What harm do these nonindigenous aquatic species cause?
In the Great Lakes alone, 139 nonindigenous aquatic species have become established since the early 1800s resulting primarily from ship-related introductions (via ballast water discharges), removal of physical barriers with the building of canals, transfer by recreational watercraft and accidental releases from aquaculture, bait, aquarium trade and horticultural activities. Under the right conditions, non-native populations can dramatically increase, displacing native species, reducing biodiversity. Once a species is established, it is difficult to manage and nearly impossible to eliminate. The zebra mussel is one of the more infamous aquatic nuisance species known to have arrived in ships’ ballast water into the Great Lakes. Due to its infestation, Great Lakes users spend tens of millions of dollars on zebra mussel control every year. In addition, the zebra mussel’s rapid reproduction, coupled with its consumption of microscopic plants and animals, affect the aquatic food web and plac
