play a role in determination of their presence. For ex- 

 ample, longline gear may be necessary to catch the 

 deeper strata of fish while trolling gear (baits, ar- 

 tificial lures, and teasers) attract those near the sur- 

 face. 



»■ 



120 

 80 

 •4 



1000 

 800 



600 



400 

 200 



10° 30°N 



NOV ~A« 



M 



F 



5°S-10°N 



MAY- OCT 





5°S-10°N 



NOV- APR. 



M 

 F 



^^_ 



^■■k- 



5°S-10°S, Wof 15°W 



NOV 



10°S-30°S, W of 15°W 



NOV- AM 



5° 30°S,Eofl5°l 



MAY ~ OCT 



MALE 



FEMALE 



OVERLAPPED 



11 



13 



277 



163 



261 

 180 



5° 10°S, Wof 15°W «♦ : 7 

 MAY -OCT 



M : 93 

 F ■ 30 



M : 2037 

 F ■ 1051 



5° 30°S, Eofl5°W M : 12 

 NOV -AMI m F 7 



<=■ -La sa u 



The behavior of white marlin toward trolling baits 

 is very indicative of his intentions according to Jaen 

 (1964). If the fish is pale green and placidly following 

 the bait, he will probably not attack. However, if he is 

 dark-colored and his fins become a shiny bright blue, 

 a reaction known to fishermen as "lighting up," he 

 will strike immediately. The raising of the first dorsal 

 fin is also considered to be an indication of excite- 

 ment. 





4 POPULATION 

 4.1 Structure 

 4.11 Sex ratio 



Extensive sampling of oceanic catches (Ueyanagi et 

 al., 1970) shows that the sex ratio of white marlin 

 varies considerably with season and area (Fig. 11). 

 Males appear to be predominant in most areas except 

 in three cases: north of lat. 30°N in May-October, 

 from lat. 10°N to 30°N in November-April and from 

 lat. 5°S to 30°S, and east of long. 15°W in May- 

 October. The proportion of 2,037 males to 1,051 

 females in the area from lat. 10° S to 30° S and west of 

 long. 15°W during November-April, the area and 

 period in which the major spawning of South Atlantic 

 white marlin evidently occurs (Ueyanagi et al., 1970; 

 Hayasi et al., 1970), is interesting. 



Sex ratios of white marlin collected in inshore 

 waters also varied considerably according to areas and 

 seasons. De Sylva and Davis (1963) examined fish 

 caught between Atlantic City, N.J., and Ocean City, 

 Md., during the summers of 1959 and 1960. They 

 found 17 males and 41 females in 1959, and 50 males 

 and 58 females in 1960. "The deviation from the ex- 

 pected 1 : 1 ratio is highly significant in 1959 

 (X 2 = 6.63; P- 0.001), non-significant in 1960 

 (X 2 = 0.44), and probably significant for the combined 

 years (X 2 = 5.02; P = 0.02)," Krumholz (1958) found 

 20 males and 22 females in a sample caught off 

 Bimini, Bahamas, in April 1956. Nakamura and Rivas 

 (1972) reported that females definitely outnumbered 

 males in samples examined at four ports in the Gulf of 

 Mexico during May-October: 



81 91 101 111 121 131 Ml IS) 161 171 Ml 191 

 90 200cn 



10DY LENGTH 



Figure 11.— Size composition of white marlin by season and 

 area. (From Ueyanagi et al., 1970, Fig. 19 and caption.) (Area 

 indications and legend added.) 



78 



