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Ecological or quality status is an integral concept that reflects the degree of deterioration of aquatic environments. To measure it, protocols have been designed that demonstrate changes in the structure and functioning of biotic communities in response to anthropogenic pressures. The ecological status of the Ánimas River was evaluated along its longitudinal axis, using the IMEERA, IMARBO, and BMWP-Col indices. The samplings were carried out in dry and rainy seasons, in four sections of the longitudinal axis. Physicochemical data of the water and hydromorphological data were taken. Macroinvertebrates were collected using a Surber net. The ions dissolved in the water were the most relevant factors of the set of physicochemical variables. The hydromorphological index indicated that the points at lower elevations in the basin presented a deficient score. Regarding the abundance and composition of macroinvertebrates, a greater abundance was reflected in the dry season and a greater richness in the rainy season. The IMEERA and BMWP-Col indices had a similar behavior with lower values in the dry season, while in the rainy phase they reached the highest records, revealing clear differences in the ecological status of the studied points. The IMARBO index presented a different behavior according to which the lowest elevation points (one and two) reflected a condition of greater deterioration compared to the highest points (three and four). In this last point, the three indices showed the best quality condition. This study contributes to the knowledge of the behavior of Andean rivers in relation to ecological quality indices. [ABSTRACT FROM AUTHOR]

Introduction: Tropical rivers are increasingly being affected by fragmentation and regulation; and, in Colombia, dams are known to endanger endemic fishes through, among others, limited migration and reduced availability of sediment-based feeding networks. However, knowledge of native ichthyofauna affected by dams in high Andean rivers is still incipient. Objective: To assess the effects of the Neusa dam on the ichthyofauna. Methods: We compared two rivers’ sections, one above and one below the dam with the Richter IHA System, we sampled three 100 m long transects in each section, every two months, between 2017 and 2019. The fishes were returned to the river after body measurements. Results: We collected 729 individuals from five families; Trichomycterus bogotense were smaller under the dam; Oncorhynchus mykiss was smaller and less abundant; and there were no differences for Grundulus bogotensis and Eremophilus mutisii. Independently of climatic factors, O. mykiss and G. bogotensis were more abundant above the dam, and E. mutisii and T. bogotense under the dam. Conclusion: The five fish species differed in how the populations differed above and under the dam, suggesting that some are benefited by the dam, while others become smaller and less abundant. [ABSTRACT FROM AUTHOR]

Aquatic macroinvertebrates are recognized as bioindicators of water quality. In Colombia, the studies have mainly been addressed by the family taxonomic level. This work analyzes the responses in abundance, richness, and diversity of the Diptera at the genus level in high Andean rivers (Bogotá River and Fucha River), in periods of low and high waters. The specimens were collected with three methods: Surber net, hand net, and rock washing. The average temperature was 12.9 ºC and oxygen saturation was close to 100 % or more, except for the lower section of the Bogotá River, before the Villapinzón town. 13 690 Diptera were collected from ten families and 40 genera. Taxonomic richness was high with the greatest variation in the lower sections of the two streams. The Chironomidae subfamilies were the most abundant. Canonical correspondence analysis (CCA) showed that Orthocladiinae were associated with water conductivity; the Gigantodax genus (Simuliidae) did not show a clear relationship with any variable; conversely, the genus Simulium was linked to the caudal. In general terms, the association between taxa and environmental variables was clearer for genera than for families, but it was not robust enough. It is suggested that to find a higher degree of biota-environment association, it is necessary to carry out analyzes at the species level, considering local and temporal variations. [ABSTRACT FROM AUTHOR]

Introduction: The structure, taxonomic diversity and functional diversity of the aquatic macroinvertebrate assemblages are estimators sensitive to variations in the surrounding environment. The physical environment is a key factor, where the substrate and hydraulic dynamics modify the availability of resources, the structuring, the functioning of the community and the ecosystem. Objective: Determine the structure, taxonomic diversity and functional diversity of the macroinvertebrate assemblages under different abiotic conditions in the Hato Laguna river, a tributary of Lake Tota. Methods: 120 biological samples were collected in four sampling events in two reaches in the river. Depth, flow velocity, channel width and roughness of the substrate were measured in situ. The functional traits evaluated were: body length, body shape, type of breathing, type of locomotion, trophic guild and functional feeding groups. Results: A total of 38 taxa were identified; Diptera, Coleoptera and Trichoptera orders presented the highest abundance of families and genera. Orthocladiinae, Andesiops sp. and Simulium sp. were more abundant groups under high-velocity conditions in the upper reaches. Nectopsyche sp. was abundant in the lower sections related to lower velocity and greater channel width. According to the taxonomic diversity indices, variation by reaches and samplings was presented without observing trends. In the upper reaches, the MOPF trophic guild (collectors), in tegument respiration, and small body size were characteristic. In the lower reaches, the assembly was of the scraper type with gill breathing and flattened body shape. The richness, divergence and functional evenness were higher in the upper reaches. In the Canonical Correspondence Analysis, the highest values of width and speed were related to categories attached to the substrate and endobenthic, while low width and roughness were related to the categories of flattened body shape, microphytes food resource, and maximum body size. Conclusions: The system presented a variation in the abiotic conditions, in the structure, taxonomic and functional diversity of the macroinvertebrates. The role of the flow velocity as a determining variable of the structure and function of the community is highlighted. Likewise, functional diversity stands out as an expression of the described traits, which is why it is related in the upper reaches with the dominance of taxa such as Orthocladiinae, Chironominae, Simulium sp. and Andesiops sp. [ABSTRACT FROM AUTHOR]

The standardized streamflow index (SSI) was developed following the theoretical concept of the standardized precipitation index (SPI) for monitoring and comparison of spatial and temporal patterns of the hydrological conditions, considering monthly streamflows as input variable. A fundamental step for its calculation is to select the probability distribution that best fits the frequencies of observed streamflows. This work compares 6 widely used probability distributions (gamma, lognormal II, Pearson III, Weibull, logistic and loglogistic) for the representation of hydrological variables in order to determine the most adequate over the watersheds of Cuyo and Patagonia (Argentina). The Anderson-Darling (AD) test was considered to evaluate the goodness of fit, which guarantees rigorous testing for extreme events analysis. Recommendations are given considering the fits based on the AD statistics and the analysis of the normality of the SSI time series, considering that none of the analyzed distributions were adequate in all the basins and months of the year. These results highlight the use of the lognormal II distribution for the representation of monthly streamflows in the Cuyo region and the assessment of hydrological droughts based on this distribution. In the case of Patagonia region, the loglogistic distribution is the most adequate for the representation of the monthly streamflows. However, it was observed that the SSI time series based on this distribution have biases in their mean values, standard deviation and percentage of months under drought conditions. These factors may affect their quality for the monitoring of hydrological droughts over Patagonia. Therefore, it is recommended the use of the lognormal II distribution for the representation of monthly streamflows over the study area and its application to the monitoring of hydrological droughts. [ABSTRACT FROM AUTHOR]

A species' reproductive tactics and life history strategy are the result of a complex evolutionary interplay where individuals constantly adjust their energy investment in accordance with the environmental conditions. Fecundity is a key feature of life that reflects the amount of energy that an individual invests in reproduction. Little is known about the response of this life history feature of species that persist in reservoirs, and for this reason, fecundity and some variables related to it were analyzed for some of the most abundant species within the fish assemblage in the area of influence of the cascading reservoirs Porce II and Porce III. Sampling was carried out from September 2011 to December 2016, during contrasting climatic periods (dry and rainy seasons), in 31 sites distributed throughout Porce II and Porce III reservoirs, and also including the river channel and tributary streams of the reservoirs. It was found that Astyanax microlepis had the highest value of total fecundity (20.202 eggs on average), while Poecilia reticulate had the lowest values (15 embryos). A relation was found between the number of eggs and the size of the fish (standard length and body weight). The fecundity of the species analyzed was similar among those phylogenetically related (species of the same family), and in turn, it was determined that this reproductive trait was specific to each species. [ABSTRACT FROM AUTHOR]

Orinoco versant, Venezuela. Most Andean mountain streams of the Orinoco Basin in Venezuela, had been suffering various disturbances. in spite of this, fish communities have been poorly evaluated in terms of spatial and temporal gradients. Thus, the generation of information about these communities is a priority, since it may support conservation of regional hydrobiological resources. For this, six sites were monthly evaluated in tributaries of upper Turbio River in Sierra de Portuguesa (770-1 305msnm), during the dry season and the beginning of the rainy season (January-April 2012); we characterized stream dimensions, substrate and water physicochemical variables. Electrofishing was used to determine the number and abundance of fish species. The fish communities and their stability were evaluated by exploring the changes in richness and abundance, coefficients of variation, hierarchical classification and non-metrical multidimensional scaling analysis. The sites conservation status was estimated with a habitat integrity index. Our results showed that richness of the 12 species found varied according to the mountain elevation, the tributaries and the conservation status of the sites. Chaetostoma dorsale, Creagrutus taphorni and Chaetostoma milesi comprised 90.8% of the relative abundance, and maintained the first ranks during the study period. The communities had little spatio-temporal variation which was associated with a gradient signed principally by the amount of shadow, rocks and gravel cover, water temperature and conductivity. Stability was moderate but varied with elevation and according to site conservation status. The tributaries in upper Turbio River were found to be under severe impacts and their fishes were found impoverished and at risk. [ABSTRACT FROM AUTHOR]