If you’ve purchased fresh salmon, it’s best to cook and eat it within three to four days. You can always freeze fresh portions as well for up to two months. If you’ve thawed frozen salmon in the refrigerator, you should eat it within one to two days. If you’ve thawed frozen salmon in the microwave or under cold water, you should be prepared to eat it right away.
As far as salmon leftovers are concerned, they can keep up to three days in the fridge. When in doubt, throw it out. It’s better to start over than to risk food poisoning.