Skipjack Tuna, Katsuwonus pelamis
Skipjack Tuna, Katsuwonus pelamis. Fish caught from coastal waters off El Tule, Baja California Sur, November 2004. Length: 45 cm (18 inches).
Skipjack Tuna, Katsuwonus pelamis. Fish caught from coastal waters off Point Palmilla, Baja California Sur, November 2017. Length: 48 cm (19 inches).
Skipjack Tuna, Katsuwonus pelamis. Fish caught by via a gill net in coastal waters off Puerto Adolfo Lopez Mateos, Baja California Sur, October 2017. Length: 46 cm (18 inches). Interesting these are considered to be a “Catch and Release” species and not sellable to local fish buyers even though they are the number two commercial fish globally.
Skipjack Tuna, Katsuwonus pelamis. Fish caught from coastal waters off San Quintin, Baja California, August 2022. Length: 50 cm (20 inches). Catch, photographs, and identification courtesy of Chris Wheaton, Fullerton, California.
Skipjack Tuna, Katsuwonus pelamis. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, September 2014. Length: 51 cm (20 inches).
The Skipjack Tuna, Katsuwonus pelamis, is a member of the Mackerel or Scombridae Family, that is also known as the Blue Bonito and in Mexico as barrilete listado. This fish is the only species in the genus Katsuwonus and is found in Mexican waters of both the Atlantic and the Pacific Oceans.
The Skipjack Tuna has an elongated rounded fusiform tuna-like body that are designed aerodynamically for speed. They are silvery overall with a purplish blue back and a series of 4 to 6 prominent wavy lines on the lower half of their body. Their mouth is moderately large and extends to the center of their eyes. They are equipped with a single row of slender conical teeth on both jaws. Their anal fin has 14 or 15 rays followed by 7 to 9 finlets; their caudal fin is deeply forked with 2 small keels separated by 1 large keel at the base; their first dorsal fin has 14 to 16 spines; their second dorsal fin is set close to the first and has 14 or 15 rays followed by 7 to 9 finlets. They have 53 to 63 gill rakers. The front of their body is covered with numerous scales.
The Skipjack Tuna is a highly migratory pelagic fish found in all global oceanic waters with temperatures between 14.7oC (58oF) and 30oC (86oF). They have the ability to regulate their body temperature to levels above their environments. They are found on the surface during the day and descend to depths up to 595 m (1,955 feet) at night. They reach a maximum of 1.08 m (3 feet 7 inches) in length and 34.5 kg (76 lbs) in weight. As of March 31, 2023, the International Game Fish Association world record for length stood at 73 cm (2 feet 5 inches) with the fish caught from within the Red Sea in February 2022. The corresponding world record for weight stood at 21 kg (46 lbs 8 oz) with the fish caught in coastal waters off Spain in November 2020. They are a schooling species known to travel with sharks, whales, and other tuna; in the Atlantic they travel specifically with the Blackfin Tuna, Thunnus atlanticus. They frequently collect under drifting objects, marine mammals or man-made structures. They compete for food with Albacore, Dorado, Frigate Mackerel, Rainbow Runners, Yellowfin Tuna, Whale Sharks, and various sea birds. They are opportunistic daytime feeders consuming fish including anchovies, herrings, and sardines, as well as crustaceans and mollusks; cannibalism is also common with this species. In turn they are an important prey for large pelagic fish and sharks. Reproduction is oviparous with each female spawning on a continual daily basis releasing small batches that total 80,000 and 2,000,000 eggs annually. Larger females produce exponentially more eggs than smaller fish. Their eggs and larvae are pelagic. They have a lifespan between eight and twelve years.
The Skipjack Tuna is a resident of Mexican waters of the Atlantic and the Pacific Oceans with the exception that they are absent from the northern 75% of the Sea of Cortez.
The Skipjack Tuna is fairly easy to identify due to the stripes on its belly. It can be confused with the Black Skipjack, Euthynnus lineatus (distinguishing black spots or blotches between pelvic and pectoral fins), the Pacific Bonito, Sarda chiliensis (5 or 6 oblique dark stripes on upper back), and the Striped Bonito, Sarda orientalis (8 to 11 broken horizontal stripes on upper back).
From a conservation perspective the Skipjack Tuna is currently considered to be of Least Concern with stable, widely distributed populations. Their populations are believed to be in decline in the Atlantic and stable in the Pacific with a noteworthy reduction in catch sizes due to increased fishing pressure. They have a wide global distribution, and are relatively abundant, fast-growing and very fecund. Their long-term viability is currently enhanced by a significant reduction in the number of their large oceanic predators which have been removed by overfishing. They are heavily fished commercially on a large global scale and represent 60% of the global commercial tuna catch with annual levels approaching 2,500,000 tons. This makes them the second most captured fish globally, second only to the Peruvian Anchoveta, Engraulis ringens. They are caught primarily near the surface during daylight hours in purse seines. Man-made floating structures are currently being employed to attract them which are monitored by aerial spotter planes. They are considered an excellent food fish and sold fresh, frozen, dried, salted, smoked, and predominately canned. They are also an important component of global artisanal fishermen and caught with hook and line. Due to their size, coastal habitats, and horrific fights when hooked they are also a favorite target of recreational sports anglers and caught on light gear using plugs, spoons, feathers, and strip bait. They are used extensively in Japanese cuisine (sashimi and sushi). However, they are known to contain mercury, tributyltin (an antifouling paint used on ship hulls) and ciguatoxin.