This is from this publication: http://www.michigandnr.com/PUBLICATIONS/PDFS/ifr/ifrlibra/technical/reports/2003-3tr.pdf


Redear sunfish hybrids in newly stocked
waters were robust and exhibited fast growth, as
determined by growth analysis using scales.
They have been observed guarding nests during
spawning season; however, it is doubtful that
many of them are fertile (John Epifanio, Illinois
Natural History Survey - personal communication).
Childers and Bennett (1961) attempted to
produce hybrids by isolating males of one
species (bluegill, redear sunfish, or green
sunfish) with females of another (six possible
combinations) in ponds that contained no other
fish. Each of the F1 crosses was attempted two
or more times. Only the green sunfish x bluegill
and redear sunfish x green sunfish crosses
produced significantly large numbers of F1
hybrids. When F1 hybrids were isolated in
ponds, the redear sunfish x green sunfish
reproduced successfully; however, the bluegill x
redear sunfish combination failed to reproduce
successfully.