Profiles of sex steroids, fecundity, and spawning of the curimatã-pacu Prochilodus argenteus in the São Francisco River, downstream from the Três Marias Dam, Southeastern Brazil.

The present study evaluated for the first time sex steroid profiles and fecundity in females of Prochilodus argenteus from two sections of the São Francisco River Brazil, downstream from the Três Marias Dam, which influences characteristics of their water habitat. The model species in the study, P. argenteus, is an important commercial and recreational species in Brazil. In the region closest to the dam (section 1), females did not reach final oocyte maturation, failed to spawn, and displayed lesser circulating concentrations of testosterone, 17(-hydroxyprogesterone (17(-P) and 17beta-estradiol (E2) than those farther downstream of the dam (section 2). The endocrine and fecundity deficiencies probably are attributed to lower water temperature and oxygen concentration in (section 1). The follicular atresia rate in the region closest to the dam (26%) was greater than those fish captured farther downstream of the dam (13%), after the Abaeté River (section 2). Variations in testosterone, E2 and 17(-P concentrations in section 2, followed gonadal maturation which are typical features of species which have seasonal reproduction, group-synchronous oocyte development, and are single batch spawners such as P. argenteus. Results document the first evidence of endocrine and reproductive dysfunctions caused by inadequate water conditions in a wild population of the migratory species P. argenteus in the São Francisco River, downstream from the Três Marias dam.