A species of Billfish living in warmer sections of all the worlds oceans, Sailfish are blue to gray in color with white underbellies and a highly distinctive erectile dorsal fin known as a sail, which can strength the full length of the fishes back. They also sport an elongated bill, similar to that of the swordfish and other marlins. Often said to have two main subspecies, Atlantic and Indo-Pacific, no differences have been in mtDNA, morphometrics or meristics between the two supposed species and they’re now considered to be the same.
Fast growing (reaching 1.2–1.5 m in length in a single year), they feed on the surface or at middle depths on smaller pelagic forage fish like sardines and anchovies, which they can shepherd with their sails to make them easier to catch. They also eat squid and octopus. They tend to grow no more than 3m in length with a maximum weight of 90 kg.
The sail is normally kept folded down and to the side when swimming, but it may be raised when the sailfish feels threatened or excited, making the fish appear much larger than it actually is. This tactic has also been observed during feeding, when a group of sailfish use their sails to “herd” a school of fish or squid. They can swim 100 m in 4.8 sec and via their nervous system, almost instantly change colour, a tactic used to confuse prey and to communicate to other sailfish.