Although it is true that salmon can stay good in the refrigerator up to 4 days, it is highly recommended that you freeze it until you are ready to eat it. After you have kept salmon in your fridge for four days or more, it is probably a good idea to throw it out, especially if there is a very fishy smell to it.
Many people have problems with being able to determine whether or not their salmon is still good, so you will need to be aware of the warming signs. Any discoloration or potent fishy smell is a sure sign that you should toss out your fish as soon as possible. Just keep in mind that your salmon will last the longest when it is put in the freezer so you will not have to worry about it going bad as if it were in the fridge.