Fish beds ?

Was on KY around sugar and Duncan bays and there are concrete squares all along the banks , looks like the tops are concave ?
I figured fish and wildlife put them out for fish beds but can anyone tell me what species they are for or if that is even what they are ?

Green carp beds put in by F&W. I guess redears could use them also.

Correct. Designed as bass beds, but once bass are through with them the bluegill, redear, and longear seem to love them too.