Smell:
* Strong, ammonia-like odor: This is the most obvious sign. It's a pungent, sharp smell that's distinctly unpleasant.
* Fishy odor: While all fish have a natural fishy smell, a stale fish's smell will be overwhelming and possibly even sour or rancid.
Appearance:
* Dull, gray, or brown eyes: Fresh fish have bright, clear eyes. As they spoil, the eyes become cloudy and sunken.
* Fleshy discoloration: Fresh fish will have a bright, translucent flesh. Stale fish will develop a grayish or dull, opaque flesh, especially near the gills.
* Slimy surface: While a thin layer of slime is normal, a thick, sticky layer of slime is a sign of spoilage.
* Soft, mushy flesh: Fresh fish will have firm flesh that springs back when pressed. Stale fish will feel soft and mushy.
* Foul-smelling gills: Fresh gills will be bright red and smell like the ocean. Stale gills will be gray or brown and have a strong ammonia-like odor.
Other characteristics:
* Texture changes: Fresh fish will be firm and have a springy texture. Stale fish will be mushy and might even have a slimy texture.
* Taste changes: Stale fish will have an off-putting, metallic or bitter taste.
Important Note: Even if a fish looks or smells okay, it's always best to err on the side of caution. If you have any doubts about the freshness of a fish, don't eat it. Eating spoiled fish can cause food poisoning, which can be dangerous.