Walleye are driven to their spawning grounds or staging areas in late fall/early winter. when photo period approaches 12 hrs they begin to spawn or attempt to. If water temps are not correct for eggs to ripen, the female will extend her time in the area until temps are right or until a time period goes by that triggers the female to reabsorb the eggs. It also takes large numbers of males present to stimulate the female to continue with the spawning process.
Several factors come into play beyond what I've mentioned here but photo period, temp and ratio of males are 3 huge factors.
