Building knowledge to save species: 20 years of ichthyological studies in the Tocantins-Araguaia River basin

Abstract

The Tocantins-Araguaia River basin is the largest basin located entirely in the Brazilian territory. The high degree of endemism of its ichthyofauna has been revealed in several studies, with the upper Tocantins River having the largest absolute number of endemic taxa within the Amazon basin. Here we provide an accurate review of the ichthyofauna of the Tocantins-Araguaia River basin, based on collections made between 2000-2020, including an extensive list of valid fish species occurring in the basin and a discussion of the major threats to its ichthyofauna. Ichthyofauna diversity was further refined based on web searches. Protected Areas and hydropower plants were mapped using shape files or coordinates from the responsible government agencies. 751 species of fishes are currently known from the Tocantins-Araguaia River basin. A considerable increase in fish diversity knowledge occurred in the last 20 years, in parallel with significant anthropic alterations in the basin and its surroundings. Dams constructed along the basin are ranked as the major threats to ichthyofauna. Although the drainage-basin holds several conservation units and indigenous lands, they have not been sufficient to guarantee the preservation of fish species. Our compilation emphasizes that the upper Tocantins River must be considered as a priority area to preserve fish species. Some mitigation actions that may achieve satisfactory results concerning ichthyofauna conservation are proposed.

Taxonomic revision of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae), with descriptions of four new species

“…Several specimens, including the holotype of O. tenuirostris, were examined here, and no significant differences were observed across samples from the Orinoco River to identify a different species from S. tenuirostre. This is in contrast with the high diversity observed for the genus along the Amazon basin, which already was confirmed through molecular evidence by Lon- 190478, 4 of 7alc, 121.8-193.6 mm SL, Portuguesa, Portuguesa River, Falcon Stream;ANSP 198951, 10 of 13alc, 151.1-218.9 and Simpsonichthys Carvalho, 1959 (Rivulidae), among others (Chamon et al, 2022). This shows a clear distinction and division among populations within the same basin, indicating that there are ecological and structural differences between both basins that should be further studied from a phylogeographic perspective to understand and describe such differences.…”

A especialização individual é maior em populações generalistas de posições tróficas intermediárias a altas em peixes tropicais de água doce

“…A alta diversidade biológica promove uma alta diversidade de recursos de todos os tipos. Por exemplo, cerca de 750 espécies de peixes habitam a bacia Tocantins‐Araguaia (Chamon et al, 2022), onde nossa área de estudo se localiza. A diversidade em áreas tropicais é tão alta que é possível encontrar espécies de peixes desempenhando funções que os insetos realizam em áreas temperadas (Winemiller et al, 2004).…”

“…Aqui, usamos peixes de água doce do rio Tocantins, um rio neotropical altamente diverso, como modelo para investigar essas relações. A bacia do Tocantins‐Araguaia abriga cerca de 750 espécies de peixes (Chamon et al, 2022), das quais 233 foram registradas em nossa área de estudo (Bartolette et al, 2012). A assembleia local de peixes apresenta grande diversidade trófica, com detritívoros, herbívoros, invertebrados, onívoros e piscívoros (Albrecht et al, 2012; Melo et al, 2004; Mérona & Rankin‐de‐Mérona, 2004).…”

Individual specialization is the highest in generalist populations from intermediary to high trophic positions in tropical freshwater fishes

“…The high biological diversity promotes high diversity of resources of all kinds. For example, about 750 fish species inhabit the Tocantins-Araguaia basin (Chamon et al, 2022), where our study area was located. Diversity in tropical areas is so high that one may find fish species playing roles that insects execute in temperate areas (Winemiller et al, 2004).…”

“…Here, we use freshwater fishes from the Tocantins River, a highly diverse Neotropical River, as a model to investigate such relationships. The Tocantins‐Araguaia basin harbours around 750 fish species (Chamon et al, 2022), from each 233 are recorded in our study area (Bartolette et al, 2012). The local fish assemblage presents great trophic diversity, with detritivores, herbivores, invertivores, omnivores, and piscivores (Albrecht et al, 2012; Melo et al, 2004; Mérona & Rankin‐de‐Mérona, 2004).…”