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Fishery Bulletin 89(4), 1991 



Within the study area, gravid females occurred 

 from April to December and nongravid adult 

 females from June to November. Ovulating fe- 

 males, females which had recently commpleted 

 ovulation, and the largest mature ovarian follicles 

 occurred in November and December. Full-term 

 embryos without the yolksac were observed in 

 November, as was also noted by De Buen (1952) 

 off Uruguay. The monthly-length frequency 

 distributions of embryos were unimodal, and 

 modal embryonic total length increased from 

 13 cm in April to 31cm in November (Fig. 7). 

 Ovulation and birth both occurred in November- 

 December, therefore gestation lasts 12 months. 



In gravid females (GR), ovarian follicles were 

 opaque white and did not grow (Fig. 8). Two 

 distinct types of nongravid females occurred 

 during the same time-periods each year. First- 

 year nongravid females (NGR-1) occurred from 

 June to September and had light-yellow ovarian 

 follicles 0.5-2.5 cm in diameter. Second-year non- 

 gravid females (NGR-2) were present July to 

 November and had golden-yellow follicles of 

 3.5-5.5 cm diameter. 



From June to September, follicle diameter of 

 NGR-1 females remained about 1.5 cm (Fig. 9), 

 while ovary weights ranged from 70 to 130 g. 

 Thus, vitellogenesis was slow. Females over the 

 full size range of adults were classified as NGR-1 

 (Fig. 5). This category included the maturing, 

 virgin phase but consisted mainly of resting 

 females. 



In NGR-2 females, the modal diameter of the 

 largest follicle increased from 4.2cm in July to 

 5.5 cm in November (Fig. 9). Accelerated vitello- 

 genesis and ovarian maturation occurred in this phase. 

 In November, these females had dilated nidamentary 

 glands (the four greatest values in Fig. 6) and uteri 

 containing a transparent viscous material resembling 

 egg white. 



The reproductive cycle of the female lasts three 

 years. During the first 12 months after parturition, the 

 oviduct remains in a resting stage and vitellogenesis 

 is slow (NGR-1 stage). During the following 12 months, 

 large mature follicles are produced, and the nidamen- 

 tary gland and uteri are prepared for ovulation, which 

 occurs in November-December (NGR-2 stage). Gesta- 

 tion lasts 12 months, during which there is no vitello- 

 genesis, and parturition takes place in November- 

 December (GR stage). 



Nidamentary gland smears from one of eight NGR-2 

 females, collected in July 1986, had a large number of 

 whole spermatophores, similar to those observed in the 

 seminal vesicle of the male (Fig. 4). Thus, mating 



apparently begins during the NGR-2 phase as early as 

 July, at least five months before ovulation, and the 

 sperm is carried to the nidamentary gland by passive 

 transport. 



Fecundity 



Fecundity increased linearly with body size of the 

 female (Table 1, Fig. 10). In 58 NGR-2 females of 

 123-146 cm TL, ovarian fecundity ranged from 12 to 

 34 with a mean of 22.7 per female. In 140 females of 

 123-154 cm TL, uterine fecundity ranged from 4 to 41 

 with a mean of 23.1. Of the items in the uteri, 94.2% 

 were normal embryos, 5.2% were nondeveloping eggs, 

 and 0.6% were dead or abnormal embryos. In 79% of 

 the gravid females, there were at least one or two 

 nondeveloping eggs, but the total number of these eggs 

 per female, ranged up to 34. 



