Asian shore crab

Hemigrapsus sanguineus

This tiny aggressive eating machine could ruin New Zealand's native ecosystems.

About Asian shore crab

This small crab is native to the rocky shores of the Western Pacific Ocean, from Russia, Korea, Japan, and China. They can live in:

  • water temperatures of 0⁰C to 30⁰C
  • estuarine waters (where rivers meet the ocean) to marine waters
  • depths down to 4m.

They've now spread to the East Coast of the United States, Northern Europe (France to Germany), and the Mediterranean Sea.

Why this is a problem for New Zealand

They eat species that are important to our rocky intertidal communities. They can also dominate these species by eating their food sources. The Asian shore crab may disrupt native food chains and affect populations of native crabs, fish, and shellfish.

These opportunistic crabs would pose a threat to aquaculture operations.

Once established, aquatic pests are extremely difficult to eradicate.

How it could get here

This pest is most likely to arrive in New Zealand in ballast water from ships. We have strict measures in place to reduce the chances of pests, like the Asian shore crab, coming here in ballast water.

It could also hitchhike on the hull of a boat. Boats visiting our waters need to keep their hulls clean.

Even if you don't travel overseas, keeping your boat hull clean can stop pests spreading.

Where it might be found

If it made it to New Zealand, you'd find this little pest in rock pools and in marine and estuarine environments down to 4m.

How to identify the Asian shore crab

The crabs grow to only 4cm across the body, not including the legs.

The shell is:

  • roughly square-shaped
  • smooth
  • mottled greenish-brown.

It has small reddish spots on it claws and 3 'teeth' on the side of its body near its claws.

Left: A mottled greenish-brown adult Asian shore crab.  Image: CC Ansel Oommen,
Right: Asian shore crab with 3 'teeth' on the side of its body. Image: CC Wikimedia Commons

Report suspected sightings

If you think you've found an Asian shore crab:

  • photograph it
  • take note of the location and any landmarks
  • capture it (if you can)
  • call 0800 80 99 66

Note: This information is a summary of this pest's global distribution and potential impacts to New Zealand.

Last reviewed: