The major cause of spoilage in fresh fish is bacterial attack. When fish dies, bacteria present in the fish's digestive system start to break down the fish's protein into simpler compounds. If the fish is not properly preserved or refrigerated, these bacteria will multiply quickly, causing the fish to spoil. Signs of bacterial spoilage include slimy texture, off odor, and discolored flesh. Therefore, proper storage and preservation techniques such as refrigeration, drying, smoking, or salting can help to prevent bacterial growth and prolong the shelf life of fresh fish.