A New Zealander who survived being shipwrecked in shark-infested Fijian waters has lost part of his arm in an accident on board a foreign fishing vessel.

Fisheries observer Martin Bowers, 47, had his arm yanked from its socket and his forearm mutilated when his lifejacket snagged on a conveyor belt on a Korean fishing vessel on Friday night.

Maritime New Zealand has launched an investigation after the accident about 105km from Bluff.

Paramedics were winched from the Otago Regional Rescue Helicopter on to the ship, and stabilised Mr Bowers, an observer for the Ministry for Primary Industries, before he was flown to Dunedin Hospital.

Mr Bowers' mother, Mary, said her son had a "total, horrible accident" as he was putting on his lifejacket.

"Part of it caught in a belt that was moving, and it tore his shoulder out and mutilated his arm a bit. He's had part of his arm cut off. Horrific."

Mr Bowers' arm had to be amputated below the elbow.

Mr Bowers' uncle, George Robertson, said his nephew had been climbing up towards the ship's deck when the lifejacket was caught. His nephew was still in a high dependency unit, and was expected to remain in hospital for at least two weeks.

But he seemed in good spirits, joking with his daughter and telling her he was now a pirate with one hand, Mr Robertson said.

In 2001, Mr Bowers and his father Earle were on a fishing trip in Fiji when a rogue wave tipped their boat and threw them on to a coral reef.

- APNZ