The Swan River is iconic to Perth and its residents, and the recent developments aiming to link the city with the river are testament to just that. But with Barrack Street pier business owners speaking out about profit losses as the Elizabeth Quay development progresses, what about the effects of construction on those whose voices aren’t so easy to hear?
Deputy Director at Curtin’s Centre for Marine Science and Technology Dr Chandra Salgado Kent is part of a team of academics aiming to uncover information on behalf of a number of these residents of Perth – or, the Swan River to be exact. The researchers are investigating whether a pod of 25 Indo-Pacific bottlenose dolphins who call the Swan–Canning Riverpark home, plus another 25 visiting dolphins hailing from the Cockburn Sound community, are potentially also being affected by the development.
“Dolphins have evolved to use sound rather than visual cues to detect, explore and communicate,” says Salgado Kent. “So, we want to understand if the Swan River noise is increasing, and what the potential implications are for dolphins’ abilities to communicate easily with one another in this environment.”
The team have placed a number of ‘acoustic loggers’ along the Swan to record sounds across a range of marine environments, from the very quiet to the very noisy.
At locations such as Fremantle, the Narrows and Freshwater Bay, these devices log underwater sounds over a period of several days or months. The recorded data is then analysed to characterise the major sources of noise in terms of sound frequency, then flagged for any potential overlap with the frequencies used by dolphins. To better understand the effects of this overlap, imagine tuning in to a radio station, only to hear two shows competing for airtime.
Salgado Kent says it is already known that this frequency overlap can have an effect on the way dolphins communicate.
“There have been studies completed elsewhere that have documented dolphins reducing communication rates in the presence of vessel noise or changing the frequency of their whistles, which is thought to allow them to communicate on frequencies in which there is less unwanted noise,” she explains.
“Other strategies might be used such as producing louder sounds, akin to how we might elevate our voices over loud music at a nightclub.
“Importantly, studies in humans show that exposure to sufficient levels and duration of noise can elevate stress levels. And we already know that long-term elevated stress can have an effect of depressing the immune system. There is no reason why dolphins would not experience the same elevated stress levels, which if sufficient, could affect dolphins’ long-term health and wellbeing.”
“Of particular concern is the combination of all man-made noise, which can come from a number of places, including from vessel traffic, trains, ships, dredging and other development activities, and which has been steadily increasing over the years as Perth continues to grow.
“By better understanding if there are any limitations in the ability of our dolphins to communicate in a environment such as the noisy Swan River, we can begin to improve how we conduct our own noise-generating activities,” says Salgado Kent.
“This will then work towards reducing potential impacts on these marine mammals.”
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