There has been much discussion about LMB vs. SMB competition. I think I stumbled on a piece of the puzzel. LMB are estimated to produce 13,000 eggs/ pound body wieght. SMB are estimated to produce only 8,000 eggs/# body wieght.

But temp. should not be a consideration.
SMB
Spawn 58-62 F
Grow 50-70 F
Upper Leathal 95 F
LMB
Spawn 60-65 F
Grow 55-80 F
Upper Leathal Unknown
So as long as some of your water stays >70F you should experience optimal growth, but if your water never gets <95F you should be able to keep them alive.
maybe SMB lower spawning temp. puts them at a disadvantage against LMB. SMB should hit the spawning beds first, but maybe they loose established nests to LMB moving in to spawn just a few days later? Just guessing, but it would be and interesting study to do... I'm need to learn how to SCUBA.