The aim of this research was to characterize population aspects of Aegla franciscana Buckup & Rossi, 1977, where the size-frequency distribution, sex ratio, recruitment, reproductive period (frequency of ovigerous females) and fecundity were evaluated. The samples were performed seasonally (February, June, August and October 2003) at river Rolante, Rio dos Sinos basin, São Francisco de Paula city, RS. The animals were collected with nets, measured and returned to the stream. A total of 1,322 individuals was obtained, among which 567 males, 579 females and 176 unsexed animals. The animals were bracketed in size classes for cephalothorax length (CL), and bimodal distribution was observed. Male sizes ranged from 3.86 mm to 22.09 mm and females from 4.06 mm to 22.48 mm. The males showed a larger median size (10.36 mm) than females (9.89 mm). The sex ratio obtained was close to 1:1 (chi2 = 0.03; p>0.05). Sex ratio in the size classes showed an anomalous pattern, with a higher frequency of females in the intermediate size classes and males in the superior classes. This may be related to a greater energy requirement for reproduction in females, thus delaying growth. The highest recruitment pulse occurred in summer and autumn as a consequence of high reproductive activity during winter. Ovigerous females produced 123.3 ± 47.8 eggs (mean ± standard deviation). A correlation between cephalothorax length of ovigerous females and number of eggs (r = 0.81) was observed.
Sex ratio; reproductive period; recruitment; fecundity
