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Streams fish from Upper Araguaia and Middle Rio da Mortes basin, Brazil: generating subsidies for preservation and conservation of this critical natural resource

Peixes de riachos das bacias do alto rio Araguaia e médio Rio das Mortes, Brasil: gerando subsídios para preservação e conservação desse importante recurso natural

Abstract:

The Araguaia River basin has the highest fish biodiversity within the Cerrado biome (Brazilian savannah), with many endemic and threatened species by human activities. Despite growing efforts to catalog Neotropical freshwater fish biodiversity, many regions are still undersampled. Our objective is to complement the information about stream fish in two hydrographic basins in the Cerrado. We sampled 72 streams with 50 m stretch in the Upper Araguaia (n = 32) and Middle Rio das Mortes (n = 40) basins. We collected 14,887 individuals distributed in 137 species, 81 genera, 30 families, and six orders. Characidae, Loricariidae, and Cichlidae were the families richer in species. We found a high diversity of rare fish species in the streams sampled, ca. 71.5% of the species had at least five individuals collected, and 18 species had only one collected specimen. The most frequent species were Astyanax cf. goyacensis, Knodus cf. breviceps, and Characidium cf. zebra. Both basins shared around 43% of the species. We caught 76 species in Upper Araguaia and 120 species in Middle Rio das Mortes. Seventeen exclusive fish species occurred in Upper Araguaia, whereas 61 were found in the Middle Rio das Mortes basin. Our analysis showed lower diversity of fish in Upper Araguaia than in the Middle Rio das Mortes basin. Considering the exclusive fish species of both basins, the human threats in those regions, and the few existent protected areas, we need a better look at the aquatic biodiversity conservation of this ecosystem.

Keywords:
Biodiversity; Cerrado; Freshwater; Neotropical fishes; Headwaters

Resumo:

A bacia do rio Araguaia apresenta a maior diversidade de peixes no bioma Cerrado, muitas dessas são endêmicas e ameaçadas pelas atividades antropogênicas. Apesar dos crescentes esforços para catalogar a diversidade de peixes neotropicais muitas regiões ainda permanecem subamostradas. O objetivo do nosso estudo é complementar a informação sobre peixes de riachos para duas importantes bacias hidrográficas no Cerrado. Amostramos um total de 72 trechos de 50 metros em riachos nas bacias alto rio Araguaia (n = 32) e médio Rio das Mortes (n = 40). Coletamos um total de 14.887 indivíduos distribuídos em 137 espécies, 81 gêneros, 30 famílias e seis ordens. As famílias Characidae, Loricariidae e Cichlidae foram as tiveram maior número de espécies. Encontramos uma grande raridade de espécies de peixes nos riachos amostrados, cerca de 71,5% das espécies apresentaram ao menos até cinco indivíduos coletados e 18 espécies tiveram apenas um único exemplar. As espécies com maior ocorrência nos riachos foram, Astyanax cf. goyacensis Knodus cf. breviceps e Characidium cf. zebra. As duas bacias compartilham aproximadamente 43% das espécies de peixes coletadas. Encontramos 76 espécies para o alto rio Araguaia e 120 espécies para médio Rio das Mortes. Observamos 17 espécies exclusivas para a bacia do alto rio Araguaia e 61 espécies exclusivas para bacia do Médio Rio das Mortes. Nossas análises mostraram que a diversidade de peixes é menor na bacia do alto rio Araguaia quando comparada a bacia do médio Rio das Mortes. Considerando as ameaças antrópicas, o baixo número unidades de conservação e o elevado número de espécies exclusivas presentes em ambas as bacias, existe uma necessidade urgente concentrar esforços na conservação desses ecossistemas.

Palavras-chave:
Biodiversidade; Cerrado; Água doce; Peixes Neotropicais; Riachos de Cabeceiras

Introduction

The Cerrado is a Brazilian biome considered one of the global biodiversity hotspots due to its high species riches, endemic rates, and human threats to its biodiversity (Myers et al. 2000MYERS, N., MITTERMEIER, R.A., MITTERMEIER, C.G., FONSECA, G.A. & KENT, J. 2000. Biodiversity hotspots for conservation priorities. Nature 403(6772):853-8.). The origins of large South American rivers (Amazonica, Tocantins-Araguaia, Paraná, and São Francisco basin) are inserted into this biome, which is informally entitled the Brazilian "berço das águas" (water cradle). The water bodies of Cerrado (e.g., rivers, lakes, and streams) harbor about 1200 cataloged fish species (ICMBio 2020ICMBio, 2020. Instituto Chico Mendes de Conservação da Biodiversidade. Cerrado. https://www.icmbio.gov.br/portal/unidadesdeconservacao/biomas-brasileiros/cerrado (last access on 28/12/2020)
https://www.icmbio.gov.br/portal/unidade...
), corresponding to 25% of South American freshwater fish species. It is important to highlight that many of the Cerrado fishes are endemic and represent more than 42% (n = 131) of the threatened Brazilian fish species (Latrubesse et al. 2019LATRUBESSE, E.M., ARIMA, E., FERREIRA, M.E., NOGUEIRA, S.H., WITTMANN, F., DIAS, M.S., DAGOSTA, F.C.P. & BAYER, M. 2019. Fostering water resource governance and conservation in the Brazilian Cerrado biome. Conserv. Sci. Pract. 1(9):1-8.). Among the river basins originating within the Cerrado, the Araguaia River basin harbors more considerable fish diversity (Dagosta et al. 2020DAGOSTA, F.C.P., PINNA, M., PERES, C.A. & TAGLIACOLLO, V.A. 2020. Existing protected areas provide a poor safety‐net for threatened Amazonian fish species. Aquat. Conserv. Mar. Freshw. Ecosyst. 1-23.), with more than 320 currently described species and many with a restricted distribution that mainly occupies the headwaters (first to third order) (Latrubesse et al. 2019LATRUBESSE, E.M., ARIMA, E., FERREIRA, M.E., NOGUEIRA, S.H., WITTMANN, F., DIAS, M.S., DAGOSTA, F.C.P. & BAYER, M. 2019. Fostering water resource governance and conservation in the Brazilian Cerrado biome. Conserv. Sci. Pract. 1(9):1-8.). Unfortunately, the Araguaia River basin landscape is undergoing a rapid transformation. Agriculture plantations or pastures replace native vegetation, and water bodies are being dammed for hydropower dam construction and agricultural irrigation intensification (Coe et al. 2011COE, M.T., LATRUBESSE, E.M., FERREIRA, M.E. & AMSLER, M.L. 2011. The effects of deforestation and climate variability on the streamflow of the Araguaia River, Brazil. Biogeochemistry 105(1-3):119-131., Latrubesse et al. 2019LATRUBESSE, E.M., ARIMA, E., FERREIRA, M.E., NOGUEIRA, S.H., WITTMANN, F., DIAS, M.S., DAGOSTA, F.C.P. & BAYER, M. 2019. Fostering water resource governance and conservation in the Brazilian Cerrado biome. Conserv. Sci. Pract. 1(9):1-8.).

The high number of fish species with restricted distribution and the human-caused environmental degradation in these basins are significant challenges for fish biodiversity conservation (Nogueira et al. 2010NOGUEIRA, C., BUCKUP, P.A., MENEZES, N.A., OYAKAWA, O.T., KASECKER, T.P., RAMOS NETO, M.B. & DA SILVA, J.M.C. 2010. Restricted-range fishes and the conservation of Brazilian freshwaters. PLoS One 5(6):e11390., Latrubesse et al. 2019LATRUBESSE, E.M., ARIMA, E., FERREIRA, M.E., NOGUEIRA, S.H., WITTMANN, F., DIAS, M.S., DAGOSTA, F.C.P. & BAYER, M. 2019. Fostering water resource governance and conservation in the Brazilian Cerrado biome. Conserv. Sci. Pract. 1(9):1-8., Dagosta et al. 2020DAGOSTA, F.C.P., PINNA, M., PERES, C.A. & TAGLIACOLLO, V.A. 2020. Existing protected areas provide a poor safety‐net for threatened Amazonian fish species. Aquat. Conserv. Mar. Freshw. Ecosyst. 1-23.). Therefore, actions addressed to preserve this biodiversity should consider the wide variation in fish community composition among the catchment systems since many of these restricted-distribution fish species are exclusive from streams (Lima 2019LIMA, L.B. 2019. Da cienciometria ao campo: fatores que estruturam as comunidades de peixes em riachos. Tese de doutorado, Universidade do Estado do Mato Grosso, Nova Xavantina.).

Stream fish are among the most threatened aquatic organisms (Nogueira et al. 2010NOGUEIRA, C., BUCKUP, P.A., MENEZES, N.A., OYAKAWA, O.T., KASECKER, T.P., RAMOS NETO, M.B. & DA SILVA, J.M.C. 2010. Restricted-range fishes and the conservation of Brazilian freshwaters. PLoS One 5(6):e11390., Castro 1999CASTRO, R.M.C. 1999. Evolução da ictiofauna de riachos sul-americanos: padrões gerais e possíveis processos causais. In Ecologia de peixes de riachos (E. P. Caramaschi, R. Mazzoni, & P. R. Peres-Neto, eds) Oecologia Brasiliensis, Rio de Janeiro, Brasil, p.139-155., Castro & Polaz 2020CASTRO, R.M.C. & POLAZ, C.N.M. 2020. Small-sized fish: the largest and most threatened portion of the megadiverse neotropical freshwater fish fauna. Biota Neotrop. 20(1):313-324. https://doi.org/10.1590/1676-0611-bn-2018-0683 (last access on 12/02/2021)
https://doi.org/10.1590/1676-0611-bn-201...
), and one of their main threats concerns habitat degradation (Barletta et al. 2010BARLETTA, M., JAUREGUIZAR, A.J., BAIGUN, C., FONTOURA, N.F., AGOSTINHO, A.A., ALMEIDA-VAL, V.M.F., VAL, A.L., TORRES, R.A., JIMENES-SEGURA, L.F., GIARRIZZO, T., FABRÉ, N.N., BATISTA, V.S., LASSO, C., TAPHORN, D.C., COSTA, M.F., CHAVES, P.T., VIEIRA, J.P. & CORRÊA, M.F.M. 2010. Fish and aquatic habitat conservation in South America: a continental overview with emphasis on Neotropical systems. J. Fish Biol. 76(9):2118-2176., Castro & Polaz 2020CASTRO, R.M.C. & POLAZ, C.N.M. 2020. Small-sized fish: the largest and most threatened portion of the megadiverse neotropical freshwater fish fauna. Biota Neotrop. 20(1):313-324. https://doi.org/10.1590/1676-0611-bn-2018-0683 (last access on 12/02/2021)
https://doi.org/10.1590/1676-0611-bn-201...
). The riparian vegetation removal (i.e., the watercourse adjacent buffer zone) is the leading habitat homogenization cause (Casatti, Ferreira & Carvalho 2009CASATTI, L., FERREIRA, C.P. & LANGEANI, F. 2009. A fish-based biotic integrity index for assessment of lowland streams in southeastern Brazil. Hydrobiologia 623(1):173-189., Teresa & Casatti 2012TERESA, F.B. & CASATTI, L. 2012. Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams. Ecol. Freshw. Fish 21(3):433-442., Zeni et al. 2019ZENI, J.O., PÉREZ‐MAYORGA, M.A., ROA‐FUENTES, C.A., BREJÃO, G.L. & CASATTI, L. 2019. How deforestation drives stream habitat changes and the functional structure of fish assemblages in different tropical regions. Aquat. Conserv. Mar. Freshw. Ecosyst. aqc.3128.). Consequently, the resulting eutrophication and silting of the river channel (Teresa & Casatti 2012TERESA, F.B. & CASATTI, L. 2012. Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams. Ecol. Freshw. Fish 21(3):433-442.) also contribute to biodiversity homogenization. Besides habitat change, the streams fish suffer other kinds of threats, such as introducing non-native species, highway and dam construction, agricultural pesticides, and fertilizer intensification (Winemiller et al. 2008WINEMILLER, K.O., AGOSTINHO, A.A. & CARAMASCHI, É.P. 2008. Fish ecology in tropical streams. In Tropical Stream Ecology (D. Dudgeon, ed.) Elsevier, San Diego, p.107-146., Reid et al. 2019REID, A.J., CARLSON, A.K., CREED, I.F., ELIASON, E.J., GELL, P.A., JOHNSON, P.T.J., KIDD, K.A., MACCORMACK, T.J., OLDEN, J.D., ORMEROD, S.J., SMOL, J.P., TAYLOR, W.W., TOCKNER, K., VERMAIRE, J.C., DUDGEON, D. & COOKE, S.J. 2019. Emerging threats and persistent conservation challenges for freshwater biodiversity. Biol. Rev. 94(3):849-873.).

Unfortunately, scientific ecological investigations advance more slowly than changes in natural ecosystems. Thus, many species can be extinct, even before they are formally described by science. Besides, there is data scarcity to fill distinct information gaps for many organisms (Hortal et al. 2015HORTAL, J., DE BELLO, F., DINIZ-FILHO, J.A.F., LEWINSOHN, T.M., LOBO, J.M. & LADLE, R.J. 2015. Seven shortfalls that beset large-scale knowledge of biodiversity. Annu. Rev. Ecol. Evol. Syst. 46(1):523-549.) regarding species proper identification (Linnean shortfalls) and the spatial distribution of the species (Wallacean shortfalls). It is essential to highlight that the Linnean shortfall is the most significant data gap to be solved because it directly affects all other biodiversity knowledge gaps (for more details, see Hortal et al. 2015HORTAL, J., DE BELLO, F., DINIZ-FILHO, J.A.F., LEWINSOHN, T.M., LOBO, J.M. & LADLE, R.J. 2015. Seven shortfalls that beset large-scale knowledge of biodiversity. Annu. Rev. Ecol. Evol. Syst. 46(1):523-549.). Furthermore, due to the growing and constant threat to streams, actions seeking to synthesize information about these ecosystems to guide research and conservation measures are needed (Dudgeon et al. 2006DUDGEON, D., ARTHINGTON, A.H., GESSNER, M.O., KAWABATA, Z.-I., KNOWLER, D.J., LÉVÊQUE, C., NAIMAN, R.J., PRIEUR-RICHARD, A.-H., SOTO, D., STIASSNY, M.L.J. & SULLIVAN, C.A. 2006. Freshwater biodiversity: importance, threats, status and conservation challenges. Biol. Rev. 81(2):163-182., Barletta et al. 2010BARLETTA, M., JAUREGUIZAR, A.J., BAIGUN, C., FONTOURA, N.F., AGOSTINHO, A.A., ALMEIDA-VAL, V.M.F., VAL, A.L., TORRES, R.A., JIMENES-SEGURA, L.F., GIARRIZZO, T., FABRÉ, N.N., BATISTA, V.S., LASSO, C., TAPHORN, D.C., COSTA, M.F., CHAVES, P.T., VIEIRA, J.P. & CORRÊA, M.F.M. 2010. Fish and aquatic habitat conservation in South America: a continental overview with emphasis on Neotropical systems. J. Fish Biol. 76(9):2118-2176., Cetra et al. 2020CETRA, M., MATTOX, G., ROMERO, P.B., ESCOBAR, S.H., GUIMARÃES, E.A., ANTONIO, R., TURIN, F., CETRA, M., MATTOX, G., ROMERO, P.B., GUIMARÃES, S.H. & ICHTHYOFAUNA, R.A.F. 2020. Ichthyofauna from "serranias costeiras" of the Ribeira de Iguape River basin, Southeast Brazil Ictiofauna das "serranias costeiras" da bacia do rio Ribeira de Iguape, sudeste do Brasil. Biota Neotrop. 20(4):2020. https://doi.org/10.1590/1676-0611-bn-2020-0994 (last access on 12/02/2021)
https://doi.org/10.1590/1676-0611-bn-202...
). Thus, our goal was to complement the information about stream fish in two important hydrographic basins in the Cerrado biome.

Materials and Methods

1. Study Area

We sampled a total of 72 streams ranging from first to fourth order (scale 1:10000 IBGE) according to Strahler's (1957)STRAHLER, A.N. 1957. Quantitative analysis of watershed geomorphology. Eos, Trans. Am. Geophys. Union 38(6):913-920. classification in the Upper Araguaia and Middle Rio das Mortes basin, belonging to the Tocantins-Araguaia ecoregion (Figure 1, Table 1). The Araguaia River is a major fluvial system of the Cerrado, draining 375,000 km2 and with an average annual streamflow of 6,500 m3.s-1 (Morais et al. 2008MORAIS, R.P., AQUINO, S. & LATRUBESSE, E.M. 2008. Controles hidrogeomorfológicos nas unidades vegetacionais da planície aluvial do rio Araguaia, Brasil. Acta Sci. Biol. Sci. 30(4):411-421., Latrubesse et al. 2009LATRUBESSE, E.M., AMSLER, M.L., MORAIS, R.P. & AQUINO, S. 2009. The geomorphologic response of a large pristine alluvial river to tremendous deforestation in the South American tropics: The case of the Araguaia River. Geomorphology 113(3-4):239-252.). The Araguaia River sources in slopes of the "Caiapós" mountain, on the boundaries of Goiás and Mato Grosso states, at 850 m elevation above sea level and travels 2110 km up to its confluence with the Tocantins River. Thus, the Araguaia basin can be divided into three stretches: upper, middle, and lower (for more details about division, see Latrubesse & Stevaux 2002LATRUBESSE, E.M. & STEVAUX, J.C. 2002. Geomorphology and environmental aspects of the Araguaia fluvial basin, Brazil. Zeitschrift fur Geomorphol. Suppl. 129(December 2015):109-127., Aquino et al. 2010AQUINO, S., LATRUBESSE, E. & BAYER, M. 2010. Assessment of wash load transport in the Araguaia River (Aruanã gauge station), central Brazil. Lat. Am. J. Sedimentol. Basin Anal. 16(2):119-128.). The Upper Araguaia River stretch, where a portion of our sampling sites are found, has an approximate extension of 450 km and is located between its source and the "Registro do Araguaia" district, draining an approximate area comprising 375,000 km2 (Latrubesse & Stevaux 2002LATRUBESSE, E.M. & STEVAUX, J.C. 2002. Geomorphology and environmental aspects of the Araguaia fluvial basin, Brazil. Zeitschrift fur Geomorphol. Suppl. 129(December 2015):109-127., Latrubesse et al. 2009LATRUBESSE, E.M., AMSLER, M.L., MORAIS, R.P. & AQUINO, S. 2009. The geomorphologic response of a large pristine alluvial river to tremendous deforestation in the South American tropics: The case of the Araguaia River. Geomorphology 113(3-4):239-252.).

Figure 1
Localization of 72 streams sampled in the Upper Araguaia and Middle Rio das Mortes basin, Tocantins-Araguaia ecoregion.

Table 1
The list of sampled sites in the Upper Araguaia River (UAR) and Middle Rio das Mortes (MRM) basin, Tocantins-Araguaia ecoregion.

The Rio das Mortes source is near to the "São Jerônimo" mountain, in the Mid-Southern Mato Grosso region at 808 m above sea level, flowing the northwest direction of the state for approximately 1,070 km until it flows into the middle section of the Araguaia River, near of São Félix do Araguaia city. The Rio das Mortes is the main tributary river of the Araguaia River basin, with a drainage area of approximately 61,684 km2 and an average annual flow of roughly 891.53 m3.s-1 (ANA 2020). The initial portion basin is inserted into a landscape with intensive agriculture activity, whereas the native vegetation is restricted to the hydrographic network margins . While in the middle stretch, where a portion of our sampling sites are located, the mainland use activity is livestock. However, due to indigenous lands (TIs) and the sharp slope of relief at the edges of the "Alcantilados" plateau, it is still possible to find relatively sizable native vegetation areas in this stretch (Lima 2009LIMA, J.D. 2009. Conectividade e análise da estrutura taxonômica e trófica da ictiofauna em lagos do rio das Mortes, Mato Grosso-Brasil. Tese de doutorado, Universidade Federal de São Carlos, São Carlos.).

Our study area is localized in the upper and middle stretches of the Araguaia and Rio das Mortes basins, respectively. The climate of the region is Aw, according to the Köppen classification (Alvares et al. 2013ALVARES, C.A., STAPE, J.L., SENTELHAS, P.C., GONÇALVES, J.L.M. & SPAROVEK, G. 2013. Köppen's climate classification map for Brazil. Meteorol. Zeitschrift 22(6):711-728.), with two seasonal periods: (i) rainy from October to April and (ii) dry from May to September. The annual mean precipitation ranges from 1200 to 1900 mm, and the yearly average temperature is approximately 24 ºC, with higher temperatures in the rainy period (INMET 2020INMET, 2020. Instituto Nacional de Meteorologia. http://www.inmet.gov.br/portal/ (last access on 17/08/2020)
http://www.inmet.gov.br/portal/...
).

2. Data Sampling

Using geography information systems (GIS) tools, we chose 32 streams in the Araguaia River and 40 in the Rio das Mortes basin, totaling 72 stretches of streams to be sampled. The sites were selected based on the independence between them and accessibility criteria. We used the collection sampling method modified from the Biodiversity Research Program (PPBIO), which consisted of sampling a 50-meter stream stretch (Mendonça et al. 2005MENDONÇA, F.P., MAGNUSSON, W.E. & ZUANON, J. 2005. Relationships between habitat characteristics and fish assemblages in small streams of Central Amazonia. Copeia 2005(4):751-764.). We collected in each stream environmental variables related to the limnological conditions and structural variables related to the environmental characterization of the streams. We measured the limnological conditions (i.e., conductivity, dissolved oxygen, pH, turbidity, and water temperature) of the streams only once at the beginning of the sample stretch using a portable multiparametric probe (Horiba U-50). We divided each sampled stretch-50 m into six equidistant transects and recorded the following structural variables, representing the average values of each one of the measured variables in each transect: width, depth obtained from five measurements from one margin to the other, surface water velocity using the method fluctuate material (Teresa & Casatti 2012TERESA, F.B. & CASATTI, L. 2012. Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams. Ecol. Freshw. Fish 21(3):433-442.), and the proportion of substrate structure (i.e., sand, gravel, pebbles, rock, slab, and silt). In addition, we visually quantified the presence of trunks, leaf-litter, and margin structure variables (i.e., thin roots, thick roots, and grass banks) (Cummins 1974CUMMINS, K.W. 1974. Structure and function of stream ecosystems. Bioscience 24(11):631-641., Teresa & Casatti 2012TERESA, F.B. & CASATTI, L. 2012. Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams. Ecol. Freshw. Fish 21(3):433-442.).

We sampled the fish of the streams during the dry periods (May to September) between 2014 - 2017 for more catching efficiency and reduced seasonality effects on collections (Ueida & Castro 1999UEIDA, V.S. & CASTRO, R.M.C. 1999. Coleta e fixação de peixes de riachos. In Ecologia de peixes de riachos (E. P. Caramaschi, R. Mazzoni, & P. R. Peres-Neto, eds) Oecologia Brasiliensis, Rio de Janeiro, Brasil, p.1-22., Pease et al. 2012PEASE, A.A., GONZÁLEZ-DÍAZ, A.A., RODILES-HERNÁNDEZ, R. & WINEMILLER, K.O. 2012. Functional diversity and trait-environment relationships of stream fish assemblages in a large tropical catchment. Freshw. Biol. 57(5):1060-1075.). Before initializing the sampling, we blocked the sample stretch limits with 5-mm mesh nets to prevent fish escape. Then, we sampled the fish through the standardized active collection, which consisted of employing four people for approximately one hour. Later, we sampled 35 streams stretch during the day using seine nets (3.0 × 1.5 m × 5.0 mm mesh) and dip nets (0.5 × 0.45 m × 5.0 mm mesh). Next, we used the electrofishing method (Honda EG1000 generator - 220 V, CA) with a single passage downstream, upstream, lasting approximately one hour to sample the other 37 streams. After the sampling, the individuals were anesthetized with benzocaine and sacrificed according to the Federal Council of Veterinary Medicine (in Portuguese CFMV 2012). In the laboratory, we measured the standard length (cm), weighted (g), and identified all specimens collected until the lowest taxonomic level possible using specialized bibliography (Venere & Garutti 2011VENERE, P.C. & GARUTTI, V. 2011. Peixes do Cerrado: Parque Estadual da Serra Azul, rio Araguaia, MT. RiMa, São Carlos.), and to elaborate the taxonomic list using the Catalogue of Fishes (Fricke et al. 2021).

The Instituto Chico Mendes de Conservação da Biodiversidade(ICMBio; Permit Nº. 45316-1) and the Animal Use Ethics Committee of the Universidade Federal de Mato Grosso (CEUA / UFMT - Nº. 23108.152116) authorized our field collections. We stored the fish collected in the Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos at the Universidade Federal de Mato Grosso, Campus Araguaia, Pontal do Araguaia, Mato Grosso.

3. Data Analysis

We used a principal component analysis (PCA) to summarize the environmental characteristics of the streams. After running the PCA, we standardized all environmental variables (except pH) to zero mean and unit variances (z transformation). Next, we analyzed the richness values (number of species) and abundance (total number of individuals by species) of the fish communities using descriptive statistics. We considered as exclusive species those that occurred only within one basin and as unique species those that occurred only in one stream reach, and singletons those with only one specimen (Novotný & Basset 2000NOVOTNÝ, V. & BASSET, Y. 2000. Rare species in communities of tropical insect herbivores: pondering the mystery of singletons. Oikos 89(3):564-572.). Finally, we evaluated the species richness differences and the efficiency of the sampling effort within both basins using the rarefaction and extrapolation (R/E) method (Colwell et al. 2012COLWELL, R.K., CHAO, A., GOTELLI, N.J., LIN, S.-Y., MAO, C.X., CHAZDON, R.L. & LONGINO, J.T. 2012. Models and estimators linking individual-based and sample-based rarefaction, extrapolation and comparison of assemblages. J. Plant Ecol. 5(1):3-21.). We based our analyses on incidence data derived from the Hill number series with a 95% confidence interval obtained with the bootstrap method (Hill 1973HILL, M.O. 1973. Diversity and evenness: a unifying notation and its consequences. Ecology 54(2):427-432., Chao et al. 2014CHAO, A., GOTELLI, N.J., HSIEH, T.C., SANDER, E.L., MA, K.H., COLWELL, R.K. & ELLISON, A.M. 2014. Rarefaction and extrapolation with Hill numbers: a framework for sampling and estimation in species diversity studies. Ecol. Monogr. 84(1):45-67., Colwell et al. 2012COLWELL, R.K., CHAO, A., GOTELLI, N.J., LIN, S.-Y., MAO, C.X., CHAZDON, R.L. & LONGINO, J.T. 2012. Models and estimators linking individual-based and sample-based rarefaction, extrapolation and comparison of assemblages. J. Plant Ecol. 5(1):3-21.) using the iNEXT function from the iNEXT package (Hsieh et al. 2016HSIEH, T.C., MA, K.H. & CHAO, A. 2016. iNEXT: an R package for rarefaction and extrapolation of species diversity (Hill numbers) G. McInerny, ed. Methods Ecol. Evol. 7(12):1451-1456.). We performed all analyses and descriptive statistics with R software version 3.6.1 (R Core Team 2019R CORE TEAM. 2019. R: A Language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.r-project.org/.
https://www.r-project.org/...
). We used the vegan package (Oksanen et al. 2018OKSANEN, J., BLANCHET, F.G., KINDT, R., PIERRE, L., MINCHIN, P.R., O'HARA, R.B., SIMPSON, G.L., SOLYMOS, P., STEVENS, M.H.H. & WAGNER, H. 2018. Vegan: community ecology package. R Package. version 2.5-2.) to perform PCA and package ggplot2 (Wickham 2009WICKHAM, H. 2009. ggplot2: elegant graphics for data analysis. Springer New York, New York, NY.) to visualize the results.

Results

In general, the studied streams had low conductivity water (mean = 59.79 µS/cm), high dissolved oxygen levels (mean = 8.02 mg/l), slightly acidic (mean = 5.87 pH), low turbidity (mean = 2.38 NTU), and substrates with sand predominance (mean = 45.58%) and gravel (mean =16.95%). The first two PCA axes explained 27.76% of the environmental variation features in the streams (Figure 2). The first axis explained 16.57% of the variation and was positively associated with water temperature, silt, and grass banks and negatively associated with trunks and leaf-litters (Figure 2). The second axis accounted for 11.19% of the variation and was negatively associated with depth and sand (Figure 2). The first axis distinguished streams with a high proportion of grass banks in margins structures from streams with a high presence internal habits structure (Figure 2). The second axis differentiated streams with a higher proportion of pools and a higher proportion of unconsolidated substrates (sand) from streams with a high proportion of consolidated substrates (rocks) (Figure 2).

Figure 2
Biplot for principal components analysis (PCA) representing the main environmental variability in the sampling sites in the Upper Araguaia River and Middles Rio das Mortes basin, Tocantins-Araguaia ecoregion.

We collected a total of 14,887 individuals distributed in 137 species, 81 genera, 30 families, and six orders (Figure 3). The most species-rich families were Characidae, Loricariidae, and Cichlidae (40, 25, and 12 species, respectively). More than half of the individuals we sampled were concentrated in eight species (Astyanax cf. goyacensis, Psalidodon xavante, Hyphessobrycon aff. tenuis, Knodus cf. breviceps, Odontostilbe sp., Phenacogaster sp., Aspidoras poecilus, Melanorivulus zygonectes) (Table 2, Figure 4). The remaining 98 species (71.5%) had at least five individuals collected, and 18 species were considered singletons. The average richness per stream was 15.5 species (SD = 11). The species richness ranged from streams with only one species to streams with 48 species. The most frequent species in our sampled streams were Astyanax cf. goyacensis (n = 51), Knodus cf. breviceps (n = 43), Characidium cf. zebra (n = 40), Imparfinis mirini (n = 40), and Moenkhausia oligolepis (n = 40). We found 36 unique species, and 45 species identified only genera level. The Hypostomus and Ancistrus genera are the richer genera, showing the largest number of species identified up to the genera level.

Figure 3
The individual abundance of six orders collected in the Upper Araguaia and Middle Rio das Mortes basins, Tocantins-Araguaia ecoregion.

Figure 4
The eight most abundant sampled species in the Upper Araguaia and the Middle Rio das Mortes basin and representative species of each family. Some families can have more than one more species represented. The total lengths mean are presented after the names of species. 1) Astyanax cf. goyacensis, 58.9 mm; 2) Psalidodon xavante, 45.9 mm; 3) Hyphessobrycon aff. tenuis, 31.4 mm; 4) Knodus cf. breviceps, 36.6 mm; 5) Odontostilbe sp., 30.9 mm; 6) Phenacogaster sp., 36.9 mm; 7) Aspidoras poecilus, 31.5 mm; 8) Melanorivulus zygonectes, 29.6 mm. Parodontidae - 9) Parodon pongoensis, 64.6 mm; Curimatidae - 10) Cyphocharax gouldingi, 71.3 mm, 11) Steindachnerina amazonica, 105.7 mm; Prochilondotidae - 12) Prochilodus nigricans, 262.0 mm; Anostomidae - 13) Leporinus sp.1, 85.7 mm; Erythrinidae - 14) Hoplias cf. malabaricus, 106.3 mm; Lebiasinidae - 15) Pyrrhulina australis, 37.0 mm; Gasteropelecidae - 16) Thoracocharax cf. stellatus, 58.3 mm; Acestrorhynchidae - 17) Acestrorhynchus falcatus, 207.5 mm; Serrasalmidae - 18) Serrasalmus spilopleura, 63.9 mm; Characidae - 19) Moenkhausia aurantia, 57.3 mm, 20) Moenkhausia oligolepis, 57.8 mm, 21) Moenkhausia venerei, 34.3 mm, 22) Tetragonopterus chalceus, 50.0 mm; Bryconidae - 23) Brycon falcatus, 250.3 mm; Iguanodectidae - 24) Bryconops giacopinii, 56.3 mm; Crenuchidae - 25) Characidium cf. zebra, 35.2 mm; Auchenipteridae - 26) Trachelyopterus galeatus, 112.0 mm; Pimelodidae - 27) Pimelodus ornatus, 150.5 mm; Pseudopimelodidae - 28) Pseudopimelodus cf. pulcher, 48.5 mm; Heptapteridae - 29) Imparfinis mirini, 52.3 mm; Cetopsidae - 30) Cetopsis coecutiens, 57.1 mm; Asprendinidae - 31) Bunocephalus sp., 79.9 mm; Trichomycteridae - 32) Ituglanis macunaima, 47.5 mm; Callichthyidae - 33) Corydoras maculifer, 50.0 mm; Loricariidae - 34) Farlowella aff. oxyrryncha, 102.6 mm, 35) Hypostomus sp.3, 53.6 mm; Sternopygidae - 36) Sternopygus macrurus, 197.6 mm; Apteronotidae - 37) Apteronotus albifrons, 139.4 mm; Rhamphichthyidae - 38) Gymnorhamphichthys petiti, 143.9 mm; Gymnotidae - 39) Gymnotus cf. carapo, 150.7 mm; Synbranchidae - 40) Synbranchus marmoratus, 166.4 mm; Cichlidae - 41) Aequidens tetramerus, 63.2 mm.

Table 2
Species list with your respective abundance in Upper Araguaia River (UAR) and Middle Rio das Mortes (MRM), Tocantins-Araguaia ecoregion.

The basins shared approximately 43% (S = 59) of the collected species. When we analyzed the species richness by basin, we found 76 species for Upper Araguaia and 120 in the Middle Rio das Mortes basin. We found 17 exclusives to Upper Araguaia and 61 species exclusive to the Middle Rio das Mortes basin. The rarefaction analysis showed that fish diversity in both Hill diversity series was lower in the Upper Araguaia River compared to the Middle Rio das Mortes basin (Figure 5a). The sampling effort analysis showed that the species richness for both basins was well represented, with a percentage of sample coverage greater than 93% of the estimated species (Figure 5b c). We sampled more than 93% of the Upper Rio Araguaia basin's estimated species richness, and 95% of the Middle Rio das Mortes basin's estimated species richness (Figure 5c).

Figure 5
Sampling effort effectiveness for the Upper Araguaia River and the Middle Rio das Mortes basin, using the rarefaction method (solid line) and extrapolation (dotted line) based on Hill's numbers. (a) Incidence‐based species accumulation curves, separated by order of diversity: q = 0 (Species richness), q = 1 (Shannon diversity) and q = 2 (Simpson diversity). (b) Sample completeness curves based on the number of sampling sites (c) coverage‐based sampling curves based on species richness. We plotted all extrapolation curves to double the sample size, and the shaded area in all figures (a-b) denotes a confidence interval at 95% obtained from a bootstrap method with 999 replications.

Discussion

The predominance of the orders and families found in our study aligns with the expected patterns for Neotropical fishes in streams (Castro 1999CASTRO, R.M.C. 1999. Evolução da ictiofauna de riachos sul-americanos: padrões gerais e possíveis processos causais. In Ecologia de peixes de riachos (E. P. Caramaschi, R. Mazzoni, & P. R. Peres-Neto, eds) Oecologia Brasiliensis, Rio de Janeiro, Brasil, p.139-155., Lowe-McConnell 1999LOWE-MCCONNELL, R. 1999. Estudos Ecológicos de Comunidades de Peixes Tropicais. EDUSP, São Paulo., Winemiller et al. 2008WINEMILLER, K.O., AGOSTINHO, A.A. & CARAMASCHI, É.P. 2008. Fish ecology in tropical streams. In Tropical Stream Ecology (D. Dudgeon, ed.) Elsevier, San Diego, p.107-146., Castro & Polaz 2020CASTRO, R.M.C. & POLAZ, C.N.M. 2020. Small-sized fish: the largest and most threatened portion of the megadiverse neotropical freshwater fish fauna. Biota Neotrop. 20(1):313-324. https://doi.org/10.1590/1676-0611-bn-2018-0683 (last access on 12/02/2021)
https://doi.org/10.1590/1676-0611-bn-201...
). The species richness and abundance of Characiformes, Siluriformes, and Cichliformes recorded in our study also follow the pattern reported in other studies with fish streams to some basins in the Cerrado biome (Leal et al. 2014LEAL, C.G., JUNQUEIRA, N.T., CASTRO, M.A., CARVALHO, D.R., FAGUNDES, D.C., SOUZA, M.A., HUGHES, R.M. & POMPEU, P.S. 2014. Ichthyofaunal structure of Cerrado streams in Minas Gerais. In Ecological conditions in hydropower basins (M. Callisto, R. M. Hughes, R. M. Lopes, & M. A. Castro, eds) Companhia Energética de Minas Gerais, Belo Horizonte, p.101-126., Barbosa et al. 2019BARBOSA, H. de O., BORGES, P.P., DALA-CORTE, R.B., MARTINS, P.T. de A. & TERESA, F.B. 2019. Relative importance of local and landscape variables on fish assemblages in streams of Brazilian savanna. Fish. Manag. Ecol. 26(2):119-130.). This pattern can be explained by the dominance of those orders in the Neotropical region (Lowe-McConnell 1999LOWE-MCCONNELL, R. 1999. Estudos Ecológicos de Comunidades de Peixes Tropicais. EDUSP, São Paulo., Albert et al. 2011ALBERT, J., PETRY, P. & REIS, R.E. 2011. Major biogeographic and phylogenetic patterns. In Historical biogeography of Neotropical freshwater fishes (J.S. Albert & R.E. Reis, eds). University of California Press, Berkeley, p.21-56., Reis et al. 2016REIS, R.E., ALBERT, J.S., DI DARIO, F., MINCARONE, M.M., PETRY, P. & ROCHA, L.A. 2016. Fish biodiversity and conservation in South America. J. Fish Biol. 89(1):12-47.). The predominance of the Characidae family in the studied streams could be because this group is the richest in the Characiformes order, containing over 550 species (Albert et al. 2011ALBERT, J., PETRY, P. & REIS, R.E. 2011. Major biogeographic and phylogenetic patterns. In Historical biogeography of Neotropical freshwater fishes (J.S. Albert & R.E. Reis, eds). University of California Press, Berkeley, p.21-56.) and displaying an extraordinary variation in morphological forms, feeding behaviors, and reproductive strategies (Melo et al. 2004MELO, C.E., MACHADO, F.D.A. & PINTO-SILVA, V. 2004. Feeding habits of fish from a stream in the savanna of Central Brazil, Araguaia Basin. Neotrop. Ichthyol. 2(1):37-44., Winemiller et al. 2008WINEMILLER, K.O., AGOSTINHO, A.A. & CARAMASCHI, É.P. 2008. Fish ecology in tropical streams. In Tropical Stream Ecology (D. Dudgeon, ed.) Elsevier, San Diego, p.107-146.). Such variety allows this group of fish to occur in the most diverse aquatic habitats. In turn, the predominance of Loricariidae fish can be due to the high species richness and diversity of the family in the Neotropical region (over 830 described species). Species in this family feed mainly on detritus and algae (Lujan et al. 2012LUJAN, N.K., WINEMILLER, K.O. & ARMBRUSTER, J.W. 2012. Trophic diversity in the evolution and community assembly of loricariid catfishes. BMC Evol. Biol. 12(1):124). Detritus are abundant resources in tropical streams and are fundamental to ecosystem function (Bowen 1983BOWEN, S.H. 1983. Detritivory in neotropical fish communities. Environ. Biol. Fishes 9(2):137-144.), allowing those streams to support the high abundance and richness of detritivores fishes (Bowen 1983BOWEN, S.H. 1983. Detritivory in neotropical fish communities. Environ. Biol. Fishes 9(2):137-144., Power 1983POWER, M.E. 1983. Grazing responses of tropical freshwater fishes to different scales of variation in their food. Environ. Biol. Fishes 9(2):103-115.). In addition, the loricariid catfishes have an extraordinary variation in mouth morphologies, allowing them to forage detritus and periphyton in different types of habitat structures (e.g., rocks, trunks, sands, margins, and fast-water environments) presents in the headwater streams (Power 1983POWER, M.E. 1983. Grazing responses of tropical freshwater fishes to different scales of variation in their food. Environ. Biol. Fishes 9(2):103-115., Lujan et al. 2012LUJAN, N.K., WINEMILLER, K.O. & ARMBRUSTER, J.W. 2012. Trophic diversity in the evolution and community assembly of loricariid catfishes. BMC Evol. Biol. 12(1):124).

Although the fish orders and families of the basin are well known, this pattern is not proper to species. We identified approximately 30% of the collected species only at the genera level. Many still need more detailed taxonomic and molecular studies (e.g., Characidium cf. zebra, Hoplias cf. malabaricus and Gymnotus cf. carapo). The significant number of species identified only at the genera level shows the need for further taxonomic studies in this basin. Considering the high fish species endemicity within these basins, there is a significant likelihood that many of these species identified only up to the genera level are new species. Previous studies on stream fish in these basins have also found similar patterns, with a great number of species not yet described (Melo et al. 2004MELO, C.E., MACHADO, F.D.A. & PINTO-SILVA, V. 2004. Feeding habits of fish from a stream in the savanna of Central Brazil, Araguaia Basin. Neotrop. Ichthyol. 2(1):37-44., Matos et al. 2013MATOS, P.R., CARMO, C.M. & MELO, C.E. 2013. Relação entre variáveis ambientais e a estrutura da comunidade de peixes em córregos das bacias do Rio das Mortes e do rio Xingu - MT, Brasil. Biotemas 26(3):139-151., Jarduli et al. 2014JARDULI, L.R., CLARO-GARCÍA, A. & SHIBATTA, O.A. 2014. Ichthyofauna of the rio Araguaia basin, states of Mato Grosso and Goiás, Brazil. Check List 10(3):483-515., Oliveira et al. 2020OLIVEIRA, F.J.M., LIMA-JUNIOR, D.P. & BINI, L.M. 2020. Current environmental conditions are weak predictors of fish community structure compared to community structure of the previous year. Aquat. Ecol. 54(3):729-740.). This large number of species to be described is one of the most important knowledge gaps in biodiversity (Linnean shortfalls) that needs to be addressed (Hortal et al. 2015HORTAL, J., DE BELLO, F., DINIZ-FILHO, J.A.F., LEWINSOHN, T.M., LOBO, J.M. & LADLE, R.J. 2015. Seven shortfalls that beset large-scale knowledge of biodiversity. Annu. Rev. Ecol. Evol. Syst. 46(1):523-549.). Even after two decades after the first studies with stream fish in the studied region, we still have a long way to know the actual diversity of stream fish in these basins. Although the number of researchers working with stream fish has increased, this advance is based less on taxonomic research than on other stream fish research (Junqueira et al. 2020JUNQUEIRA, N.T., MAGNAGO, L.F. & POMPEU, P.S. 2020. Assessing fish sampling effort in studies of Brazilian streams. Scientometrics 123(2):841-860., Lima 2021LIMA, L.B., DE MARCO JÚNIOR, P. & LIMA-JUNIOR, D.P. 2021. Trends and gaps in studies of stream-dwelling fish in Brazil. Hydrobiologia. https://doi.org/10.1007/s10750-021-04616-8
https://doi.org/10.1007/s10750-021-04616...
).

The average stream fish species richness observed in our study streams was 15 species, like the value found in other stream fish studies in this ecoregion (Melo et al. 2004MELO, C.E., MACHADO, F.D.A. & PINTO-SILVA, V. 2004. Feeding habits of fish from a stream in the savanna of Central Brazil, Araguaia Basin. Neotrop. Ichthyol. 2(1):37-44., Matos et al. 2013MATOS, P.R., CARMO, C.M. & MELO, C.E. 2013. Relação entre variáveis ambientais e a estrutura da comunidade de peixes em córregos das bacias do Rio das Mortes e do rio Xingu - MT, Brasil. Biotemas 26(3):139-151., Barbosa et al. 2019BARBOSA, H. de O., BORGES, P.P., DALA-CORTE, R.B., MARTINS, P.T. de A. & TERESA, F.B. 2019. Relative importance of local and landscape variables on fish assemblages in streams of Brazilian savanna. Fish. Manag. Ecol. 26(2):119-130., Oliveira et al. 2020OLIVEIRA, F.J.M., LIMA-JUNIOR, D.P. & BINI, L.M. 2020. Current environmental conditions are weak predictors of fish community structure compared to community structure of the previous year. Aquat. Ecol. 54(3):729-740.). However, our data showed a wide variance in the number of species per stream. We sampled streams with one species and streams with up to 48 species. We believe that such variation in species richness between streams can be explained by environmental heterogeneity and hydrographic network size (Lowe-McConnell 1987, Tedesco et al. 2008TEDESCO, P.A., HUGUENY, B., OBERDORFF, T., DÜRR, H.H., MÉRIGOUX, S. & DE MÉRONA, B. 2008. River hydrological seasonality influences life history strategies of tropical riverine fishes. Oecologia 156(3):691-702., Vieira et al. 2018VIEIRA, T.B. et al. 2018. A multiple hypothesis approach to explain species richness patterns in Neotropical stream-dweller fish communities L. U. Hepp, ed. PLoS One 13(9):e0204114.). The water physicochemical characteristics and habitat structures can vary spatially between nearby streams. This condition increases local environmental heterogeneity and makes fish diversity vary between streams (Benda et al. 2004BENDA, L., POFF, N.L., MILLER, D., DUNNE, T., REEVES, G., PESS, G. & POLLOCK, M. 2004. The network dynamics hypothesis: how channel networks structure riverine habitats. Bioscience 54(5):413-427.). Besides, streams with more extensive drainage networks should support more diverse communities than streams with smaller drainage networks (Zbinden & Matthews 2017ZBINDEN, Z.D. & MATTHEWS, W.J. 2017. Beta diversity of stream fish assemblages: partitioning variation between spatial and environmental factors. Freshw. Biol. 62(8):1460-1471.).

In our study, species with wide distribution (species that occurred in more than 50% of the sites) over the sampled streams belonged to groups of fish with more diversified feeding behaviors and reproductive strategies (Winemiller 1989WINEMILLER, K.O. 1989. Patterns of variation in life history among South American fishes in seasonal environments. Oecologia 81(2):225-241.). For the species present in our samples, we highlight the nektonic omnivores characids that feed on materials drifting in the water column and have split spawning (Astyanax cf. goyacensis; Knodus cf. breviceps, and Moenkhausia oligolepis), the benthic invertivores with fusiform bodies (Characidium cf. zebra), and the benthic omnivores catfish (Imparfinis mirini).

The species abundance patterns we found in this study are like those observed in streams with lower environmental degradation (Ferreira & Casatti 2006FERREIRA, C.D.P. & CASATTI, L. 2006. Influência da estrutura do hábitat sobre a ictiofauna de um riacho em uma micro-bacia de pastagem, São Paulo, Brasil. Rev. Bras. Zool. 23(3):642-651., Casatti, Ferreira & Langeani 2009CASATTI, L., FERREIRA, C.P. & CARVALHO, F.R. 2009. Grass-dominated stream sites exhibit low fish species diversity and dominance by guppies: an assessment of two tropical pasture river basins. Hydrobiologia 632(1):273-283.). The species rarity of our samples is relatively high, with approximately 71.5% of them having at least five individuals collected and 18 having only one sampled specimen. The rare species patterns in ecological communities vary in abundance, where few species are common, some have intermediate abundance, and many are rare (Magurran & Henderson 2003MAGURRAN, A.E. & HENDERSON, P.A. 2003. Explaining the excess of rare species in natural species abundance distributions. Nature 422(6933):714-716.). The number of rare species can vary from site to site because of natural variations in species abundance distributions or anthropogenic stressors (Preston 1948PRESTON, F.W. 1948. The commonness, and rarity, of species. Ecology 29(3):254-283., Magurran & Henderson 2011MAGURRAN, A.E. & HENDERSON, P.A. 2011. Commonness and rarity. In Biological Diversity: Frontiers in Measurement and Assessment (A. E. Magurran & B. J. McGill, eds) Publisher: Oxford University Press, New Jersey, p.97-104.). It is important to highlight that the rarity pattern for some species found in our study differs between the basins; for example, Gymnorhamphichthys petiti was rare in Upper Araguaia, but was abundant in the Middle Rio das Mortes basin. On the other hand, Hypostomus sp.4 was abundant in Upper Araguaia and rare in the Middle Rio das Mortes basin. Furthermore, the significant number of exclusive species in each basin shows distinct fish communities between them. Considering that the Araguaia River and Rio das Mortes belong to the same ecoregion (Abell et al. 2008ABELL, R. et al. 2008. Freshwater ecoregions of the world: a new map of biogeographic units for freshwater biodiversity conservation. Bioscience 58(5):403.), we assume that species dispersion (capacity for colonizing new habitats) and environmental filters are the main drivers responsible for the differences observed.

In this study, we did not find the fish species endangered. This finding can indicate a good ecological integrity of streams once the most sampled streams still have relatively preserved environmental conditions (Lima 2019LIMA, L.B. 2019. Da cienciometria ao campo: fatores que estruturam as comunidades de peixes em riachos. Tese de doutorado, Universidade do Estado do Mato Grosso, Nova Xavantina.). However, this scenario can change in the future. There is a series of threats to fish biodiversity within the basin's streams, mainly due to deforestation and the planned hydropower dams (Coe et al. 2011COE, M.T., LATRUBESSE, E.M., FERREIRA, M.E. & AMSLER, M.L. 2011. The effects of deforestation and climate variability on the streamflow of the Araguaia River, Brazil. Biogeochemistry 105(1-3):119-131., Latrubesse et al. 2019LATRUBESSE, E.M., ARIMA, E., FERREIRA, M.E., NOGUEIRA, S.H., WITTMANN, F., DIAS, M.S., DAGOSTA, F.C.P. & BAYER, M. 2019. Fostering water resource governance and conservation in the Brazilian Cerrado biome. Conserv. Sci. Pract. 1(9):1-8., Dagosta et al. 2020DAGOSTA, F.C.P., PINNA, M., PERES, C.A. & TAGLIACOLLO, V.A. 2020. Existing protected areas provide a poor safety‐net for threatened Amazonian fish species. Aquat. Conserv. Mar. Freshw. Ecosyst. 1-23., Pelicice et al. 2021PELICICE, F.M. et al. 2021. Large-scale degradation of the Tocantins-Araguaia River basin. Environ. Manage. https://doi.org/10.1007/s00267-021-01513-7.
https://doi.org/10.1007/s00267-021-01513...
). Considering the exclusive fish species of both basins, the human threats in those regions, and the few existent protected areas, we need a better look at this ecosystem's aquatic biodiversity conservation. This study contributes to filling one critical biodiversity knowledge gap (i.e., geographic distribution-Wallacean shortfalls) for fish species in streams in the Araguaia River and Rio das Mortes basins.

Acknowledgments

We are grateful UNEMAT Graduate Program in Ecology and Conservation (UNEMAT/PPGEC) and Fundação de Amparo à Pesquisa do Estado de Mato Grosso (FAPEMAT; "Projeto Veredas" 227925/2015) for financial support.. We are also grateful to colleagues at the Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos (LECEA/UFMT) for help in field collect. We would like to thank all the landowners by permission to sampling collect on their properties. L.B. Lima and F. J. M. Oliveira were partially financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) Finance Code - 001; D. P. Lima-Junior was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Grants: 448823/2014-4, 305923/2020-0).

Reference

  • ABELL, R. et al. 2008. Freshwater ecoregions of the world: a new map of biogeographic units for freshwater biodiversity conservation. Bioscience 58(5):403.
  • ALBERT, J., PETRY, P. & REIS, R.E. 2011. Major biogeographic and phylogenetic patterns. In Historical biogeography of Neotropical freshwater fishes (J.S. Albert & R.E. Reis, eds). University of California Press, Berkeley, p.21-56.
  • ALVARES, C.A., STAPE, J.L., SENTELHAS, P.C., GONÇALVES, J.L.M. & SPAROVEK, G. 2013. Köppen's climate classification map for Brazil. Meteorol. Zeitschrift 22(6):711-728.
  • AQUINO, S., LATRUBESSE, E. & BAYER, M. 2010. Assessment of wash load transport in the Araguaia River (Aruanã gauge station), central Brazil. Lat. Am. J. Sedimentol. Basin Anal. 16(2):119-128.
  • BARBOSA, H. de O., BORGES, P.P., DALA-CORTE, R.B., MARTINS, P.T. de A. & TERESA, F.B. 2019. Relative importance of local and landscape variables on fish assemblages in streams of Brazilian savanna. Fish. Manag. Ecol. 26(2):119-130.
  • BARLETTA, M., JAUREGUIZAR, A.J., BAIGUN, C., FONTOURA, N.F., AGOSTINHO, A.A., ALMEIDA-VAL, V.M.F., VAL, A.L., TORRES, R.A., JIMENES-SEGURA, L.F., GIARRIZZO, T., FABRÉ, N.N., BATISTA, V.S., LASSO, C., TAPHORN, D.C., COSTA, M.F., CHAVES, P.T., VIEIRA, J.P. & CORRÊA, M.F.M. 2010. Fish and aquatic habitat conservation in South America: a continental overview with emphasis on Neotropical systems. J. Fish Biol. 76(9):2118-2176.
  • BENDA, L., POFF, N.L., MILLER, D., DUNNE, T., REEVES, G., PESS, G. & POLLOCK, M. 2004. The network dynamics hypothesis: how channel networks structure riverine habitats. Bioscience 54(5):413-427.
  • BOWEN, S.H. 1983. Detritivory in neotropical fish communities. Environ. Biol. Fishes 9(2):137-144.
  • CASATTI, L., FERREIRA, C.P. & CARVALHO, F.R. 2009. Grass-dominated stream sites exhibit low fish species diversity and dominance by guppies: an assessment of two tropical pasture river basins. Hydrobiologia 632(1):273-283.
  • CASATTI, L., FERREIRA, C.P. & LANGEANI, F. 2009. A fish-based biotic integrity index for assessment of lowland streams in southeastern Brazil. Hydrobiologia 623(1):173-189.
  • CASTRO, R.M.C. 1999. Evolução da ictiofauna de riachos sul-americanos: padrões gerais e possíveis processos causais. In Ecologia de peixes de riachos (E. P. Caramaschi, R. Mazzoni, & P. R. Peres-Neto, eds) Oecologia Brasiliensis, Rio de Janeiro, Brasil, p.139-155.
  • CASTRO, R.M.C. & POLAZ, C.N.M. 2020. Small-sized fish: the largest and most threatened portion of the megadiverse neotropical freshwater fish fauna. Biota Neotrop. 20(1):313-324. https://doi.org/10.1590/1676-0611-bn-2018-0683 (last access on 12/02/2021)
    » https://doi.org/10.1590/1676-0611-bn-2018-0683
  • CETRA, M., MATTOX, G., ROMERO, P.B., ESCOBAR, S.H., GUIMARÃES, E.A., ANTONIO, R., TURIN, F., CETRA, M., MATTOX, G., ROMERO, P.B., GUIMARÃES, S.H. & ICHTHYOFAUNA, R.A.F. 2020. Ichthyofauna from "serranias costeiras" of the Ribeira de Iguape River basin, Southeast Brazil Ictiofauna das "serranias costeiras" da bacia do rio Ribeira de Iguape, sudeste do Brasil. Biota Neotrop. 20(4):2020. https://doi.org/10.1590/1676-0611-bn-2020-0994 (last access on 12/02/2021)
    » https://doi.org/10.1590/1676-0611-bn-2020-0994
  • CHAO, A., GOTELLI, N.J., HSIEH, T.C., SANDER, E.L., MA, K.H., COLWELL, R.K. & ELLISON, A.M. 2014. Rarefaction and extrapolation with Hill numbers: a framework for sampling and estimation in species diversity studies. Ecol. Monogr. 84(1):45-67.
  • COE, M.T., LATRUBESSE, E.M., FERREIRA, M.E. & AMSLER, M.L. 2011. The effects of deforestation and climate variability on the streamflow of the Araguaia River, Brazil. Biogeochemistry 105(1-3):119-131.
  • COLWELL, R.K., CHAO, A., GOTELLI, N.J., LIN, S.-Y., MAO, C.X., CHAZDON, R.L. & LONGINO, J.T. 2012. Models and estimators linking individual-based and sample-based rarefaction, extrapolation and comparison of assemblages. J. Plant Ecol. 5(1):3-21.
  • CUMMINS, K.W. 1974. Structure and function of stream ecosystems. Bioscience 24(11):631-641.
  • DAGOSTA, F.C.P., PINNA, M., PERES, C.A. & TAGLIACOLLO, V.A. 2020. Existing protected areas provide a poor safety‐net for threatened Amazonian fish species. Aquat. Conserv. Mar. Freshw. Ecosyst. 1-23.
  • DUDGEON, D., ARTHINGTON, A.H., GESSNER, M.O., KAWABATA, Z.-I., KNOWLER, D.J., LÉVÊQUE, C., NAIMAN, R.J., PRIEUR-RICHARD, A.-H., SOTO, D., STIASSNY, M.L.J. & SULLIVAN, C.A. 2006. Freshwater biodiversity: importance, threats, status and conservation challenges. Biol. Rev. 81(2):163-182.
  • FERREIRA, C.D.P. & CASATTI, L. 2006. Influência da estrutura do hábitat sobre a ictiofauna de um riacho em uma micro-bacia de pastagem, São Paulo, Brasil. Rev. Bras. Zool. 23(3):642-651.
  • FRICKE, R., ESCHMEYER, W.N. & VAN DER LAAN, R. 2020. Catalog of fishes: genera, species, references. http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp (last access on 12/02/2021).
    » http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp
  • HILL, M.O. 1973. Diversity and evenness: a unifying notation and its consequences. Ecology 54(2):427-432.
  • HORTAL, J., DE BELLO, F., DINIZ-FILHO, J.A.F., LEWINSOHN, T.M., LOBO, J.M. & LADLE, R.J. 2015. Seven shortfalls that beset large-scale knowledge of biodiversity. Annu. Rev. Ecol. Evol. Syst. 46(1):523-549.
  • HSIEH, T.C., MA, K.H. & CHAO, A. 2016. iNEXT: an R package for rarefaction and extrapolation of species diversity (Hill numbers) G. McInerny, ed. Methods Ecol. Evol. 7(12):1451-1456.
  • ICMBio, 2020. Instituto Chico Mendes de Conservação da Biodiversidade. Cerrado. https://www.icmbio.gov.br/portal/unidadesdeconservacao/biomas-brasileiros/cerrado (last access on 28/12/2020)
    » https://www.icmbio.gov.br/portal/unidadesdeconservacao/biomas-brasileiros/cerrado
  • INMET, 2020. Instituto Nacional de Meteorologia. http://www.inmet.gov.br/portal/ (last access on 17/08/2020)
    » http://www.inmet.gov.br/portal/
  • JARDULI, L.R., CLARO-GARCÍA, A. & SHIBATTA, O.A. 2014. Ichthyofauna of the rio Araguaia basin, states of Mato Grosso and Goiás, Brazil. Check List 10(3):483-515.
  • JUNQUEIRA, N.T., MAGNAGO, L.F. & POMPEU, P.S. 2020. Assessing fish sampling effort in studies of Brazilian streams. Scientometrics 123(2):841-860.
  • LATRUBESSE, E.M., AMSLER, M.L., MORAIS, R.P. & AQUINO, S. 2009. The geomorphologic response of a large pristine alluvial river to tremendous deforestation in the South American tropics: The case of the Araguaia River. Geomorphology 113(3-4):239-252.
  • LATRUBESSE, E.M., ARIMA, E., FERREIRA, M.E., NOGUEIRA, S.H., WITTMANN, F., DIAS, M.S., DAGOSTA, F.C.P. & BAYER, M. 2019. Fostering water resource governance and conservation in the Brazilian Cerrado biome. Conserv. Sci. Pract. 1(9):1-8.
  • LATRUBESSE, E.M. & STEVAUX, J.C. 2002. Geomorphology and environmental aspects of the Araguaia fluvial basin, Brazil. Zeitschrift fur Geomorphol. Suppl. 129(December 2015):109-127.
  • LEAL, C.G., JUNQUEIRA, N.T., CASTRO, M.A., CARVALHO, D.R., FAGUNDES, D.C., SOUZA, M.A., HUGHES, R.M. & POMPEU, P.S. 2014. Ichthyofaunal structure of Cerrado streams in Minas Gerais. In Ecological conditions in hydropower basins (M. Callisto, R. M. Hughes, R. M. Lopes, & M. A. Castro, eds) Companhia Energética de Minas Gerais, Belo Horizonte, p.101-126.
  • LIMA, J.D. 2009. Conectividade e análise da estrutura taxonômica e trófica da ictiofauna em lagos do rio das Mortes, Mato Grosso-Brasil. Tese de doutorado, Universidade Federal de São Carlos, São Carlos.
  • LIMA, L.B. 2019. Da cienciometria ao campo: fatores que estruturam as comunidades de peixes em riachos. Tese de doutorado, Universidade do Estado do Mato Grosso, Nova Xavantina.
  • LIMA, L.B., DE MARCO JÚNIOR, P. & LIMA-JUNIOR, D.P. 2021. Trends and gaps in studies of stream-dwelling fish in Brazil. Hydrobiologia. https://doi.org/10.1007/s10750-021-04616-8
    » https://doi.org/10.1007/s10750-021-04616-8
  • LOWE-MCCONNELL, R. 1999. Estudos Ecológicos de Comunidades de Peixes Tropicais. EDUSP, São Paulo.
  • LUJAN, N.K., WINEMILLER, K.O. & ARMBRUSTER, J.W. 2012. Trophic diversity in the evolution and community assembly of loricariid catfishes. BMC Evol. Biol. 12(1):124
  • MAGURRAN, A.E. & HENDERSON, P.A. 2003. Explaining the excess of rare species in natural species abundance distributions. Nature 422(6933):714-716.
  • MAGURRAN, A.E. & HENDERSON, P.A. 2011. Commonness and rarity. In Biological Diversity: Frontiers in Measurement and Assessment (A. E. Magurran & B. J. McGill, eds) Publisher: Oxford University Press, New Jersey, p.97-104.
  • MATOS, P.R., CARMO, C.M. & MELO, C.E. 2013. Relação entre variáveis ambientais e a estrutura da comunidade de peixes em córregos das bacias do Rio das Mortes e do rio Xingu - MT, Brasil. Biotemas 26(3):139-151.
  • MELO, C.E., MACHADO, F.D.A. & PINTO-SILVA, V. 2004. Feeding habits of fish from a stream in the savanna of Central Brazil, Araguaia Basin. Neotrop. Ichthyol. 2(1):37-44.
  • MENDONÇA, F.P., MAGNUSSON, W.E. & ZUANON, J. 2005. Relationships between habitat characteristics and fish assemblages in small streams of Central Amazonia. Copeia 2005(4):751-764.
  • MORAIS, R.P., AQUINO, S. & LATRUBESSE, E.M. 2008. Controles hidrogeomorfológicos nas unidades vegetacionais da planície aluvial do rio Araguaia, Brasil. Acta Sci. Biol. Sci. 30(4):411-421.
  • MYERS, N., MITTERMEIER, R.A., MITTERMEIER, C.G., FONSECA, G.A. & KENT, J. 2000. Biodiversity hotspots for conservation priorities. Nature 403(6772):853-8.
  • NOGUEIRA, C., BUCKUP, P.A., MENEZES, N.A., OYAKAWA, O.T., KASECKER, T.P., RAMOS NETO, M.B. & DA SILVA, J.M.C. 2010. Restricted-range fishes and the conservation of Brazilian freshwaters. PLoS One 5(6):e11390.
  • NOVOTNÝ, V. & BASSET, Y. 2000. Rare species in communities of tropical insect herbivores: pondering the mystery of singletons. Oikos 89(3):564-572.
  • OKSANEN, J., BLANCHET, F.G., KINDT, R., PIERRE, L., MINCHIN, P.R., O'HARA, R.B., SIMPSON, G.L., SOLYMOS, P., STEVENS, M.H.H. & WAGNER, H. 2018. Vegan: community ecology package. R Package. version 2.5-2.
  • OLIVEIRA, F.J.M., LIMA-JUNIOR, D.P. & BINI, L.M. 2020. Current environmental conditions are weak predictors of fish community structure compared to community structure of the previous year. Aquat. Ecol. 54(3):729-740.
  • PEASE, A.A., GONZÁLEZ-DÍAZ, A.A., RODILES-HERNÁNDEZ, R. & WINEMILLER, K.O. 2012. Functional diversity and trait-environment relationships of stream fish assemblages in a large tropical catchment. Freshw. Biol. 57(5):1060-1075.
  • PELICICE, F.M. et al. 2021. Large-scale degradation of the Tocantins-Araguaia River basin. Environ. Manage. https://doi.org/10.1007/s00267-021-01513-7
    » https://doi.org/10.1007/s00267-021-01513-7
  • POWER, M.E. 1983. Grazing responses of tropical freshwater fishes to different scales of variation in their food. Environ. Biol. Fishes 9(2):103-115.
  • PRESTON, F.W. 1948. The commonness, and rarity, of species. Ecology 29(3):254-283.
  • R CORE TEAM. 2019. R: A Language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.r-project.org/
    » https://www.r-project.org/
  • REID, A.J., CARLSON, A.K., CREED, I.F., ELIASON, E.J., GELL, P.A., JOHNSON, P.T.J., KIDD, K.A., MACCORMACK, T.J., OLDEN, J.D., ORMEROD, S.J., SMOL, J.P., TAYLOR, W.W., TOCKNER, K., VERMAIRE, J.C., DUDGEON, D. & COOKE, S.J. 2019. Emerging threats and persistent conservation challenges for freshwater biodiversity. Biol. Rev. 94(3):849-873.
  • REIS, R.E., ALBERT, J.S., DI DARIO, F., MINCARONE, M.M., PETRY, P. & ROCHA, L.A. 2016. Fish biodiversity and conservation in South America. J. Fish Biol. 89(1):12-47.
  • STRAHLER, A.N. 1957. Quantitative analysis of watershed geomorphology. Eos, Trans. Am. Geophys. Union 38(6):913-920.
  • TEDESCO, P.A., HUGUENY, B., OBERDORFF, T., DÜRR, H.H., MÉRIGOUX, S. & DE MÉRONA, B. 2008. River hydrological seasonality influences life history strategies of tropical riverine fishes. Oecologia 156(3):691-702.
  • TERESA, F.B. & CASATTI, L. 2012. Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams. Ecol. Freshw. Fish 21(3):433-442.
  • UEIDA, V.S. & CASTRO, R.M.C. 1999. Coleta e fixação de peixes de riachos. In Ecologia de peixes de riachos (E. P. Caramaschi, R. Mazzoni, & P. R. Peres-Neto, eds) Oecologia Brasiliensis, Rio de Janeiro, Brasil, p.1-22.
  • VENERE, P.C. & GARUTTI, V. 2011. Peixes do Cerrado: Parque Estadual da Serra Azul, rio Araguaia, MT. RiMa, São Carlos.
  • VIEIRA, T.B. et al. 2018. A multiple hypothesis approach to explain species richness patterns in Neotropical stream-dweller fish communities L. U. Hepp, ed. PLoS One 13(9):e0204114.
  • WICKHAM, H. 2009. ggplot2: elegant graphics for data analysis. Springer New York, New York, NY.
  • WINEMILLER, K.O. 1989. Patterns of variation in life history among South American fishes in seasonal environments. Oecologia 81(2):225-241.
  • WINEMILLER, K.O., AGOSTINHO, A.A. & CARAMASCHI, É.P. 2008. Fish ecology in tropical streams. In Tropical Stream Ecology (D. Dudgeon, ed.) Elsevier, San Diego, p.107-146.
  • ZBINDEN, Z.D. & MATTHEWS, W.J. 2017. Beta diversity of stream fish assemblages: partitioning variation between spatial and environmental factors. Freshw. Biol. 62(8):1460-1471.
  • ZENI, J.O., PÉREZ‐MAYORGA, M.A., ROA‐FUENTES, C.A., BREJÃO, G.L. & CASATTI, L. 2019. How deforestation drives stream habitat changes and the functional structure of fish assemblages in different tropical regions. Aquat. Conserv. Mar. Freshw. Ecosyst. aqc.3128.

Publication Dates

  • Publication in this collection
    30 Aug 2021
  • Date of issue
    2021

History

  • Received
    18 Feb 2021
  • Accepted
    05 Aug 2021
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