Parrotfish soundscapes: implications for coral reef management

Abstract

Parrotfishes are prominent members of the herbivore/detritivore feeding guild on coral reefs. Their feeding activity is important for the removal of algae and detritus, the clearing of new settlement sites for coral and other larvae, and the bioerosion and redistribution of sand across the reef. Estimates of parrotfish feeding activity are normally obtained by divers that may influence or overlook fish behaviors, and are of short duration, limited to shallow habitats, and have limited temporal resolution to associate feeding activity with ecological processes. Excavator and scraper parrotfishes have a robust beak-like jaw morphology that produces a unique sound as the teeth scrape the surface of hard coral rock. We tested the hypothesis that ambient parrotfish bite sounds can be used to estimate their temporal patterns of feeding and associations with environmental variates in the area of an acoustic recorder. Acoustic recorders were deployed on 2 Hawaiian reefs to collect ambient fish sounds for a period of 3 yr. Parrotfish bite sounds showed distinct and repetitive variations in daily, seasonal, and annual feeding patterns, and were statistically correlated with factors of day length and tide range. This study demonstrates the utility of using parrotfish bite sounds to estimate patterns of feeding at coral reef sites. We suggest that regular sampling by multiple acoustic monitors may be a cost-efficient and valuable tool for monitoring the health, degradation, and recovery of large coral reef areas.