The large number of less-known coastal drainages in the Atlantic Forest still represents an important gap in the knowledge of ichthyofauna. It is evaluated the taxonomic diversity, frequency and constancy of occurrence, and the distribution of species in the various segments of the Perequê-Açu river basin, state of Rio de Janeiro, Brazil. Twelve sampling campaigns resulted in 13,423 individuals, belonging to seven orders, 10 families, 21 genera, and 23 native species. Cyprinodontiformes and Siluriformes represented about 87.2% of the total abundance, mainly due to the contribution of Phalloceros anisophallos and Schizolecis guntheri, which account for 63.2% of the total sampled individuals. The analysis of constancy of occurrence reveals that 78.3% of the drainage species are residents, with approximately 93% of the residents of the Carrasquinho River sub-basin. The Sertões River sub-basin had the largest number of species in total: 18. The rarefaction curve did not reach an asymptote, although Chao 2 and bootstrap estimate the richness of 23.9 species and 23.7 species, respectively. The results of PERMANOVA, PCoA, and SIMPER indicate that the fish composition along the catchment is not homogeneous. The conservation status of species is also discussed, regionally, nationally, and globally.
The susceptibility of streams to anthropogenic interference raises the need for continuous assessment of their environmental condition. From early studies to recent approaches, metrics derived from fish assemblages have proven to be fundamental tools in evaluating the ecological condition of watercourses. We assessed the environmental degradation of streams inside and surrounding the Córrego Grande Biological Reserve, state of Espírito Santo, Brazil, to develop and apply a biotic index for this region based on fish metrics. We performed samplings in 19 stream sites along 2012, 2018 and 2019, and collected 24 species belonging to five orders, 11 families, and 21 genera. The sites were classified as least-disturbed (N = 9, all within the protected area), intermediate (N = 8), and most-disturbed (N = 2). Ordination analyses distinctly separated the sites according to their disturbance classes, revealing that the percentage of native vegetation cover in 100 m buffers and type of riparian vegetation played an important role in the environmental quality of these sites. From the initial 38 metrics, three were able to distinguish between disturbance classes: percentage of Siluriformes and Characiformes species, percentage of nektonic species, and percentage of omnivorous individuals. Our results show that these metrics are significant factors to be considered in monitoring the environmental degradation of Atlantic Forest streams.
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