Adelaide Dolphin Sanctuary Deaths Prompt Environmental Investigation

Environmental authorities are conducting necropsies on four dolphin carcasses recovered from the Adelaide metropolitan coastline, including a well-known resident of the Port River dolphin sanctuary.

A spokesperson for the Department for Environment and Water confirmed that park rangers were notified of a carcass, believed to be that of a dolphin named Zoom, found at Snowden Beach within the Adelaide Dolphin Sanctuary on Wednesday. Rangers did not detect any external injuries, though the carcass was in an advanced state of decomposition.

Whale and Dolphin Conservation volunteer Barb Saberton said the community had been monitoring Zoom, aged between 30 and 35 years old, for a sunburn injury. Identifiable by a white mark on his left side, the dolphin was frequently spotted swimming near a carrier ship in the sanctuary.

“I think the greater community is going to be grieving him for sure,” Ms Saberton said.

Multiple Carcasses Recovered

The department spokesperson said two dead dolphins washed up at Hallett Cove on June 5 and 6, and the remains of a third were found at Henley Beach on June 10. All four carcasses have been transferred to a pathology laboratory for necropsies.

Citizen scientists Susan Belperio and Johanna Williams discovered one of the deceased dolphins, named Naia, and provided photographs to dolphin researcher and conservationist Mike Bossley. Ms Belperio said Mr Bossley assessed the dolphin as appearing emaciated.

“It feels very confronting and extremely tragic,” Ms Belperio said.

Algal Bloom Unlikely Direct Cause

Lisien Loan, director of conservation at the Department for Environment and Water, said the current algal bloom is unlikely to be the direct cause of the deaths. There has been no sign of the algal bloom off the metropolitan coast over the last three months.

“There may well be an indirect impact from lack of food resources, but that's one of the things we're investigating,” Ms Loan said.

Necropsy results could take months to be delivered. The department spokesperson noted that marine mammal death is not an uncommon occurrence, with around 40 reported dolphin deaths in South Australia on average every year. Causes of death include age, entanglement, boat strike and disease.

A Sanctuary Under Pressure

The recent deaths add to a concerning history for the protected pod in the Port River. In 2021, six dolphins died within a few months of each other after becoming emaciated. A further three dolphins died or disappeared in 2022 and 2023. Last year, a three-year-old dolphin calf named Rocket died after a suspected boat strike.

The Port River and its adjoining inlets are home to the world's only city-based dolphin sanctuary. Established in 2005, the sanctuary was designed to protect a pod considered rare for living in an Adelaide estuary. The ongoing deaths raise questions about the long-term viability of the estuary's ecosystem and the effectiveness of current conservation measures.