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Topic

Establishing baselines for passive acoustic monitoring of kelp forest ecosystems in the Northeast Pacific

Department of Biology

Date & location

• Thursday, April 16, 2026
• 1:00 P.M.
• Clearihue Building, Room B007

Examining Committee

Supervisory Committee

• Dr. Francis Juanes, Department of Biology, ̽��ϵ�� (Supervisor)
• Dr. Fabio De Leo Cabrera, Department of Biology, UVic (Member)
• Dr. Kieran Cox, Department of Biological Sciences, Simon Fraser University (Outside Member)
• Dr. Xavier Mouy, Northeast Fisheries Science Center, National Oceanic and Atmospheric  Administration (Outside Member)

External Examiner

• Dr. Olivia Kennedy Rhoades, Aquatic Biologist, Fisheries and Oceans Canada

Chair of Oral Examination

• Dr. Yu-Ting Cheng, Department of Mathematics and Statistics, UVic

Abstract

Passive acoustic monitoring (PAM) offers a promising tool for continuous ecosystem assessment amid accelerating marine habitat change, yet its application is constrained by incomplete knowledge of sound-producing (soniferous) taxa and the ecological drivers of underwater soundscapes. These gaps were addressed in this thesis by combining a global synthesis of soniferous aquatic macroinvertebrates with an empirical investigation of kelp forest soundscapes in Barkley Sound, B.C. I conducted a systematized review of grey and peer-reviewed literature to compile the most comprehensive catalogue to date of soniferous aquatic macroinvertebrates (100 references; spanning 1877–2022). Ninety species across four phyla were identified, revealing strong taxonomic biases towards arthropods, particularly malacostracan crustaceans. Reported sounds spanned infrasonic to ultrasonic frequencies (~0–90 kHz) and were often associated with passive behaviours such as feeding. Overall, sound production is severely understudied relative to the diversity of macroinvertebrates, underscoring the need for broader taxonomic coverage, in situ validation, and context-specific sampling to establish species’ acoustic baselines. Building on this synthesis, I applied PAM in shallow fringing kelp forests to examine relationships among soundscape characteristics, soniferous fauna, and habitat condition. Acoustic surveys paired with visual assessments revealed that diel patterns in root mean squared sound pressure level (SPL_rms) were strongly influenced by tidal cycles, vessel traffic, and a nightly chorus of plainfin midshipman (Porichthys notatus). Kelp density exerted a negative influence on median SPL_rms across all frequencies, indicating that structurally complex kelp forests are quieter, likely due to attenuation of external noise. Low (0.02–0.5 kHz) and mid (0.5–2 kHz) frequency SPL_rms correlated with the proportion of soniferous fishes rather than overall fish diversity, highlighting the functional importance of soniferous taxa in PAM. Visual surveys were improved with the addition of PAM, which detected unobserved species and behavioural phenomena, including plainfin midshipman choruses associated with nesting. Finally, I attributed the source of a ubiquitous regional biological sound to a scale worm (Halosydna brevisetosa), which produces popping sounds potentially analogous in ecological function to those of snapping shrimp. Together, these findings demonstrate that kelp forest soundscapes reflect both biological community composition and habitat-mediated acoustic filtering, while revealing substantial gaps in our understanding of macroinvertebrate sound production. By integrating a taxonomic synthesis with a field-based ecosystem assessment, this thesis advances the development of acoustic-ecosystem baselines and strengthens the application of PAM for monitoring structurally complex coastal habitats.