Skipjack Tuna

The skipjack tuna (Katsuwonus pelamis) is a perciform fish in the tuna family, Scombridae, and is the only member of the genus Katsuwonus. It is also known as katsuo, arctic bonito, mushmouth, oceanic bonito, striped tuna or victor fish. It grows up to 1 m (3 ft) in length. It is a cosmopolitan pelagic fish found in tropical and warm-temperate waters. It is a very important species for fisheries. It is also the namesake of the USS Skipjack.

It is a streamlined, fast-swimming pelagic fish common in tropical waters throughout the world, where it inhabits surface waters in large shoals (up to 50,000 fish), feeding on fish, crustaceans, cephalopods, and molluscs. It is an important prey species for sharks and large pelagic fishes and is often used as live bait when fishing for marlin. 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). It commonly reaches fork 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. 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. Skipjack tuna has the highest percentage of skeletal muscle devoted to locomotion of all animals, at 68% of the animal's total body mass. 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.

It is an important commercial and game fish, usually caught using purse seine nets, and is sold fresh, frozen, canned, dried, salted, and smoked. In 2018, landings of 3.2 million tonnes were reported, the third highest of any marine capture fishery (after 🇵🇪 Peruvian anchoveta and Alaska pollock). Countries recording large amounts of skipjack catches include the 🇲🇻 Maldives, France, Spain, 🇲🇾 Malaysia, 🇱🇰 Sri Lanka, and 🇮🇩 Indonesia. Skipjack is the most fecund of the main commercial tunas, and its population is considered sustainable against its current consumption. Its fishing is still controversial due to the methodology, with rod and reel or fishery options being promoted as ecologically preferable. Purse seine methods are considered unsustainable by some authorities due to excess bycatch, although bycatch is said to be much reduced if fish aggregation devices are not used. These considerations have led to the availability of canned skipjack marked with the fishing method used to catch it. Skipjack is considered to have "moderate" mercury contamination. As a result, pregnant women are advised against eating large quantities. In addition, skipjack's livers were tested globally for tributyltin (TBT) contamination. TBT is an organotin compound introduced into marine ecosystems through antifouling paint used on ship hulls and has been determined to be very toxic. About 90% of skipjack tested positive for contamination, especially in Southeast Asia, where regulations of TBT use are less rigorous than in Europe or the US.