"They eat just about everything but are probably not a threat, toes and fingers not included."
Mud crabs, generally somewhat smaller than Mr Hall's catch, have been reported elsewhere around the North Island, including a female described as the size of a dinner plate that was caught in a net in the Pakiri estuary, and is now living at the Goat Island Marine Discovery Centre at Leigh.
A relation of the mangrove crabs found in Australia, Asia and Africa, it was suspected of having arrived as a planktonic larvae.
Mud crabs are prized by recreational fishers in Australia for their size and taste, but are seldom seen as far south as New Zealand given that they cannot survive in water colder than 18C. One was photographed on Great Barrier Island, then eaten by the man who found it, another was found in Parengarenga Harbour, and one is reportedly decorating the wall of a Kaitaia fish and chip shop.
The crabs' natural habitat extends from South Africa and the coast of the Indian Ocean to the Malaya Archipelago, southern Japan, south-east Australia, Fiji and Samoa.
They have been introduced in Hawaii and Florida.
And while the Unahi specimen might have been impressive they do grow bigger, to a weight of 3.5kg with a shell 24cm across. They are described as highly cannibalistic, eating those that have moulted and are temporarily without a hard shell, along with some small fish and marine plants.
They can be killed by putting them in a freezer for up to two hours before cooking.
Each female is capable of producing a million offspring.
