What might be a possible explanation (which doesn't even require silly conspiracy theories) is that there might be a volcano or some kind of rift occurring deep in the ocean floor which is spewing out poisonous gasses and killing these animals. It could also account for the ferocious action on the pacific plate which scientists are saying is unrelated (Christchurch, Japan, etc.)
I guess there is every chance that we really could only be seeing the beginning of the end times catastrophe. If a volcano sufficiently enormous erupted, it could black the world out (three days of darkness perhaps?)
God often uses nature for his miracles - perhaps this is the way He plans to initiate the end.
Also, regarding the moon theory; scientists here (NZ) said that it is impossible to say that the moon can cause a giant quake. BUT - they said it DOES have an influence in the cause of small ones. So can they show me the proof that it can cause small quakes but not big ones? There seems to be a serious logical flaw involved there.