Then there were 62: Late reporting of Māui dolphin death worries experts

Tuesday, 22 June 2021

WWF NZ researcher Amanda Leathers explains why Hector's and Māui dolphin are on the brink of extinction. (First published May 9, 2019)

Researchers and dolphin advocates are concerned it took the Department of Conservation four months to report the death of one of the last Māui dolphins.

The department (DOC) maintains a regularly-updated online database of all incidents involving Hector’s and Māui dolphins, including ones caught as commercial fishing bycatch, any dolphins found dead, or any that become stranded on beaches.

One of the smallest marine mammals in the world, Hector’s dolphins are only found in New Zealand waters and are considered nationally vulnerable, with a population of about 15,000.

Their North Island subspecies, the Māui dolphin, is critically endangered, with scientists estimating there were just 63 left.

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But experts are dismayed about a four-month delay updating the database, including adding information on the death of a rare Māui dolphin this year.

Zoologist Liz Slooten says Maui dolphins are teetering on the edge of extinction.

DOC marine species manager Ian Angus confirmed there had been an incident since the website was last updated in February.

“This was a Māui dolphin found at Muriwai beach in Auckland in February. The dolphin was unfortunately decomposed when found but obviously had a large shark bite taken out of it.

“The dolphin was sent to Massey University pathologists for necropsy but unfortunately a definitive cause of death was unable to be determined due to the level of decomposition.”

Slooten, a professor at the University of Otago, says the catch of just a single Māui dolphin in a fishing net could lead to extinction.

Angus said the dolphin was in poor condition and may have been unwell prior to its death, but the cause of any illness was unknown.

The pathologist was also unable to determine if the shark bite occurred before or after it died.

“Genetic analysis has shown this was a female dolphin, which is an unfortunate loss to the population.”

Information on a Hector’s dolphin killed in a fishing net last year wasn’t released for five months (file photo).

While the website update was late, Angus said this had now been rectified.

University of Otago emeritus zoology professor Liz Slooten was concerned the delay releasing information about the death was part of a long-standing pattern.

“I wish I could say I was surprised, but this is almost standard operating procedure at this point.”

There are around 15,000 Hector's dolphins left nationwide.

A Hector’s dolphin caught in a fishing net during lockdown last year was not publicly disclosed until an Official Information Act request to the Ministry of Fisheries five months later.

Slooten said reporting deaths promptly was vital to people understanding the scale of the threats native dolphins face.

“If the public were more aware of what’s going on, there’d be a lot more pressure on politicians to do the right thing.

“At the moment, [dolphins asphyxiating in fishing nets] are out of sight, out of mind… But it’s a pretty unpleasant way to die. They struggle.”

One dolphin she had seen was covered in tooth rakes, where she believed its family had tried to free it.

“MPI (Ministry for Primary Industries) estimates 58 dolphins a year are dying in trawl nets. If a media release was sent out for each one, people would demand a solution.

“Whereas if you keep it under wraps, the pressure gets taken off.”

On Tuesday the Government announced a slew of new protections for Auckland’s Hauraki Gulf, including 18 new marine protection areas, and trawl-fishing restrictions.

Slooten said it was great the gulf would be better protected.

“Fishing is impacting fish populations and kelp beds, as well as marine mammal and seabird populations.

“Deaths in gill nets and trawling are a very serious impact on marine mammals, seabirds, sharks and other species.”

There have been sightings of Hector’s dolphins in the gulf over the years, Slooten said, but it was unknown whether they were the critically endangered Māui subspecies.

The announcement lined up with the release of the International Whaling Commission’s Scientific Committee Report.

Slooten said this is the 10th year in which the commission had urged New Zealand to fully protect the Māui dolphin, by banning gill nets and trawling in their habitat up to 20 nautical miles offshore.

She said New Zealand was still falling well short of their recommendations.

“Over the years, the International Whaling Commission recommendation has increased from ‘concern’ to ‘grave concern’.

“Right now, the catch of just one Māui dolphin in a fishing net could lead to extinction.”