If you're a young person, your grandchildren will probably sample marine fish and shrimp as a rare delicacy (like venison). The common fish will be carp, tilapia, and a few other freshwater fish. Marine fish will all go the way of other animals we humans have hunted to extinction. Contrary to popular opinion, this is not a recent development - even in prehistoric times hunter-scavenger societies have wiped out delectable species, especially the bigger ones. Diamond's Guns,Germs, and Steel argues that the big animals of Australia and North America - the giant kangaroo, cow-size marsupials, the mammoth -were annihilated by humans. That makes Homo sapiens the unsurpassed predator ever. We'd have made dinner out of the dinosaurs had we evolved at the same time.
(Why the big animals? Plain economics - they provide the most food per unit of hunting effort. Rats, say, are abundant because they're too costly to hunt for food.)
Nowadays the last frontier of hunting is the sea and inland water bodies. Clearly we are repeating the pattern of terrestrial destruction, a fact that has been known for years. We are reminded of this by a NY times article, and picked up by the Environmental Economics blog.
So: looks like the we're turning our oceans, lakes, and rivers, into a haven for plankton and other inedibles. (That list doesn't even include jellyfish anymore - just check out a Chinese restaurant menu.) What about tuna, roundscad (galunggong), mackarel (alumahan), sardines (tunsoy), anchovy (dilis)? Gone from the dinner table. Maybe available in a pricey restaurant, or a five-star hotel. (Imagine, the galunggong ...)
Don't worry. There's still going to be fish - only they are all going to be farmed. And not the tasty marine fish and crustaceans either, like salmon and prawn - they need to eat smaller fish. It's going to be omnivores and herbivores - good old trusty carp (not familiar in the Philippines, but very popular worldwide), tilapia, etc. All freshwater species, by the way - I know of no farmed herbivorous marine fish.
It turns out that farming fish - like farming any other animal - is hard work, and has been successful with only few species. Domesticating animals (land or water) is a tough job, involving lots of research and selective breeding. "Closing the life cycle" - i.e. figuring out how to rear and reproduce an animal entirely in the farm - is tougher still. For example, the Tiger prawn (the most common farmed shrimp for export) has so far defied efforts of determined researchers to breed it in commercial quantities in captivity.
Freakonomics has also picked up the NYT article, if only to cite this BBC report on a method of extrapolating back to past fish stocks using old restaurant menus. Pretty freaky. We'll I've just shown you the future fish menu. Care to order?