Reef fish biophony under tourism-driven sound pollution in Northeastern Brazil

Fishes contribute to coral reef biophony by producing sounds related to courtship, feeding, and territorial defense. Tourism-related noise may overlap with the frequency range of these signals, affecting acoustic communication and associated behaviors. We evaluated the effects of tourism-induced noise on reef fish biophony in two marine protected areas in northeastern Brazil, including sites with different tourism intensities and exposure to anthropogenic sound sources. Nine types of fish sounds were identified, and their occurrence decreased in noisier areas. Power spectral density (PSD) analyses revealed biophonic profiles with two main energy peaks, whereas noisier sites showed flatter, higher-energy spectra in which the low-frequency peak was no longer evident. In these areas, anthropogenic sounds coincided with increased noise levels and reduced fish sound occurrence. Sound pollution was also associated with lower Acoustic Complexity Index (ACI) values, with exposure to noise sources showing the strongest relationship with reduced acoustic complexity. These findings indicate that tourism-related noise is associated with decreased fish sound occurrence and altered soundscape structure, highlighting the need for mitigation strategies in reef-associated marine protected areas.