size or modal size between the sexes are small. 

 Ueyanagi (1953) found, in the northwestern Pacific, 

 that the modal size of males is about 10 cm smaller 

 than that of females. Koga (1967) showed a length- 

 frequency distribution by sex for 210 fish from the Fiji 

 area in which the modal lengths for males and females 

 were 195 and 205 cm, respectively. In a sample of 105 

 striped marlin taken by longline off East Africa, 

 Williams (1967) found males did not exceed 240 cm 

 fork length (equivalent to 182 cm eye-fork length from 

 regression of Merrett, 1971). About 16 females were 

 taken above this length to a size of about 270 cm (205 

 cm eye-fork length). Merrett (1971), however, found 

 males up to 193 cm eye-fork length off East Africa. 

 Modal size differences between the sexes were not 

 found in Hawaiian fish (Strasburg, 1970) nor in the 

 eastern Pacific (Kume and Joseph, 1969b). 



3.12 Maturity 



As has been found in other pelagic species such as 

 albacore and dolphin, quantitative measure of 

 maturity for males is difficult. There is only a small 

 increase in testis size during the maturation cycle. 

 Merrett (1971) found little correlation between 

 relative testis size and maturity-stages based on 

 microscopic examinations. In fact, Merrett (1970) 

 suggests that there is continuous availability of sper- 

 matozoa in mature males based on differential 

 maturation of the testicular lobules and the posses- 

 sion of a muscular seminal vesicle. 



In the female, maturation is synchronous 

 throughout the ovary and seasonal maturation is ac- 

 companied by marked increase in relative size of the 

 gonads. Data from Kume and Joseph (1969b) showed 

 a twentyfold increase. Moreover, there is good correla- 

 tion of relative ovary weight and mean maximum egg 

 diameter (Merrett, 1971; Eldridge and Wares, 1974). 



Williams (1967) concluded from longline data in 

 East Africa that first maturity was reached between 

 180 and 200 cm fork length (50-80 lb) which is 

 equivalent to 141-157 cm eye-fork length (Merrett, 

 1971). Merrett reported similar results, 140-160 cm or 

 62-93 pounds. Ueyanagi (1957b) mentioned that 154 

 cm eye-fork length was the smallest size found in the 

 spawning group of the northwestern Pacific. Kume 

 and Joseph (1969b), using a gonad index, reported 

 that individuals from the eastern Pacific do not 

 regularly enter the spawning group until reaching 

 about 160 cm eye-fork length but found one as small 

 as 148 cm. Other data from the eastern Pacific 

 (Eldridge and Wares, 1974) agree with these con- 

 clusions. 



Since age at specific size is not known for striped 

 marlin, age at maturity is also unknown. Koga (1967), 

 however, stated "it is likely that growth rate of this 

 species shows different values between the Indian 

 Ocean and the Pacific Ocean and the groups in the In- 



dian Ocean attain maturity earlier than those in the 

 Pacific." 



3.13 Mating 



Nothing has been published relating to mating 

 habits of this species. 



3.14 Fertilization 

 Fertilization is externally. 



3.15 Gonads 



Merrett (1970) has described the gonads of billfish 

 in detail. The following description is taken from his 

 work. 



The gonads are paired organs lying in the posterior half of the 

 body cavity, on each side of the stomach and intestine. They are 

 suspended from the lateral edges of the chambered air bladder 

 by mesenteries . . . the gonads are almost bilaterally 

 symmetrical and both terminate at their point of discharge to 

 the exterior in the urino-genital papilla . . . which lies posterior 

 to, and in a common groove with, the anus . . . The urinary and 

 genital systems are closely linked. 



The ovaries are elongate sausage-shaped organs, which taper 

 at both ends, and joined only at their posterior ends ... A strong 

 muscular sheath binds the ovaries to the urino-genital papilla 

 and the basal part of the intestine. They are invested in thick 

 layers of connective tissue which sometimes contain deposits of 

 fat; fat is also occasionally found in the mesovarium. Beneath 

 the connective tissue the ovaries are pale flesh-pink to wine red 

 in colour, depending upon the stage of maturity. Internally, at 

 certain stages, a central lumen runs the length of the ovary . . . 

 the ovaries have been found to be unequal in length . . . either 

 ovary can be the longer of a pair. 



. . . Immediately posterior to . . . [the anal papilla] ... is the 

 urino-genital papilla. In the female this carries only the urinary 

 duct. The point of discharge of the ovaries is situated between 

 the bases of the anal papilla and the urino-genital papilla. 



This opening between the anal and urino-genital 

 papillae which is absent in the males should serve as 

 an external characteristic in distinguishing the sexes. 

 But in the experience of the junior author this 

 difference is difficult to observe consistently in this 

 species. It is more obvious in the sailfish. 



Nakamura (1949) stated that the fecundity of 

 billfishes ranges from 1 to 1.2 million eggs, depending 

 on fish size and species. Morrow (1964) estimated 2 

 million eggs for New Zealand marlins. These appear 

 to be low estimates, however. Merrett (1971) reported 

 an estimated fecundity of 12 million for one Indian 

 Ocean specimen of 182 cm eye-fork length, 126 pounds 

 with ovary weight of 1.53 kg, and mean maximum egg 

 diameter of 0.470 mm. Eldridge and Wares (1974) 

 reported fecundity estimates of three eastern Pacific 

 specimens which ranged from 11 to 29 million eggs. 

 These fish ranged in size from 150 to 180 cm eye-fork 

 length but the fecundities showed no relation to size of 

 the fish. Gosline and Brock (1960) estimated 13.8 



140 



