This appears to be mainly a Western phenomenon:
https://www.npr.org/sections/thesalt/2012/04/05/150061991/lust-lies-and-empire-the-fishy-tale-behind-eating-fish-on-fridayLet's start with a quick lesson in theology: According to Christian teaching, Jesus died on a Friday, and his death redeemed a sinful world. People have written of fasting on Friday to commemorate this sacrifice as early as the first century.
Technically, it's the flesh of warmblooded animals that's off limits — an animal "that, in a sense, sacrificed its life for us, if you will," explains Michael Foley, an associate professor at Baylor University and author of Why Do Catholics Eat Fish On Friday?
Fish are coldblooded, so they're considered fair game. "If you were inclined to eat a reptile on Friday," Foley tells The Salt, "you could do that, too."
Alas, Christendom never really developed a hankering for snake. But fish — well, they'd been associated with sacred holidays even in pre-Christian times. And as the number of meatless days piled up on the medieval Christian calendar — not just Fridays but Wednesdays and Saturdays, Advent and Lent, and other holy days — the hunger for fish grew. Indeed, fish fasting days became central to the growth of the global fishing industry.
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The Vikings were ace at preserving cod — they "used dried and salted cod as a form of beef jerky on their ocean passages," Fagan says. And the route the Vikings took at the end of the first millennium — Greenland, Iceland, Newfoundland — matches up with the natural range of the Atlantic cod.
It's possible that others may have followed the cod trail to Canada before Columbus sailed the ocean blue. Clues suggest that English fishermen from Bristol may have made the voyage by around 1480 but kept mum on the location lest the competition rush in. By some accounts, both Columbus and John Cabot had heard of these adventures when they set off on their own epic journeys west.
As I keep saying, every element of Western civilization sooner or later ends up assisting some other element of Western civilization.
Also from your link:
cold cuts, sausages, salamis, mortadelas, ham... This is also something that people exclude from their imaginary of meat. It's pretty common to ask for some baked goods and ask for an option without meat and people respond "there's no meat, we have only cheese and ham".
Again, how often do you imagine this happening in non-Western countries?