complimentary to that of the blue marlin, Makaira 

 nigricans, which occurs primarily in the summer 

 (Strasburg, 1970). 



In the eastern Pacific, striped marlin are present 

 throughout the year from lat. 30°N to 30°S. High 

 abundance is maintained throughout the year in the 

 areas of the Revilla Gigedo Islands, Baja California, 

 Ecuador, the Galapagos Islands, and in the high-sea 

 area bounded by long. 90°-110°W and lat. 10°-30°S 

 (Kume and Joseph, 1969b). Seasonal changes in ap- 

 parent density are marked. The concentration 

 between Baja California and the Revilla Gigedo 

 Islands, which is restricted to a narrow band in the 

 first quarter, expands southeast along the coast and 

 seaward to long. 115°W during the second quarter, 

 and then north to lat. 28°N, south to lat. 3 C N and 

 seaward to long. 125°W during the third quarter. Dur- 

 ing the fourth quarter the southern extension expands 

 further to long. 130°W. Another seasonal concentra- 

 tion develops in the second and third quarters in the 

 offshore area between long. 100° and 115°W centered 

 at about lat. 8°-13°N. The area of high density around 

 the Galapagos Islands extends eastward to the coast 

 of Ecuador in the third and fourth quarters and then 

 recedes again in the first. 



The sport fisheries for striped marlin off Mexico 

 and southern California are seasonal. In southern 

 California it is highly seasonal with almost all fish be- 

 ing taken between August and October. In Mexico 

 some fish may be taken year round, but the best 

 fishing occurs from December through March at 

 Mazatlan and April through August near the tip of 

 Baja California (Eldridge and Wares, 1974). 



In addition to differential distribution in density, 

 there is also some differential distribution in size. In 

 the eastern Pacific, fish on the southern spawning 

 grounds are larger than those on the northern. The 

 length frequency of the southern group has a single 

 mode at 180-200 cm whereas that of the northern 

 group has two modes, one at 140 cm and one at 180 cm 

 (Kume and Joseph, 1969b). In the western Pacific 

 latitudinal stratification occurs. Honma and 

 Kamimura (1958) show small marlin occurring in 

 equatorial waters; these small fish are absent in the 

 region of lat. 5°-16°S. In mid-latitudes (15°-30°S) of 

 the central South Pacific longitudinal stratification is 

 apparent; larger fish ( > 180 cm) occur in the western 

 Pacific (Koga, 1967). There may also be some vertical 

 stratification. Furukawa, Koto, and Kodama (1958) 

 found harpooned fish to be larger than longline- 

 caught fish in the East China Sea. The harpooned fish 

 were also fatter at a given length. 



Off Formosa the smaller fish, which were long 

 thought to be the separate species Kajikia formosana, 

 occur with the shortbill spearfish, Tetrapturus 

 angustirostris, offshore from the center of the 

 Kuroshio, while the larger fish occur inshore 

 (Nakamura, 1949). 



2.3 Determinants of Distribution Changes 



Probably behavioristic factors related to feeding 

 and reproduction are the primary determinants of 

 changes in distribution. These in turn are affected by 

 the seasonal cycle of warming of the surface waters, 

 development of thermoclines and currents, and 

 seasonal cycles in abundance of food organisms. The 

 subject of the factors and relationships causing con- 

 centration of striped marlin has not received much 

 discussion in the literature. 



Nishimura and Abe (1971) have found a correlation 

 between the position of the Kuroshio as indicated by 

 the latitude at which the current crosses 139°30'E, 

 and the catch made off Izu. 



Kume and Joseph (1969b) noted that the 

 appearance of the area of high hook rate centered at 

 lat. 8°-13°N from long. 100° to 115°W is associated 

 with the strong development of the Equatorial 

 Countercurrent. They noted further that a diagonal 

 band of high abundance extending from lat. 5°S, long. 

 120°W to lat. 8°S, long. 95°W was in the general 

 region of the eastern extension of the South 

 Equatorial Countercurrent. 



In the area west of Australia, both the striped 

 marlin and southern bluefin tuna grounds are 

 centered at the boundary of currents which run along 

 long. 115° E meridian in winter (Koga, 1967). 



Manning (1957) states that off Chile, striped marlin 

 are found in the green water that is normally found 

 from shore to 10 to 25 miles offshore. Their occurrence 

 in these waters was in common with bonito, sardines, 

 and anchovies and in contrast to swordfish which oc- 

 curred farther offshore in the blue and white waters. 



Furukawa et al. (1958) show the fishing ground in 

 the western Pacific associated with the surfacing of 

 the 20° C isotherm over the edge of the continental 

 shelf. 



Nakamura (1938) states that surfacing of fish is 

 associated with high waves generated by opposing 

 wind and current as in the case of the Kuroshio and 

 the northeast monsoon. 



2.4 Hybridization 

 No record. 



3 BIONOMICS AND LIFE HISTORY 

 3.1 Reproduction 

 3.11 Sexuality 



Striped marlin are heterosexual with no reported 

 intersexuality or hermaphroditism. 



Sexual disorphism has not been reported in this 

 species and the sexes are indistinguishable externally. 

 Nakamura (1949) mentioned the sexual difference in 

 body size is not great in the genus Tetrapturus in con- 

 trast to the case in Makaira. Differences in greatest 



139 



