The Atlantic sailfish, Istiophorus albicans, is a metallic blue fish with a large sail-like dorsal fin, and a long and pointed bill.
First identified in 1792, the only other sailfish is the Indo-Pacific, Istiophorus platypterus. The Atlantic sailfish is one of the smaller members of the billfishes or Istiophoridae family, with a maximum size of about 3.15 m and a weight of 58.1 kg (highest recorded weight), with the females being larger than the males.
Distinguishing features include a bill-shaped upper jaw, circular in cross-section, and about twice the length of their lower jaw. The first of this fish's dorsal fins are very long and tall (thus this name "sailfish"), running most of the length of their body, with the 20th ray as the longest. Their first anal fin is located far back on their body, and their second dorsal and anal fins are both short and concave, roughly mirroring each other in size and shape. Their pectoral and pelvic fins are long, with their pelvic fins nearly reaching the origin of their first anal fin. Their pelvic fins have one spine and multiple soft rays fused together. A pair of grooves run along the under side of their body, into which their pelvic fins are depressed. Their tail fin has double keels and caudal notches on the upper and lower surfaces. In general, their body is dark blue at the top, and white with brown spots at the bottom. They also have various bars that consist of many light blue dots on their sides, while their fins are all blackish blue, except for the anal fin, which is white.
In general, these fish are highly migratory and can be found from 40N and 40S (latitude) in the western Atlantic, and from 50N to 32S in the eastern Atlantic (map included). At the northern and southern extremes, they appear only during the warmer months. Although the instances have been few, there are recorded times of several juvenile specimens having been caught there. In the western Atlantic, its highest abundance is in the Gulf of Mexico, the Caribbean, and the Atlantic coast of Florida, where it is the official state saltwater fish; in the eastern atlantic, they are plentiful off the coast of West Africa.
While sailfish have little commercial value (their meat is relatively tough), they are highly sought after by recreational fishermen. As you can see by this video, they are not considered a threat to humans.