No marine organism, once established, has ever been successfully removed or eradicated in the US.
•Predation
•Competition
•Disturbance
•Diseases and parasites
Carlton 1997
Again according to Dr. James Carlton, no marine organism, once established, has ever been successfully removed or eradicated in the US. New introductions can cause problems for native species such as predation, competition, disturbance, and diseases and parasites.  There now may be an exception, an exotic sabellid worm which was devastating abalone population on the West Coast.  A localized population was eliminated below the detection level by eliminating the intermediate host.