A doorbell in Utrecht is meant for fish, but people around the world do the ringing.
An underwater camera watches the Weerdsluis, a historic lock on a migration route through the Dutch city. When viewers spot fish waiting, they can send a signal to the lock keeper.
A human helps open the way
The official Fish Doorbell website explains that fish travel through Utrecht’s canals toward spawning areas in spring. A closed lock can interrupt that journey.
The button does not automatically swing the gates open. It alerts a person, who can arrange passage when enough fish are waiting.
That simple distinction makes the project a collaboration between remote viewers and the people managing a real waterway.
Twelve million visits, not twelve million people
In its July 1, 2026 season review, Utrecht reported 12 million website visits and 889,000 unique viewers. The bell was rung about 220,000 times.
Those figures measure different things. Repeat visits are included in the larger number, and button presses should not be interpreted as a count of individual fish rescued.
The city said the project helped thousands of fish and recorded 12 kinds of fish during the season. Its partners include the municipality, the regional water authority and Dutch Wall Fish.
A seasonal project
The 2026 season has ended. The official website says the camera is scheduled to return on March 1, 2027.
The appeal is easy to understand: a few minutes watching a quiet underwater scene can contribute to a practical task. A small obstruction in a city becomes visible, and people far beyond Utrecht can help staff notice when fish are ready to pass.