Blue Fin Tuna

From Wiki:

"The body of the northern bluefin tuna is cigar-shaped and robust. The head is conical and the mouth rather large. Northern bluefin tuna can live for 30 years. Due to overfishing of this species, few known specimens grow to a mature age and typical specimens average 2-2.5 m (6.5-7 ft) long and around 350 kg (770 lb) in weight. The largest recorded specimen was caught off Nova Scotia and recorded at 680 kg (1,496 lb). The species can reach a maximum length of about 4.3 m (14 ft). The color is dark blue above and gray below with a gold coruscation covering the body and bright yellow caudal finlets. Northern bluefin tuna can easily be distinguished from other members of the tuna family by the relatively short length of their pectoral fins. Their livers have a unique and definitive characteristic in that they are covered with blood vessels (striated). In other tunas with short pectoral fins, such vessels are either not present or present in small numbers along the edges.

The enormous muscular strength of this animal is channelled through a pair of tendons to the sickle shaped tail and in contrast to many other fish the body stays rigid while the tail flicks back and forth, increasing the efficiency of each stroke."