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Author: (Linnaeus, 1758)

Katsuwonus pelamis (Linnaeus, 1758)

Diagnosis: body fusiform, elongate and rounded. Gillrakers numerous, 53-63 on first gill arch. 2 dorsal fins separated by a small interspace (not larger than eye), the first with 14-16 spines, the second with 13-16 rays, followed by 7-9 finlets; anal fin with 13-16 rays followed by 7 or 8 finlets; pectoral fins short, 24-28 rays. Inter-pelvic process small and bifid. Body scaleless except for the corselet and lateral line. A strong median keel on each side of caudal peduncle between 2 smaller keels. Bony keels on caudal peduncle vertebrae well developed. Swimbladder absent. Intestine straight, without folds. Dorsal and ventral branches of the cutaneous artery about equally well developed. Right lobe of liver somewhat longer than left and central lobes. Vertebrae 20 + 21 = 41. Vertebral trelliswork moves dorsal aorta ventrally less than in Euthynnus and more than in Thunnus. Colour: back dark purplish-blue, lower sides and belly silvery, with 4-6 very conspicuous longitudinal dark bands. Size: to 108 cm fork length, 35 kg, common to 80 cm.

Habitat: pelagic in the high seas in warm and warm-temperate waters. Schooling and migratory. Food: fishes, crustaceans and cephalopods. Reproduction: spawns all year long in tropical waters, from April to September off the coast of North Africa. Eggs and larvae planktonic.

Distribution: found throughout the southern part of the area except the furthest south-eastern part of the Mediterranean basin. Occasional in the Bay of Biscay. Isolated catches from the British Isles, Danish Straits and coast of Norway. Elsewhere, cosmopolitan in tropical and subtropical seas.

Eggs, larvae and young stages. Ehrenbaum, 1924: 30, fig. 7a-7c (larvae) (?) | Padoa, 1956: 499, fig. 336-338 (larvae) (?) | Marchal, 1963b: 223, fig. 12-16 (larvae and post-larvae) | Postel, 1963: 532 | Bini, 1968: 54, 3 fig. | Zhudova, 1969 (transl. Klawe, 1970): 5, fig. 5 (larva).
Otoliths (sagitta). Fitch & Craig, 1964: 204, fig. 6b.

Skipjack tuna (Katsuwonus pelamis)