The term 'Horse Mackerel' refers to a family of fish that includes the SCAD (also known as saurel or jack mackerel), which is a small, silvery-green fish found in tropical and subtropical waters. TUNA is another species of fish in the same family, and is a large, migratory fish found in temperate and tropical oceans. Both SCAD and TUNA are popular sources of food, and are often canned or smoked for consumption.