So in other words you are saying the females do not feed during the spawn? I have always believed that the females do feed a little bit during the spawn, but less than normal.
Since the females don't usually stay on the nest for more than three days it would make sense that they feed after they leave.
Furthermore, I have landed a spawning bass which had the tale of a rainbow trout sticking out of it's mouth, indicating it was feeding during the spawn. Thererfore if they feed during the spawn, the protein from the trout (or any other food) would be used for protein synthesis and muscle repair instead of the eggs.