Reproductive Activity of the Neotropical Geophagus brasiliensis (Cichlidae), Native Species in the Lower Doce River Basin, Southeastern Brazil

The ichthyofauna of the Doce River basin has been exposed to a wide variety of anthropogenic actions, including the 2015 collapse of the Fundão dams in the city of Mariana. Here we focused on the reproductive biology of the pearl cichlid, Geophagus brasiliensis, including the reproduction, length at maturity, gonadal morphology, fecundity, spawning type and reproductive season in the lower course of the Doce River basin. A total of 277 specimens were captured from October 2018 to September 2019 with similar sex ratio (χ2 = 0.43; p > 0.05). Males of G. brasiliensis exhibited higher values (p < 0.05) for total length and body weight than for females (p < 0.05) indicating sexual dimorphism in the species. The smallest female and male in mature stages of gonadal maturation were 44 and 70 mm in total length, respectively. Fully developed vitellogenic follicles had a mean diameter of 924 ± 268 μm and display asynchronous follicular development. The mean absolute fecundity was 2219 ± 1782 follicles per female, which is characteristic of fish with batch fecundity. Females reproduced throughout the year and reproductive peak is in October–January with higher gonadosomatic index. In this sense, G. brasiliensis showed reproductive characteristics of multiple spawn in the region of the lower course of the Doce River after the Fundão mining ore tailing collapse, suggesting that in this region, reproduction is not affected by environmental decline.