Flying carp: coming to a lake near you

You’ve seen the videos on the internet and even on the national news — silver projectiles weighing 10 to 20 pounds erupting from the water and occasionally landing in boats.

I’m talking about silver carp, one of four species of fish in the minnow family native to large Asian rivers that are considered threats to our lakes, rivers and the fisheries they support. The silver carp is rapidly expanding throughout the Mississippi and Missouri river basins, as is its closely related native compatriot, the bighead carp.

The other two Asian carp are the grass carp and black carp. These fish, although unwanted in our public waters, have not yet proven to be problems. Grass carp eat aquatic plants and, when wisely used, are an effective tool for controlling some nuisance weed problems.

Biologists’ fears that these fish would escape, reproduce in the wild, and defoliate wetlands was partially realized when grass carp reproduction was documented in the lower Mississippi River. Fortunately, large populations were never established.

Seeing a need for nonreproducing grass carp, aquaculturists learned how to treat the eggs of normal grass carp to create progeny with three sets of chromosomes, a condition called triploid. The triploid grass carp are genetically sterile — they will not reproduce in the ponds where they are stocked or in the wild if they escape. Triploid grass carp can be legally stocked in Mississippi.

The black carp is potentially a very significant problem because they eat snails and freshwater mussels. The waters in the southeastern United States support a rich diversity of snails and mussels, and many species are already endangered. A 1-pound black carp will eat 30 pounds of snails or mussels and grow to 2-4 pounds in 1 year. Black carp were imported by fish farmers and reared to control snails in catfish ponds. Although some fish have escaped, and several black carp have been captured in the wild, biologists are not aware of black carp establishing wild populations. Hopefully, that will not change.

Unfortunately, silver carp and bighead carp escaped rearing ponds and established reproducing populations.

Both fish get large — in excess of 50 pounds. They eat phytoplankton and zooplankton, the plant and animal life that forms the base of the food web. Thus, these two Asian carp can undermine the production of all of our native fish.

The abundances of silver and bighead carp are almost incredible. In areas where they congregate, biomass of silver and bighead carp can reach thousands of pounds per acre. Commercial fishermen in the Illinois and Mississippi rivers have found their nets packed with nothing but silver and bighead carp. In some cases, the catches were so heavy, the nets couldn’t be pulled into the boat and had to be cut. In Europe and Asia, where the fish have also been introduced, the silver and bighead carps often make up more than 90 percent of the commercial catch.

Silver and bighead carp are migratory spawners, moving more than 200 miles in a year. They have rapidly colonized the Mississippi, Missouri, and Illinois rivers.

These fish are hot news right now because of their movement up the Illinois River and potential movement into Lake Michigan and the rest of the Great Lakes. An electrical barrier has been installed in the Chicago Sanitary and Ship Canal to block the movement of silver and bighead carp from the Illinois River into Lake Michigan. Ironically, the Illinois River was not connected to Lake Michigan until the man-made Chicago Sanitary and Ship Canal was built in 1900.

Yes, these fish may be a major problem if they invade the Great Lakes, but they will be an equal or greater problem in the other rivers of the Mississippi River Basin — the Upper Mississippi, the Ohio, the Tennessee and the Arkansas. Navigation locks and dams on these systems will slow the carp down but not stop them.

After the silver and bighead carp enter the Tennessee River, it is just a matter of a few miles and time before they colonize the Tenn-Tom Waterway. I would expect the shallow and fertile Tenn-Tom to provide ideal habitat for high-density populations if the fish are able to reproduce.

I have personally witnessed the silver carp expand in the lower Mississippi River while electrofishing for catfish. Five years ago, we electrofished a bunch of silver carp in a small area. The next year, they were spread out over a larger, but still confined area. Now we encounter silver carp everywhere.

Four years ago, a team of more than 100 fisheries experts contributed their time and knowledge to develop a strategy for control and eradication of Asian carp. Eradication is not possible. Period. I don’t think containment is possible either. The multi-million-dollar electric and sound barriers may slow, but not stop, the expansion.

Developing a food fish market and intensive commercial fishing may reduce the abundance. But it will be a tough sell, and it will not eliminate these prolific fish.

Short of some breakthrough technology like a pathogen specific for silver and bighead carp, which I find extremely dangerous and scary, I see a lot of Asian carp in our future. We will pay dearly for the mistakes of a few people, namely those who allowed these fish to enter our country or failed to insist that only sterile carp be used for management purposes.