Katsuwonus pelamis
FAMILY
Scombridae
TAXONOMY
Katsuwonus pelamis (Linnaeus, 1758), "pelagic, between the tropics."
OTHER COMMON NAMES
French: Bonite à ventre rayé; Spanish: Listado.
PHYSICAL CHARACTERISTICS
Maximum fork length approximately 43 in (108 cm) corresponding to a weight of 72–76 lb (32.5–34.5 kg), commonly to 31 in (80 cm) and 18–22 lb (8–10 kg). Body fusiform, elongate, and rounded. Two dorsal fins separated by a narrow interspace, the first with 14–16 spines, the second dorsal and anal fins followed by seven to nine finlets. Pectoral fins short, with 26 or 27 rays. Body naked except for anterior corselet and lateral line. Caudal peduncle very slender with a strong lateral keel between two smaller keels. Swim bladder absent. Gill rakers numerous, 53–63 on first gill arch. Back dark purplish blue, lower sides and belly silvery, with four to six very conspicuous longitudinal dark bands.
DISTRIBUTION
Cosmopolitan in tropical and warm-temperate seas but absent from the Black Sea.
HABITAT
An epipelagic oceanic species with adults distributed within the 59°F (15°C) isotherm. Aggregations of this species tend to be associated with convergences, boundaries between cold and warm water masses. Depth distribution ranges from the surface to about 853 ft (260 m) during the day.
BEHAVIOR
Skipjack show a strong tendency to school in surface waters. Schools are associated with birds, drifting objects, sharks, whales, and other tuna species.
FEEDING ECOLOGY AND DIET
Skipjack are opportunistic feeders preying on any forage available. Feeding activity peaks in early morning and late afternoon. Food items include fishes, crustaceans, and mollusks.
REPRODUCTIVE BIOLOGY
Skipjack spawn in batches throughout the year in equatorial waters and from spring to early fall in subtropical waters. The spawning season becomes shorter as distance from the equator increases. Fecundity increases with size but is highly variable. The number of eggs per season in females 16–24 in (41–87 cm) fork length ranges from 80,000 to two million.
CONSERVATION STATUS
Not threatened.
SIGNIFICANCE TO HUMANS
Skipjack make up approximately 40% of the world's total tuna catch and have come to replace yellowfin as the dominant commercial species of tuna. Catches of skipjack were reported to FAO by 94 countries for 1991–2000, 1,584– 2,191 thousand tons (1,437–1,988 thousand metric tons) per year. The highest catches reported for 2000 were by Japan, 376 thousand tons (341 thousand metric tons), and Indonesia, 298 thousand tons (270 thousand metric tons). Skipjack are taken at the surface, mostly with purse seines and pole-and-line gear, occasionally with long lines. They are marketed fresh, frozen, and canned (as light-meat tuna). They are also a game fish, the all-tackle gamefish record is a 45-lb (20.5-kg) fish caught on Flathead Bank, Baja California.
