Efeito das cachoeiras e do pulso de inundação na estrutura das assembleias de peixes do Médio Rio Xingu, Amazônia oriental

Barbosa, TAP; Benone, NL; Begot, TOR; Gonçalves, A; Sousa, L; Giarrizzo, T; Juen, L; Montag, LFA

doi:10.1590/1519-6984.00214BM

TAP Barbosa ^**e-mail: tapbarbosa@gmail.com

Laboratório de Ecologia e Conservação, Instituto de Ciências Biológicas, Universidade Federal do Pará – UFPA, Rua Augusto Corrêa, 01, Guamá, Caixa Postal 479, CEP 66075-110, Belém, PA, Brazil

NL Benone

Laboratório de Ecologia e Conservação, Instituto de Ciências Biológicas, Universidade Federal do Pará – UFPA, Rua Augusto Corrêa, 01, Guamá, Caixa Postal 479, CEP 66075-110, Belém, PA, Brazil

TOR Begot

Laboratório de Ecologia e Conservação, Instituto de Ciências Biológicas, Universidade Federal do Pará – UFPA, Rua Augusto Corrêa, 01, Guamá, Caixa Postal 479, CEP 66075-110, Belém, PA, Brazil

A Gonçalves

Laboratório de Ictiologia, Universidade Federal do Pará – UFPA, Rua Coronel José Porfírio, 2515, CEP 68372-040, Altamira, PA, Brazil

L Sousa

Laboratório de Ictiologia, Universidade Federal do Pará – UFPA, Rua Coronel José Porfírio, 2515, CEP 68372-040, Altamira, PA, Brazil

T Giarrizzo

Grupo de Ecologia Aquática, Laboratório de Biologia Pesqueira, Manejo dos Recursos Aquáticos, Universidade Federal do Pará – UFPA, Rua Augusto Corrêa, 01, Guamá, Caixa Postal 479, CEP 66075-110 Belém, PA, Brazil

L Juen

Laboratório de Ecologia e Conservação, Instituto de Ciências Biológicas, Universidade Federal do Pará – UFPA, Rua Augusto Corrêa, 01, Guamá, Caixa Postal 479, CEP 66075-110, Belém, PA, Brazil

LFA Montag

Laboratório de Ecologia e Conservação, Instituto de Ciências Biológicas, Universidade Federal do Pará – UFPA, Rua Augusto Corrêa, 01, Guamá, Caixa Postal 479, CEP 66075-110, Belém, PA, Brazil

*e-mail: tapbarbosa@gmail.com

Figuras (3)
Tabelas (5)

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Figure 1
Sites visited during the present study for the collection of data on the local fish fauna of the middle Xingu River between July, 2012, and April, 2013. The points are represented by black circles, and the black bars show waterfalls.

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Figure 2
Plot of the PCA for the hydrological periods and sample sites surveyed on the middle Xingu River between July, 2012, and April, 2013.

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Figure 3
Results of the Non-Metric Multidimensional Scaling (NMDS) analysis of the data collected on the fish fauna of the middle Xingu River by sampling site and hydrological period between July, 2012, and April, 2013. The ellipses correspond to the three groups formed by the influence of Jericoá falls and Bacajá rapids.

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Table 1
Results of the Principal Components Analysis (PCA) for the nine sample points surveyed on the middle Xingu River between April, 2012 and April, 2013.

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Table 2
Results of Indicator Species Analysis per hydrologic period (a) and per sampling site (b) of the fish assemblages on the middle Xingu River.

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Table 3
Results of the Mantel analysis between the four explanatory matrices ̶ environmental variables, hydrological periods, the presence of barriers (waterfalls or rapids), and fluvial distance between points ̶ and their effects on the composition of the fish assemblages on the middle Xingu River.

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Period Alk C Cloa Cond BDO SIM SOM TSM N DO pH Depth Redox SolDiss Temp Transp Turb Receding Water 6.59± 3.16 0.27± 0.16 12.92± 5.82 0.02± 0.001 0.67± 0.28 3.82± 2.34 2.31± 0.55 6.13± 2.71 2.76± 5.74 7.12± 0.26 7.98± 0.30 3.16± 5.21 117.23± 14.09 0.01± 0.01 29.85± 0.68 1.06± 0.32 4.60± 2.44 Low water 7.36± 5.73 6.96± 5.96 4.87± 3.18 0.02± 0.02 1.05± 0.60 4.57± 6.21 2.58± 1.60 7.14± 7.70 0.87± 0.50 7.54± 0.22 7.47± 0.60 2.02± 4.28 77.94± 28.04 0.01± 0.01 30.85± 0.61 0.81± 0.71 5.02± 5.19 Flooding 7.05± 6.28 7.71± 6.53 7.56± 4.55 0.03± 0.02 0.77± 0.40 2.93± 6.01 2.99± 2.15 5.92± 7.98 0.44± 0.11 7.37± 0.77 7.89± 0.79 2.12± 3.60 116.42± 28.67 0.01± 0.01 31.24± 0.36 0.92± 0.86 6.43± 5.44 High water 5.00± 2.02 25.69± 35.27 10.98± 8.87 0.07± 0.03 1.75± 0.24 10.96± 6.84 5.18± 5.47 16.13± 6.13 0.31± 0.20 7.05± 0.84 13.52± 21.11 3.03± 3.41 68.47± 33.35 0.04± 0.02 28.60± 1.28 0.49± 0.21 22.17± 13.36

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Taxon / Authority Voucher High Water(ind./km2/h) Flooding(ind./km2/h) Low Water(ind./km2/h) Receding Water(ind./km2/h) Total(ind./km2/h) BELONIFORMES Belonidae Pseudotylosurus microps (Günther, 1866) LIA 404 3.741 2.721 0.000 0.227 6.689 CHARACIFORMES Acestrorhynchidae Acestrorhynchus falcatus (Bloch, 1794) MPEG 29909 6.198 0.454 1.361 4.308 12.320 Acestrorhynchus microlepis (Jardine, 1841) MPEG 28903 22.751 15.420 8.503 7.370 54.044 Anostomidae Anostomoides passionis Santos & Zuanon, 2006 LIA 417 0.227 0.227 0.000 0.000 0.454 Hypomasticus julii (Santos, Jégu & Lima, 1996) MPEG 29314 2.494 0.227 0.000 2.041 4.762 Laemolyta fernandezi Myers, 1950 MPEG 29078 0.454 0.227 0.000 0.000 0.680 Laemolyta proxima (Garman, 1890) LIA 161 6.311 5.442 0.680 0.000 12.434 Leporinus aff. fasciatus LIA 134 15.004 2.041 3.061 8.277 28.328 Leporinus brunneus Myers, 1950 LIA 418 0.454 0.000 0.000 0.227 0.680 Leporinus desmotes Fowler, 1914 LIA 313 1.663 0.000 1.701 0.113 3.477 Leporinus friderici (Bloch, 1794) MPEG 28073 10.204 2.721 2.834 3.515 19.274 Leporinus maculatus Müller & Troschel, 1844 LIA 370 12.207 3.628 2.154 4.082 22.071 Leporinus sp. 1 MPEG 28837 0.000 0.000 0.000 0.227 0.227 Leporinus sp. 2 MPEG 28938 0.756 0.000 0.227 0.000 0.983 Leporinus tigrinus Borodin, 1929 MPEG 28996 0.907 0.000 0.000 0.907 1.814 Petulanos intermedius (Winterbottom, 1980) MPEG 29626 0.529 0.227 0.000 0.000 0.756 Pseudanos trimaculatus (Kner, 1858) MPEG 29440 0.869 0.227 0.000 0.340 1.436 Sartor respectus Myers & Carvalho, 1959 MPEG 28924 0.227 0.000 0.227 0.000 0.454 Schizodon vittatus (Valenciennes, 1850) MPEG 29057 1.134 0.680 0.113 0.340 2.268 Synaptolaemus latofasciatus (Steindachner, 1910) 0.151 0.000 0.000 0.000 0.151 Characidae Acestrocephalus stigmatus Menezes, 2006 MPEG 28849 0.302 0.000 0.113 0.000 0.416 Agoniates halecinus Müller & Troschel, 1845 LIA 409 4.460 2.721 1.701 3.741 12.623 Astyanax gr. bimaculatus LIA 419 0.756 0.000 0.000 0.680 1.436 Brycon sp. 1 LIA 203 5.518 1.361 1.927 1.134 9.939 Brycon sp. 2 LIA 420 2.230 0.000 1.020 0.000 3.250 Brycon falcatus Müller & Troschel, 1844 MPEG 28992 2.381 0.227 1.361 0.227 4.195 Bryconops alburnoides Kner, 1858 MPEG 28979 2.608 0.227 0.794 1.587 5.215 Bryconops caudomaculatus (Günther, 1864) MPEG 29003 0.227 0.227 0.000 0.000 0.453 Bryconops giacopinii (Fernández-Yépez, 1950) MPEG 29402 0.000 0.567 0.000 0.000 0.566 Chalceus epakros Zanata & Toledo-Piza, 2004 LIA 157 1.134 0.000 0.680 0.000 1.814 Charax gibbosus (Linnaeus, 1758) LIA 342 0.907 0.000 0.907 0.000 1.814 Ctenobrycon spilurus (Valenciennes, 1850) MPEG 29817 2.305 0.000 0.340 1.587 4.232 Cynopotamus xinguano Menezes, 2007 MPEG 29587 3.364 0.227 1.020 2.154 6.764 Jupiaba polylepis (Günther, 1864) MPEG 29017 1.020 0.907 0.113 0.000 2.040 Moenkhausia heikoi Géry & Zarske, 2004 MPEG 28982 6.274 4.762 0.227 0.000 11.262 Moenkhausia intermedia Eigenmann, 1908 MPEG 28844 36.168 16.440 9.524 11.451 73.582 Moenkhausia lepidura (Kner, 1858) MPEG 28867 0.567 0.227 0.000 0.340 1.133 Moenkhausia xinguensis (Steindachner, 1882) MPEG 28083 8.428 3.175 0.454 1.134 13.189 Poptella brevispina Reis, 1989 LIA 410 5.329 0.000 0.227 5.669 11.224 Poptella compressa (Günther, 1864) MPEG 29019 9.259 2.381 4.875 0.000 16.515 Roeboexodon guyanensis (Puyo, 1948) MPEG 29407 0.567 0.227 0.000 0.340 1.133 Roeboides sp. MPEG 28899 2.608 0.227 2.041 0.340 5.215 Tetragonopterus argenteus (Puyo, 1948) MPEG 29871 1.474 0.680 0.000 0.794 2.947 Tetragonopterus chalceus Spix & Agassiz, 1829 MPEG 28943 3.288 1.134 1.247 0.794 6.462 Triportheus albus Cope, 1872 MPEG 29112 19.048 5.556 0.000 1.361 25.963 Triportheus auritus (Valenciennes, 1850) MPEG 29631 4.649 0.680 0.000 4.535 9.863 Triportheus rotundatus (Jardine, 1841) MPEG 29352 10.280 1.587 0.000 9.864 21.730 Chilodontidae Caenotropus labyrinthicus (Kner, 1858) MPEG 28838 27.211 4.308 6.009 15.646 53.174 Chilodus punctatus Müller & Troschel, 1844 MPEG 29059 15.684 10.091 2.041 1.814 29.629 Ctenoluciidae Boulengerella cuvieri (Spix & Agassiz, 1829) MPEG 28070 13.568 6.689 4.082 0.227 24.565 Boulengerella maculata (Valenciennes, 1850) LIA 272 1.587 1.134 0.454 0.000 3.174 Curimatidae Curimata inornata Vari, 1989 MPEG 28876 37.906 18.367 4.308 15.193 75.774 Curimata vittata (Kner, 1858) LIA 421 0.907 0.907 0.000 0.000 1.814 Curimatella dorsalis (Eigenmann & Eigenmann, 1889) MPEG 29838 1.512 0.000 0.907 0.000 2.418 Curimatella immaculata (Fernández-Yépez, 1948) MPEG 29526 10.506 7.596 0.000 0.000 18.102 Cyphocharax festivus Vari, 1992 LIA 366 39.985 43.084 0.000 0.000 83.068 Cyphocharax gouldingi Vari, 1992 MPEG 28893 16.289 2.268 4.308 37.528 60.393 Cyphocharax leucostictus (Eigenmann & Eigenmann, 1889) MPEG 29535 7.181 8.957 1.020 0.000 17.157 Cyphocharax stilbolepis Vari, 1992 LIA 367 2.230 0.454 0.000 0.000 2.683 Psectrogaster falcata (Eigenmann & Eigenmann, 1889) LIA 308 0.340 0.227 0.000 0.000 0.566 Cynodontidae Cynodon gibbus (Agassiz, 1829) MPEG 28908 2.683 0.454 0.340 1.134 4.610 Hydrolycus armatus (Jardine, 1841) LIA 401 10.242 2.948 3.855 0.227 17.271 Hydrolycus tatauaia Toledo-Piza, Menezes & Santos, 1999 MPEG 29086 3.477 0.907 1.134 0.680 6.198 Rhaphiodon vulpinus Spix & Agassiz, 1829 MPEG 29085 3.704 0.227 1.134 1.474 6.538 Erythrinidae Hoplias aimara (Valenciennes, 1847) MPEG 29904 0.680 0.567 0.000 0.227 1.473 Hoplias malabaricus (Bloch, 1794) MPEG 28067 1.701 0.680 0.794 0.113 3.287 Hemiodontidae Argonectes robertsi Langeani, 1999 MPEG 28961 21.958 10.431 2.608 1.814 36.810 Bivibranchia fowleri (Steindachner, 1908) MPEG 28883 5.102 1.814 4.195 0.000 11.111 Bivibranchia velox (Eigenmann & Myers, 1927) MPEG 29105 6.463 2.154 2.381 3.401 14.399 Hemiodus cf. semitaeniatus LIA 422 6.122 6.122 0.000 0.000 12.244 Hemiodus sp. 1 MPEG 29072 22.373 0.680 7.937 9.864 40.854 Hemiodus unimaculatus (Bloch, 1794) MPEG 28887 99.471 39.569 19.955 26.871 185.865 Hemiodus vorderwinckleri (Géry, 1964) LIA 371 16.667 7.256 2.268 6.009 32.199 Prochilodontidae Prochilodus nigricans Spix & Agassiz, 1829 LIA 298 3.401 1.361 1.020 0.454 6.235 Semaprochilodus brama (Valenciennes, 1850) MPEG 28968 6.236 2.721 2.948 1.814 13.718 Serrasalmidae Acnodon normani Gosline, 1951 LIA 181 4.611 1.927 2.608 0.113 9.259 Metynnis cf. luna LIA 423 4.157 2.494 0.454 1.134 8.238 Myleus setiger Müller & Troschel, 1844 LIA 413 3.099 0.907 1.701 0.454 6.160 Myloplus arnoldi (Ahl, 1936) MPEG 28966 6.387 0.454 0.567 5.669 13.076 Myloplus rhomboidalis (Cuvier, 1818) LIA397 2.948 1.134 0.907 0.907 5.895 Myloplus rubripinnis (Müller & Troschel, 1844) LIA 374 11.300 3.741 2.494 0.000 17.535 Myloplus schomburgkii (Jardine, 1841) LIA163 2.494 0.227 1.361 0.794 4.875 Pristobrycon eigenmanni (Norman, 1929) LIA 297 0.227 0.000 0.227 0.000 0.453 Pristobrycon striolatus (Steindachner, 1908) LIA 411 3.401 1.587 1.247 0.567 6.802 Pygocentrus nattereri Kner, 1858 LIA 300 1.474 0.000 0.680 0.794 2.947 Serrasalmus altispinis Merckx, Jégu & Santos, 2000 LIA 424 2.834 0.000 2.834 0.000 5.668 Serrasalmus gouldingi Fink & Machado-Allison, 1992 MPEG 28860 1.587 0.227 0.000 1.361 3.174 Serrasalmus manueli (Fernández-Yépez & Ramírez, 1967) LIA 393 22.978 2.494 13.152 6.689 45.313 Serrasalmus rhombeus (Linnaeus, 1766) LIA 351 17.385 1.020 4.195 10.317 32.917 Tometes sp. LIA 59 2.948 0.907 0.567 0.794 5.215 CLUPEIFORMES Engraulidae Anchoviella sp. MPEG 28064 0.680 0.680 0.000 0.000 1.360 Lycengraulis batesii (Günther, 1868) LIA 360 0.907 0.454 0.000 0.454 1.814 Pristigasteridae Ilisha amazonica (Miranda & Ribeiro, 1920) MPEG 28870 12.812 5.215 0.907 0.907 19.841 Pellona castelnaeana Valenciennes, 1847 LIA 425 0.794 0.000 0.227 0.227 1.247 GYMNOTIFORMES Electrophoridae Electrophorus electricus (Linnaeus, 1766) LIA 426 0.113 0.000 0.000 0.113 0.226 Gymnotidae Gymnotus carapo Linnaeus, 1758 LIA 427 0.529 0.000 0.000 0.000 0.529 Hypopomidae Steatogenys elegans (Steindachner, 1880) MPEG 29292 0.227 0.000 0.000 0.227 0.453 Rhamphichthyidae Rhamphichthys drepanium Triques, 1999 LIA 428 0.416 0.227 0.113 0.000 0.755 Sternopygidae Archolaemus janeae Vari, de Santana & Wosiacki, 2012 MPEG 28896 4.308 0.000 1.701 2.494 8.503 Eigenmannia aff. trilineata MPEG 29595 0.076 0.000 0.000 0.000 0.075 MYLIOBATIFORMES Potamotrygonidae Paratrygon aiereba (Müller & Henle, 1841) LIA 314 0.227 0.227 0.000 0.000 0.453 OSTEOGLOSSIFORMES Osteoglossidae Osteoglossum bicirrhosum (Cuvier, 1829) LIA 276 1.361 0.000 1.361 0.000 2.721 PERCIFORMES Cichlidae Aequidens michaeli Kullander, 1995 MPEG 28846 0.227 0.227 0.000 0.000 0.453 Caquetaia spectabilis (Steindachner, 1875) MPEG 28840 0.454 0.227 0.000 0.113 0.793 Cichla melaniae Kullander & Ferreira, 2006 LIA 64 2.268 0.000 0.113 1.587 3.968 Cichla monoculus Agassiz, 1831 LIA 63 0.227 0.000 0.227 0.000 0.453 Crenicichla gr. saxatilis LIA 429 0.113 0.000 0.000 0.113 0.226 Crenicichla lugubris Heckel, 1840 MPEG 28959 0.227 0.000 0.113 0.340 0.680 Crenicichla sp. LIA 81 1.134 0.454 0.000 0.680 2.267 Geophagus altifrons Heckel, 1840 MPEG 28081 12.094 4.422 7.143 0.794 24.452 Geophagus argyrostictus Kullander, 1991 MPEG 28962 7.521 0.794 4.649 1.247 14.210 Retroculus xinguensis Gosse, 1971 MPEG 29203 1.020 0.227 0.567 0.567 2.380 Satanoperca sp. MPEG 29334 0.340 0.000 0.113 0.113 0.566 Teleocichla sp. LIA 5 0.227 0.000 0.227 0.000 0.453 Sciaenidae Pachyurus junki Soares & Casatti, 2000 MPEG 28085 20.446 4.422 9.751 4.649 39.266 Plagioscion squamosissimus (Heckel, 1840) LIA 362 8.957 1.814 3.175 0.794 14.739 PLEURONECTIFORMES Achiridae Hypoclinemus mentalis (Günther, 1862) MPEG 29117 0.000 0.000 0.113 0.000 0.113 SILURIFORMES Auchenipteridae Ageneiosus inermis (Linnaeus, 1766) 4.308 2.608 0.454 0.227 7.596 Ageneiosus ucayalensis Castelnau, 1855 MPEG 29114 43.915 23.696 2.381 0.567 70.559 Auchenipterichthys longimanus (Günther, 1864) MPEG 28834 19.992 5.329 0.567 1.020 26.908 Auchenipterus nuchalis (Spix & Agassiz, 1829) LIA 383 63.492 22.789 1.247 0.794 88.321 Centromochlus heckelii (De Filippi, 1853) MPEG 28063 12.245 9.977 0.000 2.268 24.489 Centromochlus schultzi Rössel, 1962 MPEG 29752 0.454 0.567 0.000 0.113 1.133 Tatia intermedia (Steindachner, 1877) MPEG 28925 0.529 0.454 0.000 0.000 0.982 Tocantinsia piresi (Miranda Ribeiro, 1920) LIA 363 34.014 22.676 0.000 0.000 56.689 Trachelyopterus ceratophysus (Kner, 1858) LIA 339 0.454 0.000 0.000 0.000 0.453 Callichthyidae Megalechis picta (Müller & Troschel, 1849) MPEG 29903 0.113 0.000 0.000 0.113 0.226 Cetopsidae Cetopsis coecutiens (Lichtenstein, 1819) MPEG 28061 3.628 0.000 0.227 3.401 7.256 Doradidae Doras higuchii Sabaj Pérez & Birindelli, 2008 MPEG 29368 8.919 1.474 5.215 2.494 18.102 Hassar gabiru Birindelli, Fayal & Wosiacki, 2011 MPEG 28965 17.952 5.669 7.596 2.268 33.484 Hassar orestis (Steindachner, 1875) MPEG 28871 21.542 6.803 0.000 14.286 42.630 Leptodoras hasemani (Steindachner, 1915) MPEG 29120 2.494 1.701 2.041 0.000 6.235 Leptodoras praelongus (Myers & Weitzman, 1956) MPEG 29740 0.113 0.000 0.000 0.113 0.226 Megalodoras uranoscopus (Eigenmann & Eigenmann, 1888) MPEG 28076 1.058 0.340 0.000 0.567 1.965 Nemadoras elongatus (Boulenger, 1898) LIA 430 0.227 0.227 0.000 0.000 0.453 Ossancora asterophysa Birindelli & Sabaj Pérez, 2011 LIA 275 1.134 0.680 0.000 0.454 2.267 Oxydoras níger (Valenciennes, 1821) LIA 369 1.587 1.701 0.000 0.113 3.401 Platydoras armatulus (Valenciennes, 1840) MPEG 28062 2.343 0.907 0.454 0.567 4.270 Platydoras sp. LIA 139 4.119 2.494 0.000 0.454 7.067 Rhinodoras boehlkei Glodek, Whitmire & Orcés, 1976 MPEG 28857 0.454 0.454 0.000 0.000 0.907 Heptapteridae Imparfinis aff. hasemani LIA 431 0.113 0.000 0.000 0.113 0.226 Pimelodella cristata (Müller & Troschel, 1849) MPEG 28892 4.535 0.000 2.154 2.154 8.843 Pimelodella sp. 1 MPEG 29481 0.567 0.000 0.000 0.000 0.567 Pimelodella sp. 2 MPEG 28969 0.113 0.000 0.000 0.113 0.226 Loricariidae Ancistrus ranunculus Muller, Rapp Py-Daniel & Zuanon, 1994 LIA 131 0.227 0.227 0.000 0.000 0.453 Ancistrus sp. 1 LIA 169 0.454 0.454 0.000 0.000 0.907 Ancistrus sp. 2 LIA 77 0.680 0.340 0.227 0.000 1.247 Baryancistrus aff. niveatus LIA 170 6.236 0.227 2.948 3.288 12.698 Baryancistrus chrysolomus Rapp Py-Daniel, Zuanon & Ribeiro de Oliveira, 2011 LIA 387 1.587 0.227 1.134 0.227 3.174 Baryancistrus xanthellus Rapp Py-Daniel, Zuanon & Ribeiro de Oliveira, 2011 LIA 171 1.474 0.340 1.020 0.113 2.947 Hemiodontichthys acipenserinus (Kner, 1853) LIA 432 1.134 0.000 0.000 0.907 2.040 Hopliancistrus sp. LIA 433 0.227 0.227 0.000 0.000 0.454 Hypancistrus sp. LIA 21 0.227 0.000 0.227 0.000 0.453 Hypoptopoma inexpectatum (Holmberg, 1893) LIA 321 27.022 21.995 1.020 0.113 50.151 Hypostomus aff. plecostomus LIA 434 0.227 0.000 0.000 0.000 0.226 Hypostomus hemicochliodon Armbruster, 2003 LIA 359 2.041 0.454 0.680 0.340 3.514 Limatulichthys griseus (Eigenmann, 1909) LIA 380 5.556 0.454 2.268 0.000 8.276 Loricaria birindellii Thomas & Sabaj Pérez, 2010 LIA 85 8.163 2.268 2.041 4.989 17.460 Loricaria cataphracta Linnaeus, 1758 LIA 365 7.143 0.000 2.721 5.215 15.079 Panaque armbrusteri Lujan, Hidalgo & Stewart, 2010 LIA 137 0.794 0.227 0.340 0.227 1.587 Parancistrus nudiventris Rapp Py-Daniel & Zuanon, 2005 LIA 177 0.794 0.000 0.794 0.000 1.587 Peckoltia cf. cavatica LIA 435 0.454 0.227 0.227 0.000 0.907 Peckoltia feldbergae de Oliveira, Rapp Py-Daniel, Zuanon & Rocha, 2012 LIA 107 0.680 0.000 0.000 1.020 1.700 Peckoltia sabaji Armbruster, 2003 LIA 358 0.454 0.454 0.000 0.000 0.907 Peckoltia vittata (Steindachner, 1881) LIA 291 4.611 1.134 1.927 1.927 9.599 Pseudacanthicus sp. LIA 178 0.794 0.000 0.000 0.794 1.587 Pseudancistrus sp. LIA 309 0.794 0.000 0.794 0.000 1.587 Pseudoloricaria laeviuscula (Valenciennes, 1840) LIA 415 6.916 3.401 0.680 2.041 13.038 Pterygoplichthys xinguensis (Weber, 1991) LIA 299 2.116 1.701 0.113 0.227 4.157 Rineloricaria sp. LIA 248 0.113 0.000 0.000 0.000 0.113 Scobinancistrus aureatus Burgess, 1994 LIA 111 0.340 0.000 0.227 0.113 0.680 Scobinancistrus pariolispos Isbrücker & Nijssen, 1989 LIA 141 0.567 0.113 0.000 0.567 1.247 Squaliforma aff. emarginata LIA 294 17.763 4.989 7.370 3.401 33.522 Spectracanthicus punctatissimus (Steindachner, 1881) LIA 118 1.361 0.227 0.454 0.680 2.721 Spectracanthicus sp. LIA 136 2.381 0.227 1.474 1.134 5.215 Pimelodidae Brachyplatystoma filamentosum (Lichtenstein, 1819) 0.227 0.000 0.000 0.227 0.453 Hemisorubim platyrhynchos (Valenciennes, 1840) MPEG 29084 0.000 0.000 0.113 0.000 0.113 Megalonema sp. MPEG 29868 0.907 0.454 0.454 0.000 1.814 Phractocephalus hemioliopterus (Bloch & Schneider, 1801) LIA 389 2.646 0.680 0.000 1.701 5.026 Pimelodus blochii Valenciennes, 1840 LIA 348 22.071 10.884 2.381 9.864 45.200 Pimelodus ornatus Kner, 1858 LIA 436 0.227 0.000 0.000 0.227 0.453 Pinirampus pirinampu (Spix & Agassiz, 1829) MPEG 29383 2.759 0.680 0.567 1.814 5.820 Platynematichthys notatus (Jardine, 1841) MPEG 29083 1.134 0.000 0.227 0.907 2.267 Pseudoplatystoma punctifer (Castelnau, 1855) LIA 395 0.113 0.000 0.000 0.000 0.113 Sorubim lima (Bloch & Schneider, 1801) LIA 437 0.529 0.454 0.000 0.000 0.982 Sorubim trigonocephalus Miranda Ribeiro, 1920 LIA 438 0.113 0.000 0.000 0.113 0.226 Pseudopimelodidae Pseudopimelodus bufonius (Valenciennes, 1840) LIA 318 0.454 0.454 0.000 0.000 0.907 Trichomycteridae Henonemus sp. LIA 439 0.340 0.227 0.000 0.000 0.566 TOTAL 1157.407 460.544 241.383 323.582

Variable	Axis 1	Axis 2
Alk	–0.111	0.451
C	–0.612	0.207
Cloa	0.12	–0.594
Cond	–0.774	–0.152
BDO	–0.486	–0.57
SOM	–0.518	–0.364
TSM	–0.804	–0.229
N	0.57	0.001
DO	0.348	–0.817
pH	0.661	–0.218
Depth	0.088	0.296
Redox	0.355	0.67
Temp	0.644	–0.631
Transp	0.622	0.083
Eigenvalue	3.97	2.79
% explanation	28.35	19.92
% accumulated explanation	28.35	48.28
Broken Stick	3.25	2.25

The loading values for each environmental variable are shown for each axis, with those in bold type being characterised by a strong (>0.7) correlation between axes. The acronyms are defined in ^{Appendix 1} Appendix 1 Values recorded for the different environmental variables at the nine sampling sites on the middle Xingu River during each of the four principal hydrological periods (ebb, low water, flood, and high water) between July, 2012, and April, 2013. Alk = Alkalinity (mg-CaCO3/L), C = Total carbon (mg/g sed), Cloa = Chlorophyll a (µg/L), Cond = Condutivity (mS/cm), BDO = Biochemical Demand for Oxygen (mg/L), SIM = Suspended Inorganic Matter (mg/L), SOM = Suspended Organic Matter (mg/L), TSM = Total Suspended Matter (mg/L), N = Total nitrogen (mg/L), DO = Dissolved oxygen (mg/L), pH, Depth = depth (m), Redox = Redox potential (mV), SolDiss = Total Dissolved Solids (mg/L), Temp = Temperature (°C), Transp = Transparency (m), and Turb = Turbidity (UNT). Period Alk C Cloa Cond BDO SIM SOM TSM N DO pH Depth Redox SolDiss Temp Transp Turb Receding Water 6.59± 3.16 0.27± 0.16 12.92± 5.82 0.02± 0.001 0.67± 0.28 3.82± 2.34 2.31± 0.55 6.13± 2.71 2.76± 5.74 7.12± 0.26 7.98± 0.30 3.16± 5.21 117.23± 14.09 0.01± 0.01 29.85± 0.68 1.06± 0.32 4.60± 2.44 Low water 7.36± 5.73 6.96± 5.96 4.87± 3.18 0.02± 0.02 1.05± 0.60 4.57± 6.21 2.58± 1.60 7.14± 7.70 0.87± 0.50 7.54± 0.22 7.47± 0.60 2.02± 4.28 77.94± 28.04 0.01± 0.01 30.85± 0.61 0.81± 0.71 5.02± 5.19 Flooding 7.05± 6.28 7.71± 6.53 7.56± 4.55 0.03± 0.02 0.77± 0.40 2.93± 6.01 2.99± 2.15 5.92± 7.98 0.44± 0.11 7.37± 0.77 7.89± 0.79 2.12± 3.60 116.42± 28.67 0.01± 0.01 31.24± 0.36 0.92± 0.86 6.43± 5.44 High water 5.00± 2.02 25.69± 35.27 10.98± 8.87 0.07± 0.03 1.75± 0.24 10.96± 6.84 5.18± 5.47 16.13± 6.13 0.31± 0.20 7.05± 0.84 13.52± 21.11 3.03± 3.41 68.47± 33.35 0.04± 0.02 28.60± 1.28 0.49± 0.21 22.17± 13.36 .

(a) Periods
Period	Species	IndVal	p
Receding Water	Cyphocharax gouldingi	0.812	0.01
Receding Water	Triportheus rotundatus	0.73	0.015
Receding Water	Poptella brevispina	0.571	0.02
Flooding	Cyphocharax festivus	0.733	0.02
Flooding	Oxydoras niger	0.629	0.05
High Water	Triportheus albus	0.836	0.005
Receding Water + Low Water	Baryancistrus aff. niveatus	0.9	0.005
Receding Water + High Water	Myloplus arnoldi	0.749	0.01
Low Water + High Water	Limatulichthys griseus	0.758	0.01
Low Water + High Water	Brycon falcatus	0.684	0.035
Low Water + High Water	Brycon aff. pesu “adiposa preta”	0.667	0.02
Flooding + High Water	Ageneiosus ucayalensis	0.923	0.005
Flooding + High Water	Auchenipterichthys longimanus	0.892	0.005
Flooding + High Water	Auchenipterus nuchalis	0.861	0.005
Flooding + High Water	Myloplus rubripinnis	0.848	0.005
Flooding + High Water	Tocantinsia piresii	0.782	0.005
Flooding + High Water	Hypoptopoma inexpectatum	0.763	0.02
Flooding + High Water	Curimatella immaculata	0.745	0.015
Flooding + High Water	Chilodus punctatus	0.699	0.02
Receding Water + Low Water + High Water	Hemiodus sp. “xingu”	0.804	0.035
Receding Water + Low Water + High Water	Pimelodella cristata	0.72	0.015
Low Water + Flooding + High Water	Hydrolycus armatus	0.917	0.005
Low Water + Flooding + High Water	Boulengerella cuvieri	0.856	0.005
Low Water + Flooding + High Water	Geophagus altifrons	0.787	0.04

(b) Sites
Sites	Species	IndVal	p
IC07	Hemiodontichthys acipenserinus	0.707	0.045
IC09	Acestrorhynchus falcatus	1	0.005
IC09	Moenkhausia intermedia	0.932	0.005
IC09	Pterygoplichthys xinguensis	0.877	0.005
IC09	Pristobrycon striolatus	0.866	0.01
IC09	Ctenobrycon spilurus	0.824	0.02
IC09	Poptella compressa	0.812	0.015
IC01 + IC03	Agoniates halecinus	0.872	0.01
IC01 + IC03	Bivibranchia velox	0.799	0.01
IC06 + IC07	Ilisha amazonica	0.935	0.005
IC06 + IC07	Pseudoloricaria laeviuscula	0.935	0.005
IC06 + IC07	Hassar orestis	0.791	0.01
IC06 + IC07	Pseudotylosurus microps	0.791	0.005
IC07 + IC09	Hypoptopoma inexpectatum	0.83	0.03
IC08 + IC09	Cynopotamus xinguano	0.782	0.005
IC01 + IC02 + IC09	Hypostomus hemicochliodon	0.772	0.025
IC02 + IC03 + IC04	Geophagus argyrostictus	0.828	0.015
IC01 + IC02 + IC03 + IC04	Hemiodus vorderwinckleri	0.91	0.005
IC02 + IC03 + IC07 + IC09	Leporinus friderici	0.848	0.015
IC01 + IC02 + IC03 + IC04 + IC05	Leporinus maculatus	0.858	0.02
IC01 + IC02 + IC03 + IC04 + IC06	Chilodus punctatus	0.753	0.045
IC01 + IC02 + IC07 + IC08 + IC09	Hassar gabiru	0.874	0.005
IC01 + IC02 + IC03 + IC04 + IC05 + IC06	Caenotropus labyrinthicus	0.885	0.05
IC01 + IC02 + IC03 + IC04 + IC05 + IC06	Serrasalmus manueli	0.883	0.035
IC01 + IC02 + IC03 + IC04 + IC05 + IC09	Acnodon normani	0.764	0.035
IC01 + IC02 + IC03 + IC04 + IC06 + IC09	Pimelodus blochii	0.927	0.01
IC01 + IC02 + IC03 + IC04 + IC08 + IC09	Loricaria birindellii	0.854	0.02
IC01 + IC03 + IC04 + IC07 + IC08 + IC09	Acestrorhynchus microlepis	0.879	0.02
IC01 + IC02 + IC03 + IC04 + IC05 + IC06 + IC09	Pachyurus junkii	0.92	0.045
IC01 + IC02 + IC03 + IC04 + IC05 + IC08 + IC09	Squaliforma aff. emarginata	0.91	0.04
IC01 + IC02 + IC03 + IC04 + IC05 + IC08 + IC09	Hemiodus sp. “xingu”	0.845	0.035

	R	p
Environment x Period	0.07	0.01
Environment x Waterfall	–0.05	0.78
Environment x Fluvial distance	–0.10	0.91
Period x Waterfall	–0.05	1
Period x Fluvial distance	–0.06	1
Waterfall x Fluvial distance	0.43	<0.01
Fish assemblages x Environment	–0.25	0.99
Fish assemblages x Period	0.23	<0.01
Fish assemblages x Waterfall^*	0.39	<0.01
Fish assemblages x Fluvial distance^*	0.01	0.41

[1] *e-mail: tapbarbosa@gmail.com

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Efeito das cachoeiras e do pulso de inundação na estrutura das assembleias de peixes do Médio Rio Xingu, Amazônia oriental

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