between egg number and fish size is not given, he 

 provides the estimates of 6,200,000 and 2,100,000 eggs 

 per spawning for two T. angustirostris, both 1,390 mm 

 long (measured from center of orbit to shortest caudal 

 ray). The latter estimate is made on unovulated eggs 

 only. 



3.16 Spawning 



Nakamura (1938) assumes that spawning of the 

 billfishes probably does not, as in other fishes, take 

 place in large groups over a very short period of time, 

 but probably is continuous over a long period and over 

 a broad area of the sea. The reason for this, he states, 

 is that it is known that in a single area fish with ripe 

 eggs and those with unripe eggs are found mingled 

 together over a period as long as 2 mo. 



Nakamura (1943) mentions that spawning of the 

 sailfish in a group takes place as individuals become 

 ripe and that the male fish follows the female at the 

 time of breeding. 



3.17 Spawn 



Merrett (1970) shows the frequency distribution of 

 the diameters of eggs shed by this species, which 

 ranges roughly from 1.30 to 1.60 mm with a mean of 

 1.442 mm. 



According to Nakamura (1937, 1938), the eggs 

 released from the ovary and preserved in alcohol are 

 spherical and about 1 mm in diameter. The ovarian 

 eggs, which are nearly mature (not fully ripe), are 

 almost colorless and translucent, with slightly 

 yellowish brown oil globules which unite until they 

 grow into two fairly large globules. At this stage, the 

 egg is nearly 0.8 mm in diameter. 



3.2 Preadult Phase 



3.21 Embryonic phase 

 No information is available. 



3.22 Larvae phase 



Morphology of this fish at the postlarval stage (Fig. 

 5) was studied based on about 90 specimens ranging 

 in total length from 2.5 to 83 mm collected from the 

 tropical and subtropical areas of the Pacific Ocean 

 (Ueyanagi, 1962). 



The ratio of the snout length to body length in- 

 creases until the larva grows to about 50 mm in 

 length. Among billfishes, T. angustirostris ranging 

 from 20 to 50 mm in length has the largest snout 

 relative to the body length. 



The ratio of the head length to body length in- 

 creases rapidly until about 7 mm in length, then in- 

 creases less rapidly up to about 50 mm in length. The 

 ratio of the head length is about 50% at 7 mm and 

 about 60% at 50 mm in length. The ratio seems to con- 

 tinue to decrease gradually afterward. A wide space 



between the anus and the origin of the first anal fin, 

 which is characteristic of this species, is already seen 

 in larval fish larger than 20 mm long. 



The pterotic and preopercular spines are formed at 

 about 4 mm in length. As growth proceeds, this spina- 

 tion and the serration over the orbit and on the lower 

 edge of the lower jaw are rapidly developed until they 

 eventually undergo degeneration at about 20 mm in 

 length. At this stage, the minute spiny scales begin to 

 appear on the opercle and the surface of the body. In 

 larvae greater than 70 mm, the spiny scales cover the 

 whole surface of the body and the lateral line becomes 

 evident. The palatine teeth appear at about 4 mm in 

 length. There are 30 or more teeth on the upper jaw in 

 fish about 20 mm in length. In larvae larger than 30 

 mm in length the teeth are beginning to degenerate. 



The vertical fins are membraneous and not yet 

 differentiated in larvae smaller than 4 mm. The ven- 

 tral fins are formed in larvae over 4 mm long and at 

 about 7 mm, the dorsal fin and the caudal fin are 

 clearly differentiated. The fin rays and the hypural 

 plate are also formed. At about 20 mm in length, the 

 full complement of fin rays is reached. As develop- 

 ment further advances, the dorsal fin becomes higher 

 and saillike. The pectoral fins and the ventral fins 

 become more elongate and the caudal fin is forked. 



Melanophores are found on the body from the very 

 early stage of development. At 2.4 mm in length, the 

 melanophores appear on the head, the dorsal and the 

 lateral sides of the trunk, and the dorsal wall of the 

 body cavity. They are also visible along the urostyle, 

 inside the isthmus, on the tip and the mid-part of the 

 ventral side of the lower jaw, and on the 

 branchiostegal membrane. The melanophores on the 

 branchiostegal membrane is characteristic of T. 

 angustirostris at the larval stage. As development 

 proceeds, the pigmentation on the side of the body ex- 

 tends posteriorly and ventrally and covers the greater 

 part of the caudal region at about 7 mm in length. The 

 chromatophores appear on the dorsal fin in larvae 

 over 15 mm, and at about 20 mm the whole side of the 

 body is pigmented except for the tip of the hypural 

 plate. A trace of the melanophores on the 

 branchiostegal membrane is visible even in a 

 specimen as large as 76 mm in length. 



3.23 Adolescent phase 



The following description is for a young specimen 

 514 mm in standard length (measured from bill tip to 

 end of hypural plate) reported by Watanabe and 

 Ueyanagi (1963). 



The snout is elongate, being 26% as long as the body 

 length (posterior margin of eye to end of central ray of 

 caudal fin). The ratio of the upper jaw length to the 

 lower jaw length is approximately 2:1. There is a 

 dense growth of minute conical teeth on both upper 

 and lower jaws, giving a filelike touch. The outer teeth 

 are larger and found in rows and the inner teeth are 

 coarsely implanted. Palatine teeth present. The gill 



46 



