Salmon withdraw near every nutrient possible from their bodies committing them to their eggs and/or sperm and the energy needed for spawning efforts. Once depleted and near death, if one squeezes their flesh, it flows between ones fingers about like apple sauce. Even pre-spawn their flesh is not the most desirable.
When I used to fish the Oregon coast one would see folks retaining such with comments that they'd be good smokers. Garbage in = garbage out.
