Reproductive biology of pequira Bryconamericus stramineus (Eigenmann, 1908) in Funil Reservoir-MG, Brazil

Abstract

In order to evaluate aspects of reproductive biology of the “pequira” ( Bryconamericus stramineus) in the elevator of the Funil Dam - MG, fish capture was carried out from November 2008 to January 2009 and 317 individuals were collected. The mean standard length (SL) of the population was 4.96 cm and mean weight 1.80 g. The females had SL of 5.0 cm, while males had a SL of 4.6 cm. A sex ratio of 2.20: 1 (females: male) was observed. Our results show that 73% of the individuals analyzed were considered adults. The species presented low fecundity, mean of 470.9 oocytes per female and a mean diameter of 221.08 μm, with an increase in oocyte diameter over the evaluation period. The length of the first gonadal maturation was estimated at 5.0 cm. The results obtained in this work suggest that the reproductive cycle of the species occurs in the analyzed period. Although this species does not have migratory reproductive habits, the presence of adults in the reproductive stage was observed in the transposition area, which suggests a search for new environments for spawning.

Long-term monitoring reveals a consistent female-biased sex ratio in Pimelodus maculatus from the Upper Uruguay River Basin

“…As a consequence of these disturbances, both the bio-geochemistry processes and food webs tend to stabilize through aging, changing the conditions to supplant aquatic populations (Agostinho et al, 2008). The significant number of P. maculatus females in the Itá (filled in 1999) and Machadinho (filled in 2001) reservoirs may be related to favorable environmental conditions and food supply that contributes to the growth and maintenance of older individuals (Nikolsky, 1963;Raposo and Gurgel, 2001;Meurer and Zaniboni-Filho, 2012;Murgas et al, 2019). In contrast, the further upstream dam, and the youngest reservoir (HPP Barra Grande, filled in 2005), was the unique site where the female to male ratio did not differ from 1:1.…”