Characterizing soundscapes and larval fish settlement in tropical seagrass and mangrove habitats

Abstract

Recent evidence suggests soundscapes of coral reefs may provide acoustic cues that larval reef fish utilize during settlement. Seagrass and mangrove habitats are further important refuges for larvae and juveniles of many fishes; however, compared to reefs, less is known about the characteristics of tropical seagrass and mangrove soundscapes and their potential as settlement cues. We deployed light traps to assess fish larvae settlement and passive acoustic recorders to study the “ecoacoustics” at mangrove, seagrass, and coral reef sites around two bays in St. John, U.S. Virgin Islands. Light traps were deployed nightly around the third quarter and new moon, and 24 h periods of acoustic recordings were taken during the same time. Fish larvae were counted and identified to the lowest possible taxonomic level. Focusing on biotic soundscape components, diel trends in metrics such as sound pressure level, power spectral density, and snap counts of snapping shrimp were assessed. Although what role mangrove and seagrass soundscapes may play in fish settlement remains unclear, these soundscape and larval settlement data provide foundations for deeper investigations of the relationship between acoustic and larval ecology in these essential nursery habitats.