Abstract
Abstract: Despite increasing efforts in recent years to catalog the fish diversity of Amazonian rivers, many regions are still under-sampled, and sandy beach environments are particularly poorly understood. The present study focused on a 300 km stretch of the Acre river, in the southwestern Amazon basin, where we sampled 30 sandy beaches separated by a mean interval of 10 km. We collected 15,329 fish representing 80 species, 26 families, and nine orders. The Characiformes were the most abundant order, providing 88.24% of the individuals collected, followed by the Siluriformes, with 10.03%, while the Siluriformes had the highest species richness, with 37 species (45.0%), followed by the Characiformes, with 30 (37.5%). The most abundant species were the characiforms Knodus orteguasae and Creagruto barrigai. Reliable data on a region’s biota is fundamental for the evaluation of patterns of biodiversity, and the occurrence and management of threatened species. As fish are directly affected by pollutants and the degradation of aquatic environments, further research in areas that are still poorly sampled will be essential for the elaboration of effective conservation strategies.
Highlights
The hydrographic network of the Neotropical region supports the world’s most diverse freshwater fish fauna, with approximately 5,160 species (Reis et al 2016, Jézéquel et al 2020)
The basin of the Neotropical Amazon river is the world’s largest and most diverse freshwater system, with a total area of approximately 7 million km2, representing 20% of all the freshwater discharged into the oceans (Callède et al 2010)
2406 fish species have been recorded in the Amazon basin, including approximately 1402 endemic forms, distributed in 514 genera, 56 families, and 18 taxonomic orders (Dagosta & de Pinna 2019, Jézéquel et al 2020)
Summary
The hydrographic network of the Neotropical region supports the world’s most diverse freshwater fish fauna, with approximately 5,160 species (Reis et al 2016, Jézéquel et al 2020). 2406 fish species have been recorded in the Amazon basin, including approximately 1402 endemic forms, distributed in 514 genera, 56 families, and 18 taxonomic orders (Dagosta & de Pinna 2019, Jézéquel et al 2020). This fauna is distributed throughout an ample diversity of aquatic systems, including major rivers, lakes, streams, floating vegetation, and beaches (Beltrão et al 2019, Oberdorff et al 2019). Beaches are key environments for the maintenance of regional fish diversity, in particular due to their provision of shelter for many species (Olds et al 2018)
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