Can soundscapes be used as a proxy for monitoring coral reef fish communities?

Abstract

Passive Acoustic Monitoring (PAM) is a promising tool for assessing marine biodiversity, using underwater soundscapes to infer species presence and ecosystem health. However, its effectiveness remains uncertain due to complexities in sound propagation and species vocal behaviours. This study evaluates PAM as a rapid biodiversity assessment method for coral reef fish communities in the Northern Red Sea, Egypt. Fish community data and soundscape recordings were collected across eight reef sites, analysing eco-acoustic indices and manually quantified fish calls referred to as phonic abundance (the number of fish calls) and phonic diversity (the variety of different call types) to assess their predictive power for fish abundance, richness and diversity. No significant relationships were found between eco-acoustic indices and phonic abundance and diversity, suggesting both approaches capture different aspects of the soundscape. However, fish abundance (determined by underwater visual census (UVC) correlated positively with the amplitude index (34% increase per unit), while acoustic complexity and diversity indices showed negative correlations. Phonic diversity predicted total fish abundance (7% increase per unit), but for soniferous species, phonic abundance was a stronger predictor (38% increase per step). No clear relationships emerged between soundscape metrics and species richness or diversity, highlighting challenges in using acoustic indices as biodiversity proxies and perhaps suggesting that ecoacoustics and UVC may be measuring different components of the ecosystem. The study identified species-specific acoustic signatures, linking lyretail anthias (Pseudanthias squamipinnis) to “grunt discrete” sounds and lunar-tailed big eyes (Priacanthus hamrur) to “layered tones,” demonstrating PAM’s potential for species identification. These findings underscore the need for standardised methodologies to refine PAM’s use in coral reef biodiversity monitoring. Given the urgency of coral reef conservation, PAM offers a non-invasive, scalable tool to improve ecosystem assessments, contributing to long-term conservation strategies and marine management efforts.

Date of Award	17 Jun 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Andrew N Radford (Supervisor) & Steve Simpson (Supervisor)