Theskipjack tuna (Katsuwonus pelamis) is aperciform fish in thetuna family,Scombridae, and is the only member of the genusKatsuwonus. It is also known ascakalang,katsuo,arctic bonito,mushmouth,oceanic bonito,striped tuna orvictor fish. It grows up to 1.1 m (3 ft 7 in) in length. It is acosmopolitanpelagic fish found in tropical and warm-temperate waters. It is a very important species for fisheries.[2]
It is a streamlined, fast-swimmingpelagic fish common in tropical waters throughout the world, where it inhabits surface waters in largeshoals (up to 50,000 fish, often in combination with otherscombridaes), feeding on fish,crustaceans,cephalopods, andmollusks. It is an important prey species for sharks and large pelagic fishes and is often used as live bait when fishing formarlin. It has no scales, except on the lateral line and the corselet (a band of large, thick scales forming a circle around the body behind the head). Like other tuna, it lacks aswim bladder, and must keep swimming to stay buoyant. It commonly reachesfork lengths up to 80 cm (2 ft 7 in) and a mass of 8–10 kg (18–22 lb). Its maximum fork length is 108 cm (3 ft 7 in), and its maximum mass is 34.5 kg (76 lb). Determining the age of skipjack tuna is difficult, and estimates of its potential lifespan range between 8 and 12 years.[2]
Skipjack tuna are batch spawners. Spawning occurs year-round in equatorial waters, but it gets more seasonal further away from the equator. Fork length at first spawning is about 45 cm (18 in). It is also known for its potent smell.[2]
Skipjack tuna has the highest percentage of skeletal muscle devoted to locomotion of all animals, at 68% of the animal's total body mass.[3][4]
Skipjack tuna are highly sensitive to environmental conditions and changes. Climate change effects are significant in marine ecosystems, and ecological factors may change fish distribution and catchability.[5]
Global capture of Skipjack tuna (Katsuwonus pelamis) in million tonnes from 1950 to 2022, as reported by theFAO[6]Bell M. Shimada and Fred Cleaver examining skipjack tuna
It is an important commercial andgame fish, usually caught usingpurse seine nets, and is sold fresh, frozen, canned, dried, salted, and smoked. In 2018, landings of 3.2 million tonnes (3.5 million short tons) were reported, the third highest of any marine capture fishery (afterPeruvian anchoveta andAlaska pollock).[7]Countries recording large amounts of skipjack catches include theMaldives,France,Spain,Malaysia,Sri Lanka, andIndonesia.[8]
Skipjack is the mostfecund of the main commercial tunas, and its population is considered sustainable against its current consumption.[9][10] Its fishing is still controversial due to the methodology, with rod and reel or fishery options being promoted as ecologically preferable.[11][12][13]Purse seine methods are considered unsustainable by some authorities due to excessbycatch, although bycatch is said to be much reduced iffish aggregation devices are not used.[14] These considerations have led to the availability of canned skipjack marked with the fishing method used to catch it.[15] As much as 95% of skipjack tuna catches may be used as canned tuna.[16]
Skipjack is considered to have "moderate"mercury contamination. As a result, pregnant women are advised against eating large quantities.[17][18][19] In addition, skipjack's livers were tested globally fortributyltin (TBT) contamination. TBT is anorganotin compound introduced into marine ecosystems throughantifouling paint used on shiphulls and has been determined to be very toxic. About 90% of skipjack tested positive for contamination, especially inSoutheast Asia, where regulations of TBT use are less rigorous than in Europe or the US.[20]
Skipjack tuna is used extensively inJapanese cuisine, where it is known askatsuo (鰹/かつお). It is eaten raw insushi andsashimi, as well as slightly seared inkatsuo tataki. It is also smoked and dried to makekatsuobushi, and the shavings are commonly used to makedashi (soup stock).[21]Katsuobushi flakes are also used as seasoning, such as inonigiri (rice balls) or on top oftofu. The raw viscera of skipjack tuna is salted and fermented to makeshutō, a type ofshiokara.
The fish's fat content changes during migrations along the Japanese islands. When they migrate north in summer, they are calledhatsugatsuo ("first katsuo") ornoborigatsuo ("ascending katsuo"), and have a lesser amount of fat. When they migrate south in autumn, they are calledmodorigatsuo ("returning katsuo") orkudarigatsuo ("descending katsuo"), and have a high level of fat.
InIndonesian cuisine, skipjack tuna is known ascakalang. The most popular Indonesian dish made from skipjack tuna iscakalang fufu fromMinahasa. It is a cured and smoked skipjack tuna dish, made by cooking the fish after clipping it to a bamboo frame.[22]
Skipjack tuna is an important fish in thenative cuisine of Hawaii (where it is known asaku) and throughout the Pacific islands. Hawaiians prefer to eataku either raw as asashimi orpoke or seared in Japanesetataki style.[24]
The trade in pickled skipjack tuna is a driving force behind thecommercial fishery of this species inSpain.[25]
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