North Pacific Seastar
Northern pacific seastars were introduced to tasmanias waters via japanese ships about 20 years ago. In the cool tasmanian waters the population has exploded. There are now about 30 million living in the river derwent. This means there are more Northern Pacific Seastars living in tasmania than people. It has been provwen that ships must have been the cause of them arriving in tasmania as it would be impossible for them to come via ocean currents. A ship uses water to stabilise itself when its not full of cargo. one ship can take up to 70,000 tonnes of water to stabilise itself. Thats enough to fill 32 olympic swimming pools. How many seastars do you t6hink could fit in there? In 1998 Northern pacific seastars were found in Port Phillip Bay Victoria. these came from tasmania who had earlier recieved them from japan. There are so many seastars in tasmania that we now have more than japan ever had. Why are these seastars such a worry? ecause they will feed on ANYTHING they can find! Divers collecting seastars for science found hundreds of seastars eating a dead sailor at the bottom of the ocean. In 1954, these seastars ate 400 million yen worth of shellfish in tokyo bay. This is a lesson to future shipping industry. If we cant stop the Seastars we will have to make sure such a disatser doesn't occur again.
Perna Vi Ridis
Perna Vi Ridis (also called the asian green mussel) is classed as an invasive species because of its spread on boat hulls. Its also classified as invasive because of its difficulty to control. The asian green mussel is usually covered in dense marine overgrowth meaning that it is hidden from fish trying to eat it and divers trying to remove it from rivers and oceans were it might be growing. It grows in waters that are 11 - 32 degrees celcius, meaning that australias coast is perfect habitat. 35,000 Mussels have been found to live in one square metre. Unlike The North Pacific Seastar, Perna Vi Ridis does not directly affect the food chain. However it takes up valuable growing space in reefs and streams, meaning lack of space for other animals which will effect the foodchain.