The Chinese mitten crab poses a serious ecological threat wherever it establishes itself outside its native range. Population densities can climb rapidly, and the species is adaptable enough to outcompete native fauna for both food and living space. Sub-adult crabs are particularly destructive burrowers, tunnelling into riverbanks in ways that accelerate erosion and can ultimately cause levees to collapse. During mass migration events, fishers may find the crabs consuming bait and becoming entangled in nets alongside their intended catch. There is also a direct human health risk: the Chinese mitten crab serves as an intermediate host for the Oriental lung fluke (Paragonimus westermani), which can infect people who eat raw or undercooked crab.
Being able to identify this species is the first step in keeping it out of New Zealand waters. Look for the following characteristics:
- Brown-orange to greenish-brown in colour - Round body with four spines down each side - A distinctive notch between the eyes and legs - Legs normally twice as long as its body width - Adults have dense patches of hairs ("mittens") on both claws
This pest is not known to be present in New Zealand. If you spot something suspicious, report it to the Ministry for Primary Industries.
For more information on this species, visit the Marine Biosecurity Porthole.
