146 



Fishery Bulletin 100(1) 



to 63 cm TL had relatively short flexible claspers (Fig. 

 3B) and testes that were not fully differentiated from 

 the epigonal organ. No males between 64 and 87 cm TL 

 were caught. Three juveniles (88, 93. and 94 cm TL) had 

 claspers that were enlarged and beginning to calcify (Fig. 

 3B) and two larger specimens also had thick epididymi- 

 des (Fig. 3A). Males appear to approach sexual maturity 

 before 104 cm TL because all specimens longer than this 

 had completely developed sexual organs, including elon- 

 gate and calcified claspers, thick epididymides, and cir- 

 cumvoluted ampullae of the ductus deferens (Fig. 3). 



Discussion 



Prevalence of adult females in catches was similar to that 

 from observations made by Schwartz (1984) for stocks off 

 the southeastern United States and can be attributed to 

 a reproductive migration involving relatively large num- 



24 



22 



20 



18 



16- 



14- 



12 



^■Juvenile 

 Ig^ Pre-ovulalory 

 ^Sovulaling 

 ^Gravid 



^Postpartum 

 ^^ Resting 



3.0- 



Q 

 O 



00 



B 



Jan Feb Mat Apr May Jun Jul Aug Sep Oct Nov Dec 

 Month 



Figure 2 



Monthly distribution of (A) females in catches according to their 

 stage of reproduction and (B) MOFDs (maximum ovarian follicle 

 diameters) for mature females. 



hers of gravid individuals (114 to 130 cm TL) into the 

 sampled area. Because there was no evidence of disequi- 

 librium between sexes (i.e. there were equal numbers of 

 male and female embryos and juveniles), large numbers of 

 adult males were probably segi'egated. It is unlikely males 

 were in the sampled area and not caught because females, 

 although proportionally larger, were captured across the 

 same size range (Fig. 1), implying that the selectivity of 

 the gear encompassed the range of sizes of males. 



Evaluation of the maturation stages of males and fe- 

 males showed delineation between juveniles and adults. 

 All females longer than 103 cm TL had enlarged oviducal 

 glands and developed ovaries (Fig. 1, A and B, Table 1), 

 and males longer than 104 cm TL had elongate and cal- 

 cified claspers and thick epididymides (Fig. 3), indicating 

 that sexual maturity was probably approached at these 

 lengths. Although these estimates were derived from few 

 individuals, they are comparable to those proposed by 

 most researchers for specimens collected off the southeast- 

 ern United States (e.g. Springer, 1938; Clark and 

 von Schmidt, 1965; Compagno, 1984), with the ex- 

 ceptions of Branstetter ( 1981) who suggested 110 

 cm TL for both sexes and Schwartz ( 1984 ) who 

 suggested 110 cm TL for males. 



Size at birth, number of embryos, sex ratio of 

 embryos, and the time of parturition of C. acrono- 

 tus in our study are consistent with correspond- 

 ing data from earlier works (Springer, 1938; Clark 

 and von Schmidt, 1964; Dodrill (1977); Brans- 

 tetter, 1981; Compagno, 1984; Schwartz, 1984). 

 Size at birth has been suggested to be between 

 45 and 50 cm TL (e.g. Branstetter, 1981; Castro, 

 1993) and litter sizes commonly range from 3 to 

 6 (Springer, 1938; Dodrill, 1977; Compagno, 1984). 

 We observed gravid females caught in November 

 and December (late spring to early summer) with 

 embryos longer than 45 cm TL (Table 2). Given 

 the significant increase in size of embryos between 

 these months (indicating that embryos were still 

 developing) and the capture of several neonates 

 (46-51 cm TL) in February and March (late sum- 

 mer to early autumn), we conclude that parturi- 

 tion off northeastern Brazil probably occurs from 

 December to January (mid to late summer). A sim- 

 ilar seasonal timing has been proposed for stocks 

 off the southeastern LInited States (e.g. during 

 June — Schwartz, 1984) and is generally typical for 

 the majority of carcharhinids (e.g. Castro, 1993). 



In contrast to the inference made by Branstet- 

 ter (1981) but in agi'eement with obsei-vations of 

 Schwartz (1984), we showed that vitellogenisis 

 and gestation occur consecutively in C. acronotus. 

 Ovaries of adult females off northeastern Brazil 

 begin to mature (pre-ovulatory stage) in Febru- 

 ary (late summer) with ovulation occurring two 

 to three months later (Fig. 2, A and B). This se- 

 quence of events is illustrated by a rapid increase 

 in MOFD from February (1.5-2 cm in diameter) 

 to May (3 cm in diameter) (Fig. 2B). Given the 

 proposed summer parturition (December to Janu- 



