

O 



X 



UJ 



50 



40 



30 



20 



10 



-i_ 



-L. 



M 



M J J 

 MONTH 



N [) 



Figure 4. — Monthly growth of embryos of Sphyrna lewini. 

 Solid triangles indicate the uterine eggs. Error represent 2 SD; 

 numerals, sample size. 



Counts of the number of uterine embryos as 

 well as eggs of 110 gravid females (230-320 cm 

 TL) ranged between 12 and 38 (mean 25.8). The 

 relationship between the total number of uterine 

 embryos or eggs and the size can be described by 

 the regression equations (Fig. 5): 



N = -26.105 + 0.179L, 



where N is litter size, and L is total length in cm 

 of the female. There is considerable variation in 

 number of embryos with length, and the correla- 

 tion coefficient r is low (0.567), but obviously fe- 

 cundity is related to the size of the parent. 



Examination of all females carrying developing 

 embryos showed that occasionally some uterine 

 eggs failed to develop. The number of nondevelop- 

 ing uterine eggs carried by a single female was 

 1-4. 



As with litter size, the number of ovarian eggs 

 increased with the length of the adult female. 



The embryos from 51 gravid females were 

 sexed; of a total of 1,281 embryos, 637 were fe- 

 males. The sex ratios of embryos differed by litter; 

 for instance, some individuals had predominantly 

 male (13:5) or predominantly female (23:10) lit- 

 ters. But, as a whole, sex ratio was about 1:1. 



The ratio of males to females for immature 

 sharks in northeastern Taiwan waters was about 

 1:2 (42:91), but decreased to about 1:5 (95:446) for 

 mature individuals (Table 1). There was no ap- 

 parent increase in the relative number of males 

 in the catch during the parturition season. 



Discussion 



Scalloped hammerhead sharks are abundant in 

 the coastal seas around northeastern Taiwan, es- 

 pecially during the spring and winter, and are 

 captured by harpoon or drift longlines at or near 

 the surface. Rarely individuals smaller than 120 

 cm TL are captured because fishing gear and 

 strategy are likely selective for larger fish. 

 Clarke (1971) reported that in Hawaii, scalloped 

 hammerhead pups usually stay close to the bot- 

 tom. 



Approximately equal numbers of male and fe- 

 male scalloped hammerhead sharks are born, al- 

 though a much higher proportion of females than 

 males are caught in the studied area. We are un- 

 certain whether scalloped hammerhead females 

 are more vulnerable to the fishing gear or are 

 simply more numerous in this area. Similar pre- 

 dominances in females in the catch have been 

 found in the scalloped hammerhead in the Gulf of 

 California (Klimley 1981; Klimley and Nelson 

 1981). During the summer in 1979 off Baja Cali- 

 fornia, females outnumbered males by 1.6 x at 

 Isla Cerrolvo, 3.8 x at the El Bajo Seamount, and 



40 



38- 



32 



28 - 



o 

 > 



a: 



00 



UJ 



24 



S 20 



z 

 18 



12- 



240 280 280 300 320 



TOTAL LENGTH (cm) 



Figure 5. — Relationship between fecundity (number of 

 uterine eggs or embryos) and total length of Sphyrna 

 lewini females. 



392 



