What is a fish doorbell and why have one? Fish swim. They move through the water searching for food and to find their breeding ground. Especially during spawning season (early spring) some species of fish can travel great distances to find their preferred spawning spot.
If they swim through our waterways, and we have locks in place, they are stopped by mechanical man-made objects and have to wait to continue their journey until someone happens to open that lock. While they wait, they are easy prey for predators who have learned where to expect a ready meal.
Weerdsluis lock in Utrecht
Utrecht, a city in the centre of the Netherlands, has a lot of waterways (both rivers and canals) going through the city. These waterways are an excellent habitat for fish. Some fish stay in roughly the same area, some don’t. In springtime, when many species of fish need to travel to find their breeding and spawning ground, the locks can be an obstacle. One such lock is ‘Weerdsluis’, right in the city centre, connecting the Vecht with the Oudegracht . It is manually operated and each springtime a lot of fish want to pass the lock.
Cue ecologist Mark van Heukelum who, together with the city of Utrecht and HDSR (Hoogheemraadschap De Stichtse Rijnlanden), started the ‘Vis deurbel’, the Fish Doorbell. The first and only fish doorbell in the world. Mark now runs the project with fellow ecologist, Anne Nijs. The fish doorbell is now in its sixth year of operation.
Why a doorbell?
You may be wondering why a doorbell and not a fish ladder? Fish ladders are man-made structures designed to help migratory fish navigate barriers such as locks, culvers and dams to reach upstream breeding grounds. A fish ladder is a series of low-step interconnected pools that allow fish to swim or jump up a gradual slope rather than fighting against a high water wall. The idea is that the fish go from pool to pool resting in each pool before jumping to the next. However, not all fish can navigate these ladders and to build one requires significant time, money and infrastructure. There are also varying opinions on whether fish ladders truly work. Instead, they have used the infrastructure already there to ensure that the fish at Weerdsluis can pass safely as they did before the lock was built. Plus by installing the doorbell and the underwater camera they are allowing the public to get a unique view of life in the city’s waterways, get involved in helping nature and help the fish migrate to their breeding ground, as well as learning more about the type of fish that inhabit the waterway, their lifestyle and the waterway itself.
So how does it operate?
An underwater camera allows people to watch a livestream of the waterway and the fish that inhabit it. This camera transmits constantly during the migration season 24 hours a day. In 2026, this season will start on 2 March. The idea is that when someone sees a fish waiting to go through, they press the doorbell. Each time someone presses the doorbell a photo is automatically taken of the fish. This allows the fish to be tracked but is also a great way for people to try and identify the fish they have seen as well as learn more about that species.
The lock keeper then receives the photo of the fish and can open the lock if enough fish are waiting to go through. As the lock takes about an hour to open and close, the lock keeper decides when it is necessary to do so. In the meantime the fish just wait patiently for their door to open.
Common species to watch out for include: roach, bream, blue bream, perch, pike and rudd, but if you’re lucky, you can also spot rarer species such as: ide, bleak, flounder, tench, eel and even the European catfish! The fish doorbell does not just benefit fish though, even if that is its primary function. Lobsters, crabs, frogs and even geese have been spotted on the livestream and helped by someone pressing the doorbell for them to pass!
The project runs from early March to late May, though it can be extended if there are still a lot of fish wanting to pass by the closing date.
The doorbell is popular and does good work
In the past, people have participated from as far afield as America and Brazil. In 2025, the total views of the website was 30 million, and the bell was rung 200,000 times, helping thousands of fish to make their way to their destination.
This helps the fish population, but it is also a great way for people to learn a bit more about fish life and the Dutch waterways.
You can learn to identify the fish you see, and curiosity means many will read up a bit about that species’ lifestyle, feeding habits, mating places and about what threatens the population, and what can be done to safeguard them. The website also provides a free lesson and teacher’s guide designed for primary school students ensuring that the younger generation learns about fish migration and the fish doorbell and the work it does to help fish.
But is it fun?
It sure is fun. You know those webcams that have you waiting for eggs to hatch in a nest? It is just like that. Fun. And in this case, you can do more than just wait and watch – you can actually help the animals you look at. It will keep you awake longer than you planned at bedtime (the fish are more active at night). It becomes a ‘thing’ to see as many different types of fish as possible in a certain time. It can be addictive – you have to ring the bell at least once before bed or in the morning (when the fish are more active as well).
It is nature watching from home.
Of course you can (and people do) share on social media how many times you pressed the bell, what types of fish you saw and how long you stayed up to watch and help the fish, all the while wondering if someone at the other side of the world saw the same fish and pressed the bell at the same time as you did. Whether you’re young or older the appeal of the fish doorbell spans generations. So why not give it a go this springtime – challenge your friends and family, and see how many fish you can spot and help out along their way? But be aware, it’s super addictive!
Ring ring (or in Dutch: ding dong)!
X: @fishdoorbell
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