The Bluegill are "Nesting"
Elke and I took a stroll by the lake today. The silty bottom just past the bank was packed with Bluegill nests. Perfect circles hollowed out from the bottom of the lake, like foxholes. The outer edge of each one built right up against the outer diameter of several others surrounding it.
Every hole was manned by one Bluegill swimming in furious circles, I presume to keep the other fish away from the eggs. From above it was an interesting show.