Griffith researchers have brought the ‘freshwater orchestra’ in rivers to the surface by recording ‘singing fish’ and insects for a new river health study.
Dr Simon Linke from Griffith’s Australian Rivers Institute and his PhD student Emilia Decker led the ecoacoustic research into river health monitoring, which has recently been published in Freshwater Biology.
Dr Linke and colleagues from Monash University and France 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. They aimed 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.
Dr Linke said ecoacoustics was a non-invasive way to log ecosystem health autonomously 24/7.
“This is the first time that we have performed this work systematically. When we started doing this work 4-5 years ago, we would put a microphone in the water at general times and intervals but never got a conclusive result,” he said.
“What we have found is that – just like above water, sounds vary during the day. 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.”
Decker, who identified more than 8000 sound events for the study, said just like above water, there were certain times of the day and season when certain lifeforms could be detected.
“Fish are active throughout the day, but most detectable in the morning,” she said.
“This is just like daily rhythms above water, with bird morning choruses and evening cicadas.
“So it’s basically a fish chorus for breakfast, creekflow for lunch, and an insect orchestra for dinner.”
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 follows on from Dr Linke’s previous research published in Frontiers in Ecology and the Environment, in which he confirmed the prevalence of ‘singing fish’ as an indicator of river health.
The Griffith-led study included researchers from Monash University and the Paris Natural History Museum. It was conducted on the land of the Ewamian Aboriginal Corporation with acknowledgement and appreciation from the researchers.