A small invasive crab introduced via ballast water. Now extremely abundant along eastern US coastline. Displacing native crabs.

Also called: Japanese Shore Crab

Native status: Non-native (Asia); invasive on US East Coast

§ Quick facts

SizeCarapace 3–5 cm (1.2–2 in)
Weight10–30 g
LifespanWild 2–5 years
OrderDecapoda
FamilyVarunidae

§ Encyclopedia

Hemigrapsus sanguineus, the Japanese shore crab or Asian shore crab, is a species of crab from East Asia. It has been introduced to several other regions, and is now an invasive species in North America and Europe. It was introduced to these regions by ships from Asia emptying their ballast tanks in coastal waters.

Source: Wikipedia — Hemigrapsus sanguineus Licensed under CC BY-SA 4.0

§ Identification

Field marks. Small square-bodied crab with three teeth on each side of the carapace; alternating light and dark bands on legs; greenish to purple-brown coloration.

Similar species. Native Green Crab (more rounded carapace, five teeth). Native Rock Crab (larger, more rounded). Native shore crabs (different leg banding).

Voice. N/A

§ Diet & behavior

Diet. Algae, small mollusks, barnacles, dead matter; aggressive grazer that strips intertidal zones.

Behavior. Native to East Asia (Korea, China, Japan); first documented in the US at Cape May, NJ in 1988, likely arriving in ballast water. Has since spread along the entire US East Coast from Maine to North Carolina. Reaches densities of 100+ per square meter — far higher than native crabs. Outcompetes native green and rock crabs and dramatically alters intertidal community structure. Among the most successful marine invaders in US history.

§ Range

Native to East Asia; invasive on US East Coast

§ Habitat

Rocky intertidal zones

§ Threats

In US: they're the threat to native crabs and intertidal ecosystems.

§ Conservation status

According to the IUCN Red List, the asian shore crab (invasive) is currently classified as Least Concern.

§ What helps

Support ballast water regulations. Don't transplant marine animals.

Support our work More ways to help

§ Further reading

§ Sources cited

  • USGS Nonindigenous Aquatic Species
  • NOAA Northeast Fisheries Science Center
  • Connecticut Sea Grant