Management
Prevention of the sale and transport of Asian carp is the most cost-effective means of management. The Chicago Sanitary and Ship Canal is a major pathway in which Asian carp could enter the Great Lakes. A series of electrical barriers are established in the waterways connecting Lake Michigan to the Mississippi River system in an attempt to prevent their spread to the Great Lakes.
Photo credits: Asian carp identification photos: The Tip of the MITT Watershed Council.