All the relatives of carp pose a threat to the water systems in the U.S because each of them fit into a separate niche within the water ecosystem.  The picture shown above shows where each of these species fit.  The common carp is also an invasive species, but it has been established in the U.S for so long that the effects of it are not known.  A picture of a common carp can be seen on the ALL ABOUT ME page.

    Going into a little bit more detail:

Grass Carp (Ctenopharyngodon idella): The grass carp can grow a little bit larger than the silver carp their maxium weight and length being 59” and 99 pounds, they can also live up to 21 years. Besides the obvious morphological characteristics differing from the silver carp, the grass carp mainly feeds on aquatic plants and can eat up to 40% of its body weight in one day.  It can wipe out vast areas of aquatic plants that serve as important food for other fish as well as spawning and nursing habitat.  A reduction in these habitats can lead to depletion in numbers of native fish in those areas.

Big Head Carp (Hypophthalmichthys nobilis): The big head carp is the closest relative to the silver carp and many people will intermix the two species when talking about them because of their similar morphological features as well as them inhabiting virtually the same habitat.  The Bighead carp feeds mostly on zooplankton, they can get up to 60” and 110 pounds.  They are the largest species out of the four described.  According to the Illinois Natural History Survey bighead carp have been increasing exponentially, doubling in the upper portion of the Mississippi River. 

Black Carp (Mylopharyngodon piceus): The black carp has not exploded like any of the other three species, but if it does it could have just as damaging effects as the others.  It’s diet consists of snails, mussels and other invertebrates and it can grow up 48” and 78 pounds.  The main concern with black carp is they could reduce the abundance of already rare snails, mussels and other small invertebrates.