Post # 11.Sounds from the Amazon!
In the summer of 2012, I had the opportunity of joining an annual ecological survey of the Pacaya-Samiria National Reserve (PSNR) in Peru under the umbrella of
PSNR is contained within the confluence of the Marañón and Ucayali Rivers where the main-stem of the Amazon River originates more than 3,000 km from the Atlantic Ocean. I stayed for 4 weeks at a base camp on the very remote Samaria River working from the historic riverboat, the R/V Rio Amazonas.
I observed, collected and recorded fish from a small dock located at the base camp, and from small motor boats and canoes from which we conducted twice-daily fishing surveys.
Fishing with cane poles
Fishing with gill nets
Although staying in the same location for four weeks might seem monotonous, it was amazing how much the sights changed daily. I was there during the low water season when the vast amounts of water recedes from the flooded forest and lakes.
Vegetation choking off river as it recedes
Because of this rapidly receding water, different species of fish would be forced to migrate out of the flood zone and down the river as their species tolerances were reached.
For example, these photographs taken from on deck of the Rio Amazonas show some of the thousands of cory and doradid catfish, like the ones you may have in your home aquarium, migrating down the river.
Cory catfish migration
Dorid catfish migration
Below you can view a short movie clip of vast number of Palometa fish (multiple species) migrating out of the lake and forest and moving downstream.
Remember my post on fish fart and how many fishes need to gulp air at the surface (see post # 9)? Well that’s what all these migrating fishes are doing, though in this case I did not hear any evidence of FRTs or other air movement sounds.
When working at the base station, I was able to set up a fish holding and auditioning center right on the floating dock. I would first audition a specimen in a kiddy pool and then in the river by holding it gently under water near a hydrophone. However, I was only able to record here when the engines and electrical generators of the support ships were turned off (we had electricity for only 8 hours of the day, split between morning, noon, and night). So basically, in addition to participating on two surveys per day, I also got up at daybreak, and stayed up well after 10 pm, to record at the dock (not much sleep for me!).
Dock work station
During the fishing surveys, I had to make do with auditioning in a small plastic tube and then in the river.
All fish were released after auditioning
So far, we have measured and processed thousands of fish sounds from the auditioning and soundscape recordings. We recently published a comparison of Piranha sounds demonstrating the potential of passive acoustic monitoring of Piranha in the Amazon.
My colleagues and I are now working to describe the soundscape of the study area. On of the interesting findings is the apparent strong impact of piranha feeding on the local fishes (hmm, ouch!)
Listen to a recent Scientific American 60 second podcast:
For more information, and lots more sound samples, go to my web page at: The Amazon Soundscape
Red Piranha, Pygocentrus nattereri