?L; (j) 37.1 mm SL; (k) 55.1 mm SL; (1) 98.9 mm SL; (m) 155 

 nm SL; (n) 216 mm SL (from Gehringer, 1956, 1970). 



of marked differences from their respective adults, generally 

 speaking, in their morphological characteristics. This is par- 

 ticularly true with those of very early stage before the snout 

 develops its specific characteristics. However, the specific 

 separation of the larvae is possible throughout their entire range 

 mainly on the basis of their head profile. 



Following are the criteria for identification: 



(1) Larvae under 5 mm in length: The characters, as shown 

 in Table A [Table 2], can be used for specific separation, 

 although snout length does not provide a useful clue. 



(2) Larvae between 5 and 10 mm in length: Besides the 

 criteria given in Table A [Table 2], snout length and size of eyes 

 can be used. Black marlin larvae are recognized by their 

 snout. . . . The ratio of snout length to diameter of orbit is 

 largest in sailfish, smallest in black marlin, and is between in 

 shortnosed spearfish. More precisely, the ratio tends to be :»1 in 

 sailfish, ■= 1 in black marlin, and=l in shortnosed spearfish in 

 specimens 7 — 8 mm length. 



(3) Larvae between 10 and 20 mm in length: They are 

 grouped into two on the basis of their snout length; the long 

 snout group with shortnosed spearfish, sailfish and striped 

 marlin, and the short snout group with black marlins. In the 

 former, the snout length exceeds 1/5 of their body length, while 

 in the latter, it does not. For the specific separation of the former 

 group. Table A [Table 2); shortnosed spearfish is dis- 

 tinguishable by black chromatophores on brachiostegal mem- 

 brane, while sailfish is separated from striped marlin by the 

 difference of their head profile: Unlike striped marlin with a 

 straight snout, sailfish has a beak-like snout. And because of 

 this difference in the shape of the snout, they are separable by 

 the difference of the location of snout in terms of the center of 

 eyes. In sailfish, the center of eyes is above the tip of snout, 

 while in striped marlin, they are on a nearly same level. 



Separation of white marlin from black marlin can be made 

 on the basis of the form of the pectoral fin. 



(4) Larvae over 20 mm in length: On top of the criteria of 

 Table A [Table 2], the following characters, as listed in Table B 

 [Table 3], can be applied. 



In addition to the above, the distance between anus and the 

 first anal fin insertion works as a reference to discriminate short- 

 nosed spearfish. The distance of the said species is larger, as 

 compared with other species. 



The vertebral formulae are also useful tools for separation: 

 the formulae of shortnosed spearfish, sailfish and striped marlin 

 are all 12+12, while those of black and white marlin are 11 + 13. 



Ueyanagi (1964) discussed some of the misiden- 

 tifications of sailfish larvae made by Sun (1960). He 

 stated that Sun's specimen No. 3 (Fig. 5c; 19.1 mm 

 total length) and No. 4 (Fig. 5d; 30.5 mm total length) 

 seem to be blue marlin. Ueyanagi (1959) pointed out 

 that the larvae identified tentatively by Gehringer 

 (1956) as Tetrapturus belone are probably blue 

 marlin. He added that Gehringer 's (1956) sailfish 

 figures 6, 10, and 14 closely resemble striped marlin 

 young and hence may be the larvae of the Atlantic 

 cognate of striped marlin, namely white marlin, T. 

 albidus. 



Little is known on the biology of young sailfish. 



105 



