Bighead carp caught in St. Croix River
Bighead carp are among several invasive Asian carp species that could cause serious damage to Minnesota’s native fish species and aquatic ecosystems.
While other Asian carp have been found in the St. Croix and Mississippi rivers, authorities say the latest discovery highlights the need to rally state and national support to slow the spread of the destructive fish in Minnesota and the Upper Midwest.
“It’s a priority for the state to get an action plan in place to stop or slow the upstream spread of Asian carp,” said DNR Commissioner Tom Landwehr. “We need help from the federal government to address invasive carp in the Mississippi River. Any efforts to stop them here require coordination with the National Park Service, the U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service and commercial navigation interests.”
The bighead is not the “leaping” silver carp seen in nature videos, but it destroys habitat in a similar way by filter-feeding vast amounts of plankton and out-competing native fish. Bighead can grow up to 110 pounds.
The commercial fishing operator caught the bighead carp near the U.S. Highway 10 bridge near Prescott, Wis., which is at the river’s confluence with the Mississippi. The fish was 34 inches long and about five years old.
There is no indication bighead carp are reproducing in Minnesota waters of the Mississippi or St. Croix rivers. However, the DNR is very concerned that without decisive action to improve or implement physical barriers, authorize lock closures and fund research, that situation could change.
Gov. Mark Dayton included $16 million in his current bonding proposal to improve the Coon Rapids Dam on the Mississippi River so it can function as a physical carp barrier. The Legislature is considering the proposal.
Downstream, the locks and dams at St. Anthony Falls in Minneapolis are another likely barrier, but emergency authority doesn’t exist to close the locks if Asian carp are discovered there. The DNR would like to see that emergency authority created.
“Unfortunately, it is extremely difficult to stop Asian carp in large river systems,” Landwehr said. “Our best hope is to stop them at physical barriers on the Mississippi River.”
State and federal agencies have discussed the potential use of electric or hydro-acoustic barriers to stop the spread of carp. While those techniques may help to limit or slow the spread of Asian carp, they likely won’t completely stop carp migration in large, flood-prone rivers like the St. Croix and Mississippi.
DNR officials hope to meet soon with Minnesota’s congressional delegation to talk about these barrier options and other strategies.
The Minnesota DNR will assist partners in a monitoring program this summer called eDNA, which uses a sensitive DNA test to determine if Asian carp are present in the Mississippi River. It will help to determine whether Asian carp are widespread in the river system.
Also, a new technology called otolith (or ear bone) microchemistry will give Minnesota researchers a chance to learn more about this recently discovered bighead carp. “We’ll be able to tell where this carp was born and where it has been,” said Brad Parsons, DNR central region fisheries manager.
This is the seventh incident of bighead carp being caught in the St. Croix and Mississippi rivers in Minnesota, but only the second bighead caught in the St. Croix River.
History of Minnesota bighead carp captures:
- 2011: St. Croix River – Single fish caught near U.S. 10 bridge near Prescott
- 2009: Mississippi River – Single fish caught near Winona; another caught near the Iowa border
- 2008: Mississippi River – Single fish caught in Pool 8 near Brownsville
- 2007: Mississippi River – Single fish caught in Lake Pepin
- 2003: Mississippi River – Single fish caught in Lake Pepin
- 1996: St. Croix River – Single fish caught upstream of confluence with Mississippi River.
Since the 1960s, the DNR has been monitoring fish populations in the Mississippi River. The agency uses electrofishing and netting to assess all species, including invasive carp. Every river pool is sampled annually.
The agency works with commercial fishing operators to look for Asian carp, and the Wisconsin Department of Natural Resources does intensive netting and monitoring of the river for carp as well.
Asian carp were imported from China in the 1970s to control plankton in aquaculture ponds. By the early 1980s, both the bighead and the silver carp had escaped into open waters in the southern states. The fish have the potential to inhabit about one-third of Minnesota’s waters.
The species is very difficult to control once established. In some states with high Asian carp densities, such as Missouri, they can represent more than 90 percent of the fish biomass.