Fish in a can is a term used to describe canned fish products, such as sardines and TUNA. Sardines are small, oily fish that are typically found in the Mediterranean Sea and Atlantic Ocean. They are usually canned in oil or water and are a popular snack food. TUNA is a larger species of fish that is found in tropical and subtropical oceans around the world. It is also commonly canned in oil or water and is a popular ingredient in salads and sandwiches. Sardines are also sometimes referred to as 'sardines in a can' due to their small size and packaging.