Catching fish in the process of spawning and actually laying eggs are two different animals. If the water doesn't stabilize they aren't going to be in one spot for very long. The magic number is hard to know for sure, but science says if it's not on up in the 60's, they aren't going to lay any eggs due to their hatch survival percentage going down. You're going to catch some nice females when the process starts, but most likely more fish once the temps rise into the 60s due to both males and females visiting the nest/staging areas temporarily throughout the day.
http://depts.washington.edu/oldenlab...latus_Riso.pdf
http://www.temperatureworld.com/ctable1.htm Temperature Conversion Table