Surely that only means the price will rise to become an exotic delicacy, rather than "gone"?
http://www.abc.net.au/news/2016-04-01/cobia-to-kick-start-mu...
A somewhat recent development in packing fish is automated cutting and vacuum packing - alive to wrapped in less than 30 (or so) seconds.
This is afaik also being done on factory ships, with fish like cod. Still rather new (a few years?) and expensive - but a great way to treat fish. Many of the advantages of flash freezing without the down sides.
https://www.britannica.com/list/6-animals-we-ate-into-extinc...
For example, the high price of tusk and horn isn't saving the elephants and rhinos.