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Ash runoff into freshwater systems from fire events, coal combustion, and volcanic activities threatens to biodiversity conservation, given its toxicity to various aquatic organisms. However, despite many studies reporting a negative relationship between ash exposure and the biological traits of freshwater fish, non-significant and even positive associations can also be found in the literature. Here, a systematized review was conducted to explore patterns and biases in studies examining the impacts of ash on freshwater fish. Out of the 43 studies included in this review, 38 reported harmful effects of ash exposure on fish traits. The median lowest concentration of ashes capable of inducing negative effects on fish traits was found to be 2 g/L. Diet restrictions (84.6%), behavioral changes (83.3%), cytological and genetic damages (64.7%), and bioaccumulation of toxic compounds (57.1%) exhibited the highest proportions of negative results in statistical evaluations testing ash effects on fish traits. In contrast, biomarkers related to reproduction (94.7%) and metabolism (66.4%) had the highest proportion of non-significant associations between fish traits and ash exposure. Statistical models indicate that the ash source does not determine the direction (positive or negative) of its effect on fish traits. Furthermore, no evidence supports the hypothesis of similar sensitivity levels to ash exposure among phylogenetically closely related fish species. Together, the evidence provides a cohesive perspective on the detrimental effects of ash on fish, highlighting the effective necessity to manage the influx of ash into watercourses. [ABSTRACT FROM AUTHOR]

An initial and comprehensive map of ecological regions across the conterminous United States was provided by Omernik in 1987. Because that paper was the most-cited published by the Annals of the American Association of Geographers, we sought to assess and quantify its contribution to science. To do so, we conducted a scientometric analysis to address the following main questions: 1) What are the temporal and spatial citation trends? We expected that Omernik's paper would still be employed 36 years after its publication, and mostly in the United States of America. 2) For what types of environments and organisms has it been applied? Based on its generality, we expected that it had been applied to both terrestrial and aquatic ecosystems. 3) What are the main applications of Omernik's article? We predicted that it would mostly be used for describing and delineating study sites and management areas, as well as for selecting regional reference sites. The number of citations presented a positive temporal increase, indicating its continued applicability. Most papers dealt with aquatic environments, mainly in streams carried out predominantly in the United States of America, as was one of its earliest applications. The usefulness of ecoregions for assessing and managing biotic and abiotic patterns and distributions were the main topics addressed by scientists. Ecoregions have offered a general framework for developing regional expectations and rational regional management policies across large areas, as was their original intent. In addition, ecoregion maps were used for communicating patterns—or the lack of them—to interested scientists, citizens, and decision-makers. That comprehensiveness of Omernik's ecoregion approach has led to its widespread applicability and continued usefulness to a diverse set of scientific and management disciplines. [ABSTRACT FROM AUTHOR]

Multimetric indices (MMIs) are common tools used to assess the biological status of ecosystems. However, not all the components of biological integrity have been equally addressed, since most of MMIs do not consider nonnative species, which are a great threat to ecosystems integrity. We performed a systematic review of how nonnative species have been considered in MMIs to assess biological conditions worldwide. Using a systematic review of the literature we identified to what extent nonnative species have been included as a disturbance factor for determining reference conditions and if specific metrics related to both nonnative and native species have been taken into account in the MMIs around the world. We also identified the most frequent species origin metrics that have been included in the MMIs. We searched for articles published in English up to 2016 that applied or developed an MMI in the Web of Science database (Clarivate Analytics). Following the PRISMA guidelines, we analyzed 409 articles. We found that only 1.2% of the studies used nonnative species as a disturbance factor in determining reference conditions. About 66% of articles did not test or did not provide the information if they tested metrics on native or nonnative species. Most of the articles (53%) that tested native or nonnative metrics were fish-based MMIs. We found 97 different metrics, of which 69% were related to native species, whereas 31% were related to nonnative ones. Native richness was the most used metric in studies that considered species origin (23.5%). Our main results evidence that nonnative species are overlooked in biomonitoring programs. Owing to the well-known impacts of them on ecosystem integrity, their inclusion in definition of reference conditions and in MMIs metrics should be considered as bioassessment criteria. [ABSTRACT FROM AUTHOR]

A systematic review was conducted to identify trends and gaps in studies concerning nonnative populations in a neotropical floodplain and identify which population ecology topics has been predominant among studies in such floodplains. The large majority of the articles were field observational studies based on nonnative fish populations. A focus on ecological interactions, in particular competition and predation, was predominant in these studies. Hypotheses related to environmental filters and biotic resistance were used most frequently to support studies on river the floodplain, but many studies not addressed the invasion theory. Impoundment was the introduction vector associated with the largest number of studies of nonnative populations. We present conceptual aspects that may guide future studies on nonnative population ecology and inform conservation policies in floodplain ecosystems. [ABSTRACT FROM AUTHOR]

We developed MMI models that combine responses of fish and benthic macroinvertebrates for the evaluation of the biotic integrity of streams. The MMI was developed using a dataset covering stream sampling sites in the South of Brazil. Reference streams were identified based on the physical and chemical conditions and riparian vegetation. Thirty-four metrics were calculated and evaluated for their range, redundancy, and responsiveness to the environmental perturbation. We applied a robust approach to select the most sensitive metrics and MMI models based on the complexity and ability of the index in distinguishing impacted and reference sites. The four best MMI models selected are composed of different combinations of the eight metrics: % fish herbivorous, fish evenness, fish abundance, % macroinvertebrate shredder; % macroinvertebrate predator; % macroinvertebrate tolerant, % macroinvertebrate swimmer, and % macroinvertebrate burrower. All of the MMI models selected presented good performance in distinguishing reference streams from those impacted by different forms of land use. This study is one of the few attempts to use more than one biological assemblage in a single-multimetric index. Accordingly, we believe that the unified MMI we developed could be a useful tool to assist in the conservation and management of water resources in Neotropical regions, specially, in the implementation of ecological integrity tools more cost-effectively. [ABSTRACT FROM AUTHOR]

Climate change threatens freshwater fish by severely modifying water quality and hydrological dynamics, hence altering the species distribution. We assessed the climate change effects on the geographical distribution of Salminus brasiliensis, a keystone species of economic interest in the La Plata River basin. Using ecological niche models, we estimated the species range in the present time and assessed the range shift phenomena through climatically suitable areas in the future. We also quantified the predictive uncertainty from niche models, atmosphere–ocean general circulation models, and carbon emission scenarios. Our predictions indicated a great range contraction of S. brasiliensis in the future. The south-central portion of the basin should retain the climate refuge function for the species at 2050. Nonetheless, the segregation of this climate refuge in two smaller parts was predicted at the end of the century. Our study also revealed that the greatest source of uncertainty in forecasts of species range shifts arises from using alternative niche algorithms in modeling process. Our results contribute to more effective measures for conservation of S. brasiliensis, thus helping to ensure the ecosystem processes and socioeconomic activities in the basin dependent on this species. [ABSTRACT FROM AUTHOR]

The Neotropical region has the greatest taxonomic and functional diversity of fish in the world. However, this biodiversity has been threatened by the introduction of non-native species. Therefore, we present a systematic review of the literature concerning the introduction of non-native fish species in Neotropical freshwaters. We examine the origins of non-native fish species, as well as the invaded ecoregions and introduction vectors. Oncorhynchus mykiss, Salmo trutta, Cichla kelberi, and Oreochromis niloticus were the most frequent introduced fish species and rivers and reservoirs were the most studied freshwater ecosystems. Impoundments, aquarium trade, sport fishing, and aquaculture were recorded as the main vectors for the introduction of non-native fish species. Most of the studies were conducted in Brazil. The Upper Parana ecoregion exhibited the largest number of non-native fish species, of which the majority originated from the Lower Parana ecoregion. We noticed that the origins of non-native fish species are linked to their introduction vectors, as several non-native fish species arrive from areas near to where they are introduced, mainly by impoundment and sport fishing. On the other hand, species from regions outside the Neotropics are especially introduced by aquarium trade and aquaculture. [ABSTRACT FROM AUTHOR]

The use of multimetric indices (MMIs) became a common practice for evaluating ecological integrity of aquatic ecosystems. However, most developed MMIs ignore non-native species as an impact source to establish reference conditions. We developed an MMI to identify if non-native fish species are associated with Neotropical stream integrity by considering the presence of non-native species as an impact source. We calculated and evaluated responsiveness to the presence of non-native species using fish metrics, which were selected with a bootstrap procedure. Streams for calibration and validation were also selected with a bootstrap procedure. From the candidate MMIs generated, we selected models with different combinations of fish metrics. The generated MMIs presented a satisfactory performance in distinguishing reference streams from those impacted by non-native species. The abundance of non-native species was highly correlated with urbanization and seems to be more important than urbanization to drive native abundance loss. Our study is one of the first attempts to develop MMIs in which non-native species are considered as impact sources and used to identify impacted and reference sites. The final MMI that we developed might be a useful tool for aquatic biodiversity conservation and the development and application of non-native species control actions. [ABSTRACT FROM AUTHOR]

The biomonitoring of aquatic ecosystems in developing countries faces several limitations, especially related to gathering resources. The present study aimed at comparing the responses of fish and benthic macroinvertebrates to environmental change, to identify which group best indicates the differences between reference and impacted streams in southern Brazil. We determined reference and impacted sites based on physical and chemical variables of the water. For the analysis and comparison of biological responses, we calculated 22 metrics and submitted them to a discriminant analysis. We selected from this analysis only six metrics, which showed that the two studied assemblages respond differently to environmental change. A larger number of metrics were selected for macroinvertebrates than for fish in the separate analysis. The metrics selected for macroinvertebrates in the pooled analysis (i.e., fish and macroinvertebrates together) were different from those selected in the separate analysis for macroinvertebrates alone. However, the metrics selected for fish in the pooled analysis were the same selected in the separate analysis for fish alone. The macroinvertebrate assemblage was more effective for distinguishing reference from impacted sites. We suggest the use of macroinvertebrates as bioindicators of Neotropical streams, especially in situations in which time and money are short. [ABSTRACT FROM AUTHOR]