This isn't an April Fool's joke. I don't mean to sound like a raging environmentalist, but global warming raises the water temperature in the ocean slightly, and with that happening, phytoplankton are dying. They are pretty much the base for most food chains, and they create most of the oxygen in the ocean. Since they're dying there are fewer of them to feed sea animals who eat them, and less oxygen in the water. Fishes are starving and suffocating!
Emaciated fish aren't the only issue, though. Jellyfish get their freak on & breed more in warmer water. Their larvae eat the same stuff the baby fish eat, but they also eat the baby fish! It sounds bad, but that's nature right?
Sushi prices are gonna skyrocket! Check out the Baked Salmon Roll before caviar gets to be too pricey.
I guess the solution to this would be to find better ways to combat global warming. Even if we do figure out how to reverse global warming, Wikipedia says we're screwed anyway, but that's way down the road.