What does it look like?
Chinese mitten crabs usually have a light brown to olive green shell, reaching up to 10cm wide. Hairy 'mittens' on its front claws is a feature not shared by any native New Zealand crab or other introduced species of crab. These claws have white pincer tips. There are four spines or serrations present on each side of the shell and a distinct raised notch between the eyes.
Chinese mitten crabs burrow into sand, mud, or clay banks. Adult specimens inhabit the bottom and banks of freshwater rivers and tidal creeks, before migrating to brackish and saltwater to reproduce. Their larvae develop into juveniles in marine coastal areas, which then migrate back to rivers and creeks. Chinese mitten crabs are able to survive in highly polluted habitats.
Why is it a problem?
Burrowing by this species weakens banks and speeds up erosion. Damage to fishing nets and catch is also common. Where there are high densities of the species, other species are displaced and water blockages can be an issue. This species also hosts liver fluke (Paragonimus sp.) that is harmful to human health.
The Chinese mitten crab is also a generalist feeder, impacting on the freshwater and brackish environment where in high densities tends to cause an imbalance in the local ecosystem.
Control methods
You can help prevent the spread of marine pests by:
- Regularly cleaning your boat’s hull – ideally keep fouling growth to no more than a light slime layer.
- Applying a thorough coating of antifouling paint and keep it in good condition.
- Ensure your hull is clean and free of fouling before you travel to a new area.
- Clean and dry any marine equipment (e.g. ropes, lines and pots) before using in a new area.
- Inspect areas on your boat that retain water for signs of marine life.
- Check for aquatic weeds tangled around anchors, trailers and other equipment.
Related links
Management Programme
Notifiable Organism
Any organism specified under the Biosecurity Notifiable Organisms Order 2016 must be reported to MPI if spotted. If any of these organisms become established in New Zealand, they could severely affect our primary production, trade, and market access. If you spot a notifiable organism, you have a legal obligation under section 44 of the Biosecurity Act 1993 to tell MPI. Call the pests-and-diseases hotline on 0800 80 99 66.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
More informationRules
Plan Rule 1
The operator of a vessel entering the waters of the Hawke's Bay Regional Council must ensure the hull (includes hull area, niche areas and wind and water line) or any structure or navigation aid of any origin, is sufficiently cleaned and antifouled so that there is no more than a slime layer and/or goose barnacles
More informationSections 52 and 53 of the Biosecurity Act (1993)
No person shall knowingly communicate, cause to be communicated, release, or cause to be released, or otherwise spread any pest or unwanted organism, in accordance with Sections 52 and 53 of the Biosecurity Act 1993
More informationTaxonomies
FamilyVarunidae
TypeAnimals
GroupCrustacean
HabitatMarine
Management ProgrammeNotifiable OrganismUnwanted Organism
RulesPlan Rule 1Sections 52 and 53 of the Biosecurity Act (1993)
