When people talk about Asian carp threatening the Great Lakes and its fisheries, they typically are referring to bighead and silver.
But a third species also potentially could damage this vast freshwater ecosystem if it becomes established in substantial numbers.
The grass carp was introduced into U.S. waters about 50 years ago, with the intent of using it to manage invasive aquatic vegetation. It has done its job--- and then some. Too often it has obliterated all vegetation in a water body, including beneficial native plants.
Additionally, it has escaped and established wild populations, as did the bighead and silver. Today the grass carp is believed to be in at least 45 states.
And now this invader poses danger for the Great Lakes.
Researchers recently documented that grass carp have spawned in the Great Lakes, specifically in Ohio’s Sandusky River, a tributary of Lake Erie. They also point out that 45 of them were caught in the Great Lakes between 2007-2012. That’s not a lot, but it’s 45 too many, especially since about half of those were capable of reproducing, meaning that an established population might already exist.
That does not bode well for bass, pike, and other inshore species that thrive in and around aquatic vegetation.
Read more here.
By the way, I have personal experience with grass carp. Years ago, ignorant property owners illegally stocked grass carp in the little lake behind my house because, they said, “they filter the water and improve the water quality.” They did so, even though the lake contained little, if any, aquatic vegetation.
Somehow, the carp have survived and today some of them weigh 30 pounds or more. They’re the equivalent of big aquatic cows, degrading water quality, not improving it, as their wastes feed alga blooms during summer.
Also, hundreds of pounds of carp prevent growth of hundreds of pounds of bass, bluegill, and catfish. Like a farm field, a lake can sustain just so much biomass.