Researchers have listened to the ‘freshwater orchestra’ of singing fish to study river health.

A Monash University team recorded underwater sounds continuously over seven days in two waterholes on the land of the Ewamian Aboriginal Corporation in the Einasleigh River in Far North Queensland.

The idea was to better understand the underwater soundscape relevant to the time of day and the environment as indicators of river health.

It is the first study in Australia to document all underwater noises, and the first time in the world that all biological sounds from fish and aquatic insects in an underwater location were identified. 

“What we have found is that – just like above water, sounds vary during the day,” Dr Simon Linke said.

“If you arrive somewhere at a certain time of day, you might miss what you’re interested in hearing, whether that’s fish or insects or change in waterflow. 

“By recording 24/7 you get an encompassing overview of life underwater.”

The team identified more than 8,000 sound events for the study. Just like above water, it showed there were certain times of the day and season when certain lifeforms could be detected.

The team discovered that the daily pattern could be detected using acoustic indices – similar to ecological community indices – that measure the soundscapes as a whole, proving that an automated method could continuously monitor ecosystem change in a simple way.

The study has been published in Freshwater Biology.