Oily fish

Oily fish, also known as blue fish, greasy fish or fatty fish, are species of fish with oil (fats) in soft tissues and in the coelomic cavity around the gut (These cavities help produce fat thus making the fish more oily). Their fillets may contain up to 30% oil, although this figure varies both within and between species. Examples of oily fish include small forage fish such as sardines, herring and anchovies, and other larger pelagic fish such as salmon, trout, tuna, swordfish and mackerel. Oily fish can be contrasted with whitefish, which contain oil only in the liver and in much less overall quantity than oily fish. Examples of whitefish are cod, haddock and flatfish. White fish are usually demersal fish which live on or near the seafloor, whereas oily fish are pelagic, living in the water column. Oily fish meat is high in fat-soluble vitamins such as Vitamin A and D and is rich in omega-3 fatty acids (white fish also contain these nutrients but at a much lower concentration). For this reason, the consumption of oily fish rather than white fish can be more beneficial to humans, particularly concerning heart diseases such as stroke and ischemic heart disease; however, oily fish are known to carry higher levels of contaminants (such as mercury or dioxin or POPs) than white fish. Among other benefits, studies suggest that the omega-3 fatty acids in oily fish may help improve inflammatory conditions such as arthritis.