Istiophorus albicans, Atlantic Sailfish
Description & Behavior
First described as a species in 1792, the Atlantic sailfish carries the scientific name of either Istiophorus albicans (Latreille, 1804) or Istiophorus platypterus (Shaw in Shaw and Nodder, 1792). The former, more commonly used name distinguishes it from the Pacific sailfish; some scientists disagree on whether the two are in fact different species. The Atlantic sailfish is one of the smaller members of the Family Istiophoridae, with a maximum size of about 3.15 to 3.40 m in length and 100 kilograms. Females are generally larger than males. Distinguishing features include a bill-shaped upper jaw which is circular in cross-section and about twice the length of the lower jaw.
Atlantic sailfishThe first of the fish’s two dorsal fins is very long and tall (hence the name “sailfish”), running most of the length of the body, with the 20th ray as the longest. The first anal fin is set far back on the body, and the second dorsal and anal fins are both short and concave, roughly mirroring each other in size and shape. The pectoral and pelvic fins are long, with the pelvic fins nearly reaching the origin of the first anal fin. The pelvic fins have one spine and multiple soft rays fused together. A pair of grooves run along the ventral side of the body, into which the pelvic fins can be depressed. The caudal peduncle has double keels and caudal notches on the upper and lower surfaces. The lateral line is readily visible. Body color varies depending upon the fish’s level of excitement, but in general the body is dark blue dorsally and white with brown spots ventrally. About 20 bars, each consisting of many light blue dots, are present on each side. The fins are all blackish blue except at the anal fin base, which is white.
World Range & Habitat
The Atlantic sailfish’s habitat varies according to water temperature and in some cases wind conditions. At the northern and southern extremes of their distribution, Atlantic sailfish appear only during the warmer months. These seasonal changes in distribution may be linked to prey migrations. Usually found in the warmer, upper layers above the thermocline, the species often migrates into near-shore waters, preferring temperatures between 21° to 28°C, but is also capable of descending to rather deep water. In general, the Atlantic sailfish is highly migratory and can be found from approximately 40°N to 40°S in the western Atlantic Ocean and from 50°N to 32°S in the eastern Atlantic Ocean. There is an aggregation off the coast of West Africa. Although few records exist for the Mediterranean sea, several juvenile specimens have been caught there. In the western Atlantic Ocean, its highest abundance is in the Gulf of Mexico, the Caribbean Sea, and the Atlantic coast of Florida, where it is the official state saltwater fish.
Feeding Behavior (Ecology)
The Atlantic sailfish feeds mainly on small pelagic fishes—particularly mackerels, tunas, jacks, halfbeaks, and needlefish—but also eats cephalopods such as squid and octopus. Some feeding occurs at the surface, as well as in midwater, along reef edges, or along the bottom substrate.
Spawning may begin as early as April, but occurs primarily during the summer months. (The exception is the eastern Atlantic, where spawning can occur year-round.) Spawning in offshore waters beyond the 100 fathom isobath has been reported from south of Cuba to the Carolinas. However, off southeast Florida, the Atlantic sailfish moves inshore to shallower waters to spawn near the surface in the warm season, with females swimming sluggishly with their dorsal fins above the water’s surface, accompanied by one or more males. Fertilization is external. A 33-kilogram female may shed up to 4.8 million eggs in three batches during a single spawning. Atlantic sailfish larvae are approximately 0.3 cm at hatching, and they lack the elongated jaw characteristic of adult sailfish, which only begins to develop at about 0.6 cm. At 20 cm, all larval characteristics have disappeared and the juvenile has all the features of an adult.
~ Ref: http://marinebio.org, Aug, 2010