Biosecurity staff narrowly avoided a nipping when five large crabs were discovered in a Vietnamese traveller's luggage by Auckland Airport biosecurity staff.
While the passenger declared the giant crabs, language barriers meant staff got a surprise when the creatures started moving.
"On opening the container and inspecting the specimen we realised there was a bit of movement there - we got quite a fright," team leader Nick Willis said.
"As they warmed up they got a bit of movement which made putting them back in the container quite interesting too.
"One actually crushed a pen when we were taking photos."
Biosecurity staff saw a lot of fish and crustaceans but live crabs were unusual.
Because the passenger declared the biosecurity risk he avoided a fine.
The crabs were placed in a fridge to immobilise them before they were placed in a freezer to kill them. They would be picked up by the passenger on his way out of the country, Willis said.
He was charged a $20 fee for the service.
"We were unable to ascertain their destination but imagine it's the dinner table."
The crabs' species was not identified, but it could have posed a significant risk to other marine life.
Authorities were already battling the invasion of the Asian paddle crab which was spreading through the Waitemata Harbour after it arrived 13 years ago, Willis said.
The Chinese mitten crab was an example of what impact pest crabs can have on habitats.
"This crab has invaded Europe and North America from its native region of Asia," Willis said.
"It wipes out local invertebrates. Its intensive burrowing activity causes erosion. And it costs fisheries and aquaculture hundreds of thousands of dollars each year by eating bait and trapped fish, and by damaging gear."