There is no general sauger ban now, and I have not heard any talk about enacting one; this sounds like someone getting confused about the closed season below the dams in Dubuque, Bellevue, and Clinton. In those cases, the water below Lock and Dams 11, 12, and 13 is closed until March 15 for all fishing, not just saugers. (The Iowa fishing regs. give the exact boundaries of the closed waters.) The regulations are pretty clear in stating that you may not wet a line in the closed zones between December 1 and March 15.
The closed season was put in place to protect sauger populations in those three pools from over-fishing; DNR surveys found that sauger populations in those pools had declined by 70-80% in the late nineties, when warm winters allowed people to fish all year round below the dams when the sauger were concentrated there. There was also some concern about fish mortality if they were released, as many winter sauger are pulled from deep water, and do not handle the rapid pressure change well, as the previous post noted. That is why the DNR enacted a no-fishing zone, rather that tighter bag limits or C and R only.
The closed seasons were enacted for a minimum of five years, and then the DNR will have the option of extending them, altering them, or ending them. A few weeks ago when I was fishing in Bellevue, there was a USFWS agent checking boat registrations and such at the ramp, and I asked him if he knew how the closed season there was working. He said that from what he had heard, it was working very well in boosting sauger populations. I saw no evidence of it that day, as all I caught were white bass.