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.… Show more
“…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).…”
Water development threatens rivers and their biodiversity. Amphidromous shrimp are particularly vulnerable as they require migration between freshwater and estuaries to complete their life cycle. The Fitzroy River is a large tropical intermittent river undergoing water development that is home to the amphidromous shrimp Macrobrachium spinipes (cherabin), yet little is known about its habitat use and flow‐ecology making it difficult to inform sustainable water‐take.
We investigated habitat associations, distributional patterns suggestive of amphidromy, and the influence of water availability by sampling main channel and floodplain pools along a 350‐km river length during 2 contrasting flow years. Applying a size‐specific abundance model, we estimated abundance per size class, site, and year. We then predicted abundance at the landscape scale with remotely sensed water to reveal the impact of water availability on the meta‐population.
Our model revealed that juveniles were in greatest abundance in downstream main channel pools, whereas adults were in greatest abundance in upstream floodplain pools. Abundance varied by year with lower numbers predicted in the low‐flow year. Longitudinal and habitat patterns remained when our pool‐level results were scaled to the landscape, and the positive relationship of abundance to wet‐season flow was strengthened. The predominance of smaller cherabin in the lower reaches of the river provides indirect support for an estuarine nursery and amphidromous life history; however, small individuals observed in landlocked pools, during late dry season suggests possible within‐river recruitment.
The importance of water development policies that protect wet‐season flow and passage along the Fitzroy River is supported by this work. These types of policies are likely to be important for this and other amphidromous shrimp species across Australia, Southeast Asia and further afield. Further research detailing the species life history and describing flow–recruitment relationships will be important contributions to understanding this important taxonomic group and refining policies for current and future water resource development.
“…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).…”
Water development threatens rivers and their biodiversity. Amphidromous shrimp are particularly vulnerable as they require migration between freshwater and estuaries to complete their life cycle. The Fitzroy River is a large tropical intermittent river undergoing water development that is home to the amphidromous shrimp Macrobrachium spinipes (cherabin), yet little is known about its habitat use and flow‐ecology making it difficult to inform sustainable water‐take.
We investigated habitat associations, distributional patterns suggestive of amphidromy, and the influence of water availability by sampling main channel and floodplain pools along a 350‐km river length during 2 contrasting flow years. Applying a size‐specific abundance model, we estimated abundance per size class, site, and year. We then predicted abundance at the landscape scale with remotely sensed water to reveal the impact of water availability on the meta‐population.
Our model revealed that juveniles were in greatest abundance in downstream main channel pools, whereas adults were in greatest abundance in upstream floodplain pools. Abundance varied by year with lower numbers predicted in the low‐flow year. Longitudinal and habitat patterns remained when our pool‐level results were scaled to the landscape, and the positive relationship of abundance to wet‐season flow was strengthened. The predominance of smaller cherabin in the lower reaches of the river provides indirect support for an estuarine nursery and amphidromous life history; however, small individuals observed in landlocked pools, during late dry season suggests possible within‐river recruitment.
The importance of water development policies that protect wet‐season flow and passage along the Fitzroy River is supported by this work. These types of policies are likely to be important for this and other amphidromous shrimp species across Australia, Southeast Asia and further afield. Further research detailing the species life history and describing flow–recruitment relationships will be important contributions to understanding this important taxonomic group and refining policies for current and future water resource development.
“…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).…”
Section: Description Of the Study Areamentioning
confidence: 99%
“…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.…”
Section: Description Of the Study Areamentioning
confidence: 99%
“…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).…”
Section: Description Of the Study Areamentioning
confidence: 99%
“…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.…”
This study aimed to verify the spatial and temporal population parameters of Macrobrachium olfersii over of ~150 km of the Ribeira de Iguape River (SP). Prawns were collected monthly (January to December 2007) in Eldorado, Sete Barras, Registro, and Iguape, using traps and sieves. We analyzed 9,691 individuals with carapace length (CL) from 2.2 to 25.4mm. In our results, smaller individuals were found close to the estuary, i.e., Iguape, whereas larger individuals were recorded as they moved away from the estuary. Reproduction was continuous but more intense in the summer, when temperature and rainfall were higher. The total sex ratio differed from the expected favoring males (1:0.73), and this deviation was also observed in Eldorado, Registro, and Iguape. Female sexual maturity was at 10.9 mm CL, without significant variation along the river. The regions closer to the estuary (Iguape/ Registro) presented lower CL∞ and longevity, and higher k, due to the greater number of juveniles. In conclusion, the results suggest that the variation in size, recruitment, sexual maturity, and growth of individuals are related to the population structure along ~150 km of the river, and are triggered by the upstream migration of juveniles after larval development, which takes place in the estuarine region.
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