User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-5020152-20131018191930/@comment-5043481-20131022205519

He wouldn't need to boil the ocean to kill all the fish in it, as when water warms up it can dissolve less oxygen. Lack of oxygen leads to dead fish. This is often a factor mass fish deaths in ponds and rivers.

I thought the red colour of the tainted sea was due to something coming out of Miralis, probably to do with his volcanoes.