Fish , Machado River basin , Cacoal urban area , state of Rondônia , Brazil

The Pirarara and Tamarupa rivers are two urban tributaries of the Machado River in Cacoal municipality, state of Rondônia (RO), Brazil. Here we report a list of species of fishes from urban areas of Cacoal, being the first ichthyological study in this region. Field work at Cacoal was carried out from November 2004 until July 2005, using gill nets, casting nets, and long lines. Two hundred and twenty-two specimens were collected, and are distributed in 48 species, 14 families and 4 orders. The most representative order was Characiformes, with seven families and 23 species, followed by Siluriformes, with three families and 20 species. Introduction The Pirarara and Tamarupa rivers are two urban tributaries of the Machado River in Cacoal municipality, state of Rondônia, Brazil. When compared to southern and southeastern regions, relatively few studies on fishes were published in the Amazon, especially in the Rondônia State (e.g. Santos 1987; Barthem 2001). Among the causes that may be restraining the occurrence of certain fish species in urbanized environment, we have the removal of riparian forest, effluent discharges, channel alteration and introduction of exotics species (e.g. Barthem 2001; Oliveira and Bennemann 2005). Here we report a list of species of fishes from urban areas of Cacoal (RO), being the first study of the kind in the region. Materials and methods The survey of the fishes was carried out in the Pirarara and Tamarupa rivers, affluents of the Machado River, city of Cacoal (11o26’S, 61o26’W), state of Rondônia, Brazil (Figure 1). The region was covered by tropical rainforests (“Amazônia” sensu Ab’Saber 1977), but during the 1980s the greatest human occupation of RO along the BR-364 highway caused progressive deforestation (Vanzolini 1986; Kemper 2002). Figure 1. South America, showing the situation of state of Rondônia and Cacoal municipality. Field work at Cacoal was made from November 2004 until July 2005, using gill nets, casting nets, and long lines. The identification of species followed Eigenmann (1917; 1921), Pearson (1924), Lauzane and Loubens (1989) and Lima et al. (2005). Classification of species is presented according to Reis et al. (2003) except Serrasalmidae, considered as subfamily of Characidae in that study. Voucher specimens were deposited in the fish collection of Museu de Zoologia (MZUEL), Departamento de Biologia Animal e Vegetal, Centro de Ciências Biológicas, Universidade Estadual de Londrina (UEL), state of Paraná, Brazil. Results and discussion Two hundred and twenty-two specimens were collected, and are distributed in four orders, 14 families and 48 species (Table 1). The most representative order was Characiformes, with seven families and 23 species, followed by Siluriformes, with three families and 20 species. Check List 2007: 3(2)


Introduction
The Pirarara and Tamarupa rivers are two urban tributaries of the Machado River in Cacoal municipality, state of Rondônia, Brazil.When compared to southern and southeastern regions, relatively few studies on fishes were published in the Amazon, especially in the Rondônia State (e.g.Santos 1987;Barthem 2001).Among the causes that may be restraining the occurrence of certain fish species in urbanized environment, we have the removal of riparian forest, effluent discharges, channel alteration and introduction of exotics species (e.g.Barthem 2001;Oliveira and Bennemann 2005).Here we report a list of species of fishes from urban areas of Cacoal (RO), being the first study of the kind in the region.

Materials and methods
The survey of the fishes was carried out in the Pirarara and Tamarupa rivers, affluents of the Machado River, city of Cacoal (11º26'S, 61º26'W), state of Rondônia, Brazil (Figure 1).The region was covered by tropical rainforests ("Amazônia" sensu Ab'Saber 1977), but during the 1980s the greatest human occupation of RO along the BR-364 highway caused progressive deforestation (Vanzolini 1986;Kemper 2002).Field work at Cacoal was made from November 2004 until July 2005, using gill nets, casting nets, and long lines.The identification of species followed Eigenmann (1917;1921), Pearson (1924), Lauzane and Loubens (1989) and Lima et al. (2005).Classification of species is presented according to Reis et al. (2003) except Serrasalmidae, considered as subfamily of Characidae in that study.Voucher specimens were deposited in the fish collection of Museu de Zoologia (MZUEL), Departamento de Biologia Animal e Vegetal, Centro de Ciências Biológicas, Universidade Estadual de Londrina (UEL), state of Paraná, Brazil.

Results and discussion
Two hundred and twenty-two specimens were collected, and are distributed in four orders, 14 families and 48 species (Table 1).The most representative order was Characiformes, with seven families and 23 species, followed by Siluriformes, with three families and 20 species.Few fish surveys were conducted in the rio Madeira basin, but studies made in the rio Mamoré basin revealed 280 (Lauzanne and Loubens 1985) to 329 species (Sarmiento 2000).
In the protected area of Río Beni, Sarmiento (2000) found 211 species.Therefore, the number of species observed in this study is a small parcel of the total richness of species in the basin.Maybe it is consequence of small size of sampled rivers, habitat degradation by organic pollution of their waters, and like in other Amazon regions (Barthem 2001), by marginal deforestation.
Tamarupa river had the major number of species (43), or 89.6 % of the total collected species (= 48).Although the differences in composition of species between Pirarara and Tamarupa rivers, the number of orders were quite similar (Pirarara had missing only Gymnotiformes).
From the total of species, 89.6 % in Tamarupa and 92.9% in Pirarara were from the orders Characiformes and Siluriformes, a common tendency in Neotropical rivers (Lowe-McConnell 1999) (Table 2).

Figure 1 .
Figure 1.South America, showing the situation of state of Rondônia and Cacoal municipality.

Table 1 .
Species captured in the Pirarara and Tamarupa rivers, city of Cacoal (RO, Brazil).

Table 2 .
Proportions of species per Order in Tamarupa and Pirarara rivers, and general (Tamarupa + Pirarara).Hoplias is tentatively identified as H. malabaricus that, in fact, represent a complex of species collected in all hydrographic basins of the Neotropical region above La Plata basin.Other species with large distribution in the Amazon basin are: Steindachnerina leucisca, Prochilodus nigricans, Leporinus friderici, Astyanax aff.bimaculatus, Brycon melanopterus, Serrasalmus humeralis, S. rhombeus, Acestrorhyncus falcatus and Rhamdia quelen.In the other hand, Parodon buckleyi has a restricted area of distribution, occurring only in the headwaters of Napo/Ucayali and Madeira/ Steindachnerina fasciata and Creagrutus anary have type-locality in Madeira River.