THE TUNA INDUSTRY 89 



mercial bluefin may consist of more than one species. A fifth species, Uttle 

 tuna, has been taken in some years but in amounts of less than 1 per 

 cent of the whole catch. 



The tunas are pelagic, fast-swimming fish of compact, rounded, but 

 streamlined appearance. They are distinguished, apart from their general 

 shape, by a number of small finlets along the dorsal and ventral lines 

 posterior to the second dorsal and anal fins. Their anatomy is described 

 in some detail by Kishinouye^^, GodsiP\ Godsil et al}^, and more briefly 

 by Nakamura^^ The taxonomy of the tunas is still a matter of some dis- 

 pute, and in consequence, alternative systematic names are often used 

 by different writers for each species. Although virtually only the four 

 species mentioned are used for canning in the United States, several 

 others are known, and the United States Federal Standard of Identity 

 for Canned Tuna^ lists additional species which may be used. However, 

 these do not include the yellowtail and bonito which are generally clas- 

 sified as ''tuna-like" fishes and may not be identified as ''tuna." It does 

 not distinguish the big-eyed tuna (Parathunnus sibi), which is similar to 

 yellowfin in appearance and is, in fact, caught and included with yellow- 

 fin in commercial catch records. 



The tunas are carnivorous and consume a widely-varied diet, the 

 composition of which appears to be largely influenced by availabihty^-^. 

 They are found in the mixed warm upper layers of water which cover 

 much of the surface of the temperate and tropical oceans. These layers 

 which run down to the thermocline or region of abrupt temperature 

 lowering are mostly fairly shallow in the Eastern Pacific and Eastern 

 Atlantic but as deep as 200 fathoms in the Western Ocean areas. The 

 different species are located and harvested in their characteristic fashions, 

 and so each will be separately described below. 



Albacore {Thunnus germo). Albacore is a large tuna distinguished by 

 a long pectoral fin. It is regarded by the consumer as a premium fish 

 owing to the light color of the cooked flesh. The American fishery located 

 on the Pacific Coast is seasonal, operating from June to October, and 

 the catch is quite variable from year to year. Trolling and live-bait fish- 

 ing methods are used to catch albacore, although recently seiners have 

 had some success. The Japanese albacore fishery is mostly a long-line 

 operation, except seasonally around the home islands. Long-liners which 

 freeze their own catches and mothership-catchers units which range into 

 the South Pacific, Indian, and South Atlantic areas account for the 

 greater part of the production. Much of the fish from these is sold locally 

 or transhipped for United States canneries. 



Yellowfin (Neothunnus macropterus). This fish derives its name from 

 the bright irridescent color seen on the fins and finlets of the live or 



