Fish oils come from fatty or oily fish, such as trout, mackerel, tuna, herring, sardines, and salmon. They contain omega-3 fatty acids, and many contain vitamins A and D. Fish oil is produced whenever fatty fish is processed into meal. It is a 100% marine oil with high content of omega-3 fatty acids and is mainly used to produce feed for farmed fish and refined fish oil for human consumption (fish oil capsules). Fish oil is an important ingredient in aquafeed industry as it offers major benefits to animal health, including improved immunity against disease, higher survival and growth, and reduced incidences of deformities. It is considered to increase feed appeal. This encourages farmed fish and crustaceans to locate feed and increases consumption, thereby reducing wastage. Fish oil is an industrial product of high nutritional value because of its Omega-3 polyunsaturated fatty acids content, currently valued for their beneficial effects on health. Fish Oil is produced by a cooking process, are pressed and purified in several steps. The proteins are denatured and removed by pressing. Thereafter, the oil is separated. Fish oils differ in their fatty acid composition depending on the species of origin and seasonal variations. 

Oil and water are pressed from cooked fish during the manufacture of fish meal and are separated by a centrifuge. This oil is further centrifuged before storage. 

Fish oil used in the manufacture of many products, such as cosmetics, lubricants, paints, industrial coatings, water repellents, soaps, and candles. It is also used in the tanning of leather, the manufacture of rubber, and the production of chemicals used for making synthetic wax.