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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 Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications. [ABSTRACT FROM AUTHOR]

Peacock basses (Cichla spp.) have been introduced in impoundments for decades, and their negative impacts on the native fish fauna have been documented. However, previous studies largely focused on the overall responses of fish assemblages, often neglecting specific predator–prey interactions and the underlying effects of environmental characteristics.Here, the effects of peacock bass introduction on the size structure (<120, 120–180 and >180 mm in total length) of fish assemblages in reservoirs of the Paraíba do Sul river basin were assessed. The abundance and time since the introduction of peacock basses were used as predictors, together with reservoir features, limnological variables and habitat composition as potential influencing factors.Descriptors of the overall community (richness, abundance and species composition) were only marginally associated with the occurrence of peacock basses. However, small and (to a lesser extent) medium‐sized fish were adversely affected by the abundance and introduction time of peacock basses. Two pelagic native characids – namely Astyanax cf. bimaculatus and Oligosarcus hepsetus – were the most affected.Redundancy analysis showed that reservoir age and macrophyte cover were the best predictors of fish assemblage composition. Older reservoirs and reservoirs with a higher cover of macrophytes showed a greater abundance of catfish and characids, respectively.Peacock basses appear to affect fish assemblages through predation on small fish. Therefore, analyses of assemblages by size are recommended, as the use of overall assemblage descriptors may not be sufficient to capture the adverse effects of peacock basses. Moreover, these findings underscore the importance of conserving and restoring habitats in littoral zones, which function as refuges for native fish species in reservoirs. Further educational and management measures are warranted to prevent the spread of peacock basses to other reservoirs in Brazil. [ABSTRACT FROM AUTHOR]

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]

South American peacock basses (genus Cichla) have been widely introduced within and outside the Neotropical region due to their importance to fisheries, despite threats to the native fish fauna. We performed a literature review on the worldwide distribution of valid Cichla species by focusing on records of species richness and populations in their native and non‐native ranges. We tested for an effect of area, the number of large dams, human population density and gross domestic product as drivers of the distribution of peacock basses across the Freshwater Ecoregions of the World (FEOWs). A total of 544 studies led to 1,289 records of nine species. Their distributions within their native range (19 native FEOWs) were narrower than their distributions in their non‐native range (23 non‐native FEOWs), which encompass tropical and subtropical ecoregions of the Americas, Africa, Southeast Asia and the Pacific islands. Several of these FEOWs harboured more than one species, usually C. ocellaris and C. piquiti. Ecoregion areas were positively associated with species richness and population records in native FEOWs, whereas the number of reservoirs was positively related to the records of non‐native populations. These patterns provide further evidence of the role played by reservoirs as the main pathway for the introduction of peacock basses; thus, special attention should be given to the continuous monitoring of the spread of these invaders across watersheds in invaded ecoregions. Considering their broad distribution and the potential for peacock basses to thrive in human‐modified systems, severe damage to the native fish fauna is predicted. [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]

Aim: Fish community composition is shaped by current and historical factors. In recently formed ecosystems, however, as the Quaternary coastal lagoons of South America, the influence of historical factors has less frequently been investigated. The low rate of endemism in these lagoons suggests a limited role for speciation while their dynamic formation history suggests local extinction and dispersal limitation could have affected present species composition. We aimed to assess the influence of past and current factors on the beta diversity of those communities and explore the main processes involved. Location: Atlantic coast of South America. Taxon: Fishes (173 species). Methods: We built a dataset of species occurrence in 129 lagoons across eight freshwater ecoregions of the world (FEOWs) located between latitudes 0° and 36°, and calculated beta diversity (βjac) and its turnover (βjtu) and nestedness (βjne) components. We used a partial Mantel test and multiple regressions on distance matrices to evaluate the importance of past and current factors, and of geographical distance in determining beta diversity. Past variables were those representing the historical freshwater habitat during the last glacial maximum (LGM), and contemporary variables were those related to current habitat. Results: We found high values of βjac within the FEOWs, with βjtu prevailing over βjne. Both past (palaeodrainage) and current (drainage area, salinity and lagoon area) factors affected species dissimilarity (βjac = 46%) and its components (βjtu = 44% and βjne = 20%), although explanation was, in part, shared with geographical distance. Individually, the influence of past factors was prevalent in beta diversity and its components. Main conclusions: The large influence of the past factors on beta diversity suggests that major changes in the availability of freshwater habitats and connectivity since the Pleistocene must have affected the colonization, extinction and recolonization processes of fishes along the eastern coast of South America. We suggest that the high beta diversity values result from limited dispersal after extinctions in the LGM. The dissimilar freshwater fish communities currently seen result from heterogeneous subsets of the regional species pool that persisted in landscape refuges during past sea level increases and then recolonized coastal lagoons. [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]

The interest in understanding ecosystem functioning has grown in recent years due to the effects of species loss on ecosystem processes. Even though biotic and abiotic factors control ecosystem processes, their relative influence may vary according to ecosystem dynamics. In flood and coastal plains, these dynamics are mainly represented by flood pulses and hydroregime, respectively. The objective of this study was to investigate the importance of abiotic and biotic factors for the ecosystem processes represented by zooplankton secondary production (SP), biomass (ZB), and resource use efficiency (RUE) in lentic waterbodies subjected to different hydrological regimes. We hypothesised that abiotic factors would more strongly determine the ecosystem processes in temporary waterbodies and floodplain lakes, given their greater susceptibility to environmental changes. Biotic factors would be more relevant in coastal lagoons due to their greater temporal stability.Sampling was undertaken quarterly over 1 year in eight coastal lagoons, 10 temporary ponds and five floodplain lakes. The environments were characterised in relation to limnological variables, and zooplankton functional divergence, functional dispersion (FDis), functional evenness, functional richness, and taxonomic richness were measured. Analysis of variance (ANOVA) was used to verify seasonal changes in SP, ZB, RUE, functional diversity, richness, and abiotic factors. Linear mixed models were used to determine which abiotic and biotic factors were the most important for ZB, SP, and RUE.In the coastal lagoons, RUE differed over time. In the temporary ponds and floodplain lakes, no seasonal significant differences were observed for any of the zooplankton production variables. The linear mixed model analyses showed that models composed mainly of biotic factors were better fitted to the production variables. For coastal lagoons, phytoplankton density affected ZB, SP, and RUE increasing them by 9.9 mg DW/m3, 12.4 mg DW/m3, and 1.23, respectively. For temporary ponds, FDis lowered ZB by 6.9 mg DW/m3 and taxonomic richness increased SP and RUE by 14.2 mg DW/m3 and 1.17, respectively. For floodplain lakes, FDis lowered ZB it by 9.9 mg DW/m3 and functional divergence lowered RUE by 0.81.The present study demonstrates that biotic factors are the main determinants of ecosystem processes in neotropical lentic waterbodies, irrespective of their annual hydrological regimes. Complementarity effects and high functional diversity are more important in more stable environments, whereas redundancy and low functional diversity prevail in environments subject to more frequent environmental changes. Biotic factors play a major role in ensuring the functioning of aquatic ecosystems and indicate the important role of biodiversity in enabling ecosystem states to be maintained after disturbances and to prevent changes in ecosystem processes. [ABSTRACT FROM AUTHOR]

Understanding whether and how different habitat features affect patterns of life-history variation is an intriguing aim in evolutionary ecology. We tested how a suite of biotic and abiotic factors simultaneously affect life-history patterns in six populations of the livebearing fish Poecilia vivipara inhabiting coastal lagoons in southeastern Brazil, varying greatly in salinity and fish communities. We sampled potential competitors (cyprinodontiform fishes) and piscivores, and we measured nine limnological variables in the wet and dry seasons during 2 years. We found that size at maturity and offspring size were strongly and negatively influenced by the abundance of piscivores, and that reproductive allocation was strongly and positively influenced by variations in resource abundance and temperature among seasons. Effects of salinity on size at maturity, female reproductive investment and offspring size were indirect, via piscivore abundance, highlighting the potential for indirect effects that can be detected only by analysing multiple habitat features simultaneously. This suggests caution in interpreting associations between life histories and salinity in wild populations. Observed patterns generally matched theoretical predictions and prior empirical work, but some predictions were not met. Our results suggest that life histories result from a partly predictable complex combination of direct and indirect effects of habitat features, which can sometimes act antagonistically. [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]

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Understanding whether and how ambient ecological conditions affect the distribution of personality types within and among populations lies at the heart of research on animal personality. Several studies have focussed on only one agent of divergent selection (or driver of plastic changes in behavior), considering either predation risk or a single abiotic ecological factor. Here, we investigated how an array of abiotic and biotic environmental factors simultaneously shape population differences in boldness, activity in an open-field test, and sociability/shoaling in the livebearing fish Poecilia vivipara from six ecologically different lagoons in southeastern Brazil. We evaluated the relative contributions of variation in predation risk, water transparency/visibility, salinity (ranging from oligo- to hypersaline), and dissolved oxygen. We also investigated the role played by environmental factors for the emergence, strength, and direction of behavioral correlations. Water transparency explained most of the behavioral variation, whereby fish from lagoons with low water transparency were significantly shyer, less active, and shoaled less than fish living under clear water conditions. When we tested additional wild-caught fish from the same lagoons after acclimating them to homogeneous laboratory conditions, population differences were largely absent, pointing toward behavioral plasticity as a mechanism underlying the observed behavioral differences. Furthermore, we found correlations between personality traits (behavioral syndromes) to vary substantially in strength and direction among populations, with no obvious associations with ecological factors (including predation risk). Altogether, our results suggest that various habitat parameters simultaneously shape the distribution of personality types, with abiotic factors playing a vital (as yet underestimated) role. Furthermore, while predation is often thought to lead to the emergence of behavioral syndromes, our data do not support this assumption. [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]