How do you know if store bought fresh salmon is spoiled?

As with ANY fish, look for the following: * The fish must be gutted. Unless you saw it caught right in front of you, 10 minutes ago, guts are a fail. * The eyes should be clear. Cloudy eyes are a bad sign. * The gills should be bright red (ideally) or at least a strong dark red. Pale gills are a very bad sign. * Even though it's a fish, it should not smell "fishy" -- it should smell fresh and clean. * Salmon, like so many fish, have striations in their muscle tissue. Ideally, there should be no air gap between the striations. Which a few gaps are acceptable, they are an indicator of dessication. * Touch the fish: It should be firm and not slimy. * The skin shoudln't present a "rainbow" effect from surface oils. While not a complete fail, if this sign is present, it indicates some age and poor preservation on the fish. * Look at the tag which, by law, must tell you where the fish was harvested. If the location is very remote, be on guard. If it smells bad, forget it. The scent of amonia is a killer. If the fish is obviously warm to the touch, forget it.