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
Some organisms must be notified to MPI if they're spotted in New Zealand. These include serious pests and diseases like foot-and-mouth disease, the rabies virus, fruit fly and disease-carrying mosquitoes. If a notifiable organism established in New Zealand, it could severely affect our primary production or 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.
The Biosecurity (Notifiable Organisms) Order 2016 lists notifiable organisms. New additions can be made by the Governor-General and MPI periodically reviews the list to ensure it is up-to-date.
Unwanted 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.
Taxonomies
FamilyVarunidae
TypeAnimals
GroupCrustacean
HabitatFreshwaterMarine
Management ProgrammeNotifiable OrganismUnwanted Organism
