WASHINGTON D.C., NOVEMBER 5, 2018 -- A piranha's bite is definitely worse than its bark, but the bark has uses too. A new study of the sounds made by piranhas in the Amazon finds that their underwater "barks" are an effective tool for identifying different species in murky waters.
Scientists have previously documented several noises that piranhas make by contracting muscles near their gas bladders, but these studies primarily occurred in a laboratory.
Next month, Rodney Rountree, "The Fish Listener," will talk about his work with Francis Juanes of the University of Victoria, to document calls made by fish in the Pacaya-Samiria National Reserve in Peru in a presentation at the Acoustical Society of America's 176th Meeting, held in conjunction with the Canadian Acoustical Association's 2018 Acoustics Week in Canada, Nov. 5-9 in Victoria, British Columbia. These calls may be useful for tracking piranha populations through passive acoustic monitoring.
"In the Amazon, most of the habitats are very turbid so you usually can't put cameras down and watch the behavior. The only way to survey fish is to catch them," Rountree said. "Passive acoustics lets you potentially locate fish just by their sounds."
During routine surveys at the reserve in 2012, Rountree "auditioned" captured fish by holding them gently underwater next to a hydrophone to record any noises. In total, he auditioned more than 550 individuals from at least 70 fish species, including four types of piranhas. Using statistical analysis, Rountree could differentiate between piranha species, even closely related ones, based on the pattern of their barks.
Rountree also recorded underwater soundscapes at 22 sites in the reserve. He heard similar piranha barks at locations where piranhas were known to be feeding, as well as startled calls from catfish and other prey. "When piranha are present and feeding, they're nipping and biting, so the other fish are making lots of sounds," he said.
How could this be extended to monitor piranhas in the wild? Scientists potentially could deploy hydrophones from small boats to track how piranhas affect the ecosystem. Such studies could also help us understand how fish navigate their natural soundscape and whether human activity creates disturbances.
Further studies will be needed, however, to determine the best ways to differentiate between piranha species and to verify the range of barks made by each type. Factors such as the ambient water temperature and the size of the fish can affect the sounds.
As a simple, noninvasive method, passive acoustic monitoring could 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."
###
Presentation #1pAB9, "Sounds from the Amazon: Piranha and prey," by Rodney A. Rountree and Francis Juanes will take place Monday, Nov. 5, 3:30 p.m. in Crystal Ballroom (FE) of the Victoria Conference Center in Victoria, British Columbia, Canada.
USEFUL LINKS
Main meeting website: https://acousticalsociety.org/asa-meetings/
Meeting technical program: https://ep70.eventpilotadmin.com/web/planner.php?id=ASAFALL18
Hotel information: https://acousticalsociety.org/asa-meetings/#hr
WORLD WIDE PRESS ROOM
In the coming weeks, ASA's World Wide Press Room will be updated with additional tips on dozens of newsworthy stories and with lay language papers, which are 300-800 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio, and video. You can visit the site, beginning in late October, at http://acoustics.org/world-wide-press-room/.
PRESS REGISTRATION
We will grant free registration to credentialed journalists and professional freelance journalists. If you are a reporter and would like to attend, contact Rhys Leahy or the AIP Media Line (media@aip.org, 301-209-3090). We can also help with setting up interviews and obtaining images, sound clips or background information.
LIVE MEDIA WEBCAST
A press briefing featuring a selection of newsworthy research will be webcast live from the conference Tuesday, Nov. 6, 2018. Times and topics to be announced. Members of the media should register in advance at http://aipwebcasting.com.
ABOUT ASA
The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world's leading journal on acoustics), Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. For more information about ASA, visit https://acousticalsociety.org.
ABOUT CAA
The Canadian Acoustical Association (CAA) is a professional, interdisciplinary organization that fosters communication among people working in all areas of acoustics in Canada; promotes the growth and practical application of knowledge in acoustics; encourages education, research, protection of the environment, and employment in acoustics; and is an umbrella organization through which general issues in education, employment and research can be addressed at a national and multidisciplinary level. For more information about CAA, visit http://caa-aca.ca.