There’s a “Fish Doorbell” in the Netherlands. Yes, a Doorbell—for Fish.

It’s a rainy Friday morning in Utrecht, a town just outside Amsterdam, and I’m looking for a boat lock. The city is full of them, but I’m looking for a very special one—the Weerdsluis lock. It’s on the edge of the historic center, and once I arrive, it looks like, well, the average boat lock. (A boat lock is, for the uninitiated, basically an elevator for boats. It helps raise and lower them between areas with different water levels. There are a lot of them in the Netherlands.) There are lock attendants in a booth, waiting for boats to pass. But if you look closely enough, you can see a camera submerged in the water. Which from my vantage point, looks like … muddy water. But I know about 1,000 people are tuning in to the footage in real time to see what’s below the muck. They are waiting to ring the fish doorbell.

The doorbell “opened” for the season at the end of March. Fish will gather on one side, where the underwater camera keeps watch and livestreams the view on a website. People anywhere in the world can spot a fish, and press a button (the doorbell), signaling for the lock operator to open the barrier—which resembles a backyard gate submerged in the water—and let the fish go on their merry way.

The idea came to ecologist Mark van Heukelum in 2021. He had been studying the barriers to fish migration in Utrecht. Like many Dutch cities, the city is laden with canals, fixed channels, and boats. Although picturesque, some of these structures physically get in the way of fish that swim through the city during spawning season. One of the most troublesome barriers to fish swimming through Utrecht: the Weerdsluis lock.

“One of the main issues for fish was that the boat lock is in the way,” van Heukelum told me over Zoom, with three little decorative fish in the background. During that initial visit, he could literally see the fish queuing up at the lock—which is typically closed in the spring, and operated manually by lock operators.

Van Heukelum, who works as an environmental consultant, thought it would take a lot of effort and bureaucracy to implement a way for the fish to get through. But the lock operator offered a simpler solution. “He listened to me and said, ‘Well I can also open the lock right now for the fish.’ ”

In fact, the lock operator was willing to open the lock more often, as long as he knew fish were present. Within a year, van Heukelum and his team had installed a camera, livestreaming the ecosystem below the water so that the public could monitor—and aid—the marine creatures.

“A camera on the water isn’t necessarily a new thing, but the fact you can actually do something and push a button and help out, that is definitely a first,” van Heukelum said.

The fish doorbell launched for the first time on March 29, 2021—unfortunate timing, van Heukelum noted, as it was just a few days before April Fool’s Day. “We didn’t think about it,” he recounted. “Media jumped on it because they thought it was so funny, it had to be a joke.”

“Fish and river crayfish passing through Utrecht have been given their own doorbell, so they can continue the trek to their spawning grounds without having to wait too long,” read one report.

And still, it took off. In the first two weeks that the doorbell was deployed, it was pressed 32,000 times. This year has been even more successful—even just a few weeks into the season.

“There have been enough people to help out the whole time, even at night, and that’s pretty amazing,” said van Heukelum. The team has since even had the site upgraded so that they can host 1,500 visitors at a time. If more people log on to watch, users will be redirected to a general YouTube livestream where unfortunately they don’t have doorbell capabilities, but they can still watch the fish.

“Sometimes I squeeze myself and think, ‘We’re just talking about a small camera. It’s nothing more than this,’ ” he says. “But at the same time, I do believe in a concept like this. If you look at the response of the people themselves, it just gives so much joy to people who had no idea that you can help fish out by pressing a button.”

Van Heukelum also often fields questions about whether the process can be automated—that is, whether A.I. can be trained to recognize fish and send a signal to the operator that they are present. “Of course we can; why should we?” he says. “This is much more fun.”