What is Sound?

For a better understanding on fish communication, we need to go for the basics. Here, we can find a short animation that will introduce you into it.

video_what is sound.mp4


Fishes are distributed in marine and freshwater ecosystems, from 100 families at least 800 species have been described to produce sounds. Some of them have hearing adaptations from specialized bones to an expansion of their hearing range.

They also possess a large diversity of sound mechanisms. They can use their bones, creating friction mechanisms, vibrations with a specialized muscle, and external or internal air movement.

Even though there are a high number of species producing sound, fish can produce few sound types.

The sound variability can depend on:

  • Sound amplitude

  • Number and rate of muscle contraction

  • Calling rate


Steps for working with fish communication

Field and Lab setups

Field Recordings required specialized equipment according to the desired species to study. In Laboratory, vibrations from the environment can be recorded, therefore, during experiments, it is quite useful to insulare the setup from external sounds. We need to take into account the environmental noise we can get, for example, on-field, boats passing by, in the lab, people talking.

Analyzing Sounds

Once we have the recording, the information can be extracted using dedicated software. RavenPro, Cool Edit, WaveSurfer are some examples of software that can help to this process, The program selection depends on the user. Depending on the aim of the study, we can measure different features from the recording, and for each sound type (which are marked manually), for example, sound amplitude, high, low frequency, pulse duration, etc.

Biological information within the sound

The information content in sound can be determine by sound amplitude, frequency, calling rate, porcentaje time on calling, etc.

Professional Practice Results


My professional practice was a 7 weeks online internship with the Instituto Universitário (ISPA) which is located in Lisbon, Portugal. The internship was developed in two phases, the first one with 15 seminar sessions that gave me an introduction to basic knowledge on bioacoustics, going through basic concepts of sound, fundamentals of sound recordings, soundscapes, examples of study cases from other researches, and so on.

The second part wast the analysis of fish sounds recorded in the coral reef at the north of Mozambique Island. My aim was to check if different species vocalised during different times of the day or used different sound frequencies (i.e. used temporal or frequency partitioning) to optimise communication.



For the second part, I worked with another master student. We create a catalog of sound types for the area. Using this catalog, I worked with the identification of the sound types for a one-hour recording during the night. Also, determining the day-time partitioning and frequency partitioning.

More detail about this can be found in the coming months when the paper is published.


Here are two examples of how fish sound is heard underwater, most of the time, we won't have a clear vocalization this is due to the environmental noise coming from different sources:

  • Other fishes

  • Other species of animals

  • Waves, wind or rain

  • Anthropogenic noise

ST 11.mp3
ST 6.mp3