As ships travel from port to port they carry marine hitchhikers glued to the hull. The marine life living on the hull is called hull fouling. Many of these foreign species will slip unnoticed into our ports and will not interfere with our marine environment. But some cause dramatic changes.
Invading marine species might affect native marine life by:
Studies report that around 250 species have been introduced into our Australian seas from foreign regions and one in every six introduced marine species will establish itself as a pest. This foreign marine life may come in ballast water or attached to ship hulls and other equipment.
In 1999 black striped mussels were found in a Darwin marina. With knowledge of the damage caused in America by its near relative the zebra mussel, the Northern Territory and Commonwealth governments responded to the threat. It took $2.2 million and three hundred people to successfully eradicate this pest (and kill most of the native marine life in the marina at the same time). However, the eradication of pest species populations may not be as successful in the future.