Bottlenose dolphins in the Swan and Canning rivers would benefit from a sanctuary similar to a 118 sqkm dolphin protection zone in Adelaide, according to a Murdoch University report.
The study found that the Swan and Canning rivers were home to 20 dolphins, including four calves — about the same as a decade ago.
But the report paints a picture of a vulnerable community, with only four adult females remaining after three died in a spate of dolphin deaths in 2009.
Murdoch University dolphin expert Hugh Finn, who co-authored the report, said the dolphin population in the rivers was small and was always going to be precarious.
“Because they’re dependent on the females that reside in the river to keep things going it makes each and every dolphin very important,” he said.
Dr Finn said the Adelaide Dolphin Sanctuary could be used as a model for the Swan and Canning rivers.
“It has a number of mechanisms for protecting and conserving dolphin habitat, which are very valuable, but the other thing that it does is it really focused people on protecting the estuary as a home for dolphins,” he said.
The study also identified 16 dolphins that visited the rivers, including two female dolphins that were seen in consort relationships with resident male dolphins.
It is believed resident dolphins may bring females into the estuary to keep them away from other males.
The study found male dolphins formed strong bonds with their companions while females had a looser network of acquaintances.
Two visiting males, named Backpack and Fingers, have been constant companions for more than 20 years.
A third generation river dolphin was also identified for the first time, with resident dolphin Moon, who was seen with her mother Socket in 2001, now having her own three-year-old calf, Night.
In releasing the report yesterday, Environment Minister Bill Marmion said it showed the dolphin population had recovered since the virus four years ago.
“It does show that the Swan River is healthy,” he said.
Mr Marmion said the Swan Canning Riverpark already embodied many of the components of a sanctuary and through research and programs such as Dolphin Watch and River Guardians the public was now very aware of the dolphins and the need to keep the rivers clean.
He said a draft protection strategy for the riverpark was currently being finalised by the Government.