Fish create part a rich orchestra of underwater sounds as they hunt, spawn and defend their nests and these sounds are now forming the basis of new methods to monitor the health of waterways.
Dr Simon Linke, an ecologist and sound engineer with Griffith University's Australian Rivers Institute, said studying the sounds made in nature could provide valuable information about the environment.
"We record the sounds of fish in a system, just like you would record a bird sound," Dr Linke said.
"You can monitor fish species, you can monitor fish stocks but you can also monitor little critters that you can use as indicators of river health."
An underwater microphone, or hydrophone, is cast into the water, which records audio and can transmit the sound and data back to an office.
Particular sounds like fish calls have been catalogued and can be identified by computer systems, meaning data can be automatically processed from the passive audio recordings and used to construct findings on the health of the river system.
In a world first, Dr Simon Linke and a colleague identified every single biological sound recorded underwater in the Einasleigh River in far north Queensland.
Research assistant Christopher Karaconstantis said the field of eco-acoustics was gaining momentum as a valuable research tool.
"A lot of people think that the underwater world is quite silent. Every time we've taken someone new out on a field trip, we always get a photo of their face the first time they hear some of these sounds underwater," he said.
"It's a very non-invasive way of monitoring an eco-system, we don't have to take anything out, we don't have to interfere with the system at all, we just listen and we can find out a lot about what's going on based on the sounds.
"Long-term it means we can set it up, sit there and leave it and tap into it any time we want."
Dr Linke said eco-acoustics would change the frequency of river health studies from once a year to every day.
"Traditionally we had to go to a site, unpack all of our gear and even the driving to the site takes a really long time," he said.
"With an autonomous recorder, on the other hand, we can record 24/7."
The scientists also hope the system could be used as an early detection system for invasive pest species like Tilapia.
"Tilapia make noises when they spawn or when they defend their nests," Dr Linke said.
"What we could do is set up an autonomous recording system and when it hears a Tilapia it pipes back a signal back to headquarters and we can go about eradicating the pest early."
The researchers hope to begin rolling out the hydrophones in river systems Australia wide from 2019.
