Grass Carp: Grass Carp (White Amur) - Ctenopharyngodon idella Courtesy USGS

Grass carp, which sound like the kind of fish you would find in Cheech and Chong’s aquarium, have been turning up in the rivers around Minnesota. And authorities aren’t excited by the possibilities of this invasive species making a home in northern waters.

In early April, a commercial fisherman caught a 45- to 50-pound grass carp in the St. Croix River near Prescott, Wisc. While it was a thrilling fish to pull in for the angler, it does raise concerns about the changing dynamics of the fish population in the Mississippi River and its tributaries.

The grass carp is one of three reported catches in the Minnesota/Wisconsin river in the past two years. The others came in the past two falls, with one being caught in Lake Pepin on the Mississippi River and the other caught further downstream near the southern Minnesota border. While the Minnesota Department of Natural Resources is concerned about these intruders, it hasn’t found any evidence that they’re breeding yet in northern waters which would accelerate their numbers.

Further downstream in Mississippi River tributaries, other invasive species of Asian carp are having a bigger impact on anglers. Silver Carp are actually jumping out of the water into boats injuring anglers and people riding personal water crafts. The other “invasive” carp to have been found in Upper Mississippi waters are the Blackhead Carp.

Grass Carp, a non-native species, are turning up more frequently in Upper Mississippi River waterways.

All of these non-native species can cause bigger problems than being an inconvenience to recreationists. They can be harmful to aquatic ecosystems because they eat aquatic plants that are important for native fish and wildlife. They can also harm water quality by increasing nutrients. Grass carp were originally imported to the United States for use as a biological control for nuisance aquatic plants in southern states.

The Minnesota and Wisconsin DNRs are proposing getting federal funds to deal with the situation in a unique way. Following the results of a 2004 study of the situation, the agencies want to install underwater barriers of sound and bubbles to keep the carp from heading farther upstream. Other strategies being considered include developing pheromones to attract the carp to nets or repel them from locks and dams or other points along the river.

Fisheries managers point out that it’s easier and cheaper to keep non-native fish species from establishing themselves in an area than to have to try to eliminate them later on down the road.

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

I'm afraid I have little hope for saving our streams, lakes, rivers, and wetlands from another invader. We have not all been doing our job educating people about invasive species and we have not all been doing our job telling people what to do about them (though many of us, especially many folks with the DNR, have done quite a lot!). In fact, even though we can see the devastation caused by invasives (the carp turning our streams into muddy messes where nothing else can live) people who should know better continue to promote their spread. For instance, the Wildlife Rehabilitation Center, right here in Minnesota, rehabilitates and releases House Sparrows and European Starlings!!! To be fair, they claim it doesn't make a difference in the long run, but that doesn't even matter, what matters is that they are in a place where they could be educating the public but they are not. And yes, it does matter. Every time I scoop House Sparrow eggs out of one of my Bluebird houses and a Bluebird then uses it, I have made a difference. I wish everyone cared, and I bet they would, if we would get our butts in gear and help teach them!!!

posted on Sat, 05/13/2006 - 2:21pm
Anonymous's picture
Anonymous says:

There are hundreds of Minnesota Lakes that would benefit greatly from the introduction of Grass Carp. Weeds are choking these lakes to death.

posted on Thu, 11/02/2006 - 2:10pm
Fisherman's picture
Fisherman says:

What would really help grass choked lakes clear themselves is to control / reduce / eliminate the use of the fertilizers that cause the vegatation explosions in the first place.

posted on Mon, 12/03/2007 - 11:25am

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