Ray,
Your correct! I read information on quite a few sites and there are opinions from the Dams are the cause, predation in the rivers, low snowpack in the mountains, too much water taken from rivers for irrigation, not enough food for the salmon in the rivers / ocean, the ocean temp too high, the American commercial fishing, the Foreign commercial fishing, gene pool problems with hatchery salmon, farmed salmon escaping into the population, bait fish being commercially overfished in the ocean.
Doug