Chinese mitten crab

General description

The Chinese mitten crab is a small to medium sized crab, named for the dense patches of bristles (“hair”) on its claws.

• Hairy “mittens” of bristles on both claws (males tend to have thicker hair)
• White tips on the front claws
• Distinct notch between the eyes
• Four spines on each side of the carapace (upper shell)
• Carapace width typically 5 cm to 7 cm; can reach up to ~10 cm
• Carapace colour: light brown to olive green
• Crabs start their life in saltwater, migrate upstream to mature, then return to the ocean to breed.
• Adults usually live in burrows in muddy riverbanks or near aquatic plants and marshes.

What you need to know

To help protect our environment:

• You must not breed, distribute, release or sell Eriocheir sinensis within the Auckland region.

Take a clear photograph (top, side, claw detail), record precise location (map / coordinates) and nearby landmarks, if safe to do so, capture the specimen. Report it immediately to the MPI / biosecurity hotline 0800 80 99 66.

Dispersal

Larvae transported in ballast water of ships. Could hitchhike in sea chests or other parts of vessels. Possible risk via live trade of crabs (in some countries).

Impact on environment

• Can form dense colonies, disrupting ecosystems.
• Omnivorous diet: feeds on aquatic plants, algae, detritus, fish eggs, and various invertebrates, thereby displacing native species. 
• Damages fishing nets and catches.
• Burrowing behaviour weakens river and estuary banks, which can lead to bank collapse.
• Potential vector for a liver fluke parasite that can affect humans. 
• Once established, aquatic pests are very difficult (or impossible) to eradicate.

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 Chinese mitten crab or to report a sighting contact Biosecurity New Zealand 0800 80 99 66. Visit MPI's Chinese mitten crab page for more details.