Indonesia and the Philippines pretty universally considered southeast asia and not pacific island nations. They are in-fact the majority of southeast asia, which they are supposedly fleeing to?

Also, they're quite developed countries and to the relatively small extent their food consumption is fish, it comes from trade and commercial fishing, not subsistence fishing, so their food supply will be no more impacted than any other asian country. And even that impact will look more like more seafood coming from fish farms as commercial fishing becomes less viable, as we've seen in China.

There are people, predominantly in the pacific islands proper, who rely on subsistence fishing and the decline of fish stocks will be hugely disruptive for them. It's still a big tragedy, but the number is more like a couple hundred thousand. I don't think it helps the debate to exaggerate by three orders of magnitude.