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Fishery Bulletin 1 10(3) 
Our estimate of the slope (6) for males and females 
combined is similar to the one (6 = 3.13) reported by 
Torres (1991) for species of the A. narinari complex in 
South African waters. 
Sex ratio and reproductive period 
In our study area, females were more abundant than 
males during most months of the period analyzed. Cue- 
vas-Zimbron et al. (2011) reported differences in sex 
ratios depending on depth and distance from shore in 
the southeastern Gulf of Mexico, where males were domi- 
nant in shallow waters close to shore and females were 
more abundant in deeper, more distant waters. Such 
spatial segregation by sex may explain the observed 
sex ratio patterns in our study. Additionally, sex ratios 
showed no significant differences in February, March, 
and June 2006 and March and April 2007; it is likely 
that these periods correspond to increased mating activi- 
ties. Cuevas-Zimbron et al. (2011) observed an increased 
proportion of adult females during March and April in 
the nearshore, shallow waters of Campeche Bank. These 
results indicate that migratory inshore-offshore move- 
ments relate to mating activity in adult A. narinari. 
To our knowledge, this study is the first one to pres- 
ent A. narinari reproductive periodicity on an annual 
basis. Females in different maturity stages were found 
year round in the Los Frailes Archipelago. However, 
postgravid females were present in August 2005, Feb- 
ruary-May and July-September 2006, and January- 
April, July-October, and December 2007. Therefore, 
it appears that parturition occurs mainly during the 
periods of February-May and July-October. Similarly, 
Cervigon and Alcala (1999) reported the presence of 
gravid females in March and April around the Los 
Roques Archipelago off central Venezuela. In India, 
gravid A. ocellatus females in “good number” were re- 
ported during April-May (Raje et al., 2007). 
Schluessel et al. (2010b) observed mature oocytes 
and embryos in the same individual of A. ocellatus, and 
Uchida et al. (1990) reported that copulation followed 
immediately after parturition in aquarium conditions 
for A. ocellatus. For A. narinari in our study area, it is 
likely that mating occurs more intensely during Feb- 
ruary-May, considering the more balanced sex ratios 
and presence of postgravid females observed during 
this period. 
Fecundity and embryo lengths 
Fecundity of A. narinari has been reported by different 
authors to be 1-4 embryos (Gudger, 1914; McEachran 
and de Carvalho, 2002), a level similar to the fecundity 
observed in A. ocellatus ( see Devadoss, 1984; Uchida 
et al., 1990). In our study, 75% of gravid females had 
3-5 embryos, and the remaining 25% had 1-2 embryos. 
These minimum values may have been caused by abor- 
tions associated with stress during the capture process. 
However, captive A. ocellatus have been observed to give 
birth to only 1 or 2 pups (Uchida et al., 1990). From our 
results, mean fecundity was 3.09 (SD = 1.31) embryos per 
female. Additionally, no relationship was found between 
the length of gravid females and the number of embryos 
present. Gravid females of A. narinari had only one 
functional uterus in which all embryos were located — an 
observation also reported for A. ocellatus (see Schluessel 
et al., 2010b). 
McEachran and de Carvalho (2002) indicated lengths 
at birth for A. narinari to be between 18 and 36 cm 
DW. In our study, the maximum embryonic length was 
44.5 cm DW, and 40% of observed embryos were >36 cm 
DW. It is, therefore, likely that length at birth is >40 
cm DW in our study area. This size is larger than the 
30-40 cm DW reported for newborns in northeastern 
Brazil (Yokota and Lessa, 2006) but consistent with the 
44 cm DW observed by Cuevas-Zimbron et al. (2011) for 
neonates in the southeastern Gulf of Mexico. 
Size at sexual maturity 
To our knowledge, there has been only one previous 
report of size at sexual maturity for A. narinari. Dubick 
(2000) estimated that size at maturity was 122 cm DW 
for males and 124 cm DW for females in southwestern 
Puerto Rico. These results are slightly lower than the 
lengths obtained for males in our study, L 50 = 129.2 cm 
DW (95% confidence interval [CI] = 125— 134.9 cm DW), 
and lower than the results we obtained for females, 
L 50 =134.9 cm DW (0 = 128.8-139.8 cm DW). For A. ocel- 
latus in the western Pacific and Indian Oceans, size at 
first maturity for males has been estimated at 99.8 cm 
DW in Indonesia (White and Dharmadi, 2007), 130 cm 
DW in Australia and Taiwan (Schluessel et al., 2010b), 
and 135 cm DW in Madras, India (Raje et al., 2007). 
Female size at first maturity has been reported for 
Australia and Taiwan at >150 cm DW (Schluessel et al., 
2010b) and for India at -150 cm DW (Raje et al., 2007). 
Several factors may determine variations in estimates 
of length at first maturity: true differences between 
populations, sample size, sampling bias, differences or 
errors in assigning maturity stages, and estimation 
methods. Because Aetobatus spp. are captured mainly 
throughout their range as bycatch in industrial and 
artisanal fisheries, the collection of adequate sample 
sizes has been a major limitation in studying these 
species. For example, White and Dharmadi (2007) and 
Schluessel et al. (2010b) studied only 28 and 55 male 
A. ocellatus, respectively. In the study by Schluessel et 
al. (2010b) only 1 of 56 female individuals was mature 
and the length at maturity was estimated at >150 cm 
DW. The directed nature of the fishery for A. narinari 
in northeastern Venezuela allowed us to obtain a much 
larger sample than in previous studies of length at 
maturity of Aetobatus spp. 
Conclusions 
Aetobatus narinari has been classified as near threat- 
ened in the IUCN Red List of Threatened Species. How- 
