A piranha’s bark can never be worse than its bite but it could be more useful, according to new research. A recent study of sounds made by piranhas in the Amazon has discovered that their underwater ‘barks’ can be used as an effective indicator of the different species that lurk in these murky waters.
Rodney Rountree, also known as ‘The Fish Listener’, and Francis Juanes of the University of Victoria, surveyed over 70 species of fish, including four types of piranha, over the month of July 2012, within the Pacaya-Samiria National Reserve, Peru. They auditioned over 550 captured individuals by holding them gently underwater next to a hydrophone to record any sounds.
“In the Amazon, most of the habitats are very turbid so you usually can’t put cameras down and watch the behaviour,” Rountree told Phys.org. “The only way to survey fish is to catch them. Passive acoustics lets you potentially locate fish just by their sounds.”
Rountree also recorded over 641 minutes of underwater soundscapes at 22 sites within the reserve and heard similar piranha ‘barks’ at known active feeding locations, accompanied by calls from catfish and other known prey. “When piranha are present and feeding, they’re nipping and biting, so the other fish are making lots of sounds,” he said.
Using statistical analysis, the researchers could differentiate between the piranha species, based on the pattern of their barks.
While it is not the first time that scientists have documented the range of sounds made by the carnivorous fish contracting muscles near their gas bladders, previous studies have generally been carried out within a laboratory.
Rountree and Juanes presented their research on Monday, November 5, at the Acoustical Society of America’s 176th Meeting, held in conjunction with the Canadian Acoustical Association’s 2018 Acoustic Week in Canada, in Victoria, British Columbia.
The researchers also hope to use their work to expound upon the benefits of using passive acoustic monitoring to complement or even replace traditional methods of surveying fish through capture. “A lot of times, the most difficult thing is finding where they are,” said Rountree. “So any tool that helps you find the fish is very helpful.”
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