Are you talking about a summer-run that has already spawned and has reconditioned its body? In this case the fish is chrome, fins have healed and, because it is actively feeding, dosen't have a sunken-in belly. I've caught a few of these on my namesake river in February. These have been hatchery hens that I thought were just bonus late winter brats. While cleaning them, they have immature eggs skeins, the size of a pencil. They also have poor quality flesh.
The only thing I've noticed is that they have an enlarged head, but only because the width of its back isn't proportioned to its head.