There are a lot of possibilities, Redge.
1. Too many smaller fish caught and kept during the last several years.
2. Lots and lots of saugeyes, hybrids, and catfish eating the crappie fry, since the water was so low and the fry had no cover for several years.
3. Cormorants and pelicans. There have been a lot of crappie that have stab wounds from the cormorants.
4. The great shad spawn this past year has them stuffed to the gills and not in a hungry mode.
5. The vagaries of fish reproduction.
The good news is that last spring's spawn should have had a much greater survival rate, since the brush was flooded, giving more cover for the fry. We may see some excellent fishing when that crop reaches adulthood.