No need to look for an explination. There most likely isnt one. It could be a stray, hatchery fish offspring, a very early winter run, Maybe it a sign of a healthy river system where the run is expanding.

We get fresh wild steelhead out here 12 months out of the year in some systems still in sustainably numbers. Other systems out here dont have that anymore but im sure they all did in the past before overharvest.