Ric - without any further information, I'd be hesitant to make that call.
If non-oxygenated water from the deeper areas is rapidly mixed with questionably-oxygenated surface water, the entire pond could be rendered into a homogenous mixture of insufficiently-oxygenated water (below the tolerance of fish).
I received four calls from clients this week reporting fish-kills - each asking "why?". The kills all appeared to be oxygen-related, but there were too many variables involved to absolutely determine the triggers. However, I believe that phytoplankton-crashes played a role in each case (along with water temps).
NOTE: none of the ponds were aerated.... two had been treated for vegetation control, but not enough time had lapsed for the herbicide to cause ANY plant mortality.... one pond had a lake dye (of unknown type) added to it the day before the fish-kill.... we had a very calm and VERY HOT Memorial Day down here.
