212 



BULLETIN OF THE BUREAU OF FISHERIES 



Size. — This bonito grows to a length of about 30 inches. 



General range. — Warmer parts of all the great oceans — Atlantic, Pacific, and 

 Indian. 



Occurrence in the Gulf of Maine. — A single specimen obtained at Provincetown 

 in 1S80 by J. Henry Blake is the only record for this oceanic fish in the Gulf. It 

 sometimes appears in numbers about Woods Hole, where 2,000 to 3,000 were 

 taken in 1878, but where it did not show again until October, 1905.'- 



77. Tuna {Thvnnus thynnus hmnmus,) 

 Horse-mackerel; Great albacore; Tunny; Albacore 



Jordan and Evermann, 1896-1900, p. 870. 



Description. — The two dorsal fins of the tuna are practically continuous — a ciiar- 

 acter, with the large number of finlets, sufficient in itself to separate a small one 

 from the true mackerels. It is readily separable from the striped bonito and little 

 tunny by the fact that the entire trunk, including the belly, is scaly, and from the 



Fig. 90.— Tuna ( Tliunnus thynnus). After Schmidt 



common bonito (p. 215) by the height and outline of its second dorsal and anal fins 

 as well as by the small size of its jaw teeth, and by the fact that its vomer (on the 

 midline of the roof of the mouth) is armed with hairlike teeth. The tuna is shaped 

 like a bonito rather than a mackerel, with robust body, about one-fourth as deep 

 and one-sixth as thick as long, tapering to pointed nose and very slender caudal 

 peduncle which bears a strong median longitudinal keel on either side. The first 

 dorsal (13 or 14 spines), originating just behind the axil of the pectoral, is triangular, 

 tapering regularly backward from its first spine and with the last spine very short 

 indeed. The second dorsal (about 13 rays) is almost confluent with the first — 

 slightly lower than the latter in young and higher in old fish. It is much liigher 

 than long, falcate, deeply concave behind, and its angle sharp pointed. The anal 

 originates under the rear end of the second dorsal to which it is similar in outline 

 and size (about 12 rays). There arc usually 9 or 10 dorsal and S or 9 ventral finlets 



" Tie little tunny or bonito, Gymnosarda atteterata, is much commoner in the Woods Hole region, appearing regularly in July 

 and August, and is more apt to be caught in the Oulf of Maine than is the striped bonito, though not actually recorded there. 

 It is separable from the latter by the fact that its lower sides are plain silver without the stripes of the striped bonito: that the hind 

 part of its back is marked with wavy bands and spots, whereas in the latter it is plain; that its lateral line is not curved below the 

 second dorsal; and that its anal fin originates farther back, under the first dorsal finlet. 



