[header] How to know if salmon is bad [title] Make sure the fish doesn't have a strong, ammonia-like smell. [step] Smell the raw salmon to see if it has a bad odor. If the fish smells pungent, fishy, or ammonia-like, it is probably bad. 
Fresh salmon should have a very mild scent. [title] Look for a milky coating to indicate the fish has gone bad.