<P> The Northern Pacific starfish, (Asterias amurensis) is an invasive species in Australia . The starfish is native to the coasts of northern China, North Korea, South Korea, Russia and Japan and distribution of this species into other countries has increased . It is on the Invasive Species Specialist Group list of the world's 100 worst invasive species . </P> <P> In Australia spawning occurs from July to October at temperatures of 10 ° C to 12 ° C. Fertilized eggs develop into free - swimming larvae that live in the water for around 90 days before settling and metamorphosing into juvenile seastars . In one year the northern Pacific seastar is capable of increasing its diameter by 8 cm; when fully grown the northern Pacific seastar lives up to five years, and can reach sizes up to 40 to 50 cm in diameter . Larval survival is constrained by temperature and salinity of the surrounding marine habitat, with the optimal ranges respectively 8 ° C to 16 ° C, and 3 ‰ to 8.75 ‰ . Generally, seastars are sensitive to salinity fluctuations, and are unlikely to be found in places of high salinity . In Japan its numbers increase and reach outbreak proportions for two to three years; outbreaks have been found to occur in three or ten year cycles . Native to the coasts of northern China, Korea, Russia and Japan, the northern Pacific seastar lives in waters between 7 ° C and 22 ° C. It lives in mainly shallow water, but also is found as deep as 200 metres . It is rarely found on reefs or high wave action areas, instead sitting on mud, sand or pebbles . </P>

Where did the northern pacific seastar come from
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