Quiet aids dolphins

A dolphin has a splash in Fremantle Harbour. Photo by Chandra Salgado Kent.

BOTTLENOSE dolphins could benefit from the reduced number of boats in the Swan River during the COVID-19 pandemic.

Marine mammal scientist Chandra Salgado KentSalgado Kent has been studying bottlenose dolphins in the river for more than a decade, and says a noisy river full of boats can make it difficult for the animals to communicate with each other and locate prey.

Other studies reveal that scuba divers can get stressed by underwater noise and experience health issues, and it’s likely dolphins react similarly.

Dr Salgado Kent says the river has been quiet since access to Rottnest was cut off and restrictions imposed on public gatherings.

“It may be that with less boat traffic, they would be able to use a broader area and communicate over longer distances due to less boat noise,” she says.

Dr Ben Fitzpatrick of Oceanwise Australia said less boat traffic means less animals are harmed. 

“Boats disturb wildlife, seabirds, marine mammals and others,” he says. 

“This can result in direct injuries to animals, separation of mother calf pairs and interruption of critical processes like breeding, feeding and nursing.” 

Last year, five dolphins died in the Swan River from the naturally occurring cetacean morbillivirus.

“While morbillivirus has been an issue,” Dr Salgado Kent said, “reducing stress on dolphins will improve their overall health, and carefully disposing of plastics such as fishing line is critical to reducing entanglement-related mortalities we see in the river.”

Dr Salgado Kent says there are about 20 dolphins in the Swan and Canning river park and she’s able to identify them by the unique nicks and notches in their dorsal fins.

“We are able to identify individuals and track them. Some dolphins are over 20 years old.” 

 Dr Salgado Kent, an associate professor at Edith Cowan University, is collaborating with Murdoch and Curtin universities, and the Department of Biodiversity, Conservation and Attractions.

Her research includes a citizen science dolphin research program called Dolphin Watch. 

It’s partly funded by Fremantle Ports and Dr Salgado Kent can sometimes be seen observing dolphins herd fish against the harbour walls, before diving in for a big feed.

All clear for river

REGULAR paddlers in the Swan River say the water is noticeably clearer since COVID-19.

This week Bicton resident Andrew Davenport went for his usual paddle and was pleasantly surprised by the water quality.

Oceanwise Australia director Ben Fitzpatrick says less boat wake means less erosion of the river banks and vegetation.

“All the murk and muck that is stirred up by boats is often associated with pollutants like nutrients, toxins and heavy metals.”

Dr Fitzpatrick hopes some lockdown routines benefiting the environment continue. 

“I hope people understand how working from home can fit into their daily lives. I am hopeful some habits we have been forced to adopt actually becomes normal for people.”


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