- Unpleasant Odor: A strong, pungent smell is one of the most obvious indications. Fresh fish has a mild, briny scent, whereas spoiled fish has a sharp, ammonia-like odor.
- Slimy Texture: As fish begin to deteriorate, their skin becomes slimy and slippery to the touch. Fresh fish should have a firm, moist, but not slimy texture.
- Dull Eyes: Fresh fish have bright, clear, and slightly bulging eyes. Cloudy, sunken, or milky-looking eyes indicate spoilage.
- Gills: The gills of fresh fish are bright red and may have a slight sheen. As they spoil, the gills turn pale, grayish, or even brownish.
- Discolored Flesh: The flesh of fresh fish is usually translucent and pinkish or whitish in color. Spoiled fish flesh may be dull or develop an opaque appearance.
- Soft Flesh: Fresh fish should be firm and springy to the touch. If the flesh feels mushy or easily breaks apart, it's likely spoiled.
- Taste: If you're unsure about the fish's freshness, cook a small piece and taste it. Spoiled fish will likely have a bitter, off flavor.
- Gut Contents: If the fish has been ungutted, check the condition of the gut contents. Fresh guts should be firm and white. If they are soft, mushy, or have a greenish color, the fish is likely spoiled.