Population biology of Astyanax lacustris (Pisces, Characiformes) in a Neotropical reservoir and its tributaries.

The aging process of reservoirs has been extensively investigated; however, little is known about how fish populations are adjusted after many years of impoundment. Thus, this study aimed to compare the diet, length-weight relationship, sizes classes, variation in size, and age of Astyanax lacustris Lütken, 1875 collected from lotic and lentic habitats of an aging reservoir. The study group consisted of 730 captured fishes. We found that specimens collected from lotic habitats had a wider range of size classes (1.0 to 12.0 cm), were linked to a high frequency of juveniles (48.7%), and had greater feeding activity (higher stomach fullness). In contrast, fishes collected from lentic environments exhibited high rates of capture (78.4%), increased frequency of adults (87.3%), and higher values of mean standard length. The length-weight relationship indicated that lentic fishes were heavier than fish collected from lotic areas. Moreover, we observed 37 food items in A. lacustris diet, mainly plant material, algae, Cladocera, Hymenoptera, Coleoptera, and Ephemeroptera. Differences among the diet of fishes between sites were evidenced with Permanova (p < 0.05). Astyanax lacustris can be considered a persistent species in Chavantes Reservoir after aging, encountering conditions to complete its life span and adjusting to food resources.

Plastic pollution: A focus on freshwater biodiversity.

Plastics are dominant pollutants in freshwater ecosystems worldwide. Scientific studies that investigated the interaction between plastics and freshwater biodiversity are incipient, especially if compared to the marine realm. In this review, we provide a brief overview of plastic pollution in freshwater ecosystems around the world. We found evidence of plastic ingestion by 206 freshwater species, from invertebrates to mammals, in natural or semi-natural ecosystems. In addition, we reported other consequences of synthetic polymers in freshwater ecosystems-including, for instance, the entanglement of animals of different groups (e.g., birds). The problem of plastic pollution is complex and will need coordinated actions, such as recycling programs, correct disposal, stringent legislation, regular inspection, replacement of synthetic polymers with other materials, and ecological restoration. Current information indicates that the situation in freshwater ecosystems may be as detrimental as the pollution found in the ocean, although highly underappreciated.

Species richness and functional structure of fish assemblages in three freshwater habitats: effects of environmental factors and management.

In this study, the inverted trophic hypothesis was tested in the freshwater fish communities of a reservoir. The distribution of fish species in three freshwater habitats in the Jurumirim Reservoir, Brazil, was examined using both species richness and the relative proportions of different trophic groups. These groups were used as a proxy for functional structure in an attempt to test the ability of these measures to assess fish diversity. Assemblage structures were first described using non-metric multidimensional scaling (NMDS). The influence of environmental conditions for multiple fish assemblage response variables (richness, total abundance and abundance per trophic group) was tested using generalised linear mixed models (GLMM). The metric typically employed to describe diversity; that is, species richness, was not related to environmental conditions. However, absolute species abundance was relatively well explained with up to 54% of the variation in the observed data accounted for. Differences in the dominance of trophic groups were most apparent in response to the presence of introduced fish species: the iliophagous and piscivorous trophic groups were positively associated, while detritivores and herbivores were negatively associated, with the alien species. This suggests that monitoring functional diversity might be more valuable than species diversity for assessing effects of disturbances and managements policies on the fish community.