Hundreds of invasive carp have been captured by wildlife officials from Minnesota and Wisconsin in the Mississippi River.

Hundreds of invasive carp have been caught from the Mississippi River near Trempealeau, Wisconsin by wildlife officials.

On Friday, the Minnesota Department of Natural Resources reported that they captured a total of 296 silver carp, 23 grass carp, and four bighead carp on November 30. This was the biggest catch of invasive carp in Minnesota so far, according to the agency.

The Wisconsin Department of Natural Resources reported that they monitored six identified invasive carp in that section of the river during the past week, which alerted officials to larger groups of the fish moving towards the upper stream. Input from professional fishermen also aided officials in identifying the location of the carp.

During the 1960s and 1970s, carp were brought into the United States with the purpose of controlling algae, weeds, and parasites in aquaculture farms in the southern region. However, due to flooding and unintentional releases, they were able to escape and enter the Mississippi River. From there, they have been able to rapidly spread northward through various rivers and streams in the central part of the country.

Carp are voracious eaters — adult bigheads and silvers can consume up to 40% of their body weight in a day — and easily out-compete native species, wreaking havoc on aquatic ecosystems. There is no hard estimates of invasive carp populations in the U.S., but they are believed to number in the millions.

Authorities are currently engaged in a fight to prevent their invasion of the Great Lakes and safeguard the area’s fishing sector, which generates $7 billion in revenue.

According to Grace Loppnow, the coordinator for invasive carp at the Minnesota Department of Natural Resources, the high number of carp captured on November 30th is worrisome. However, it is probable that they migrated upstream and were not born in Minnesota’s waters.