Good points by all, particularly RT and Salmo g.
However, let me throw in another thought.

Just because there are lots of salmon in hatcheries, I believe the stocks are MORE at risk, not less. If the justification for not listing a stock is the prescence of a hatchery, the likely scenario is that the majority of the fish will end up being hatchery origin. That's the situation we have today.

But what happens when the hatchery experiences a power outage, or a landslide upstream of the water source, or a major disease outbreak, or vandalisum, or an interuption of the water supply, or some other technological/natural/human caused problem? You lose virtually the entire stock!! This has happened many times, just ask anyone who has worked on a hatchery. Just last year Coleman National Fish Hatchery (in Northern. California) lost 500,000 juvenile Chinook salmon because they lost their water supply at night and the alarm failed.

This does not happen in nature. Fish runs are segregated both in time and in space. They spawn over many months and in various tributaries. So if a stock is wiped out by, say a landslide, there are usually several generations of that stock in the ocean or some of the stock may have spawned upstream or elsewhere. They will, over time, recolonize the habitat.

So just because there are lots of hatchery fish, doesn't mean they are not endangered. After all, they represent the majority, or sometimes the overwhelming percentage, of the ESU. I can easily make the argument that listing these fish is every bit as important because they are so vulnerable and there are so few wild fish. In other words, when you are totally dependent on a hatchery system for your fish, all your eggs are in one basket (literally). A better definition of endangered would be hard to find.