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Marine scientist Steve O'Shea is well known for his love of giant squid, but faced with an ocean sunfish the size of a station wagon he admits his loyalties are challenged.

"It's sensational," he said yesterday. "I've never seen anything like it."

The director of Auckland University of Technology's Earth and Oceanic Sciences Research Institute, Dr O'Shea spent the day organising a mould of the dead 3.3m long, 3.2m high sunfish - believed to be a world record - in preparation for dissecting it today.

"We've got to fillet it so we can take out the skeleton and do an autopsy."

The sunfish, or mola mola, was found floating off Whangarei Heads three weeks ago and offered to Dr O'Shea by the Department of Conservation.

He spent $5000 shipping it to Auckland in a refrigerated railway container, and said he was likely to spend another $5000 before the week was out on the silicone mould and preserving the skeleton.

Though not a rich man, Dr O'Shea said it was money well spent.

"It's a world record [size] as far as we can ascertain. It's a monstrosity."

The sunfish is estimated to weigh 2.2 to 2.3 tonnes and caused Dr O'Shea plenty of grief when he moved it from the railway container, first by truck and then on a trailer attached to his car, to a carpark at AUT.

"It just about buggered my car."

Once in the carpark on Wednesday night, the frozen creature caused a sensation among people in nearby apartments and walking through the carpark.

"It's definitely a big, random-looking fish," said AUT student Jason Gordon, who took photos that were quickly forwarded to the Herald.

Ocean sunfish are the world's largest bony fish, feeding on jellyfish and plankton.

Little is known about them, including how long they live, but they are rare in New Zealand waters and usually found in tropical regions.

The largest specimen found in the past was 3.1m long.

Dr O'Shea said it was unclear why the sunfish found near Whangarei Heads died, but it showed no signs of injury and had not been in a net.

It was possible it had swallowed plastic bags, a common cause of death among sea turtles and other creatures that mistook the bags for jellyfish.

Dr O'Shea hopes to turn the sunfish into an attraction rivalling Squid Vicious, the 8.23m-long dead giant squid he gave to Kelly Tarlton's Underwater World for display in September.