Most marine plants and animals start life at a tiny stage that floats around the sea. It is finding a new home. The new home might be on the hull of a ship or it may be sucked up with the ballast water. Only a few of these animals or plants will survive to find a new home.
As Australia is a continent surrounded by water nearly all our international trade depends on ships and the ocean.
Approximately 12000 international vessels arrive in Australian ports each year.When a plant or animal does survive away from its natural home, they no longer have their enemies. Often their numbers will explode affecting the environment around them.
250 species have accidentally been introduced into Australian waters. Some of these have become serious pests threatening the Australian marine environment they have invaded.