A second sea lion has died in just over a month at Marineland after 22-year-old Makea failed to recover from a general anaesthetic on Friday.
Fellow sea lion Rufus died on December 9.
A Napier City Council spokesperson said Makea had begun showing signs of being unwell for several days before his death.
Makea failed to recover from anaesthetic that had been given to him by veterinarians from Massey University who arrived to check him out.
He had initially been "uninterested" in his food and was closely monitored by the Marineland vet.
"Unfortunately, Makea was proving difficult to medicate due to his unwillingness to eat," the spokesperson said.
After being advised of Makea's deteriorating condition Massey University sent a team of vets, support staff and specialist equipment, including x-ray machines and scanners.
A post-mortem was carried out at the scene by the specialists although the results were not available at this stage.
At 22 Makea had exceeded the average life expectancy in the wild, which is 17 years.
Rufus died while being transferred to Massey University for a medical assessment after he had shown signs of being unwell.
Napier City Council manager of tourism services Neil Fergus was not available for comment yesterday.