Ichthyofauna of the Aiuruoca River basin, Minas Gerais, Brazil

: Although the Aiuruoca River is recognized as a very important area for fish fauna, the species composition of this river remains unknown or restricted to technical reports of licensing projects. The aim of this study was to describe the composition and distribution of the ichthyofauna in the Aiuruoca River basin. Fifty-eight collection points were sampled along the Aiuruoca River basin during 2010 and 2011, including 38 streams, 11 lagoons and 9 points along the Aiuruoca River main channel. A total of 8562 specimens were collected belonging to 6 orders, 15 families, 33 genera and 47 species. The pirapetinga fish ( Brycon nattereri ) is listed on Brazil’s endangered species, and the rainbow trout ( Oncorhynchus


Introduction
There is a scientific consensus that the long-term maintenance of biodiversity would benefit greatly from conservation plans that act on a regional scale or include large tracts of land (Center for Applied Biodiversity Science 2000). The identification of areas with high species diversity is an essential component for protecting biodiversity (Allan and Flecker 1993).
The Aiuruoca River basin is considered as one of very high biological importance for conservation of the ichthyofauna in Minas Gerais State, Brazil (Biodiversitas 2005) because it is an important lotic remnant of the Upper Grande River basin and has high water quality. River damming is one of the major threats to the fish found in Grande River basin.
Although the Aiuruoca River is recognized as a very important area for fish fauna, practically all of the basic requirements for adequate conservation strategies are lacking, especially because the species composition remains unknown or restricted to technical reports of licensing projects. Therefore, the aim of this study was to describe the composition and distribution of the ichthyofauna in the Aiuruoca River basin.

Study Area
The study basin is located in the Upper Grande River region in southern Minas Gerais. The Aiuruoca River has a drainage area of 2,094 km² and is located upstream of the Camargos Reservoir (Figure 1), and it drains areas designated as buffer zones for the Conservation Unit APA Mantiqueira (Environmental Protection Area of the Mantiqueira mountain) . (Lino and Albuquerque 2007). The streams and rivers in this region have cold, clean and well-oxygenated water, which are characteristics unique to headwaters (Uieda and Castro 1999).
Abstract: Although the Aiuruoca River is recognized as a very important area for fish fauna, the species composition of this river remains unknown or restricted to technical reports of licensing projects. The aim of this study was to describe the composition and distribution of the ichthyofauna in the Aiuruoca River basin. Fifty-eight collection points were sampled along the Aiuruoca River basin during 2010 and 2011, including 38 streams, 11 lagoons and 9 points along the Aiuruoca River main channel. A total of 8562 specimens were collected belonging to 6 orders, 15 families, 33 genera and 47 species. The pirapetinga fish (Brycon nattereri) is listed on Brazil's endangered species, and the rainbow trout (Oncorhynchus mykiss) was the only exotic species captured. Altitude is one of the main factors that influence fish community structure in the Aiuruoca River basin, confirming its importance for fish conservation. randomizations, and the total richness was compared via the Jackknife1 and Chao1 estimators, using the EstimateS 8.0 software (Colwell 2006).
Samples of the collected specimens were subsequently deposited in the Federal University of Lavras (UFLA) Fish Collection (Table 2). Fish were collected under the IBAMA license # 10 327.

Results and Discussion
A total of 8562 specimens were collected belonging to 6 orders, 15 families, 33 genera and 47 species ( Table 2). One of them, the Pirapetinga (Brycon nattereri) is listed on Brazil's endangered species official list as vulnerable (Machado et al. 2005). The distribution area for this species confirms its preference for small, protected rivers and headwaters (Pompeu et al. 2009). Additionally, the rainbow trout (Oncorhynchus mykiss) was the only exotic species captured. It was introduced by the hatchery industry in the cold-water regions of the Mantiqueira mountains. Due to its unique biological traits, such as being omnivorous and hiding its offspring from predators, this species is considered a pest that causes adverse ecological effects in the various countries and regions where it has been introduced (Magalhães et al. 2002).The majority of the biodiversity occurred in the Characiformes (53%) and Siluriformes (36%) orders, which also had the largest number of individuals collected (78% of the total catch). This pattern has been identified repeatedly throughout similar research in South America (Lowe-McConnell 1987). However, although Siluriformes from the Loricariidae and Trichomycteridae families were the most common fish in the streams, the most common species found in the river were from the Characidae family. The Characidae ichthyofauna consists of fish with very diverse feeding habits (i.e., herbivores, omnivores and carnivores) that exploit a wide range of habitats (Kavalco and Pazza 2007). Conversely, Siluriformes were preferential to rapids typical of headwater streams, which are characterized by high water velocity, low temperature and rocky bottoms (Casatti and Castro 2006).
Although 52 sampling stations had been sampled, the collector's curve was not totally stabilized ( Figure  2). The estimated richness by Jackknife1 and Chao1 estimators indicated that the number of registered species represented 84% and 98% of the richness in the region, respectively. The areas where the majority of the species were recorded were lagoons, followed by streams and the Aiuruoca River. Thirty-four species had previously been identified in the Rio Grande (Cemig 2007), 41 species in the Capivari River (Pompeu et al. 2009) and 25 species in the Itutinga reservoir (Alves et al. 1998). With the addition of 16 species in this study, 88 species have been identified in the Rio Grande basin in Minas Gerais. Among the additional species, 11 were collected from streams and the other 5 species were collected from lagoons and the river channel, indicating that much of the unknown fauna in this basin is likely concentrated in small water bodies.
We also observed that only small species of the Loricariidae family, Pareiorhina carrancas and Pareiorhaphis sp. n., were recorded at altitudes above Table 1. Geographic information of sampling stations in Aiuruoca River basin (* water bodies without denomination in the IBGE cartographic map).  (Figure 3). A total of 9 species were found above an altitude of 1050 m, while 25 where restrict to areas under 1000 m of altitude. Although the studies available considering the upper Rio Grande fish fauna do not cover the same altitudinal range, degree of conservation, altitude and width have been considered important parameters to explained fish species richness (Pompeu et al., 2009). In the same study, P. carrancas and Pareiorhaphis sp. n. were among those with higher distribution considering the altitudinal gradient.

SAMPLING STATION
Relief is also probably one important factor that influences fish community structure in the Aiuruoca River basin. Its importance can be observed in the altitudinal distribution of species, which revealed the role of a large waterfall, located in the Aiuruoca River channel at an altitude of 1040 meters, as a barrier to species dispersal. A larger diversity of fish in the lower streams may be linked to increased habitat variability and more water volume. The headwater regions of river basins have less diverse habitats (both in volume and complexity) and unstable environmental variables (Schlosser 1990).