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Probe for poor health of Port Adelaide river dolphins amid ‘disturbing’ population decline

By on August 24, 2021 0

An investigation has started into the deteriorating health of the Port Adelaide river dolphins after a male was found dead and two of his friends were reported missing.

After showing signs of emaciation and poor skin health, a 12-year-old dolphin known as Talulla – famous for its tail walking on the surface of the water – was found dead in the dolphin sanctuary Adelaide (ADS) this weekend.

Two other Port River dolphins, Twinkle and Doc, are missing after showing similar symptoms and are now presumed dead.

South Africa’s Environment and Water (DEW) Minister David Speirs said he had ordered an investigation into the failing health of the dolphins at the sanctuary.

“In view of recent events, it is important that we take a closer look and hope to learn more about the possible causes of dolphin death by autopsy [animal autopsy] procedures and other tests. “

Mr Speirs said the SA Museum is assessing recent dolphin deaths and carrying out further testing.

Doc and Twinkle both looked emaciated before they vanished.(

Provided: Marianna Boorman

)

Declining number of dolphins

The 118 square kilometer Dolphin Sanctuary encompasses the Port River and adjacent Barker Inlet, and stretches north through the Gulf of St. Vincent to the Adelaide International Bird Sanctuary.

Port River dolphins were once 40 in number, with around 30 remaining almost entirely in the river zone, but in recent times the main river population has declined to around 10, with another 10 coming and going from the Gulf.

Whale and Dolphin Conservation volunteer and ADS researcher Marianna Boorman said she was deeply concerned about the dwindling population.

“We have had terrible years with a number of dead calves,” she said.

two dolphins swim close to shore in a river while a child watches
Marianna Boorman’s daughter Lily watches Doc and Twinkle swim nearby.(

Provided: Marianna Boorman

)

Ms Boorman said boat collisions, tangled fishing lines and shark attacks were constant threats to dolphins, but the reason for the recent deaths was unknown, making them “of great concern”.

“It is certainly possible that pollution causes calves to die, but if the pollution passes into breast milk, we don’t know enough about it,” she said.

She said the deaths could also be due to a virus, and if that was the case, “there’s not much we can do.”

“And the three dolphins [Talulla, Doc and Twinkle] were collecting and collecting discarded fish scraps, which was a very concerning behavior, ”said Boorman.

The autopsy took place this week

A spokeswoman for the SA Museum said Talulla’s autopsy would be undertaken this week, but an investigation into the cause of her death could take up to six weeks to be finalized.

“Once the autopsy is completed, the museum will work with DEW and the University of Adelaide to analyze the results and a report will be made public at that time,” the spokesperson said.

Ms Boorman was also concerned that the leak of hypersaline water in St Kilda, where it killed mangroves and salt marshes, could be linked to the failing health of the dolphins, as Talulla, Doc and Twinkle were known to spend a lot of time in the adjacent area. The entrance to Barker.

Dead mangroves rise from the water beside a boardwalk
The hypersaline water killed around 10 ha of mangroves and 35 ha of salt marshes near St Kilda.(

Provided: Chad Buchanan

)

Mr Speirs said consideration would be given to “informing other areas which may require investigation”.

“DEW will lead the investigation and solicit input from a Dolphin Expert Reference Group comprised of independent and qualified veterinarians and experts with experience in marine mammal management, as well as researchers and others. relevant ministries, ”he said. .

A tangled story

In 2019, a dolphin named Star died after getting tangled in a fishing line and having hooks in his throat for almost three weeks.

A woman sits near a dolphin with her camera
Marianna Boorman, pictured here with Talulla, is an avid photographer of Port River dolphins.(

Provided: Barry Hurrell

)

Another dolphin, Marianna – named Ms Boorman – was found dead in October last year, an autopsy revealing he was most likely dead from blunt trauma from a collision with a boat.

Doc himself had to be rescued from a tangle just three days before he was last seen alive on July 27.

Ms Boorman said Doc started showing symptoms of poor health in October last year and appeared to improve slightly before deteriorating again.

She said Talulla and Twinkle started showing symptoms about three weeks before they were last seen alive on July 7.

“It is fortunate that Talulla’s body could have been recovered [for necropsy] because Doc’s and Twinkle’s bodies were gone, so we sort of had no response, “Ms. Boorman said.

Many ADS male dolphins, such as Talulla, Twinkle, and Marianna, have female names, as enthusiasts can take years to learn that a dolphin that might have originally appeared as a female was actually a female. male.

“They brought so much joy”

Ms Boorman said Talulla learned to step on her mother’s tail, Wave, who was among the other dolphins who learned the technique from another dolphin, Billy.

Billy had returned to the Port River after being released from Marineland, a West Beach aquarium and wildlife park that closed in 1988.

A dolphin's tail walks in the distance from the surface of a river
Talulla often surprised spectators with his spectacular tail parades. (

Provided: Marianna Boorman

)

“Talulla’s mother Wave was doing this regularly and then Talulla started to copy the behavior, so it’s an amazing site to see and certainly spectacular when you see a dolphin walking backwards on its tail,” Ms. Boorman said. .

“We also knew Twinkle very well because we had to save him four times due to tangles, and Doc was seen playing regularly and people could watch them from the land of Garden Island.

In 2019, the state government reduced boating speed limits in key ADS areas from unlimited speed to seven knots, and it is illegal to feed dolphins or dump fish waste in them. South African waters.


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