Here is one from Penn - see archives,

Stocking bass-bluegill ponds
When small bass and bluegills of the
same age were stocked simultaneously
in Alabama, balanced populations
always resulted. When this
stocking strategy was followed in the
North, the result nearly always was
a stunted bluegill population and
a bass population unable to spawn
successfully. Research at Cornell
University showed that to achieve
successful bass-bluegill populations
in northern states, the initial stocking
must consist of bass that are at least 1
year older than the bluegills. This can
be achieved by stocking yearling bass
1 year ahead of yearling bluegills or
combining 2-year-old bass (over 6
inches) with yearling bluegills less
than 2 inches long. Researchers currently
believe that the proper number
of fingerling fish to stock is 100 bass
and 200 to 500 bluegills per surface
acre. This stocking strategy has been
shown to be successful in Pennsylvania
ponds.