I'm a little late to this party, but if/when PS are substituted for RES in northern regions, what are the trade-offs? My shallow understanding is as follows...
PS more cold-tolerant, more prolific (closer to BG than RES), sometimes more prone to broaden diet beyond snails.
RES grow larger, less prone to overpopulation/stunting, key in on snails unless forced to forage for other foods.
If RES are used in many ponds as low-risk bonus fish with the benefit of snail (parasite) control, are PS really an viable substitute? Depending on the species combo present, could they pose a problem via prolific spawning and/or niche overlapping? I'm thinking mostly of the SMB/YP/RES combinations common on this forum or a SMB/RES only as recommended by the late Dr. Willis in a smallmouth article I read on BassResource.
