The Atlas Obscura Podcast The Fish Doorbell of Utrecht
Mar 4, 2026
Mark van Heukelum, an urban ecologist who studies how wildlife navigates cities and invented Utrecht’s livestreamed “fish doorbell.” He explains how migrating fish get trapped by city locks and the quirky idea to alert a lockkeeper. The story covers designing the camera and tech hurdles, then a surprising viral response that helped free fish and raised awareness.
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Historic Canals Serve As Surprising Fish Habitat
- Utrecht's historic canals double as unexpected urban wildlife habitat with steep brick walls and dredged bikes creating fish-friendly microhabitats.
- Mark van Heukelum noticed fish living in these canals despite murky water and manmade obstacles, sparking study of urban freshwater ecology.
Lockkeeper Shows Fish Waiting At Closed Gates
- Mark observed fish waiting at closed lock doors and confirmed the problem by talking to the local lockkeeper who saw fish gather in currents.
- The lockkeeper demonstrated by opening the gate, revealing fish at the surface and agreeing to open locks more if alerted.
Crowdsource Wildlife Monitoring With A Livestream
- Use public livestreams to crowdsource monitoring and trigger volunteer or staff actions in real time.
- Mark installed a camera and live stream so anyone could spot fish and ring a virtual bell to prompt the lockkeeper to open the gate.