Or sonar interference possibilty.
There is problem with the food system phytoplankton. There reports its declined by 40%.
http://www.theecologist.org/News/new...l_warming.html
Although dont think its global warming argument. I more inclined to believe the mainy morine human accidents such eron oil spill the big one in america the reason.
Espicially BP's this destroyed alot areas would naturally caused phytoplnkton shortage. It was massive spill remember they said vast parts ocean became dead zones.
This maybe tiping point might be mass starvation.
The other is possible suicede runs but usually it dont have cross species.