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

Abstract

In this study we investigated the distribution of Macrobrachium olfersii (Wiegmann, 1836) along ~150 km of the Ribeira de Iguape river, São Paulo, Brazil. We compared the abundance and spatio-temporal distribution, and checked for differences in size and proportion of each sex in the collections, using two sampling methods. Shrimps were collected monthly at four sites (Eldorado, Sete Barros, Registro, and Iguape), from January to December 2007, using traps and sieves. We obtained a total of 23,818 individuals. The abundance was significantly higher at the Iguape-site, which was the closest to the estuary. There was a positive cross-correlation between abundance and rainfall, indicating an increase in abundance with a decrease in rainfall. The body size increased significantly upstream, suggesting a juvenile upstream migration, controlled by the rainfall regime and the amphidromous behavior of M. olfersii. More than 95% of the individuals were captured by sieving through the marginal vegetation of the river. The average size and sex ratio of each sample varied depending on the capture method: traps captured more and larger males than the sieve. Therefore, we recommend the combined use of these methods to obtain a better coverage of the population biology of freshwater shrimps.

Modelling the longitudinal distribution, abundance, and habitat use of the giant freshwater shrimp (Macrobrachium spinipes) in a large intermittent, tropical Australian river to inform water resource policy

“…The concentration of juveniles in the lower reaches of the Fitzroy River strongly suggests an amphidromous life history. A similar pattern was found in the perennial Daly River, some 740‐km north‐east of the Fitzroy River (Novak et al, 2015) and has been reported for other amphidromous Macrobrachium species (Bauer & Delahoussaye, 2008; Novak, Bayliss, Crook, et al, 2017; Ribeiro et al, 2020). Amphidromy in the Fitzroy River is also supported by photographic documentation of small shrimp migrating upstream en masse at the Camballin Barrage during the late wet season (mid‐February in 2019 and early April in 2020).…”

Evaluation of population dynamics of Macrobrachium olfersii (Palaemonidae) along ~150 km extension of the Lower Ribeira de Iguape River, São Paulo, Brazil

“…1). According to Ribeiro et al (2020), the river margins are similar in these four regions, surrounded by pastures and banana plantations. The vegetation on the banks mainly comprises grasses (Brachiaria subquadripara, Brachiara platyphylla, and Panicum dichotomiflorum).…”

“…1). We followed the collection method proposed by Ribeiro et al (2020). In each area, samples were obtained using traps and sieves in two locations, 2 km apart.…”

“…In individuals with 10.0 mm or less, CL was measured (to the nearest 0.025 mm) under a stereomicroscope using a graduated ocular micrometer. All prawns smaller than 4 mm CL that lacked masculine appendix were considered juveniles (sexually undifferentiated), following Ribeiro et al (2020).…”

“…According to Ribeiro et al (2020), the abundance and spatiotemporal distribution of M. olfersii along the Ribeira de Iguape River are related to its amphidromous habit and regional rainfall regime. However, there are no studies on this species along the river extension to verify if there are changes in its population dynamics.…”