Tooger-thats what happened to my lake in 2005-2007 my lake had lots of water stargrass (60acre gravel pit) fishing was good bass very fat, homeowners wanted all weeds gone enter 250 lovely grass carp + chemicals, weeds all killed. The next 2 years fishing was off the charts, why best guess was those bass had lots of easy meals as tons of black crappie, gizzard shad, bluegill had no place to hide people were catching 4-7lbers easily. This lasted 2 summers then all of a sudden no big fish just an occasional 5lber, now its 2015 tonight I caught 20 bass in an hour all 12-15 inches and kept them all. Having lake shocked next week to get this thing fixed, really sad.