"The Mitsubishi conglomerate controls a forty per cent share of the world market in bluefin tuna; they are freezing and hoarding huge stocks of the fish every year. While they claim this is to smooth supply on a year-to-year basis, conservationists believe they are acting in the expectation that in the event of the fish’s extinction in the wild, prices will skyrocket. Frozen in great stacks at –60oC by the same company who made my childhood cassette player, the bodies would be sold for astronomical prices.

It has a name, this uniquely vile game: it is called extinction speculation. It’s practised by those who collect Norwegian shark fin, rare bear bladders and rhino horn; men and women with hearts that sing along only to the song of money. There are collectors known to be building up huge piles of tiger pelts and vats of tiger bone wine. (The wine is made by soaking portions of a tiger’s skeleton in rice wine; it takes eight years to ferment, and can then be stored indefinitely.) If tigers go extinct in the wild, which is wholly possible by 2050, the value of these assets will soar."[0]

The tuna is not on brink of collapse because it competes with sperm whales for food. They were here for ... i don't know ... millions of years? It's near die off because we eat them and work tirelessly towards their extinction.

Also ... if you want to know more why it's bad when some species die off, I highly recommend the movie Seaspiracy [1]

[0] https://granta.com/tuna/ [1] https://www.seaspiracy.org/