Acoustic communication in fish and ecoacoustics
An acoustic experience on a reef area in Mozambique!
Supervised by Clara Amorim and Paulo Fonseca
A BRIEF INTRODUCTION TO BIOACOUSTICS
ppt summarysound.mp4 FISH COMMUNICATION
Fish vocalize!
How do fish produce sounds?
What do they use vocalization for?
In a medium where visual information is limited, sound becomes essential for marine fauna.
Some remarkable functions are:
communication during reproduction (e.g. mate selection)
agonistic interaction (e.g.territorial defense)
alarm sounds (distress, presence of predators)
Besides, sound has an important role for larval-settlement as well as for predator-prey interactions.
Even though there are several adaptations in the sound-genereting mechanisims, the variablity of sound types is low. In general, fish have a low frequency range (tipically 100 Hz to a few kHz).
POTENTIAL EFFECTS OF ANTHROPOGENIC UNDERWATER NOISE
Why is it so important to keep a low artifitial noise level?
Anthropogenic noise has increased in the marine environment over the last century. Given that noise has been proved to have negative consequences for individuals as well as populations, the need to study the role of sound in the ecology of fish and the potential impacts of a noisy habitat is accentuated.
EXAMPLES OF ACOUSTIC EXPERIMENTS CONDUCTED IN THE FIELD / LAB by the host organization (ISPA) in collaboration with CE3C/FCUL :
Field set-up: (a) Experimental concrete nets designed for the Lusitanian toadfish and placed in the intertidal area of the Tagus estuary. (b) Detail of a nest with the hydrophone to monitor male vocal activity and a restriction mesh. (c) Muting experiment to deflat the swimbladder.
Lab set-up: (a) Aquarium on marble stones and rubber foam (insulators) (b) Painted Goby in the nest under a built chimeny in which the hydrophone was placed (c) Scheme of the acquarium partition prior to the courtship.
MY REMOTE PROFESSIONAL PRACTICE
Due to the global lockdown, the lab and field work in the Tagus estuary were cancelled. Nevertheless, the possibility of deepen my knowledge in the fundamentals of bioacoustics and sound analysis arose.
Throughout the 7-weeks internship collaborating in the fish communication lab (ISPA), I have attended fifteen seminars about bioacoustics imparted by different members of the research group, many of which have incorporated practical exercises, links to information, and sites of interest. Also, weekly meetings were organized and relevant literature was searched.
This training had as its main goal to provide me with the necesary tools to face my final project.
(See below)
Seminars
Meetings
Exercises
Research centre and area of interest
The host organization: ISPA - Instituto Universitário de Ciências Psicológicas, Sociais e da Vida
Lisbon, Portugal.
Mozambique Island, Mozambique.
Studied area: Coral reef soundscapes, Mozambique Island
Experiment led by Paulo Fonseca (CE3C).
This habitat has been acoustically explored during two consecutive years (2018-2019) by the deployment of several hydrophones at different locations to collect data on the diversity of fish sounds. In these seasonal field cruises, the hydrophones were placed during 24 hours for each station at 5-12 meters depth, mainly at the inner part of the reef including both pristine and human- impacted areas.
MY PROJECT
From the third week onwards, I performed a manual analysis of a subsample of the acoustic dataset recorded in the Mozambique Island to characterize the sound types of the vocal fish community of the reef and its occurrence. This will allow the validation of previous automatic analysis, i.e. acoustic indices.
Development of a sound type catalogue with another IMBRSea student by manually scrolling through different sound files.
Once the catalogue was done, I analyzed the sound types present during the mid-day recording to explore the time and frequency domains.
Settings: time window = 5 s, Fast Fourier Transform FFT, 4096, Hamming window, 50% Overlap
How are sounds analyzed?
There are several acoustic software's that can be used to analyze acoustic data. Raven Pro 1.6., Cool Edit Pro 2.0 and Wavesurfer are some examples that I learnt to use during my professional practice.
Peak frequency (frequency at which peak power occurs within the selection), 1st and 3rd Quartile Frequency (frequency that divides the selection into two frequency intervals containing 75% and 25% of the energy in the selection), Sequence duration, Pulse Period, Pulse duration, and Nº of pulses, are the main measurements that were used to describe the diversity of the sound types.
The recognition and classification of sounds and its possible sources (Biophony, Antropophony or Geophony) were mainly based on the hearing discrimination of the observer and the visual information given by the chosen views: Waveform, Spectrum and Power Spectrum.
While the Waveform view displays a graph of the sound showing amplitude versus time known as Oscillogram, the Spectrogram view represents changes in frequency along time, and relative power at each point as a color. The Power Spectrum represents amplitude over frequency.
Scroll right to see how the selections were commited to measure the chosen variables!
RESULTS
Overall, the results showed a higher number of vocalizations during the day and some temporal partitioning, i.e. sounds found only during the day / night.
More than 800 sounds were found in 1 hour of recording!!!
Some examples of the variablity of fish sound types found during mid-day:
A few examples of the sound types described in the catalogue:
CATALOGUE WEB.mp4
Did you know that the snapping shrimps are one of the loudest biophony sources in marine soundscapes?
The sound is so loud it could hide a submarine!!!
Time and Frequency partitioning
Occurrence of sound types in 1 hour of recording during mid-day
Power Spectrum overlap of 5 examples of the sound type 1 (1.1, 1.2, 1.3, 1.4, 1.5), the most abundant thoughout the analyzed recordings = evaluation of the dessimilarities within sound types.
Frequency partitioning of some of the sound types found during the daytime
*This analysis will be expanded to other areas in the reef during the following months to map the abundance and diversity of fish sounds, and the results are expected to be published.
CONCLUSION
Despite the challenges that arose due to the remote format, I have managed to make the most of this situation and acquire a good knowledge in bioacoustics, fish communication and sound analysis.
After many hours diving into these amazing soundscape and classifying sounds, I am very excited to continue the analysis and see what comes out of it!!
Some interesting links
Bibliography
Amorim, M. C. P., Conti, C., Sousa-Santos, C., Novais, B., Gouveia, M. D., Vicente, J. R., … Fonseca, P. J. (2016). Reproductive success in the Lusitanian toadfish: Influence of calling activity, male quality and experimental design. Physiology and Behavior, 155, 17–24. https://doi.org/10.1016/j.physbeh.2015.11.033
Bass, A. H., & Ladich, F. (2008). Vocal–Acoustic Communication: From Neurons to Behavior. Fish Bioacoustics, 253–278. https://doi.org/10.1007/978-0-387-73029-5_8
Gazey, B. (1972). Underwater acoustics. by Leon Camp. Published by Wiley Interscience, Great Britain, Price: £8.25. Applied Acoustics, 5(2), 149–150. https://doi.org/10.1016/0003-682X(72)90020-5
Mann, D. A. (2006). Propagation of Fish Sounds. Communication in Fishes, 1, 107–120. Retrieved from http://www.ispa.pt/ui/uie/pdf/Ch3sound diversity in fish2006.pdf
Pedroso, S. S., Barber, I., Svensson, O., Fonseca, P. J., & Amorim, M. C. P. (2013). Courtship Sounds Advertise Species Identity and Male Quality in Sympatric Pomatoschistus spp. Gobies. PLoS ONE, 8(6). https://doi.org/10.1371/journal.pone.0064620
Slabbekoorn, H., Bouton, N., van Opzeeland, I., Coers, A., ten Cate, C., & Popper, A. N. (2010). A noisy spring: The impact of globally rising underwater sound levels on fish. Trends in Ecology and Evolution, 25(7), 419–427. https://doi.org/10.1016/j.tree.2010.04.005
