When spawning fish travel through the canals of Utrecht, they're often blocked by the city's Weerdsluis lock - particularly in the spring, when it rarely opens. Citizens are now helping the fish to get through, though, using an online "fish doorbell."
Every year, thousands of spawning fish swim through the canals of Utrecht in the Netherlands. When they reach the Weerdsluis lock though, they often cannot travel further because the barrier. A new initiative, however, is now allowing local people to help the fish get through, using an online “fish doorbell.”
Officially known as a visdeurbel, the system consists of an internet-connected underwater camera located next to the lock gate. Using an app, members of the public can view the camera’s recording in real-time where and whenever they want.
If they notice that a significant number of fish are crowded outside the closed gate, users can notify the lock operator by ringing a digital doorbell on the app. At that point, the operator checks the camera and, if there are indeed enough fish present to make it worthwhile, they will then manually open the gate and let the fish swim through.
The fish are thus able to commence breeding that much sooner. Additionally, because they're no longer stuck in one place ("like fish in a barrel"), they stand less chance of being killed by predators such as grebes and cormorants.