It's the food supply. Acidity (rising), warming (increasing) and phytoplankton are declining. This means the entire food chain in the oceans is collapsing, something well-recognized by biologists and marine scientist now. So the whales are 'adapting' to these conditions, as they must. We've left them with no choice. Therefore, it's pretty silly for fisherman to be complaining about this (while burning diesel) and every other two-legged creature (while continuing to destroy the planet). Nature does not operate in a vacuum - it will respond to our impacts.