Do fish need doorbells?

That sounds like the beginning of a joke. But it’s a real question. 

Utrecht, the Netherlands, has a fish doorbell on a river lock. (A river lock is a device that helps raise and lower boats on sections of a river or canal that have different water levels.)

In spring, the fish in the river migrate. They go to shallow spawning grounds. An underwater camera captures their movement. The footage streams online. Viewers watch the fish move. And if several fish get stuck at the lock? Viewers notice. They ring the online “fish doorbell.” 

This doorbell alerts a water worker. The worker opens the lock to let the fish swim through.

The Dutch have used the “fish doorbell” for five years. Its website attracts millions of viewers from around the world.

Much of the time, the screen is just a murky green with occasional bubbles. But sometimes a fish swims past. More fish show up as the water gets warmer.

Without the doorbell, native freshwater fish like bream, pike, and bass can get stuck behind the lock. They become easy prey for predators. 

Mark van Heukelum invented the fish doorbell. He’s been happily surprised that people like his idea so much. People find the fish cam relaxing. They like that they can do something to help stuck fish.

“I guess the combination of a good cause, a beautiful story, and just a simple idea generates all this attention,” he says.

God said to them, “Be fruitful and multiply and fill the Earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the Earth.” — Genesis 1:28