Mark Cahill has reported seeing breaking fish in the South River in January. I got plausible reports from Henry Weston's of post-migration stripers being taken in the North.
Considering that this is my own backyard, I would like to be able to report first-hand, but I can't. It's thoroughly plausible that there are catchable winter-over stripers in the North/South river and marsh system, and anyone who has figured out the trick is welcome to share it with me.