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The Northern Pacific seastar is a five-armed sea star of cold coastal waters in northeast Asia. In the United States it lives in Alaska, where it makes up a large share of the seafloor animal life on the eastern Bering Sea shelf. Carried in ships' from Asia to southern Australia, it is on the list of the world's 100 worst invasive species.

Appearance

Appearance
Five arms on a small central disk, with the arm tips usually turned up. The top side ranges from yellow and orange to red or purple, while the underside is yellow. Arms are usually around 6 in (16 cm) long, and rare giants reach about 20 in (50 cm) across.

Where it lives

Typical habitats
  • Sheltered bays
  • Estuaries
  • Shallow sand and mud bottoms
Range
Northern China, Korea, Japan, and the Russian Far East, with records along the Aleutians and Alaska from the Bering Sea to the Gulf of Alaska, and in British Columbia. Whether the Alaska and Canada animals are native or arrived with people is still debated.
Preferred conditions
Prefers cold water around 45–50°F (7–10°C) and calm, sheltered spots. It can handle estuary water and has been found as deep as about 720 ft (220 m), but in the eastern Bering Sea it is most common nearshore, shallower than about 165 ft (50 m).

Behavior

Diet
Mainly large clams, mussels, and scallops, which it pulls open with all five arms before pushing its stomach inside the shell. It also eats snails, crabs, barnacles, sea squirts, and dead fish.
Activity
It moves toward light and can travel up to about 8 in (20 cm) a minute. Sometimes it floats at the surface with air trapped in its body.

Life cycle

Reproduction
Eggs and sperm are released into the water. A large female can carry up to 20 million eggs, and the larvae drift as plankton for about 6 weeks to 4 months before settling. A single arm attached to part of the central disk can regrow a whole new seastar.
Lifespan
Usually 2–3 years in the wild, sometimes 4 or more.

Connected species

Ties with other wildlife
In the eastern Bering Sea it is a top seafloor predator with few enemies, and it competes for food with commercially important bottom fish and red king crab.
Close relatives
  • Asterias rathbuni

    A same-genus sea star that shares this species' cold northern waters, from western Alaska and the Bering Sea to Kamchatka.

  • Forbes's sea starAsterias forbesi

    Its Atlantic counterpart in the same genus, common along the coast from Maine south to the Gulf of Mexico, where the Northern Pacific seastar does not live.

  • Common starfishAsterias rubens

    The same genus's North Atlantic member, found on both European and North American coasts rather than in the Pacific.

Conservation

IUCN Red List
NENot EvaluatedNot yet assessed
Status
The European Union lists it as an invasive species of concern, restricting its import, sale, and release.
Threats
In Tasmania it preys heavily on native shellfish and has been linked to the decline of the endangered spotted handfish, whose egg masses it eats. In Japan, outbreaks have cost shellfish farming millions of dollars in control work and losses.

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Northern Pacific Seastar (Asterias amurensis) — identification, habitat & look-alikes | Moeyo