Footage of the southern right whale visiting Wellington Harbour, including some biopsy dart sampling and recovery carried out by the Department of Conservation.

The presence of a rare whale in Wellington Harbour may mean the capital's Matariki fireworks display will need to be postponed this weekend.

Wellingtonians have been enjoying spotting the rare southern right whale this week. It was first seen swimming south near the Wellington coast, then popped up in the harbour intermittently, and eventually put on a bit of a show near the Interislander ferry terminal on Wednesday.

But the presence of the whale has raised concern over how this weekend's big Matariki fireworks display could affect the mammal.

DEREK QUINN/SNPA A whale swims and plays in the harbour just off from the ferry terminal on Wednesday.

A Wellington City Council spokeswoman said staff were waiting on advice from the Department of Conservation before making any decisions on a contingency plan for the Sky Show this Saturday.

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Scheduled for July 7, this year is supposed to be the first time in 22 years that Wellington coincides its big annual fireworks display with Māori New Year celebrations.

Allan Mansfield/Supplied A rare southern right whale in Wellington Harbour entertains onlookers.

The Sky Show, which is usually held in November for Guy Fawkes Day, is the largest annual fireworks display put on by a city council in New Zealand. Its postponement day is July 8.

"We appreciate that people are concerned about the timing of the Sky Show on Saturday while a southern right whale is visiting Wellington Harbour," the council spokeswoman said.

"No decision has been made yet in terms of postponement but we are monitoring the situation along with DOC and will be taking advice from them. We will keep everyone updated via our social media channels if anything changes."

KARL HALVORSEN/SUPPLIED The southern right whale surfaces behind a Niwa research boat in Wellington Harbour, near the Interislander ferry terminal.

A Department of Conservation spokesperson said their staff were also monitoring the situation and consulting experts.

In the meantime, the department has urged whale watchers to keep at least 50 metres away from the whale.

Collectively, no more than three vessels – including kayaks – or aircraft should be within 300 metres of any marine mammal. Swimming with whales was not permitted either.

ROBERT KITCHIN/STUFF Rare southern right whale sighting in Wellington Harbour

Marine species officer Hannah Hendriks said staff had taken a sample from the whale for research purposes and are confident that its behaviour is normal.

"We did this in conjunction with Niwa, who have a special permit to be closer than 50 metres."

The last reported sighting of southern right whales in Wellington Harbour was in 2010, so this sighting is rare, Hendriks said.

MAARTEN HOLL/STUFF While rain is forecast for this weekend, it would typically take particularly strong winds to postpone the annual fireworks display at Wellington Harbour. (File photo)

"During the breeding season in winter and spring, these whales are mostly found in the waters around the sub Antarctic Auckland and Campbell Islands. However, there are occasional sightings around mainland New Zealand."

Event company PyroStar, which organises the fireworks display on behalf of the council, referred queries to the council.

The New Zealand population is distinct from neighbouring populations in Australia.

"DOC is leaving it to do its own thing unless we see something to suggest there is something wrong with it. We're working with the harbour master and the police to monitor people's behaviour in its vicinity."

Southern right whales can be recognised by their strongly arched mouth, lack of dorsal fin and V-shaped blowhole spray.

Nadine Bott, from the Department of Conservation, said on Tuesday that the whales were hunted to near extinction in the 18th century, but sightings were slowly starting to increase.

There were two right whale populations in New Zealand – one in the sub-antarctic Auckland Islands and another that travelled along the coast and stuck closer to the mainland.

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