Asian Shore Crab

Learn about Asian Shore Crab, including its identifying features, habitat, spread, impacts and our response.

On this page

• Identifying features
• Distribution
• Habitat
• Impacts
• Response
• For further information
• Photo gallery

Identifying features

Asian Shore Crab (Hemigrapsus sanguineus) are small crabs native to the rocky intertidal zone. You can identify one by:

• a small hard bubble at the crux of its claws
• three spines along each side of its shell (carapace)
• the light-and-dark banding pattern on its legs
• its colour, which is mottled or dotted with reddish brown, greenish, or dark purple areas
• the small, dark purple-red dots on its dorsal side
• its size: the maximum carapace width is around 44 mm

The Asian Shore Crab shares similar features with the European Green Crab, but is smaller, with three spines along each side of its carapace where a European Green Crab has five.

Distribution

Asian Shore Crabs are native to northern Asia, with previously established populations in the USA and Europe, from the English Channel to Germany, and has been reported from the Black Sea and northern Adriatic Sea. In the USA, the Asian Shore Crab was first reported in New Jersey and has since established populations ranging from North Carolina to Maine.

The Asian Shore Crab was first detected in Canada in July 2020 in multiple parts of Nova Scotia, spanning from St. Mary’s Bay to Shelburne. The potential for spread is high since larvae are planktonic for 16-54 days.

Natural dispersal of Asian shore crab occurs by means of the planktonic larvae, carried on ocean currents, or as benthic adults. Shipping vectors are typically implicated in dispersal outside the native range.

Habitat

Asian Shore Crab native habitat consists of low-energy, intertidal, boulder/cobble beaches. The crabs also utilize sand/pebble beaches, mussel beds, eelgrass beds and salt marshes, rock jetties, wooden bulkheads and pilings, and submerged and floating aquaculture gear (cages and spat collectors) and move to subtidal depths during winter.

Impacts

Ecological Impacts

Asian Shore Crab are generalist omnivores known to consume molluscs (like mussels, clams, and snails), small crustaceans, polychaetes, and algae. In the USA, the Asian Shore Crab may reach population densities greater than 300 per square meter and have the potential to impact multiple species in the intertidal and subtidal zones by out-competing for food.

Socio-economic impacts

No significant impact to aquaculture has been identified, but Asian Shore Crab:

• have been found in fishing gear
• are known to consume mussels and oysters
• may compete with some aquaculture species for food and habitat

Our response

We will be working to complete field work and a risk assessment to fully assess the distribution of the species and determine next steps.

Fisheries and Oceans Canada previously conducted a Biological Synopsis on this species in 2012.

For further information

Identification Booklet of marine species in Eastern Canada

Photo gallery