Dutch citizens are using a "doorbell" to help fish get past barrier
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. Regular citizens are now helping the fish to get through, though, using an online "fish doorbell."
Officially known as the visdeurbel, the system incorporates an internet-connected underwater camera located adjacent to the lock gate. Utilizing an app, members of the public can view the real-time output of that camera when and wherever they want.
If they see that a significant number of fish have gathered outside the closed gate, they're able to notify the lock operator by pressing a digital doorbell on the app. That person will then check the camera for themselves. If they agree that there are indeed enough fish present to make it worthwhile, they will open the gate to let the animals 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.
Partners in the fish doorbell project include the Municipality of Utrecht; the Water Board Hoogheemraadschap De Stichtse Rijnlanden; and the Regional Public Water Authority Amstel, Gooi and Vecht. The system can be seen in use, in the Dutch-language video below.