Population biology and size at the onset of sexual maturity of the amphidromous prawn Macrobrachium olfersii (Decapoda, Palaemonidae) in an urban river in southeastern Brazil

Abstract

Information on population biology is essential for a better understanding of the ecological stability of a species and the ecosystem in which it lives, especially in areas affected by anthropogenic activities. This study investigated the population biology of Macrobrachium olfersii in an ecosystem under human impact, focusing on sex ratio, reproductive period, and juvenile recruitment. The onset of sexual maturity was also estimated. Samplings were performed monthly in the daytime from June 2006 to May 2007 on the Taquaral River in the city of Ubatuba, São Paulo State, Brazil. The sex ratio was skewed towards females, and both the reproductive period and the juvenile recruitment were continuous. The estimated size at which the species reached sexual maturity corroborated studies on populations from other locations. Results from the current study strongly indicate that the ecosystem studied may have suffered environmental stress, which probably interfered with the migration and establishment of the species: during the study, the species was found in significant abundance, but six years later, it was not captured in samplings.

Population structure, mortality, and recruitment of Macrobrachium amazonicum (Heller, 1862) (Caridea: Palaemonidae) in the eastern Amazon region, Brazil

“…The reproductive period was characterized by the breakdown of the monthly frequency modes of ovigerous females (Davanso et al, 2013;Taddei et al, 2015;Pescinelli et al, 2016) using FISAT II (Gayanilo et al, 2005), which determined the magnitude of reproductive pulses, which were then compared to the periods of recruitment. The sex ratio was calculated using the chi-square test (χ 2 ) with a significance level of 5% (Sokal & Rolph, 1995), which measured deviation from the expected 1.0 male:1.0 female for the total number of individuals in each size class and each month.…”

Abundance and spatio-temporal distribution of the amphidromous shrimp Macrobrachium olfersii (Caridea: Palaemonidae) along the Ribeira de Iguape River (São Paulo, Brazil)

“…In the Mangues river, south of Bahia (Brazil), Teixeira and Couto (2012) noticed that the shrimps were absent in places lacking the riparian vegetation and where the riverbed was altered. Pescinelli et al (2016) also attributed the disappearance of M. olfersii from the Taquaral river (Ubatuba, Brazil), over a five-year interval, to anthropogenic impacts. In Sarapiquí (Costa Rica), Snyder et al (2013) compared the relative abundance of M. olfersii over a 20-year gap between the predisturbance and post-disturbance and observed strong changes in the abundance in the places affected by the anthropogenic impacts.…”

“…Previous studies about the distribution patterns and ecology of M. olfersii addressed only populations from relatively small rivers (Müller and Prazeres, 1992;Ammar et al, 2001;Mossolin and Bueno, 2002;Teixeira and Couto, 2012;Pescinelli et al, 2016). Thus, in this study we investigated the distribution of M. olfersii in the Ribeira de Iguape river, covering four sites along an ~150 km transect from the estuary.…”

“…After evaluating all individuals, we concluded that the size of the smallest male bearing an appendix masculina was 4 mm. Thus, all shrimps smaller than 4 mm were considered as juveniles, following Pescinelli et al (2016).…”

Relative growth and population dynamics of Macrobrachium iheringi (Decapoda, Palaemonidae)

“…The population structure of species of Macrobrachium has a similar pattern: the majority of individuals belonging to the smaller size classes, with fewer individuals in the larger ones (Barros-Alves et al, 2012;Pereira & Chacur, 2009;Pescinelli et al, 2016;Taddei et al, 2017). Part of this is due to the relative growth of structures related to agonistic behaviors, such as the second pair of chelipeds.…”