in maturation through June and July, at which time 

 our sampling stopped. Several factors suggest that 

 striped marlin move away from our sampling area at 

 this time. Migration patterns indicated by Kume and 

 Joseph (1969a) and Squire (1974b) showed that 

 striped marlin move west-southwesterly from the 

 coastal areas as the year progresses. Also, the data 

 from the sport fishery (Fig. 2) show concentrations 

 of striped marlin decreasing after March at Mazatlan 

 and after July at Buena Vista. During July, Japanese 

 longline fishermen have noted fully mature striped 

 marlin in increased concentrations around the Revil- 

 lagigedo Islands (G. Adachi, pers. comm.). The fish 

 appeared in pairs and when one was hooked the 

 other would remain alongside until the fish was 

 hauled aboard. This behavior was not noticed in 

 other areas of the eastern North Pacific or during 

 other times of the year. Ovaries provided to us by 

 the longliners from that area were all ripe and 

 ranged in gonad index from 4.42 to 9.53 and the 

 ova diameters were all in excess of 1.25 mm. 



Sex ratio for striped marlin showed a slight but not 

 significant predominance of males at Mazatlan from 

 late February to July. In the larger and seasonally 

 later catches at Buena Vista, males tended towards 

 60% from April through early June. The ratio then 

 remained close to 50% into August. The October- 

 early November ratios were also near 50%. Off San 

 Diego, male striped marlin averaged only about 30% 

 up to late September but rose to almost 50% for the 

 rest of the season. 



From these data it is logical to suggest that striped 

 marlin migrate away from the coastal areas near the 

 Gulf of California to spawn during July and possibly 

 August. Females sampled at San Diego in August 

 were in a post spawning condition and all had gonad 

 indices less than 1.0. 



Available evidence suggests that sailfish spawn 

 nearshore in the eastern North Pacific with a north- 

 ward progression of spawning activity during the 

 year. Kume and Joseph (1969b) noted that some 

 sailfish from Costa Rica coastal waters were in 

 spawning condition from February to March. At the 

 same time sailfish from offshore waters from lat. 0° 

 to 15° were immature. Yurov and Gonzales (1972) 

 reported spawning in the Gulf of Tehuantepec ex- 

 tending from February to April. We measured 36 

 larval and juvenile sailfish collected by Scripps In- 

 stitution of Oceanography and the National Marine 

 Fisheries Service along the Central American coast. 

 Estimated spawning dates for these specimens based 

 on back calculations using the growth rates of de 



Sylva (1957) indicated spawning of Costa Rican 

 specimens from December through March, 

 Guatemalan specimens mostly from January 

 through April (with two in August), and Mexican 

 specimens from April through November. 



Our data conform to this pattern. Sailfish began to 

 mature in late May and reached spawning condition 

 in June and July (Fig. Hand 15). The average gonad 

 index showed a rapid decline in July, but this may be 

 an artifact of a sharply reduced sample size. The ova 

 remained large. 



From April through July the sex ratio of Mazatlan 

 sailfish remained close to 50%. Slightly more 

 females than males were found until early June, after 

 which time the ratio tended towards males. The 

 smaller numbers of sailfish caught in Palmas Bay 

 were predominantly female with males never ex- 

 ceeding 50%. 



PARASITES 



Among the incidental observations of parasites 

 perhaps the most significant was the discovery of 

 Philichthys xiphiae Steenstrup in the opercular bone 

 in several striped marlin at Buena Vista and 

 Mazatlan. Previously this species had been reported 

 from the mucous canals of swordfish (Xiphias 

 gladius) but not from any of the istiophorids and not 

 from the eastern Pacific. The parasites were embed- 

 ded in the preopercle just beneath the skin. The 

 differences between parasitized and normal bones 

 are readily seen in the x-ray photos in Figure 16. 

 Other possible infection sites (bones) were not 

 checked for this parasite nor were other billfish 

 species. 



MP OCT NOV OtC 



Figure 14. — Mean gonad index distribution and the 

 number of sailfish sampled by month from Buena Vista 

 and Mazatlan. 



97 



