Nonindigenous species have been ranked second only to habitat loss as the greatest threat to biodiversity.
U.S. Congress 1993
Unfortunately, aquaculture represents one the greatest sources for future introductions of invasive species into North American waters.  One reason for the importing of foreign species is that aquaculturists believe they will receive a higher return on their investment if they market a species that has the mystique of being “exotic”, especially in the aquarium trade.