Jack Mackerel in Chile, South America, once existed in vast quantities, just like the buffalo did in North America. The buffalo are all gone. Now, most of the Jacks are gone, too. They formed a substantial part of the global fish meal feed for fish farms. Now the anchovy in Peru is in the same decline.
Here is a graph of the Chilean catch, and how it has declined over the years, showing that the industry is not sustainable, despite what fish farm companies may claim:
This is part of the reason that the fish farm industry has moved to wanting plant-based feed for its salmon. The downward curve is indicative of other fish-based protein sources and oils. And the industry is now fishing down the krill in the Antarctic, even below fish in the food chain, but perhaps the most important feed in that ocean, particularly for mammals, baleen whales for example.
Some more background:
"In Chile, a small number of wealthy families own 87% of the jack mackerel
harvest. With government agreement, they have been allocated quotas which
scientists say are not sustainable.
In 2012, a heated dispute developed between Peru and Chile over the fishing of
Attempts have been made since 2006 to empower the South Pacific Regional
Management Organisation so it can effectively regulate the jack mackerel
industry on the high seas and across national boundaries. Geopolitical
rivalries and lack of international cooperation is preventing this.
In an interview with the International
Consortium of Investigative Journalists, the French marine
biologist Daniel Pauly compared jack mackerels
bison, whose populations also collapsed in the 19th century from over hunting:
"This is the last of the buffaloes. When they’re gone, everything will be
gone ... This is the closing of the frontier."
Chilean jack mackerels are canned or marketed
fresh for human consumption;
they are a staple food in Africa. They are also processed into fishmeal,
which is fed to swine and salmon; five kilograms of jack mackerel are needed to
raise one kilogram of farmed salmon."
The answer is to raise vegetarian fish, like tilapia, and to raise them on land.
This is a good news article on fishing down Jack mackerel off Chile by the world fleet that is, if you can believe it, subsidized by their home nation, typically fuel costs:
"In the southern Pacific, industrial fleets find fewer and fewer jack
mackerel after years of aggressive fishing: European Union-flagged
vessels collectively caught more than 111,000 metric tons of jack
mackerel in 2009; the next year, the ships hauled in 40 percent fewer
fish; by last year, vessels reported just 2,261 tons."
The source of this quote is: https://www.publicintegrity.org/node/7900/.