Adding a traditional fish ladder isn't really a realistic option at this location.
> Fish ladders have a mixed record of effectiveness. They vary in effectiveness for different types of species, with one study showing that only three percent of American Shad make it through all the fish ladders on the way to their spawning ground
I guess that’s what they call artificial selection pressure.
So the think with salmon is that they orient by sound. If they don’t know where to go next they head toward the sound of running water - the next rapids upstream. To get them to traverse a dam you have to make waterfall noises in the correct spot and not make them in the wrong spot. I believe I’ve read of people using this to trick salmon into going through locks, but the ladders seem to be simpler.
Yes they are. It's a fully functional sluice, and the water level on the city centre-side is higher than the water level of the Vecht outside the city. They cannot open both sluice doors at once. During summer, sluice operators are active all day to guide boats through, and they cannot pass the sluice after the operators' working hours.
(Also, the footbridge already exists.)
Perhaps it's related to this being a _lock_, not a dam. In addition to having water loss from the lock, the middle part of the lock goes up and down, so you'd have to have separate fish ladders for each part.
For the most fun fish transport I've seen, check out the Salmon Cannon: https://www.youtube.com/watch?v=nopg9JSTTzg and https://www.youtube.com/watch?v=eGzdOpCisnQ. It uses a pressurized tube to transfer salmon from the low to high side. In the second video, the distance is over a kilometer.