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.

Morphological deformities in the invasive driftwood catfish Trachelyopterus galeatus in the Upper Paraná River basin, Brazil: a sign of human impact?

In this study, the authors report morphological deformities in driftwood catfish Trachelyopterus galeatus (Auchenipteridae), an invasive catfish occurring in the Upper Paraná River basin, Brazil. The frequency of anomalous individuals reached 18.3% of all catches. X-ray images showed anomalies, or total absence of structures, in the pelvic girdle. The authors also observed the absence of the adipose fin and mental barbels. These findings are of extreme importance for evidencing the anthropogenic impact on aquatic communities as the region suffers within fragmentation by dams and pollution from several human activities. This sort of information can be used in management systems and environmental monitoring, especially to protect other species and the native fish assemblage.

Taxonomic loss and functional reduction over time in the ichthyofauna of the Taquaruçu Reservoir, lower Paranapanema River, Southern Brazil

We evaluated the fish composition and ecological attributes of the ichthyofauna collected in a limnological zone of the Taquaruçu Reservoir, lower Paranapanema River. Information about the fish community was updated when compared to the previous study (2006). Non-metric multidimensional scaling (NMDS) showed differences in species composition between periods and community weighted means (CWMs) exhibited changes in functional composition over time. Four functional indices were used in the principal coordinate analysis (PcoA) to measure changes in the functional space of species, whereas functional β-diversity inspected differences in the traits composition between the periods. 1,203 individuals were sampled of 43 species, being 16 non-native and 14 new records. Compared to 2006, 27 species were absent, most of them native to Loricariidae and Anostomidae, while Curimatidae and Pimelodidae decreased in abundance. Functional indexes showed a reduction in functional diversity, whereas new species records exhibited functional redundancy. It might have occurred a simplification of the fish community over time, excluding the migratory and specialists species such as the herbivores and detritivores. Accordingly, we concluded that the ichthyofauna of the Taquaruçu Reservoir might have been undergoing a process towards biotic homogenization.(AU)

Avaliamos a composição de peixes e atributos ecológicos da ictiofauna coletada em uma zona limnológica do reservatório de Taquaruçu, baixo rio Paranapanema. As informações sobre a comunidade de peixes foram atualizadas quando comparadas ao estudo anterior (2006). O escalonamento multidimensional não métrico (NMDS) mostrou diferenças na composição de espécies entre os períodos, e as médias ponderadas da comunidade (CWMs) exibiram mudanças na composição funcional ao longo do tempo. Quatro índices funcionais foram utilizados na análise de coordenadas principais (PcoA) para medir as mudanças no espaço funcional das espécies, enquanto a β-diversidade funcional inspecionou diferenças na composição de traços entre os períodos. Foram amostrados 1,203 indivíduos de 43 espécies, sendo 16 não-nativas e 14 novos registros. Em comparação com 2006, 27 espécies estavam ausentes, a maioria nativa de Loricariidae e Anostomidae, enquanto Curimatidae e Pimelodidae diminuíram em abundância. Os índices funcionais mostraram redução na diversidade funcional, enquanto novos registros de espécies exibiram redundância funcional. Pode ter ocorrido uma simplificação da comunidade de peixes ao longo do tempo, excluindo as espécies migradoras e especialistas como os herbívoros e detritívoros. Dessa forma, concluímos que a ictiofauna do reservatório de Taquaruçu pode estar sofrendo um processo de homogeneização biótica.(AU)