Help me Id this fish

I took my family out fishing yesterday about ten miles down the river from from Lake Pend Oreille I caught and released this one fish. I thought it was a rainbow or cutthroat as I reeled it in. Upon closer inspection it was definitely not a cutthroat (no orange slits) and I don’t believe it was a rainbow either. Had i been positive it was a rainbow it would have came home with me for dinner. The little bit of black on the bottom gum made me think possible salmon so I released it.

Brown trout, 100%. Large black spots surrounded by light blue "halos" are a signature trait.

After looking at a lot of brown trout photos in the internet I think your right. I have caught brown trout in the past and have never seen one anywhere near that light in color.

I've landed probably thousands of browns over the years. The ones found in large lakes will typically develop that silvery shine without red spots outside of spawning season. Helps them blend in with living a "pelagic" lifestyle chasing bait in the open water, versus the typical brown/golden colors observed in stream-dwelling browns.