'Fresh fish' is a highly nutritious and palatable protein source for dogs. It can be made of any parts of any fish but usually consists of the leftovers from human-grade fish, such as viscera, which is minced into a fine paste before being added to the food. All fish, but particularly oily fish like tuna, mackerel, herring and salmon, contains fish oils, which is high in health promoting omega-3 essential oils.
Fresh fish is widely used in wet dog foods and is also becoming increasing popular in dry foods. When comparing the fish contents of dry foods it is important to remember that since fresh fish contains roughly 70% water (compared to just 8% in fish meal) it is far less nutritionally concentrated than meal and so more is required. For example, in order to provide the same levels of protein and fat as 20% fish meal a dry food would need 72% fresh fish!