How do you know if fish is rotten?

Smell: Fresh fish should have a mild, briny smell. If the fish smells fishy, sour, or ammonia-like, it's likely spoiled.

Eyes: The eyes of fresh fish should be clear, bright, and slightly bulging. Cloudy, sunken, or dull eyes indicate spoilage.

Skin: Fresh fish should have a shiny, iridescent skin. If the skin is dull, slimy, or has discoloured patches, it's a sign of spoilage.

Flesh: When you press on the flesh of fresh fish, it should be firm and spring back quickly. If the flesh is soft, mushy, or leaves an indentation, the fish is likely spoiled.

Gills: The gills of fresh fish should be bright red and free from slime. If the gills are brown, grey, or have excessive slime, the fish is likely spoiled.