The world’s first ever fish doorbell at the Oude Gracht in Utrecht, which allowed migrating fish free passage, has been a great success and will be repeated next year.

Thousands of fish make the journey upstream in the river Vecht each spring but because the gates of the Weerdsluis lock were not opened frequently enough, the fish were facing long waits in the city’s Oudegracht.

To remedy this, Utrecht local council and the local water board installed a camera which live streamed the goings-on under water.

People who spotted a waiting fish could ring the bell and alert the lock keeper who would receive screenshots of the fish and then open the gates to let them through.

Some 32,000 people rang the bell in the first two weeks of the scheme which began in March. Over 100,000 people in total rang the bell and the live stream attracted two million visitors.

Now that the migration season has come to an end the fish doorbell has been taken offline but will return next year, city ecologist Marc van Heukelum, who thought of the scheme, said.

‘We have managed to involve people in nature in a very direct way. People could actually do something and it was really cool how Utrecht embraced the fish doorbell and kept ringing it,’  he told RTV Utrecht.

Van Heukelum also said the project had shed light on the variety of fish that frequent the Utrecht waterways. ‘We know now that Utrecht is an important hub for fish such as bream, eel and carp on their way to their spawning grounds.’

The fact that pike were spotted as well means the water quality is good too, Van Heukelum said.