608 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Fig. 326. Lateral views of scombrid larvae from top to bottom: Scomber japonicus. 5.0 mm NL, modified after Kramer (I960); and Gram- 

 matorcynus bilineatus, 4.1 mm SL, modified after Nishikawa (1979). 



tirostris and T. helone. the latter to T. albidus (Robins, 1974). 

 Nakamura (1974) recognized two species of blue marlins, the 

 Atlantic A/, nigricans and the Indo-Pacific M. mazura instead 

 of only M. nigricans. Morrow and Harbo (1969) considered 

 Istiophorus monotypic; Nakamura (1974) recognized the At- 

 lantic sailfish /. albicans as specifically, or subspecifically, dis- 

 tinct from the Indo-Pacific /. platypterus. 



Development 



Eggs. — No information is available on the identification of is- 

 tiophorid eggs, except for a brief account of eggs identified as 

 Tetrapturus belone by Sparta (1953). 



Larvae.— Three studies, all of which appeared in 1974, sum- 

 marized the identification status of istiophorids (Richards, 1974; 

 Ueyanagi, 1974a, b). These larvae are extremely difficult to 

 identify. Two types of larvae are generally recognized— those 

 with short bills and those with long bills. The short-billed group 

 is generally referable to Makaira, the long-billed group to Is- 

 tiophorus and Tetrapturus (Fig. 322). Specimens less than 7.0 

 mm in length are all very similar. Other useful characters include 

 melanophore distribution on thegularand branch iostegal mem- 

 branes, relation of the pterotic and preopercular spines with the 

 body axis, shape of the orbit and position of the eye. 



Meristic factors such as fin ray counts and vertebral formula 

 are not particularly useful in distinguishing istiophorid species 



from each other (Richards, 1974; Tables 154and 155). Vertebral 

 counts can be used to distinguish Istiophorus and Tetrapturus 

 (12 + 12 = 24) from Makaira (11 + 13 = 24) at sizes greater 

 than about 20 mm (Richards, 1974). Probably the most useful 

 character is head morphology (Ueyanagi, 1963a). The snout is 

 short in all istiophorid larvae under about 5 mm in body length, 

 but in larger specimens the snout lengthens greatly in Istiophorus 

 and Tetrapturus. At lengths greater than about 1 2 mm, the 

 elongate snouts of Istiophorus and Tetrapturus readily distin- 

 guish them from the shorter-snouted Makaira. Thus, in ver- 

 tebral numbers and relative snout length, Istiophorus and 

 Tetrapturus are more similar to each other than to Makaira, 

 confirming the first subdivision in the family shown in Fig. 321. 

 For Pacific species, larval and juvenile stages are known for 

 all species except juvenile black marlin, M. indica. Makaira 

 indica larvae have a characteristic pectoral fin which is erect 

 from the body in larvae and adults and presumably juveniles, 

 too. Makaira mazara lai^ae are characterized by a short snout, 

 large eyes, and forward placement of the anterior edge of the 

 orbit. The characteristic lateral line appears in juveniles at about 

 30 mm SL. Tetrapturus aiida.x larvae do not have forward pro- 

 jecting orbits and the center of the eye is located at the same 

 level as the tip of the snout. The pterotic spine is parallel to the 

 body axis, and the preopercular spine is inclined sharply down- 

 ward, forming a large angle with the body axis. Melanophores 

 occur above the midline of the gular membrane or on the mid 



