Notice in the bottom studies, there are no RES included, so can't tell anything specifically about RES.
But look how few fish were found in the stomachs of the various sunfish. Some studies none and others only a very few. Even the much maligned GSF has not eaten many fish. Mostly other stuff.
Seems strange to me. Must have had plenty of other preferred stuff to eat. Or maybe time of year study was done?????
Bottom three studies on the page 
