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   Asterias amurensis (sea star)     
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      Northern Pacific seastar (Photo: Jan Haaga) - Click for full size   Asterias amurensis dorsal view (Photo: Wikimedia Commons) - Click for full size   Asterias amurensis ventral view (Photo: Wikimedia Commons) - Click for full size
    Taxonomic name: Asterias amurensis Lütken, 1871
    Synonyms: Allasterias rathbuni nortonens Verrill, 1909, Allasterias rathbuni var. anom Verrill, 1909, Allasterias rathbuni var. nort Verrill, 1914, Asterias amurensis f. gracilispinis Djakonov, 1950, Asterias amurensis f. acervispinis Djakonov, 1950, Asterias amurensis f. flabellifera Djakonov, 1950, Asterias amurensis f. latissima Djakonov, 1950, Asterias amurensis f. robusta Djakonov, 1950, Asterias anomala Clark, 1913, Asterias nortonensis Clark, 1920, Asterias pectinata Brandt, 1835, Asterias rubens Murdoch, 1885, Parasterias albertensis Verrill, 1914
    Common names: flatbottom seastar, Japanese seastar, Japanese starfish, Nordpazifischer Seestern (German), North Pacific seastar, northern Pacific seastar, purple-orange seastar
    Organism type: sea star
    Originally found in far north Pacific waters and areas surrounding Japan, Russia, North China, and Korea, the northern Pacific seastar (Asterias amurensis) has successfully invaded the southern coasts of Australia and has the potential to move as far north as Sydney. The seastar will eat a wide range of prey and has the potential for ecological and economic harm in its introduced range. Because the seastar is well established and abundantly widespread, eradication is almost impossible. However, prevention and control measures are being implemented to stop the species from establishing in new waters.
    Asterias amurensis (northern Pacific seastar) can grow upto 50cm in diameter. It is yellow with red and purple pigmentation on its five arms, and a small central disk. Its distinctive characteristic is its upturned tips which are its identification key when compared to similar starfish. The undersides are completely yellow and arms are unevenly covered with small, jagged-edged spines (CSIRO, 2004). These spines line the groove in which the tube feet lie, and join up at the mouth in a fan-like shape (NIMPIS, 2002).
    Similar Species
    Pisaster brevispinus, Pisaster giganteus, Pisaster ochraceus

    Occurs in:
    estuarine habitats, marine habitats
    Habitat description
    While Asterias amurensis (northern Pacific seastar) prefers waters temperatures of 7-10°C, it has adapted to warmer Australian waters of 22°C. It is typically found in shallow waters of protected coasts and is not found on reefs or in areas with high wave action. The starfish is capable of tolerating many temperatures and wide ranges of salinities. It is often found in estuaries and on mud, sand or rocky sheltered areas of intertidal zones (CSIRO, 2004). The maximum temperature for Asterias amurensis is 25°C and the minimum is 0°C (NIMPIS, 2002). The salinity range for this species is between 18.7 and 41ppt, while the maximum depth at which individuals have been found is 220m (NIMPIS, 2002).
    General impacts
    Asterias amurensis (northern Pacific seastar) has the potential to establish large populations in new areas. Estimates made in Port Philip Bay (where they were first detected), indicate that numbers reached as much as 12 million individuals in two years. In their native range they are known to go through 'bust and boom' cycles reaching high abundance and then rapid decline (NSW, 2007).

    The northern Pacific seastar is a voracious feeder, preferring mussels, scallops and clams. It will eat almost anything it can find, including dead fish and fish waste (CSIRO, 2004). The seastar is considered a serious pest of native marine organisms. It is implicated in the decline of the critically endangered spotted handfish (see Brachionichthys hirsutus in IUCN Red List of Threatened Species) in Tasmania It preys on handfish egg masses, and/or on the sea squirts (ascidians) that handfish use to spawn on (NSW, 2007). The seastar is also considered a mariculture pest, settling on scallop longlines, spat bags, mussel and oyster lines and salmon cages (CSIRO, 2004). Oyster production on some marine farms in southeastern Tasmania have been affected by the seastar (NSW, 2007).

    In Japan seastar outbreaks cost the mariculture industry millions of dollars (NSW, 2007; NIMPIS, 2002).

    No valuable human use has been documented. Hunting incentives have been suggested, such as catching and drying as souvenirs of the Australian coast (Goggin, 1999).
    In its native Japan, Solaster paxillatus (a sunstar) has been noted as a predator of Asterias amurensis (northern Pacific seastar). The predation of A. amurensis by king crabs in Alaskan aquaria has also been observed (NIMPIS, 2002). The size of prey eaten by A. amurensis usually equals the length of the seastar's arm. Organisms that compete with A. amurensis include: Uniophora granifera, Coscinasterias muricata and Odobenus rosmarus divergens (Pacific walruses) (NIMPIS, 2002).
    Geographical range
    Native range: Native to Japan, North China, Korea, Russia, and far North Pacific waters.
    Known introduced range: Invasive in South-eastern Australia including Tasmania and Victoria (CSIRO, 2004).
    Introduction pathways to new locations
    Live food trade: Asterias amurensis (northern Pacific seastar) can be transmitted via seawater in live fish trade
    Ship ballast water: Asterias amurensis (northern Pacific seastar) larvae can be distributed through ballast water
    Ship/boat hull fouling: Asterias amurensis (northern Pacific seastar) can be distributed on ship hulls
    Translocation of machinery/equipment: Asterias amurensis (northern Pacific seastar) can be unintentionally transferred via recreational boats
    Transportation of habitat material: Asterias amurensis (northern Pacific seastar) settles on scallop longlines, spat bags, mussel and oyster lines, and salmon cages.

    Local dispersal methods
    Water currents: Asterias amurensis (northern Pacific seastar) larvae are transported in water currents.
    Management information
    A two-year study was undertaken for the Department of Environment and Heritage (Australia) by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to identify and rank introduced marine species found within Australian waters and those not found within Australian waters.
    All of the non-native potential target species identified in this report are ranked as high, medium and low priority, based on their invasion potential and impact potential. Asterias amurensis is identified as one of the ten most damaging potential domestic target species, based on overall impact potential (economic and environmental). A hazard ranking of potential domestic target species based on invasion potential from infected to uninfected bioregions identifies Asterias amurensis as a 'medium priority species' - these species have a reasonably high impact/or invasion potential.
    For more details, please see Hayes et al. 2005.
    The rankings determined in Hayes et al. 2005 will be used by the National Introduced Marine Pest Coordinating Group in Australia to assist in the development of national control plans which could include options for control, eradication and/or long term management.

    For details on preventative measures, chemical, physical and biological control options, please see management information compiled by the ISSG.

    Asterias amurensis (northern Pacific seastar) eats bivalves, gastropod molluscs, barnacles, crabs, crustaceans, worms, echinoderms, ascidians, sea urchins, sea squirts and other seastars, including conspecifics if food source becomes exhausted (CSIRO, 2004).
    Asterias amurensis (northern Pacific seastar) reproduces sexually and asexually. Spawning occurs between July and October in Australian waters . The female seastar is capable of carrying up to 20 million eggs. Fertilisation is external and larvae remains in a planktonic stage for up to 120 days before settling and metamorphosing into juvenile starfish (NSW Department of Primary Industries, 2004). Sperm half life at 10°C > 2 hours, at 17°C < 30 minutes (NIMPIS, 2002).
    Lifecycle stages
    Juvenile Asterias amurensis (northern Pacific seastars) grow up to 6mm per month in the first year and continue to grow 1 - 2mm per month until maturity. The female is able to reproduce at about 12 months of age, when they are around 10cm in diameter.
    This species has been nominated as among 100 of the "World's Worst" invaders
    Compiled by: Chantal Stevens supervised by Dr. Deborah Rudnick University of Washington, Tacoma & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Wednesday, 10 March 2010

ISSG Landcare Research NBII IUCN University of Auckland