The first bighead carp documented from Rathbun Lake is also a new Iowa state record. The 93 pound, 8 ounce bighead carp was caught by Larry Sparks on June 15 and confirmed by fisheries biologists with the Iowa Department of Natural Resources (DNR).
This is not the first report the DNR has had of bighead or silver carp in Rathbun Lake, but it is the first one verified by a specimen.
Bighead carp are part of a group of invasive fish known as Asian carp, which includes silver carp, grass carp, and black carp. Bighead and silver carp were introduced into southern U.S. fish farms in the 1970s to help control algae. They subsequently escaped into the Mississippi River Basin during floods and have developed self-sustaining populations in rivers throughout the basin.
The first bighead carp documented in Iowa was in the Missouri River at Sergeant Bluff in 1988. They are now present in the Mississippi, Des Moines, Cedar, Iowa, Missouri, Chariton, Big Sioux, and Little Sioux rivers and smaller tributaries and East Okoboji, Elk, and Snyder Bend lakes in Iowa.
"The only thing stopping Asian carp from moving into additional lakes and stretches of rivers in Iowa is the larger dams," said Kim Bogenschutz, aquatic invasive species program coordinator for the DNR.
Rathbun Lake is an 11,000-acre impoundment on the Chariton River located in Appanoose, Wayne, Lucas, and Monroe counties. It is unknown how the bighead carp got into Rathbun Lake, but they have been below the dam since 1995.
"At this time, we do not know how many bighead carp are in Rathbun Lake or if silver carp are present, too," said Mark Flammang, DNR fisheries biologist at Rathbun Lake.
The DNR will continue to monitor the status of Asian carp populations in Rathbun Lake and the Chariton River.
Bighead and silver carp feed on plankton and compete with native fishes for food and space. Silver carp are an additional concern for boaters because of their tendency to jump out of the water when disturbed by boating activities.
"These fish are spreading and we are definitely concerned. I know it goes without saying, but don't collect these fish and move them to another area," Flammang said. "If anglers and other recreational users see Asian carp in places where they have not been seen before, they should call their conservation officer or their local fish management biologist."
The DNR has laws to help protect waterbodies from aquatic invasive species, including making it illegal for someone to stock fish in state waters. "The best way to control the negative impacts of aquatic invasive species in Iowa is to prevent their spread to new waterbodies," said Bogenschutz.
"People who collect bait should use it in the same water where it was caught and not transfer the bait to other water bodies," she said. "It is tough to identify species when the fish are that small." She also cautioned people who purchase bait to empty their bait containers in the trash and not in the water when they are done fishing because it is illegal to release live bait into any waterbody.