Swan River dolphins bounce back after shock deaths

  By Shannon Verhagen Recent studies show the dolphin population in the Swan Canning Riverpark has recovered following six deaths in 2009 to a rare virus. Morbillivirus was found as the cause of at least two of the deaths, a virus which breaks down the immune system causing respiratory and brain infections. The mortalities prompted the Murdoch University Cetacean Unit and Swan River Trust to investigate the long-term health of the dolphins. With the riverpark population being so small, researchers say events like this are a big threat. “It’s still 18-20 dolphins only, which is a really, really small population, especially when you compare it to the east coast of Australia where they’re talking about 50 resident dolphins, and at 50 they’re saying it’s a small population,” says PHD candidate at Murdoch University Delphine Chabanne. Suspicions the virus entered the river from coastal dolphins have fuelled research into their interactions with coastal populations to prevent another outbreak. “If anything happens to them, it’s critical,” Delphine says. “They regulate and control the amount of fish… without this control the ecosystem is going to be unbalanced and you may not have a very nice ecosystem anymore.” Dolphins are not only important to our estuarine ecosystems but to WA tourism as well, with many places along the coast offering up-close and personal interactions with them. “They are very animated and demonstrate curiosity… and of course their huge smile always attracts us to them,” says Phil Coulthard, a Marine Biologist at the Bunbury Dolphin Discovery Centre . But experts worry these small, local populations are at risk with WA’s once pristine waterways becoming increasingly urbanised. “Human impacts have had a significant impact on the local dolphins. From direct harm through boat strikes, fishing line entanglements right through to long term impacts caused from unregulated feeding, harassment and constant interaction,” Phil says. When the study is complete, the Swan River Trust will use Murdoch University’s research to better manage recreational uses of the river to minimise harm to the dolphins in the future. “Hopefully I’ve got a result, something concrete for them in a year or two’s time,” says Delphine.   Find out more about the project from Delphine here: