First Catalog of Fish Sounds on the Coast of Mainland Portugal

A new study conducted a pioneering investigation revealing the acoustic diversity of fish communities in the Professor Luiz Saldanha Marine Park, using acoustic recordings (Passive Acoustic Monitoring) and underwater video systems. This is the first catalog of its kind in the coastal waters of mainland Portugal, providing valuable data for monitoring marine biodiversity.

The analysis of acoustic recordings allowed the identification of 33 different types of sounds, most likely produced by fish. This diversity of fish sounds is relatively high, exceeding what has been recorded in some other locations, such as the Mediterranean or even certain coral reefs. Based on a literature review assessing current knowledge of fish in this region, out of the 150 fish species present, only 29 (less than 20%) are known to produce sounds. This highlights the need for further studies on most species. Identifying and characterizing these sounds is crucial for understanding the ecology and behavior of these species and for enabling ecological monitoring through passive acoustics. This study underscores the great potential of passive acoustics as a non-invasive monitoring tool that could help assess biodiversity and the impacts of human activities on the oceans.

But do fish really produce sounds?Yes! Many fish produce sounds using different mechanisms, such as vibrating their swim bladders, moving specific muscles, or even rubbing bones and pharyngeal teeth together. These sounds serve various functions: they can be used for communication among individuals of the same species, defense against predators, or as warnings of potential threats. In many species, sounds play a crucial role in reproduction, helping attract mates and establish territory.

Can we hear them?It depends on the intensity and frequency of the sound. Many fish sounds occur at low frequencies, making them difficult to hear without specialized equipment such as hydrophones or headphones. However, some sounds are audible to humans, and in certain environments, divers can hear them even without any specialized equipment. The sounds vary significantly: while the toadfish emits deep, rhythmic, and intense sounds, scorpionfish produce higher-pitched sounds similar to "kwas." Most of these sounds can be captured using underwater cameras or hydrophones, allowing scientists to study fish communication and behavior in greater depth.

Despite growing scientific evidence, the public remains largely unaware that fish produce sounds and that acoustic communication plays a fundamental role in their behavior. This study highlights the need for increased awareness of the importance of underwater sounds and emphasizes the value of developing automated techniques for acoustic monitoring of marine fauna.

The results of this research lay the foundation for future studies that can expand knowledge of the acoustic patterns of fish communities and integrate underwater acoustics into marine management and conservation programs. This study represents a significant step forward in understanding fish sounds and reinforces the importance of acoustics in marine science and conservation.

This research was conducted by Noelia Ríos Ruiz from MARE-ISPA, with contributions from researchers at MARE-Ciências ULisboa, cE3c, MARDIVE, and FishBioacousticsLab, as well as the collaboration of IMBRSea students.

Access the article here:

​Ríos, N., Pereira, J., Muñoz-Duque, S., Silva, G., Pais, M. P., Fonseca, P. J., Vieira, M., & Amorim, M. C. P. (2025). Acoustic fish community in a biogeographic transition zone of the Northeast Atlantic. ICES Journal of Marine Science, 82(3), fsaf027. https://doi.org/10.1093/icesjms/fsaf027