Well.....going on what I remember from fisheries biology 101 in college and the thousands of hours over my life spent around these fish I voted nook' . Unless it's a hybrid(rare but it happens) there is only 1 species with larger, oval, non-round spots on the back and that is a chinook.

I don't buy the white gumline argument on this fish that would make it a coho. Many times smaller jacks have incomplete or inconsistent color on the gumline....especially nook' jacks.

As others said, a tail shot would be more conclusive.

That's my story and I'm stick'in to it!