Indo-Pacific sailfish are epipelagic marine fish that spend most of their adult life between the mixed layer near the surface and the thermocline. Although they spend a majority of their time near the surface of the ocean, they occasionally dive into deeper waters where temperatures may reach as low as -8°C, though preferred water temperatures range between 25° to 30°C. Indo-Pacific sailfish migrate annually to higher latitudes during summer and migrate towards the equator in autumn. Larger adults tend to inhabit the easternmost regions of the Atlantic and Pacific oceans. (Hoolihan and Luo, 2007; Mourato, et al., 2010; Nakamura, 1985)
Trophy specimens of Indo-Pacific sailfish have measured up to 340 cm, weighing as much as 100 kg. Their fusiform body is long, compressed, and remarkably streamlined. Indo-Pacific sailfish are dark blue dorsally, with a mix of brown and light blue laterally, and a silver-white color on their ventral side. This coloration is a form of obliterative countershading. This species is easily distinguished from other billfish by the approximately 20 stripes of light blue dots present along their lateral sides. Their head bears a long bill and jaws filled with file-like teeth. Their massive first dorsal fin is sail-like, with 42 to 49 rays, with a much smaller second dorsal fin, with 6 to 7 rays. The pectoral fins are long, stiff, and falcate in shape, bearing 18 to 20 rays. Pelvic fins are thoracic in position and up to 10 cm in length. Scale size decreases with maturity and scales are nearly absent in adults. Members of this species are exceptional swimmers, with a minute drag coefficient range of 0.0075 to 0.0091, which allows individuals to reach burst speeds of up to 110 km/hr. At cruising speeds of 11 km/hr, they can fold down their first dorsal fin to reduce drag. (Nakamura, 1985; Sagong, et al., 2013)
Mature eggs are translucent and roughly 0.85 mm in diameter. The eggs contain a small globule of oil that provides nourishment for the developing embryo. Newly-spawned fertilized eggs average 1.30 mm in diameter. Although the larval growth rate is influenced by season, water conditions, and food availability, size of newly-hatched larvae generally averages 1.96 mm in notochord length, increasing to 2.8 mm after 3 days and up to 15.2 mm by 18 days. Juveniles grow at an exponential rate during the first year, with females tending to grow faster than males and reaching sexual maturity sooner. After the first year, growth rate decreases. Indo-Pacific sailfish are estimated to reach adulthood at the length of 162 cm. Based on this size, it is inferred that individuals generally reach sexual maturity at the age of 3 to 4 years and continue to grow throughout their lifespan. (Cerdenares-Ladron de Guevara, et al., 2011; Chiang, et al., 2006; Chiang, et al., 2004; Luthy, et al., 2005; Nakamura, 1985)
Indo-Pacific sailfish breed year round in the thermocline layer. Females extend their dorsal fin to attract potential mates. Males have been observed chasing females in a competitive manner, which ends with spawning for the winning male. (Nakamura, 1985)
During the spawning season in the western Pacific Ocean, Indo-Pacific sailfish over 162 cm in length migrate from the East China Sea and head southward towards Australia for spawning. Indo-Pacific sailfish located off the coast of Mexico appear to follow the 28°C isotherm southward. In the Indian Ocean, there is a high correlation with the distribution of these fish and the months of the northeast monsoons when the waters reach ideal temperatures above 27°C. Indo-Pacific sailfish spawn throughout the year in tropical and subtropical regions of the oceans, while their primary spawning season is during summer in higher latitudes. During this time, these fish can spawn multiple times. Female fecundity is estimated between 0.8 million to 1.6 million ova. During mating, a male and female pair up and swim together and release both their eggs and sperm into the water column. (Jolley, 1972; Luthy, et al., 2005; Nakamura, 1985)
As a broadcast spawning species, Indo-Pacific sailfish do not provide any investment for their offspring. (Nakamura, 1985)
Indo-Pacific sailfish have an estimated maximum lifespan of 13 to 15 years; however, the average age of catch and release specimens is 4 to 5 years. (Prince, et al., 1986)
Spending most of their time in the upper 10 m of the water column, Indo-Pacific sailfish occasionally dive down to depths up to 350 m to find food. They are opportunistic feeders and eat whenever possible. As migratory animals, they prefer to follow oceanic currents with surface seawater ranging in temperatures above 28° C. Indo-Pacific sailfish tagged with Pop-up Satellite Archival Tags have been monitored traveling over 3,600 km to spawn or find food. Individuals swim in dense schools structured by size as juveniles and organize into small groups as adults. Occasionally, sailfish swim in a solitary manner. Trophic overlap of prey between juveniles suggests that Indo-Pacific sailfish feed in groups according to their size. (Arizmendi-Rodriguez, et al., 2006; Mourato, et al., 2010; Nakamura, 1985)
This species does not maintain a home range or territory.
While there is little specific information on communication between individuals, sailfish can "flash" their body colors via activity of their chromatophores, and utilize other visual signals (like dorsal fin movements) during breeding. Their large eyes are flush to their head and are sensitive to low light conditions. A pair of nares are located in front of their eyes, Indo-Pacific sailfish use these nares to detect dissolved chemicals in the water column. Like other bony fish, this species has a lateral line used to sense movement and pressure changes in the environment and otoliths in their ear canals assist in detecting auditory stimuli. (Nakamura, 1985)
Typical foods of Indo-Pacific sailfish are epipelagic fish such as mackerels, sardines, and anchovies, as well as cephalopods. Sailfish been observed at cruising speeds with their dorsal fins folded back halfway in pursuit of prey. When sailfish attack a school of fish, they fold their fin back completely, achieving attack speeds of up to 110 km/hr. Once they approach their prey, they turn their bill quickly and hit the prey, stunning or killing it. Indo-Pacific sailfish either hunt alone or in small groups. Aside from hunting schools of small fish, Indo-Pacific sailfish are also opportunistic feeders, occasionally preying on neritic and benthic prey, a behavior similar to other billfish such as blue marlin, swordfish, and striped marlin. The particular species eaten by Indo-Pacific sailfish depend on the spatio-temporal distribution of their prey populations. Remnants of cephalopod and fish mandibles found in their stomachs suggest the rapid digestion of soft muscles. (Arizmendi-Rodriguez, et al., 2006; Nakamura, 1985)
Indo-Pacific sailfish are apex predators that affect the population of their epipelagic prey in the open ocean ecosystem. Furthermore, these fish serve as hosts for symbionts, as their stomach can be infected by the parasitic copepods Plannella instructa and the flatworms Callitetrarhynchus gracilis and Floriceps minacanthus. (Nakamura, 1985; Speare, 1995)
Indo-Pacific sailfish are frequently taken as bycatch by commercial tuna longliners in the Indian Ocean. They are also caught by gillnets, trolling, and harpooning by artisanal fishers. In 2011, an estimated 28,800 metric tons of Indo-Pacific sailfish were caught within the Indian Ocean. These fish are generally considered a prized sport fish, and their meat is often used for sashimi and sushi in Japan. (Nakamura, 1985)
There are no known adverse effects of Indo-Pacific sailfish on humans.
Although not formerly listed as threatened or endangered, Indo-Pacific sailfish are considered a data-poor fishery by the Indian Ocean Tuna Commission due to the increased fishing pressure the species experiences there, with an average annual catch between 2008 to 2012 estimated at 26,283 metric tons. Informed management decisions are difficult to make, due to the lack of sufficient data on the stock, catch statistics, and reporting data from various countries fishing in the region. ("Status of the Indian Ocean Indo-Pacific sailfish (SFA: Istiophorus platypterus) resource", 2013)
Daniel Duong (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
Animals with indeterminate growth continue to grow throughout their lives.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
mainly lives in oceans, seas, or other bodies of salt water.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
breeding takes place throughout the year
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Speare, P. 1995. Parasites as biological tags for sailfish Marine Ecology Progress Series, 118: 43-50. Accessed May 12, 2014 at http://www.int-res.com/articles/meps/118/m118p043.pdf.from east coast Australian waters.