My shad die-off only lasted for a few days. All of the dead were small and thin (I have some very large shad in my pond). My water is very low, down about three feet. I have about six to eight feet left in the deepest part. The water isn't extremely clear, but not muddy either. This is the only time this has happened in the twelve years I've managed this pond. They may have just become overpopulated and nature did its thing. Now if I could just get some good rains. Thanks for the info!