I can't tell from the video if the water is just muddy or if it's actually, y'know, gross. Is it safe to eat the fish from that river?
Also, I'd always heard they didn't do that unless they were starving. Which makes me think not much is surviving in that water, making me think it might not be safe to eat the fish :/
Though, I imagine if you're desperate for protein, such things are secondary concerns at best
Brazilian here. Perfectly safe (color-wise; of course it can be polluted as hell despite its color, just like any other river).
Our ground/mud has a different color. Some areas on the south even have a red soil (very fertile, but makes everything about ground level look dirty very quickly):
https://en.m.wikipedia.org/wiki/Red_soil
There's great variety of water colors even in the same area, just search for images "meeting of the waters Manaus":
Just jumping in to say that red soils are not very fertile. They are nutrient-poor in the necessary macro-nutrients (nitrogen, potassium, and phosphorus) and have a very poor ability to retain water. They are very rocky - little organic matter content - which limits both water retention and cationic exchange capacity (affecting N+ and K+ bioavailability), and tend to be acidic.
Cultivation is possible, but it requires large amounts of fertilizers and soil conditioning agents (liming to raise pH and add calcium, addition of organic matter). In effect, recreating an artificial soil that is closer in nutrient availability to the black soils present in the world's most fertile regions (which today are also heavily fertilized).
I wrote red soil, but more specifically, where I lived there was Terra Roxa (purple soil?), which seems to be a kind of red soil according to the English Wikipedia page:
https://en.m.wikipedia.org/wiki/Terra_roxa
Water can be like this when it rains a day or a couple hours before. Every river become like this when it rains. It is perfectly fine to eat fish from this river.
the issue today is thinking that mud is the definition of dirt, that river is probably 100 times cleaner than any tank/pond/lake used to farm fish, also i swan in pont that were way muddier, with piranhas too, sometimes