Reproduction and population dynamics of Cheirodon interruptus (Ostariophysi: Characidae) in El Portugués, a stream in the upper watershed of the Samborombón River, Argentina

Abstract

The reproductive period of Cheirodon interruptus was determined by analyzing 1658 individuals collected monthly in the stream El Portugués, Argentina, from May 2004 to April 2005. Two prolonged spawning seasons, one in spring and another in autumn, were observed based on the maturity stages and gonadosomatic index (GSI) of female specimens. The mean monthly GSI of males was significantly correlated with depth. In females, the GSI exhibited a significant correlation with photoperiod and depth. The remaining environmental variables, including temperature, pH, conductivity, and monthly rainfall, did not show a correlation with the mean monthly GSI. The first sexual maturity in females and males was reached within the 24-26 mm standard length class. The mean absolute fecundity was 448 oocytes (SD = 217.8), and the mean relative fecundity was 0.33 (SD = 0.097) oocytes per milligram of body weight; this species is a multiple spawner. The oocyte diameter ranged from 0.05 to 0.70 mm, with a mean of 0.48 mm (SD = 0.16).