Istiophorus platypterus

Geographic Range

Indo-Pacific sailfish ( Istiophorus platypterus ) can be found in both temperate and tropical waters throughout the world's oceans. They generally have a tropical distribution and are particularly abundant near the equatorial regions of the Atlantic, Pacific, and Indian Oceans from 45° to 50° N in the western North Pacific and from 35° to 40° N in the eastern North Pacific to approximately 35° S in the eastern South Pacific. In the western Indian Ocean and in the eastern Indian Ocean, Indo-Pacific sailfish range between 45° to 35° S, respectively. This species is essentially found along the coastal regions of these latitudes, but can also be found in the central regions of these oceans.

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • native native
• oriental oriental
  • native native
• ethiopian ethiopian
  • native native
• neotropical neotropical
  • native native
• australian australian
  • native native
• oceanic islands oceanic islands
  • native native
• indian ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native
• mediterranean sea
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

Physical Description

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

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.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

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.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

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.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• broadcast (group) spawning
• oviparous oviparous

As a broadcast spawning species, Indo-Pacific sailfish do not provide any investment for their offspring.

• Parental Investment
• no parental involvement

Lifespan/Longevity

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.

Behavior

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.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• migratory migratory
• solitary solitary
• social social

Home Range

This species does not maintain a home range or territory.

Communication and Perception

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.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical
• magnetic magnetic

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans

Predation

Indo-Pacific sailfish hooked by longlines have been attacked by great white sharks and killer whales . However, predation of free-swimming sailfish is very rare.

Ecosystem Roles

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 .

Economic Importance for Humans: Positive

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.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no known adverse effects of Indo-Pacific sailfish on humans.

Conservation Status

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.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Daniel Duong (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Leila Siciliano Martina (editor), Texas State University.

References

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Cerdenares-Ladron de Guevara, G., E. Morales-Bojorquez, R. Rodriquez-Sanchez. 2011. Age and growth of the sailfish Istiophorus platypterus ( Istiophoridae ) in the Gulf of Tehuantepec, Mexico. Marine Biology Research , 7: 488-499.

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