Blackfin tuna (Thunnus atlanticus) is the smallest tuna species in the Thunnus genus, generally growing to a maximum of 100 centimetres (39 in) in length and weighing 21 kg (46 lbs). Blackfin have oval shaped bodies, black backs with a slight yellow on the finlets, and have yellow on the sides of their body. Blackfin are only found in the western Atlantic from Cape Cod to Brazil. They are a short-lived, fast-growing species; a 5 year old fish would be considered old. Blackfin tuna are a warmer water fish, preferring water temperatures over 68°F (20°C). What they lack in size, they make up for in numbers and willingness to bite.