Foreign species of carp invades Great Lakes watershed

Bottom-feeders are useful when it comes to keeping a glistening home aquarium, but they can pose a huge threat when haphazardly introduced into the wild.
Scientists have confirmed for the first time that grass carp, an Asian carp species used in sewage treatment facilities that escaped into the wild, have reproduced within the Great Lakes watershed.
The fish were originally used for their advantages: they were imported decades ago to control the amount of algae and undesirable vegetation in controlled environments.
Grass carp are a less destructible type of carp because they eat larger plants rather than plankton, but all Asian carp have close to the same needs for successful reproduction.
Bighead or silver carp, for example, would burn through large numbers of plankton and are dangerously good breeders—which could drive a wedge in the aquatic food chain and put a $7 billion fishing industry at risk. Though they are less harmful, grass carp could damage the vegetation where native fish spawn.
Four grass carp were captured last year and kept for examination after being pulled from Ohio’s Sandusky River (a tributary of Lake Erie). Scientists were able to confirm that the fish had lived their whole lives in the tributary of Lake Erie, and were not the product of “stocking,” a process of purposefully releasing a population of fish in an environment to balance its population or create one where it never existed.
In fact, the U.S. government has invested $200 million on driving these types of foreign species out—the biggest example of which is an electric barrier in Illinois waterways.
Scientists previously believed that approximately two dozen rivers in the Great Lakes watershed would allow carp to spawn.
But the analysis of the grass carp found, and the fact that the miles of flowing waters the grass carp reproduced in was shorter than believed necessary, mean the number may be higher.