Post-mortem of orca washed up on Whatipu beach suggests it may have died at sea
The orca that washed up on Auckland's Whatipu Beach likely died at sea and drifted ashore, a post-mortem has revealed.
Coastal-Marine Research Group director Karen Stockin said no evidence of blunt force trauma was found during necropsy, indicating it was unlikely the whale was hit by a boat.
There was also no evidence of trauma in the whale's blubber - suggesting the mammal most likely died at sea.
Areas of reported bruising on the whale's head and pectoral flipper were considered both small and relatively localised once examined, Stockin said.
Stockin said that due to the decomposed state of the carcass, they could not find a definitive cause of death, but could rule out other scenarios.
Images of the dorsal fin suggest the whale might have been known to the Orca Research Trust as 'Nibble,' Stockin said.
Nibble had a history of live-stranding while chasing prey, most recently in the Whangarei Harbour in September 2016.
While there was no evidence the whale had recently fed, Stockin said they could not rule out the theory that the whale might have accidentally stranded, if it were identified as Nibble.
A spokeswoman for Whale Rescue said they couldn't be absolutely sure if the whale was Nibble, or an orca with similar markings, named Bullet.
She said the orca's death was extremely sad, but was relieved to hear that it wasn't the result of boat-strike.
Between 150 and 200 orca whales are estimated to live in New Zealand's waters.
They are considered 'nationally critical' in New Zealand, with known threats being fisheries interactions and boat strike.
The presence of boats is also known to disrupt their normal behaviour, particularly in resting, according to the Department of Conservation. Underwater noise can also disrupt echolocation signals.
Marine mammals in New Zealand are legally protected under the Marine Mammal Protection Act (1978).
Anyone who accidentally kills or injures a marine mammal is required to report the incident to a fishery officer or Doc within 48 hours.
Under the Marine Mammal Protection Regulations (1992) vessels should not be within 50m of an orca whale.
DOC advise vessels should avoid rapid changes in both speed and direction and operate quietly within 300m of an orca.
Vessels travelling at speeds over 15 knots are more likely to kill a whale or dolphin if they hit it and can still cause severe damage if travelling over five knots.
It is an offence to kill marine animals in New Zealand.
Anyone charged with harassing, disturbing, injuring, or killing a marine mammal faces a maximum penalty of two years imprisonment or a fine up to $250,000.