FISHERY BULLETIN: VOL. 86, NO. 1 



OVERALL 

 Xtot= 13456 ±4022 (N=I48) 



V,f 



13449+5513 {N-79) 



30 -] H% - I356.3±59.27(N = 66) 



20- 



10- 



z 



UJ 



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UJ 



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 u. 



lij 



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 CD 



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30nx,<„: 



20- 



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MARCH -APRIL 



1211 1±I52 30 (N = I5) 

 II28.81I6I 34(N = I0) 

 I346.0±370.37(N = 4) 



£22. 



rr-irT^rrr-iEin. i .h^. 



30 



20- 



10- 



JUNE 



Xtot= 1401 22+39.45 (N=76) 

 X^j.:l38l42±55 22(N^43) 

 Xjj:l42703±55 I0(N = 33) 



NOVEMBER -FEBRUARY 



Xtot = 95969±42 75(N-I6) 

 Xj.jt = 86733±48l(N-3) 

 X^j =987 46±52 26(N = II) 



D TOTAL 

 E3 ?? 





□73. 1 



MAY 



Xtot= 1435 4 + 69 87 (N = 37) 

 Xj.^ = 1436.61 107.98 (N: 20) 

 Xj^ = l433.9±87.27(N=l7) 



r^m. , .mm 



i 



lA. 



JULY 



X,0T = 15I275±341.72(N = 4) 

 X^^ = 1409 67 ± 385.40 ( N = 3) 



K^ 



:|80I(N=I) 



950 1150 1350 1550 1750 950 1150 1350 1550 1750 



DISC WIDTH (mm) 



Figure 2. — Size-frequency distributions of Mobula Ihurstoiii (means ±2 SE). 



spring (Fig. 2) suggested that larger rays began to 

 move into the area in the spring from their un- 

 known wintering grounds. 



Mature testes are large, elongated structures 

 attached by the mesorchia to the upper anterior 

 wall of the pleuroperitoneal cavity, on either side 

 of the vertebral column. A large epigonal organ is 

 associated with each testis. Both testes appeared 

 to be functional. They were usually about the 

 same size, although occasionally the left testis 

 was nearly 25''f larger. The paired ducti defer- 

 entes remain separated from each other through- 



out their length and open into the cloaca at the tip 

 of the urogenital papilla through two distinct 

 pores, rather than merging in the urogenital 

 sinus, as in most elasmobranchs (Daniel 1934), 

 including Manta ehrcnhcrgi (Gohar and Bayoumi 

 1959). Clasper length was plotted against DW for 

 43 M. thurstoni (Fig. 3), to determine the onset of 

 male maturation. Rapid increase in relative size 

 of the claspers, beginning at a DW of about 1,500 

 mm, was concomitant with the incipient presence 

 of abundant seminal fluid in the lower portion of 

 each ductus deferens. The pelvic fin area, and 



50 



