Hacker News Reader

Comment by zck | Hacker News Reader

For places humans have dammed a river, a fish ladder can be installed to let fish continue to swim upstream: https://en.wikipedia.org/wiki/Fish_ladder. I wonder why that's not used here.

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.

View on HN

It's a tiny monumental lock dating back to the middle ages. It has a history going back to the 1300s, as do the buildings around it.

Adding a traditional fish ladder isn't really a realistic option at this location.

From the Wikipedia article you referenced to:

> 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.

If we're going the route of applying selection pressure to other species for human amusement, then we should just go straight to unicycles.

... so, you think fish will need unicycles more than they do bicycles?

Are you aware that computers are a “bicycle for the mind”?

It's more of an awareness campaign than purely for the benefit of the fish. One of the people involved with it said in a Dutch interview that there are other locations where this is automated.

There are some locks in Seattle with a ladder: https://en.wikipedia.org/wiki/Ballard_Locks#Fish_ladder

They achieved this by putting the ladder on the opposite side of the channel from the locks.

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.

I'm from the city in question and not that happy the municipality chooses to throw away money on a vanity campaign. If all they wanted was to transport fish this webcam wouldn't be necessary.

Wouldn't an automated system cost more money than this system, which is essentially just an underwater webcam?

This sluice is ornamental. Water levels aren't any higher or lower before or after. The 'automated solution' would just be to open it most of the time and perhaps lay down a small footbridge so pedestrians and cyclists can still cross it.

> Water levels aren't any higher or lower before or after.

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.)

Reply on news.ycombinator.com