NOTARBARTOLO-DI-SCIARA: NATURAL HISTORY OF MOBULA 



WT = 4.29 X 10-10 (DW)'^^ 



r = 0.98 



where WT is given in kg, DW in mm. The overall 

 male to female ratio was 0.89 (A'^ = 781. Females 

 dominated the June through December period; 

 males were predominant in April and May. Sex 

 ratios, however, never significantly differed from 

 1 (x" test P > 0.05). Sex segregation, behavioral 

 or geographical, was never observed in M. japan - 

 ica (both sexes were caught together in nets and 

 by harpoon); sampling bias (N = 3) may explain 

 why only males were caught in May. Geographi- 



cal size segregation, by contrast, was an evident 

 feature of sexually mature specimens in the Gulf 

 of California (Fig. 7). 



No pregnant females were found, although in 

 some specimens the left uterus had a flabby and 

 dilated appearance, suggesting recent delivery. 

 Tissues at the base of the claspers of most of the 

 larger males were swollen and reddened in June 

 and July when the tips of the claspers were flex- 

 ible and the rhipidion could be easily spread, and 

 in doing so a white, viscous fluid would ooze from 

 the hypophyle; all this suggested mating activity. 

 The clasper length-DW relationship for M Japan - 

 ica (Fig. 8) did not exhibit a clear pattern as in M. 



30 -I 



20 



10 - 



OVERALL 



Xtot = 2I25 I±3674 (H-7Q) 

 ^^^ = 21016167 12 (N-34) 

 Xjj -2143.3139 28 (N = 44) 



frrn r-[7^ r-TH , i 



.^^ 



I. 



i 



DECEMBER 



Xtot = I86I4± 385 74 {H-5) 

 X^^ = I3I6(N = I) 

 Xj^:l997.8± 352 22(N = 4) 



rmrTTi. i ., i .. i ., i .. i ,. i .1 ^. i ,. i 



> 

 u 



z 



LU 



O 



UJ 



o 

 en 

 m 



< 



30 n 



20 - 



10 - 



APRIL 



X,o,^ 2156 166 58 (N^5) 

 X^^ = 2l050i28.84(N-3) 



H% 



= 22325 + 53.00(N = 2) 



mm , 



MAY 

 Xtot = X^^= 2057 33 1122 56 (N^ 3) 



.■ I  I  I 



 I .Fxl— I, 



30 



20- 



10 - 



JUNE 



Xtot=2I45 5131.32 (N^26) 

 X^<?^2I40 4 150 78(N=I0) 

 5(jo =2I48.814I04(N-I6) 



D TOTAL 

 E3 ^^ 

 %% 



I  I  I 



i. 



n]za_ 



JULY 



XT0T = 2l466i42.94 (N = 39) 

 7^^ = 2132.2 + 88.06 (N= 17) 

 X^j =2157713598 (N = 22) 



I .n-i. 



I  I .r-iT^ 



ii 



hi 

 4. 



i 



1450 1650 1850 2050 2250 1450 1650 1850 2050 2250 



DISC WIDTH (mm) 



Figure 7. — Size-frequency distribution.s of Mobula japanica (means ±2 SE). 



57 



