The appearance of a southern right whale scarred by a ship's propeller is seen as a timely reminder of issues that will arise as the animal's population recovers.

The scarred whale was seen by members of a scientific expedition in the sub-Antarctic Auckland Islands.

The animals visit the islands during the winter, giving birth and nursing calves in the sheltered habitat.

"We saw very high densities of whales in Port Ross, the sheltered harbour at the northern end of the islands," expedition leader Dr Will Rayment, from Otago University's Marine Science Department, said.

"Sadly we also witnessed a whale that had been struck by a ship - evidenced by the succession of scars across its back from the ship's propeller.

"We can tell it's a propeller strike because of the regular, repeated pattern of scarring. In this case it seems that the propeller cut into the whale's thick blubber layer, which healed but left large scars. In more serious cases the cuts can result in serious fractures or penetrate vital organs. This animal is lucky to survive this encounter.

"This is the first time we have seen a southern right whale in New Zealand waters with prop scars, and is a timely warning about the impacts the whales will face as their range overlaps more with human activities."

Ship strike was the leading cause of mortality in the closely related North Atlantic right whale.

The 25-day expedition on Otago's ship Polaris II involved 12 scientists and crew from Otago, Massey University and the National Oceanic and Atmospheric Administration in the US.

As well as studying the recovering population of southern right whales in the Auckland Islands, researchers also did work on the diet of New Zealand sea lions and the foraging behaviour of yellow-eyed penguins and Auckland Island shags.

- © Fairfax NZ News