The grass carp, an invasive species of fish not natural to U.S. waters, has entered three of North America’s Great Lakes sparking great concerns among wildlife biologists. The large foreign species of carp has been discovered in lakes Ontario, Erie and Michigan.
They hold the potential to wreak great damage upon the Great Lakes’ aquatic environment. What worries experts further is that 9 out of the 10 of the recent grass carp caught are fertile. Most previous grass carp found in American waters have been infertile.
What Is the Grass Carp and How It Got Here
The grass carp is a freshwater fish that can reach weights up to 90 pounds. It’s an herbivorous species meaning it eats only plant life. They are native to eastern Asia, with a natural range from northern Vietnam to the Amur River on the Siberia-China border. The fish was imported to the United States in 1963 from Taiwan and Malaysia to aquaculture facilities in Alabama and Arkansas.
It was hoped that the grass carp would be an effective weapon against weed control in some American waters. As early as 1966 a number of grass carp escaped from a Fish Farming Experimental Station in Stuttgart, Arkansas. Several more subsequent escapes, and several illegal releases have resulted in the unwanted spread of the species into greater American and Canadian water systems.
Trouble For Native Fish
The reason grass carp can be devastating to American water systems is that they are extremely aggressive feeders on a variety of aquatic plants. Native species of fish, such as Great Lakes salmon, lake trout, smelt, walleye, northern pike, perch and many others also rely on the same vegetation not just for food, but to provide underwater habitat conducive to maintaining an overall environment for survival.
Too many grass carp can essentially “deforest” underwater ecosystems, leaving behind barren aquatic landscapes that starve out native fish. Grass carp eat about three times their own body weight daily – a lot of food for those reaching 90 pounds.
Still Time to Control
Scientists estimate they have about 10 years to counter the incursion of grass carp into the Great Lakes. The fish still require several generations to gain sufficient numbers before they can radically alter the aquatic ecosystems here. One suggested tactic is to place nets over areas where the carp are likely to spawn during mating season. Another is to simply control the number of new invaders from being released from other U.S. locations where the fish are legally cultivated.
Another possible weapon against the grass carp are fisherman. This fish possesses many of the qualities that angling enthusiasts enjoy – it’s large, puts up a good fight on the rod and reel, and they are good to eat. A problem, however, is that because grass carp are strictly vegetarians, baiting them is a challenge.
A preferred method to lure the grass carp is chumming – scattering foods like corn, cherry tomatoes or bread on the surface of the water – and then floating a hook “pinch-baited” with corn or bread nearby. Spearing and bow fishing are other popular methods.
Other Invasive Carps
The grass carp is just one of several Asian species of carp causing great concern in American waters. The bighead carp and the silver carp — also called the flying silver carp — have been found in great numbers in many U.S. waterways. These species were also imported from Asia for the purpose of weed and plankton control, but escaped through either accidental or illegal release.