Hello Gates,
Yes, it would be a good assumption with the weather and possible increase in algae growth this time of year that the pond did go through a flip flop or as Walt described, the turnover.
Ponds are diurnal or naturally mix in the fall and spring. If the area of anoxia (low or no oxygen water) is not too large it will have no affect on the fish. I would make a hypothesis that this zone was farily large which is common in ponds this time of year and a drastic flip will cause an oxygen drop in the zone where your fish have set up house.
Right now, yes I have suggested to clients to put a boat in the pond, I say keep it hooked up to the trailer and trim the motor so it will spray the water up. The fish will come to area of more oxygen content.
Secondly, now is the time to look into some sort of emergency aeration like a surface aeration unit. **Do not use a lake bed aeration unit for emergency** They are so efficient at bringing the bottom water to the surface and right now we do not want to do that. It will though be a great choice to prevent this turnover from happening again by creating a constant flip once a day.
Lastly, I have had clients use the local Volunteer Fire Department to draft water with their engines and spay it over the surface with the deck gun. As a former Capt. on a Fire Department, we don't mind doing this because it allows us to practice and helps keep the pumps working properly.
Good luck!
