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Biodiversity is declining worldwide due to anthropogenic impacts, especially noxious for freshwater ecosystems, considering their close relationship with human activities. Damming is one of the most harmful human impacts that leads to the loss of several riverine fish through habitat loss or change. Herein, we aimed to assess the relationship between the composition of fish assemblages in reservoirs and the availability of littoral habitats, and whether these patterns differ between native and non-native species. Fish assemblages of fifteen reservoirs from up to downstream the Paraíba do Sul river basin were evaluated. Habitat availability was more important for native than for non-native species, after controlling for the influence of reservoir features. Local drivers were crucial for the occurrence of non-native species which thrived in the absence of complex habitats. Macrophytes seemed to play two key but quite antagonistic roles for fish species. They were positively related to native small characids, probably acting as shelter against predation, but they were also related to hypoxic conditions in eutrophic reservoirs. These findings stress the importance of preserving or restoring physically complex habitats as beneficial for native fish species through providing grounds for feeding (catfishes on leaves) and recruitment (juveniles of characids in macrophytes banks). [ABSTRACT FROM AUTHOR]

With the aim to assess how environmental heterogeneity affect fish assembly patterns, we evaluated species co-occurrence and nestedness in 16 lentic environments in a drying coastal plain of Southeast Brazil. We calculated the frequency of co-occurrence and nestedness for 13 quarterly campaigns exclusively for fish species tolerant to a narrow range of low water salinity (stenohaline) and to wider range of water salinity (euryhaline) and for all species together, and assessed its significance with null models. We employed a Principal Component Analysis (PCA) to explore temporal trends in physical and chemical parameters of water and to detect those that most influenced environmental heterogeneity. Linear regressions assessed the potential effect of each parameter that most influenced the PCA on co-occurrence. Few campaigns presented nonrandom patterns of community composition, and only for euryhaline or for all species considered together. Communities shifted to anti-nested and negative species co-occurrence with the increase of environmental heterogeneity. Parameters related to desiccation (salinity and depth) affected euryhaline species co-occurrence. Together, these results revealed group-dependent responses to drought according to physiological tolerances. This study improves our understanding of how the predicted increase in precipitation anomalies may disassembled aquatic communities of coastal plains in the face of climatic changes. [ABSTRACT FROM AUTHOR]

To understand how Neotropical freshwater fishes (NFF) benefit society, we conducted a broad literature survey to (i) map and list the ecosystem services (ES) generated by these organisms, and (ii) investigate how human activities have affected the ecosystem service chain. We found sound evidence that NFF contribute directly and indirectly to the generation of several provisioning, regulating, supporting, and cultural services. Provisioning services have been widely recognized, especially those related to fisheries, but this class also included ornamental fish, genetic pools, medicines, aquaculture, and bioindicators. Other services remain less understood and largely ignored by society. Regulating services included seed dispersal, decomposition, and top-down control, while supporting services included nutrient cycling, habitat quality, and ecosystem engineering. Cultural services associated with NFF included recreational fishing, tourism, fishkeeping, education, production of scientific knowledge, in addition to values linked to traditional communities, such as local knowledge, cosmology, and existential foundations. Human activities have negatively impacted the generation of ES, especially those related to fishing and food provisioning. This review indicates that Neotropical fishes benefit society in multiple ways, but it is imperative to improve our understanding about those benefits, and to increase conservation efforts directed to this important component of global biodiversity. [ABSTRACT FROM AUTHOR]

The article "Correction: The effect of shoreline habitats on native and non-native fish species in a set of Neotropical reservoirs" by Ana Clara Sampaio Franco et al. discusses the impact of shoreline habitats on fish species in Neotropical reservoirs. The authors have opted for Open Choice, making the article an Open Access publication under a Creative Commons license. The study was conducted by researchers from Brazil and Spain, focusing on the ecological dynamics of fish populations in reservoir environments. [Extracted from the article]

In this study, we explored the association between land use and fish species richness on 52 coastal lagoons in Southeast and South Brazil. We measured the proportion of agriculture and urbanization around lagoons over 26 years and used the coefficient of variation (CV) as a surrogate of the temporal land cover variability. We compiled species occurrences from primary data, from the literature and from museum records, and assigned each recorded species to different habitat use groups: benthic/bottom or water column, and littoral or limnetic zones. In the Southeast, where most lagoons are subject to marine influence, richness was negatively associated to agriculture and positively associated to urbanization. In the South, where freshwater lagoons predominate, richness was negatively associated to urbanization and positively associated to agriculture. The results suggest that fish communities from freshwater coastal lagoons are more sensitive to land use than brackish lagoons. Differently from brackish lagoons, that are colonized by both freshwater and marine species, freshwater lagoons rely on neighboring lagoons as species donors. However, this apparent resilience of the brackish lagoons must be regarded with caution, since the increase in marine connections due to artificial sandbar openings may impair freshwater species with time. [ABSTRACT FROM AUTHOR]

The Brazilian strategy to overcome the spread of COVID-19 has been particularly criticized due to the lack of a national coordinating effort and an appropriate testing program. Here, a successful approach to control the spread of COVID-19 transmission is described by the engagement of public (university and governance) and private sectors (hospitals and oil companies) in Macaé, state of Rio de Janeiro, Brazil, a city known as the National Oil Capital. In 2020 between the 17th and 38th epidemiological week, over two percent of the 206,728 citizens were subjected to symptom analysis and RT-qPCR testing by the Federal University of Rio de Janeiro, with positive individuals being notified up to 48 h after swab collection. Geocodification and spatial cluster analysis were used to limit COVID-19 spreading in Macaé. Within the first semester after the outbreak of COVID-19 in Brazil, Macaé recorded 1.8% of fatalities associated with COVID-19 up to the 38th epidemiological week, which was at least five times lower than the state capital (10.6%). Overall, considering the successful experience of this joint effort of private and public engagement in Macaé, our data suggest that the development of a similar strategy countrywise could have contributed to a better control of the COVID-19 spread in Brazil. Quarantine decree by the local administration, comprehensive molecular testing coupled to scientific analysis of COVID-19 spreading, prevented the catastrophic consequences of the pandemic as seen in other populous cities within the state of Rio de Janeiro and elsewhere in Brazil. [ABSTRACT FROM AUTHOR]

With the aim of assessing whether hydrological alterations differently affect non-native and native fish species in coastal systems, we investigated fish assemblages along the fluvio-estuarine ecotone of the Neotropical São João River, Brazil. During a year, samplings with standardized efforts and limnological parameter records were carried out bimonthly at 15 sampling points in the last 50 km of the São João River, representing natural (meandering riverine and estuarine) and modified (reservoir, channelized and drained floodplain) stretches. We recorded 48 marine and 51 freshwater fish species, with 12 non-native species among the latter. Several native species were exclusively found within natural stretches, whereas non-native species presented significantly higher biomass catches in modified stretches. Only three species occurred in the entire study area, all of which were non-native species. Non-native species were associated with low dissolved oxygen and pH levels below the dam, whereas native freshwater species responded negatively to water transparency, and marine species responded positively to water conductivity at the hydrologically unaltered points. The hydrological alterations disrupted the fluvio-estuarine ecotone of the lower São João River, which plays the role of a dispersion source for non-native species and where invasive species are favored. [ABSTRACT FROM AUTHOR]

Peacock basses (Cichla spp.) are native to the Amazon basin but introduced to different parts of the world. Almost thirty years ago, Cichla kelberi was introduced in an impoundment of the São João River, a coastal system in southeastern Brazil. Recently, this cichlid invaded the estuarine section of the basin. This study aims to analyze spatial and temporal variations in catch of C. kelberi and fish assemblage structure along the estuarine stretch of this river and how abiotic variables affect their distribution. Sampling was performed in four segments downstream of the dam. Principal component analysis revealed that abiotic variables displayed temporal and spatial variation, in part due to the salinity gradient, that were more pronounced in the dry season. Cichla kelberi occurred in all segments, but mainly in shallow and vegetated habitats of the middle course and barely in the most downstream. Eighty-one fish species were recorded, nine of which were non-native, representing 33.4% of total catch. A redundancy analysis indicated that the fish assemblages showed marked spatial variation, mostly related to the salinity gradient. The lowermost segment of the river was dominated by marine species, the only locality where non-native species summed less than 40% of the catches. In the upstream segments, higher oxygen levels and lower temperatures influenced the occurrence of most species. Higher salinity of the estuary seems to limit the spread of C. kelberi, but the invader may reach adjacent basins in years of exceptional floods. The eurihalinity and piscivory of C. kelberi partly explain its invasive success. [ABSTRACT FROM AUTHOR]

Neotropical freshwater ecosystems are experiencing a great expansion in the number of invasive species, which is especially alarming since this region harbours 30% of the world’s fish biodiversity with high levels of endemism. We aimed to evaluate the main predictors of peacock basses (Cichla spp.) abundance outside their native range, which are the Amazon and Tocantins-Araguaia river basins. We used multivariate ordination techniques and multimodel inference to analyse peacock basses abundance in twelve reservoirs of the Paraíba do Sul river basin, southeastern Brazil. Interestingly, reservoirs at higher (southernmost) latitudes, located in more populated areas, had higher water temperature and lower turbidity, due to increased water residence time, and these three variables were also positively correlated with abundance of this warm-water invasive fish. Habitat structure was less important in explaining peacock basses abundance, which was not significantly related to biotic factors (fish species richness and time since peacock basses introduction). We hypothesize that the observed effects of reservoir management on limnological features and peacock bass abundance, particularly water residence time (as a mediator of temperature and turbidity), may apply to other Neotropical basins and could influence the impact of this invader. [ABSTRACT FROM AUTHOR]

This study aimed to characterize species composition and abundance of fish assemblages of low-order streams of the Machado River Basin and to identify the main environmental factors associated to fish assemblages along the elevational gradient. Fishes were collected by seine and dip nets, along an 80-m stretch of 71 streams. In each site, we recorded physical, chemical, and land–water ecotone variables. We collected 22,702 specimens of 91 species. Species richness and abundance varied negatively with elevation. Ordination and similarity analyses detected that streams located in higher and middle elevation ranges differed in species composition from those in the lower elevation range. Almost one-third of the recorded species were selected as indicator species. Species of the families Trichomycteridae, Cichlidae, Gymnotidae, and Characidae were closely associated with the land–water ecotone and structural characteristics of lower elevation range, whereas several other Characidae species were more abundant in middle elevation range, where aquatic vegetation cover and conductivity values were higher. By assuming that composition and relative abundance of fish respond to environmental changes, hydrological characteristics may be viewed as environmental filters for stream assemblages by ultimately selecting the pool of species able to reach for specific elevation ranges and meet their biological requirements. [ABSTRACT FROM AUTHOR]

We performed an experimental manipulation of trahira Hoplias aff. malabaricus in a series of isolated lakes of the upper Paraná River floodplain to evaluate its short-term impact on the structure of fish assemblages. The effects of trahira density (treatment groups: addition, removal, and reference) in two habitat categories (open and macrophyte-covered areas) on attributes of the fish assemblage structure were evaluated (using rm-ANOVA) over 120 days. Reductions in species richness were recorded in all assemblages and were more pronounced at the end of the experiment within macrophyte-covered areas of the lakes where H. aff. malabaricus was removed. In these lakes, the number of fish was also significantly smaller and evenness was significantly higher than in those in which trahira were added or maintained at natural densities. The increase of the relative abundance of all size classes over the first 60 days on the assemblages where trahira was present, and the decrease of the small-sized fish where trahira was absent contributed to the lack of pronounced alterations in total biomass. The absence of the predator from its preferred habitat was found to negatively affect the less abundant species, which seemed to be highly sensitive to the effects of interspecific competition among prey species. In addition to the well-known effects of hydrological seasonality, the role played by native predators might be important in determining the persistence of local species in the fish assemblages of Neotropical floodplains. [ABSTRACT FROM AUTHOR]

Modern biological invasions represent a major facet of the Anthropocene, yet the invasive potential of species remains poorly understood. In this context, this study compared ecological traits of native and non-native populations of Cichla kelberi, a powerful invader, to investigate the hypothesis that this fish exhibits phenotypic and behavioral variations, which may confer adaptability to different conditions. Data on population structure, trophic ecology, and reproduction were collected from populations in different Neotropical impoundments. We found differences in population structure, with larger mean sizes and a lower proportion of juveniles in the native population. All populations exhibited piscivore behavior, but a higher incidence of empty stomachs and a less diverse diet characterized some non-native populations, with the consumption of non-fish resources and cannibalism. Non-native populations also showed prolonged reproduction and early maturity. In general, differences were not restricted to the contrast native vs. non-native, as introduced populations showed considerable divergence among themselves. Results confirmed the existence of phenotypic and behavioral variation in C. kelberi, which must affect its invasive potential by conferring adaptability to novel conditions in specific localities and contexts. These aspects make C. kelberi an almost certain invader of artificial impoundments located in tropical ecosystems of the world. [ABSTRACT FROM AUTHOR]