Dr Trnski said he had looked carefully for signs of what caused the shark's death, but couldn't find any evidence of injury, such as being caught in fishing lines, or of complications from birth.
"It may be something that a researcher in the future may be able to find out."
It was unusual to find one in New Zealand waters, particularly at this time of year, as oceanic whitetip sharks are typically found in warmer, tropical seas.
"These sharks also typically prefer off-shore, deep-ocean areas so this is an unexpected find."
Dr Trnski said the shark would be the only oceanic whitetip in a museum in New Zealand, and the mature 150kg female was also the largest recorded in the southern hemisphere.
The pups will also remain in the museum's collection, but have not yet been preserved.
Earlier this year the oceanic whitetip shark was given full protection in New Zealand territorial waters under the Wildlife Act 1953.