Welcome to the forum Don! Double Crested Cormorants (Phalacrocorax auritus) also called Water Turkeys, or Anhingas (Anhinga anhinga) (also called water turkeys), could very well clean out a pond that size in that length of time. Like Cecil said, they may not have eaten ALL the Bluegills, but they probably ate the majority of them.
Can you tell us what your water temperature is? That might give us a better idea where the BG could be in the water column.
Thanks for the welcome,
I need to get myself a thermometer to check. I know the bottom stays pretty cool since I have to pump so much water from my well into the pond since it leaks so darn bad. I did feel the top water and it felt pretty good the other day but hard to say actual. Maybe it's a good time to get what fish I have left out and try to find my leakers.
