Abstract
Coral reefs are biodiversity hotspots under increasing pressure. Passive acoustic monitoring (PAM) offers an inexpensive and non-invasive option for monitoring ecological change on reefs by linking their soundscapes to biological activity. In this thesis, I test whether phonic activity (the abundance and diversity of fish sounds) can predict fish abundance and diversity on coral reefs at fine spatial and temporal scales. I conducted 32 simultaneous visual–acoustic surveys across 10 northern Red Sea reefs, using 360° video cameras and co-located HydroMoths. This enabled direct pairing of visually identified fish assemblages with phonic activity, quantified using a reproducible classification framework developed for this study. Surveys were complemented by a controlled playback experiment to estimate the practical detection ranges of common fish sounds, providing an effective listening radius of singular PAM recording devices on shallow reefs.Phonic activity did not reliably predict total fish abundance or species diversity. However, it reflected aspects of functional composition: higher sound abundance was linked to higher proportions of omnivores and more temporally stable fish counts, while higher phonic diversity coincided with greater proportions of herbivores and carnivores. Playback results showed that typical reef fish sounds were reliably detectable over a distance of a few metres (~5–7 m), with detectability varying by sound type, establishing a small approximate spatial footprint that must be considered when quantifying phonic communities.
These findings indicate that, under shallow reef conditions, phonic activity provides more insight into the functional composition of fish assemblages than their overall abundance or diversity. Simultaneous, co-located survey designs help ground-truth fish phonics and reveal their ecological relevance, providing a foundation for scaling and interpreting PAM on reefs. Future PAM studies should account for the limited spatial footprint of single recorders and focus on interpreting fish sounds in the context of functional and behavioural groups.
| Date of Award | 20 Jan 2026 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Steve Simpson (Supervisor) & Andrew N Radford (Supervisor) |
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