A mackerel is any one of a number of different species of fish, mostly in the family Scombridae. They live in tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel (Scomberomorus maculatus) enter bays and can be caught near bridges and piers. The largest mackerel is the king mackerel (Scomberomorus cavalla) which can grow to 66 inches (168 cm). They are easily identified by having a slim, cylindrical shape (as opposed to tuna, which are deeper bodied) and numerous finlets on the dorsal and ventral sides behind the dorsal and anal fins. They are prized for their meat and fighting ability, and are an important recreational and commercial fishery. Mackerels are high in Omega 3 fats. Omega 3 and Omega 6 are also known as essential fatty acids. Omega 3 has been proven to have a role in preventing heart disease and is thought to help treat bi-polar disorder and depression.