Northern Pacific seastar in Australia

[2] Their presence has been recorded in the state from as far north as Banks Strait (between Cape Portland and Clarke Island[3]) and south to Recherche Bay, with the highest population densities in sheltered waters in south-east Tasmania, particularly the Derwent Estuary.

[4] It then spread northwards,[4] and was detected in Port Philip Bay, Victoria, where it was observed to reach up to 12 million individuals over a two-year span,[1] and is now considered established there.

[1] Although the species prefers shallow, sheltered areas, it has also been observed in other habitats, including on rocky reefs and bedrock, and, in its native range around Japan, at depths of up to 200 metres (660 ft).

[4] The Northern Pacific seastar is considered a serious pest of native marine organisms in Australia, and is a major factor in the decline of the critically endangered spotted handfish.

Immersion in freshwater has been shown to kill the larvae, and this is a potential method of control, and commercial harvesting of the animal where populations are established has been mooted, but there are problems associated with this idea, including the lack of a market for the fertiliser produced from them.

Other methods considered and/or tried have been dredging, the use of quicklime (calcium oxide) to poison them, netting, trapping and manual removal; however, none of these has proven successful and effective, for a range of reasons.