Definitlely a spring time event. I am not sure if the spawn coincides with them running up into creeks from larger water bodies, but if that is what you are looking for, just keep checking this site in the spring. I am sure someone will post a few threads when they are catching them in the creeks.
I usally catch some when prospecting for wipers to move up into the creeks in May/June. They seem to move at about the same temps (mid 50s to low 60s as Grumpy said), but the wipers might move in later and a little warmer.
As for the months...May would probably be about right, maybe early June. Don't quote me on that as I usually stumble into them