How the Dutch Fish Doorbell helps migrating fish each spring

Ring the fish bell to help migrating fish navigate a Dutch canal

By K. R. Callaway edited by Andrea Thompson

In a canal in the Dutch city of Utrecht, fish begin to mass behind a lock called Weerdsluis. Now, for the sixth year in a row, you can help them attract the attention of the lock operators. The fish bell – or Visdeurbel in Dutch – is back.

Launched in 2021, this project allows viewers around the world to monitor the feed from an underwater camera. When they see a fish wanting to go through the lock, they can ring the doorbell and alert operators to the finned animal waiting outside.

“The project is a good mix of doing something for nature and inspiring people to join in and do something,” says Anne Nijs, an ecologist from the city of Utrecht and one of the initiators of Fish Doorbell.

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Many species of fish, including bleak, catfish, eel and pike, cross the Netherlands’ many rivers in spring to reach their spawning grounds upstream. Even as aquatic creatures begin to fill the canals, ships are still rare in early spring and the locks that allow travel through the water are often closed. This creates an obstacle for migratory fish, most of which begin their journey this time of year, when the water begins to warm.

In Utrecht, until the lock gates open again, the fish wait nearby. For some, this means not being able to reach spawning grounds in time to lay eggs in favorable conditions. And for others, it means not being able to escape wandering predators.

Operators and municipal workers have long wanted a way to let fish pass through the Weerdsluis, but it’s not as simple as pressing a button. The lock dates back to the 1600s and requires operators to manually turn an iron wheel for between 30 minutes and an hour. Because this is such a large commitment, operators wanted a way to ensure there were fish at the door. That’s when Nijs and environmentalist Mark van Heukelum decided to ring their doorbell.

They placed an underwater camera on the lock. And every year since 2021, conservationists have livestreamed the footage on a website that allows people to notify lock operators when they have spotted a fish trying to pass through. Nijs and van Heukelum did not expect the doorbell to become a global community science exercise.

“We put flyers on the streets about Fish Doorbell because we were afraid no one would join, but… a lot of people joined, [and] every year, more” have done so, says Nijs.

Last year, the site welcomed more than 2.3 million unique visitors who collectively pressed the doorbell 200,000 times and let thousands of fish continue their journey.

Nijs says being able to ring the doorbell gives people a “positive feeling,” and many people have told him about the calming effects of watching the canal fish. But the greatest benefit was for the fish themselves. In the Netherlands, a country home to thousands of locks, dams and other man-made water control structures, the doorbell is a way to balance the needs of humans and other creatures. And the project team says other countries facing similar challenges are already starting to consider their own creative solutions.

You can keep an eye on the fish and ring the doorbell here.

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