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Fri May 22, 2020, 02:47 AM

Every flood drives destructive Asian carp further into North American waters

Carp can starve out native fish by eating all their food supplies and taking over breeding grounds

Olivia Box
Natural Resources and Forest Ecology
University of Vermont

May 22, 2020

As spring arrives, so do the floods. The National Ocean and Atmospheric Administration (NOAA) is forecasting intense flooding in the Midwest. The good news is that the floods are predicted to be less severe than those in 2019 that cost the Midwest $6.2 billion, but they’re still coming — and they may bring in some unwanted visitors.

Scientists have long feared the arrival of silver and bighead carp — invasive fish native to Asia — to the Great Lakes. Invasive carp are already found in many Midwestern states in the Mississippi River Basin and its tributaries. Another extreme flooding event could allow carp to move further upstream and head toward the Great Lakes, where scientists worry they could overtake the native fish species. Just a few carp in a new area can start a new a population.

Silver and bighead carp can grow up to 60 inches long and weigh over 100 pounds. They can eat up to 40 percent of their bodyweight in plankton, snails, and grasses in one day, which is why they pose such a big threat to an ecosystem. They were imported to the Midwest in the 1970s for aquaculture and were used to control algae in fish farms, but during the Great Flood of 1993 they escaped into the Mississippi River and moved north.

In 2019, floods inundated 6.5 million acres near the Mississippi River, stretching from Missouri to Louisiana. The dams on the Mississippi are meant to maintain water flow for commercial navigation; as an unintended effect, they also slow the movement of fish with hydraulic pressure and gates that make it challenging to swim upstream. During the floods, however, many dams were deluged and at risk of physical damage due to high-pressure conditions. The dams were opened, allowing water — and fish — to flow through.


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