The genius of fishing with tidal weirs | Hacker News Reader

The genius of fishing with tidal weirs

nautil.us

41 pointsdnetesn19 comments

We used something like these when I was a kid. In the village where I grew up someone had made a concrete barrier about ~70cm high between some rocks (see [0], it's now a bit ruined) that created a rockpool as the tide went out. Fish (usually little shoals of young mackerel we called "sile") would collect there and it was pretty easy and fun to catch them with a net. Oh and there was a small pipe in the barrier that drained the water so if you were really lazy you could just sit there with a net and grab them as it drained.

[0] = https://www.google.com/maps/@56.793725,-2.3355133,3a,28.8y,5...

My uncle’s cabin on the Susquehanna River has a rock formation a hundred yards off shore: a low, stacked rock dam with a channel in the middle. As kids we would stand in the channel with minnow nets. Now I learn it was possibly a Native American eel weir (though the eel population is now only a small fraction of what it was prior to the 1950s). It doesn't quite have the classic V-shape, but looks like it may have been a partially natural formation that was then modified.

https://www.bayjournal.com/news/fisheries/dozens-of-ancient-...

Interestingly this method has been dated back to the Mesolithic era (roughly 12,000 years ago) and seems to have been a widely used (as in world-wide).

Further reading for those interested (best search engine term is 'intertidal fishing weir')

https://www.thoughtco.com/fish-weir-ancient-fishing-tool-170...

https://en.wikipedia.org/wiki/Fishing_weir

https://www.academia.edu/Documents/in/Fish_Weirs

It's a simple enough structure that it likely happens by chance now and then, and once seen it wouldn't be hard at all to realize you could duplicate it.

My point was - How would they have seen it elsewhere and how?

It's not like they could have fired up Wikipedia to do some research

This will come in handy when the World War 3 really gets going.

World Weir 3

There's a lot less fish in the ocean then there used to be, will be a while before you're feeding your tribe with one of these

I've seen some suggestions that humans have already over fished the sea's and fish stocks are close to collapse.

In Hawaii they’re called fish ponds:

https://keolamagazine.com/sustainability/fishponds-in-hawaii...

You can see many preserved examples made out of lava rock and even explore them on foot.

Kalahuipua’a Historic Park near Kona on the Big Island also has some petroglyphs and traditional buildings near the fish ponds at Kakaiwa Bay.

https://www.hikespeak.com/trails/kalahuipuaa-trail-lava-tube...

There also used to be an amazing ocean fed hot spring tide pools in Kapoho (near Hill) that served as natural fish ponds but sadly they were destroyed in the lava flow in 2018 which incredibly turned the entire bay into a peninsula.

Works for shrimp as well. On some of the bayous south of New Orleans, people will set up metal arms like the ones used to control entry into parking lots (though obviously larger) and attach shrimping nets to them. When the ebb tide begins, they lower the boom. When the flow velocity gets lower, they raise it and harvest what's inside. Most are not very large, but (unsurprisingly) they are home to a lot of fishing camps, and small shrimp make good bait for redfish or black drum (which, in addition to being fun to catch, are absolutely delicious).

There is a major difference though, as called out in the article. With stone weirs fish collect in pools and you can pick and choose what to take. And can specifically choose not to take more than needed that day, as well as avoid taking or harming undersized younger fish two things to help ensure sustainability. While possible with the net route, it would be notably harder to be selective about limiting the fish that get tangled in nets.

from what i have been told by family who work in the fishing industry, catching only the fish over a certain size is often a missguided and damaging policy not founded im science. Mature fish can reproduce regularly with the expectation that the vast majority of their young will not survive to sexual maturity, by taking only those fish you are removing the source of new fish. Better to throw back the big ones.

Big fish lay significantly more and more viable eggs than small fish. It is indeed smarter to only harvest smaller and younger fish

This is one of the big reasons why marine protected areas (MPAs) are such an important strategy for both fisheries and conservation.

When areas totally free from fishing pressure are created, the fully mature individuals within them are much more reproductively successful. This can fairly quickly lead to spill-over into the unprotected adjacent areas, which in turn can become a more productive fishery than if the entire area was open to begin with.

I am not a shrimper or a commercial fisherman, but clearly some factor makes nets appropriate for one or the other. These are not large tides, less than a meter between high and low. Any creatures caught will miss a meal (or possibly become one), but considering that the net is quite literally dipped into the waterway they live in and pulled up later, they should live. Any fish will be thrown in after a minute or two in the net. These are not commercial harvests, just private ones that might garner 5 kg total catch.

Wow, first with a distributed ledger system and a sustainable fishing invention. The Yapese are a bright bunch.

It’s a literal no brainer. I’ve always though the problem is that they catch all the fish which is undesirable.

That’s actually one of the highlighted feature of these - they allow selective harvest and prevent a lot of harm.

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