Northern Pacific seastar

General description

The Northern Pacific seastar is a starfish species with five arms. Key identifying features:

• Arms: usually five, sometimes with upturned tips
• Colour: It shows a wide range of colours on its dorsal side: orange to yellow, sometimes red and purple; underside usually yellow
• Surface: small, irregular spines or tubercles covering the arms and central disc
• Size: commonly up to ~24 cm across, potentially larger in optimal conditions
• Behaviour: can occur in dense aggregations

What you need to know

To protect our coastal ecosystems, it’s critical to stay alert. If you suspect this species in Tāmaki Makaurau, follow these steps:

• Do not release, move, or translocate specimens.
• Take clear photographs (top view, underside, close-ups of arm features).
• Record the exact location (GPS/map), landmarks, and date/time.
• If safe, collect the specimen (in a sealed container) for verification.
• Report sightings immediately to MPI / the biosecurity hotline 0800 80 99 66.
• Share the information with local conservation / marine biosecurity contacts in Auckland or Tiaki.

Dispersal

Larvae are planktonic and may travel long distances via ocean currents or in ballast water of ships. Adults or juveniles may hitchhike on vessel hulls or marine infrastructure (e.g. aquaculture gear, nets). Settlement on structures and transport of infested equipment may facilitate its spread.

Impact on environment

• Predatory: feeds on mussels, clams, scallops, and other shellfish, upending native marine communities.
• Capable of forming dense aggregations, potentially overwhelming local species.
• Can alter habitat structure by removing bivalve beds, affecting ecosystem dynamics.
• May cause economic harm in aquaculture (fouling, damage).
• Once established, eradication is challenging or impossible.

Control

Recommended approaches

Prevention is critical (keep it out), strict biosecurity measures on vessels (ballast water treatment, sea chest inspection). Surveillance in high-risk areas (ports, estuaries), rapid response if detected. For more information about the Northern Pacific seastar or to report a sighting contact Biosecurity New Zealand 0800 80 99 66. Visit MPI's Northern Pacific seastar page for more details.