It's possible, but seems pretty odd. More likely a mis-identified brown trout, which are a fairly common by-catch in the lake. That said, the DNR has been raising Atlantics at the Platte River Hatchery upstream for a couple years now, but they should not be large adults yet. I guess it could be a juvenile that escaped and was living in the river for a year or so and they made it down to the lake. How big was it?
