To analyze the effect of the Irapé reservoir on the reproduction of "curimba", Prochilodus hartii, a migratory species, 503 specimens were collected during the reproductive period from February 2012 to January 2013. Specimens were collected from two river sections within the Jequitinhonha River Basin: Site 1 - a section of the Itacambiruçu River, a tributary of the Jequitinhonha River upstream of the Irapé reservoir; and Site 2 - a section of the Jequitinhonha River immediately downstream from the Irapé dam. Specimens (n = 270) were captured at Site 1 (160 males and 110 females), and 233 specimens at Site 2 (136 males and 97 females). The following were determined for each specimen: gonadosomatic index (GSI), hepatosomatic index (HSI), stomach repletion index (SRI), coelomic fat index (CFI) and condition factor (K). Both male and female fish were captured at all stages of gonadal maturation at Site 1, whereas only fish in the inactive and initial maturation stages were captured at Site 2. Length and mean GSI were greater (P < .05) at Site 1. Mean HSI and SRI of females was less in the advanced maturation stage. There were lesser values ​​for temperature and dissolved oxygen at Site 2 than 1. It is possible that the lesser values ​​for the physical and chemical characteristics of the water at Site 2 failed to promote advanced gonadal maturation, spawning, and spermiation of P. hartii, thus there are associations that are indicative of a negative effect of the Irapé reservoir on the reproduction of this migratory species.