Some Aspects of the Systematics and Distribution of Billfishes 



IZUMI NAKAMURA' 



ABSTRACT 



Until recently the classification of billfishes (Xiphiidae and Istiophoridae) was confused. Recent 

 worl^ers have consolidated the nominal species and reduced the number of species considerably. A key, with 

 figures, is presented which includes two families, four genera, and 1 1 species. Makaira mazara is considered 

 distinct from M. nigricans because of consistent differences in the pattern of the lateral line system. 

 Tetrapterus platyplerus is tentatively separated from T. albicans although existing differences are minor 

 and could be referable to the subspecific level. The worldwide distribution of billfishes is given; distributions 

 are based primarily on data from the Japanese longline catch for 1964-69. 



Despite their importance to sport and commercial 

 fisheries and the large size attained by many of them, 

 the fishes of the superfamily Xiphiicae (families 

 Xiphiidae and Istiophoridae) have been little under- 

 stood and until recently their systematics have been 

 highly confused. The separation and nomenclature 

 of the species of billfishes has been a difficult prob- 

 lem; this arises partly because the structure and 

 characteristics of some "'species"" are quite similar, 

 and also because the original description of most of 

 the species has been inadequate. Thus, it is impossi- 

 ble to identify the different species immediately from 

 the original descriptions. 



Goode (1880. 1882) classified the billfishes of the 

 world into one family, two subfamilies, four genera, 

 and 17 species. Jordan and Evermann (1926) clas- 

 sified the billfishes into two families, four genera, 

 and 32 species. Recently LaMonteand Marcy (1941) 

 and Rosa (1950) classified the billfishes into four 



genera, 13 species and four subspecies, and four 

 genera, 15 species and four subspecies, respectively, 

 in their re visional works. Several authors have con- 

 tributed substantially to the knowledge of the Indo- 

 Pacific billfishes (e.g. Nakamura, 1938, 1949; 

 Royce, 1957; Howard and Ueyanagi, 1965). Robins 

 and de Sylva (1960, 1963) provided comprehensive 

 discussions of the systematics of the Atlantic bill- 

 fishes. 



Nakamura, Iwai, and Matsubara ( 1968) classified 

 the billfishes of the world into two families, four 

 genera, and 1 1 species, using external and internal 

 characters such as shapes of snout, fins, skull, ver- 

 tebrae, viscera and nasal rosette, compression of 

 body, position of anus, pattern of lateral line system, 

 arrangement of scales, relative position of second 

 dorsal and second anal fins, color and color patterns. 

 The key given below is modified after that paper. 



Key to Families, Genera and Species of Billfishes (See Figure 1 for illustration of key characters) 



la. No pelvic fin. A single caudal keel on side. Snout long and swordlike in shape and 

 depressed in cross-sectional view. No scales on body. No teeth. Base of first dorsal 



fin short and well separated from base of second dorsal fm (Xiphiidae, Xiphias) 



Swordfish, Xiphias gladius Linneaus, Figure 1 A 



'Fisheries Research Station. Kyoto University, 

 Kyoto 625, Japan. 



Maizuru, 



45 



