The aim of this study was to evaluate 209 samples (100 females and 109 males) of Astyanax fasciatus (Cuvier, 1819) collected from the Ceará Mirim River, Rio Grande do Norte State, (5°37'S e 35°39'W), between February 1996 and April 1997. The sex ratio was 1:1 and the the total length varied from 3.0 to 9.0cm, with most classes between 4.0-5.0 cm and 7.0-8.0 cm. The estimated value for the parameter (q = 2,59) suggests that this specie has an alometric growing pattern. The IGS value started to increase in November-December-January, following the rainfall while the condition factor values showed.
Fish; Neotropical; reproduction
