Exposure to anthropogenic noise affects feeding but not territory defence in damselfishes

Anthropogenic noise is a recognized global pollutant with well-documented effects on the behaviour, physiology and survival of many marine species. However, there is a gap in our understanding of how noise impacts reef fishes under natural conditions without direct manipulation. To address this, we conducted field experiments to examine how two types of sound sources affect the behaviour of an endemic southwestern Atlantic reef fish, Stegastes fuscus . Both motorboat noise playback (0.2–1 kHz) and pure tone (0.4 kHz) influenced behavioural traits of the species. Specifically, individuals reduced their foraging rates when exposed to either sound and spent more time refuging during pure tone exposure. Despite these changes, fish did not exhibit increased agonistic interactions during any of the sound exposures. Our findings indicate that both motorboat playback and pure tone negatively affect damselfishes by increasing antipredator behaviour, seen through increasing refuge time and decreasing foraging rates, which could potentially impact their fitness and population dynamics. • We assessed the effects of anthropogenic noise on damselfish behaviour in situ. • Damselfishes decreased foraging during exposure to motorboat playback and pure tone. • There was no significant difference in agonistic interactions during noise exposure.