I still believe photo period at peak spawn will be 12+ 10-15. I also believe normal spawning begins at near 11;45+ 10-15. With WAE (very close cousin) this is very predictable. Temp can cause the peak to vary a few days either way but generally temp only affects hatch time-in general-not saying this is absolute on YP. Glad someone is seeing ribbons.. mine have been a few days earlier than today and my water temp is "normal". 11:55 today