Northern Pacific Sea Star

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html Reproduced with permission of Craig Macaulay, CSIRO

1 Northern Pacific Sea Star The Northern Pacific Seastar Reproduced with permission of Craig Macaulay, CSIRO Page 1 of 5

2 Media & Information : Information Sheets The Northern Pacific Seastar The northern Pacific seastar, Asterias amurensis, is believed to have been introduced to south-eastern Tasmania in the late 1970s or early 1980s either as larvae in ballast water, or as juvenile or adult seastars on the hulls of international ships. The northern Pacific seastar, Asterias amurensis, is one of more than 100 exotic marine species known in Australian waters. It is a potential threat to the biological diversity of shallow-water marine communities, and could cause significant problems for the mariculture industry and temperate wild fisheries. The first specimen of the seastar was collected from the Derwent River estuary at Rosny Point near Hobart in By 1995, it had become well established in the lower Derwent River and parts of the D'Entrecasteaux Channel, Huon River estuary, Storm Bay and Norfolk Bay. It has also been seen at Triabunna and Port Arthur. Late in 1995, two specimens of the seastar were found in Port Phillip Bay. Since then two further specimens have been found in widely separated parts of the bay but it is hoped that the seastar has not yet established a breeding population in Port Phillip Bay. The potential distribution of the seastar is from Perth to Sydney. The natural habitats of the seastar are the coasts of Japan, northern China, Korea and Russia as far north as the Bering Straits. It is also found in Alaskan and northern Canadian waters. It is commonly found in the intertidal or shallow subtidal zones but has been reported at depths of around 200 metres. In the north-west Pacific, the seastar is generally found in cooler regions where summer water temperatures do not exceed 21 C. In Japan some populations show 'boom and bust' cycles - rapid increases in seastar populations are followed by equally rapid declines. Page 2 of 5

The seastar may reach sexual maturity in 12 months and females can carry up to 19 million eggs; the larger an individual the more eggs it can carry.

Fertilised eggs develop into free-swimming larvae that remain in the plankton for around 90 days before settling and metamorphosing into juvenile seastars.

Mostly yellow and purple, often with distinctive darker tips. Also all yellow, white or purple. The rays have distinctive pointed tips.

3 The seastar may reach sexual maturity in 12 months and females can carry up to 19 million eggs; the larger an individual the more eggs it can carry. In Tasmanian waters it spawns between July and October. The onset of spawning appears to coincide with rising water temperatures. Fertilised eggs develop into free-swimming larvae that remain in the plankton for around 90 days before settling and metamorphosing into juvenile seastars. Size and Shape Colour Distinguishing Feature Five rays (arms), broad flattened body with distinctive pointed tips. Can grow to over 46 cm in diameter, rays over 190 mm long. Mostly yellow and purple, often with distinctive darker tips. Also all yellow, white or purple. The rays have distinctive pointed tips. In the north and north-west Pacific region, the seastar is regarded as one of the most predatory nearshore invertebrate species. It is a voracious feeder, preferring mussels, scallops and clams, and will also scavenge dead fish and fish waste products and eat other starfish. It can detect potential food from some distance and can dig shallow pits to extract buried prey. Little is known about natural predators or pathogens of the seastar. In Tasmanian waters, adult seastars often have one or more arms in some stage of regeneration, which suggests some predation by local species. Page 3 of 5

4 Research and control After the CSIRO assessed the potential distribution of the seastar in Australian waters and its possible impacts on the mariculture industry and wild fisheries, the Tasmanian Government set up the National Seastar Task Force to coordinate research on the seastar. An identification poster, produced jointly by the Task Force, the Tasmanian Museum and CSIRO, was distributed widely in coastal areas of southern Australia to encourage the community to report sightings of the seastar, assisting scientists to monitor its spread. Studies of the biology and impacts of the seastar were funded by the Australian National Conservation Agency and carried out by the Tasmanian Museum and the University of Tasmania. The Department of Primary Industries and Fisheries carried out trials with a Tasmanian-designed trap that has the potential to control seastar numbers around marine farms. CSIRO scientists have established valuable links with Japanese and Russian scientists who have been studying the seastar in its native habitat. This has led to the identification of several parasites that warrant further investigation as potential biological control agents. Work is underway to assess the specificity of the hosts of the most promising of these parasites CSIRO scientists are also conducting research on the distribution and abundance of seastar larvae in the Derwent Estuary, the length of larval period, and the temperature and salinity tolerances of larvae. In the Derwent in late winter the numbers of seastar larvae are very high, which presents high potential for their transport in ballast water to other Australian ports. CSIRO, with the cooperation of shipping companies, is taking samples to assess the survival of larvae in ballast tanks. The Strategic Ballast Water Research Program, administered by the Australian Quarantine and Inspection Service (AQIS), includes several research projects whose objective is to limit the translocation of introduced species such as seastars. Page 4 of 5

5 CRIMP -- a national research centre Monitoring the spread of seastars and investigating possible control methods is an important task for the Centre for Research on Introduced Marine Pests, a group in the CSIRO Division of Marine Research. CRIMP's aims are to develop and promote techniques to: detect, in the early stages, invasions of marine pests predict the physical and biological impact of the pests assess the risks and costs of the invasion control the spread of the pests minimise the impact of the invasion Further reading Australian Nature Conservation Agency, 1996, The Introduced Northern Pacific seastar, Asterias amurensis (Lütken), in Tasmania. (Contains two research reports), ANCA, Canberra. Produced January Information sheet No. 1 Updated: 30/03/04 Copyright CSIRO Australia, 2005 Use of this web site and information available from it is subject to our Legal Notice and Disclaimer Page 5 of 5

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