b-well and Bruce and BM :

The question is open for comment. It does not matter if you know the answer feel free to join in the speculation. I don't know but a fraction of the answer either. I think it means at the spawn (bed) location but I have not seen it stated that way. I think you need both temp. and photo period and there is a range for both (some variance). If you mix up a bunch of cold water all of the sudden it could delay the spawn.

I never take pre spawn BG or RES at least not the biggest best conditioned ones. I would release the RES. That may not be right for your pond but that is my approach. I don't think it is smart to harvest my best fish . I leave them for genetic purposes. This is certainly true for BG because of their spawning methods (sneakers cuckholders etc.).To much evidence exists that provides that it is not good to take out your best prespawn male lepomis. I would think that applies to your best conditioned most prolific females also.

Bruce I agree that there are several conditions wrt spawning. Water temps , photo period , population dynamics (crowding), fish condition , spawning suppression (ie gizzard shad , sunfish ,crappie) adequate spawning areas (dominance) and I am sure I missed some. In addition to visual clues there are auditory ones also and chemical (hearing and smell). Photo period should be about the same each year at the same time. I know photo period has been manipulated in lab studies on spawning and they usually just give an approximate time like 12 hrs.

In the question above I should have been more specific. Could this result in a reduced spawn and survival of the predators (not a total failure). No doubt they will stop and start and adjust to conditions and string things out especially the further south in the LMB range as that is an option (longer period of water temps. in the acceptable range). The dynamics of the spawn and the various species adaptation are amazingly complex and fascinating. I think I will find some spawners and drop the temp. probe to the actual spawn location and see what it reveals.