River soundscapes: the human-altered acoustic world of migratory fish

Velde, K. te (2026)

Doctoral Thesis

This thesis investigates how freshwater fish utilize natural sounds and how they may be impacted by anthropogenic noise. Through field recordings in European rivers, I disentangled biotic (biophony), abiotic (geophony), and human-made (anthrophony) soundscape components. I helped design the MIGRADROME, an innovative swim-tunnel to conduct acoustic exposure experiments investigating how natural and anthropogenic sounds influence migratory fish behavior. Findings reveal that diverse organisms, including amphibians, fish, insects, and aquatic plants, contribute to river soundscapes, which are further shaped by sediment, river size and flow speed. Boats and urban road traffic are the primary anthropogenic noise sources, significantly masking natural soundscapes in high boat- and road traffic density areas. I identified flow and sediment-related sounds as potential orientation cues for migrating fish. Specifically, three-spined sticklebacks responded to these cues by showing attraction to turbulent flow and avoidance of boat noise. These results highlight the likely importance of river soundscapes to aquatic animals in general and migratory fish in particular, and we raise serious concern on the potential threats of anthropogenic noise on freshwater ecosystems.

• Anthropogenic noise
• Freshwater ecology
• Underwater acoustics
• Biophony
• Geophony
• Masking
• Urban
• Aquatic animals
• Vessel noise
• Soundscape orientation

• All authors: Velde, K. te
• Supervisor: Slabbekoorn, H.W.
• Co-supervisor: Tudorache, C.
• Committee: Meijer, A.H.; Richardson, M.K.; Voogd, N.J. de; Parmentier, E.; Kemp, P.
• Qualification: Doctor (dr.)
• Awarding Institution: Institute of Biology Leiden (IBL), Faculty of Science, Leiden University
• Date: 2026-05-13
• ISBN (print): 9789465441221