Gd post above. It's very true that salmon don't eat when coming back into fresh water from the salt. It's not so much that they don't eat, they can't, or to be more specific, they can't digest food because of the physiological changes they went through as smolts going to sea. Food has been found in the stomach of adult salmon when back in fresh water but it is usually undigested.
There are many theories as to why salmon will take our flies and lures. They are quite aggressive creatures, even more so come mating time, usually around late Nov through Dec and into Jan. Running fish are wide