The giant sea creature, an infrequent visitor to Dunedin's inner harbour, washed up on the beach.
"Sunfish in the Otago Harbour are not uncommon. We hear reports of them about two or three times a year," Otago Museum natural science curator Emma Burns said.
"Sometimes they get caught out by tides and end up beached in shallow parts of the harbour, and they have also been spotted cruising off Taiaroa Head."
Three species of sunfish are found in Otago waters, but the animal was in too poor a condition to identify its species.
"We did a dissection on one last year and the digestive system was about 8m long," Ms Burns said.
"That one was almost 2m from its tip to its tail.
"They have interesting innards. They don't have a very discernible stomach.
"It's almost like one long tube which goes right the way through it."
