Ichthyofauna of the “ Cachoeira de São Roberto ” and fishes of lower Preto River , upper Paraná River basin , Brazil

Rheophilic environments typically houses fish species with specific ecological requirements. Thus, the suppression of these environments can lead to damaging impacts to local and regional fauna. In this work the ichthyofauna of the “Cachoeira de São Roberto” was inventoried, with a historical review of fish collected in the lower Preto River basin. The sampling sites included two reaches (named R1 and R2): R1 in the “Cachoeira de São Roberto” and R2 refers to two km upstream. The fishes were sampled bimonthly during one year (April 2013 to February 2014) using small and dip nets. Voucher specimens were catalogued in the Fish Collection of “Departamento de Zoologia e Botânica do Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista ‘Júlio de Mesquita Filho’, câmpus de São José do Rio Preto, SPˮ (DZSJRP). Historical records from lower Preto River basin were composed by fish species sampled downstream of spillway of the dam in the municipality of São José do Rio Preto, SP, using the database of fish collection of DZSJRP. The ichthyofauna of the sampled reaches was composed by 53 species, distributed in 16 families and seven orders. The greatest richness was found in the upstream site (R2) with the presence of Aphyocheirodon hemigrammus and Myleus tiete, two Brazilian threatened fish species. Chao index suggested the occurrence of 64 species for the inventoried reaches. Considering all portion of lower Preto River basin, including historical records, 69 species were found, four of these species have not described yet. The present study highlights the importance of inventories in rheophilic environments, which usually includes sensitive, threatened, and species with restricted distribution. Besides that, inventories can provide technical data to support decisions about potential environmental impacts helping with the management and conservation of fish fauna.


Introduction
The Northwest of São Paulo State, Brazil, shows few riffle or waterfall areas, most of them not completely inventoried.Some of these areas have been target and submerged by hydroelectric plants (Agostinho et al. 2007, Júlio Junior et al. 2009)."Salto do Ferrador" (in municipality of Icém, SP) and "Cachoeira dos Índios" (in municipality of Ouroeste, SP) are two examples of these waterfalls situated in the Grande River and replaced by "Marimbondo" and "Água Vermelha" hydroelectric plants, respectively.In addition to the hydroelectric plants in the principal rivers of the region (e.g.Tietê and Grande rivers), Small Hydroelectric Plants (SHPs) have been employed in tributaries of these drainages (Agostinho et al. 2007).Recently, two riffle areas were target by this kind of project: "Cachoeira do Talhadão", in the Turvo River, Duplo Céu District, municipality of Palestina, SP, and in the confluence of Preto and Turvo Rivers near to "Cachoeira de São Roberto", lower Preto River basin, municipality of Pontes Gestal, SP (HABTEC 2010).
Riffle areas with rocky substrates and high water velocity are important to the maintenance of a specific biota (Garavello & Garavello 2004).The suppression and/or simplification of these areas by dam-buildings is undeniably associated to biological homogenization of aquatic ecosystems (Rahel 2002, Agostinho et al. 2008).Environmental homogenization can lead to the increase of generalist species and decrease of specialist species (Hoeinghaus et al. 2009).Moreover, conversion of lotic to lentic environment can favor species with preference to lentic waters, specially non-native Cichlidae [e.g.Coptodon rendalli (Boulenger), Oreochromis niloticus (Linnaeus), Cichla spp.] found in the upper Paraná River basin (Langeani et al. 2007).The "Cachoeira de São Roberto", a recreation riffle area, was target by a Small Hydroelectric Plant project without a previous or appropriate ichthyofaunistic inventory.The dam-building adjacent to this area could suppress this riffle environment and jeopardize fish fauna in the lower Preto River.Due to the lack of knowledge about the ichthyofauna and the possibility of SHP's building in this area, the aims of this study were to inventory the fish fauna of "Cachoeira de São Roberto" and to regain the fish historical records of the lower Preto River, Northwest of São Paulo State.

Material and Methods
The Preto River is one of the most important rivers of Northwest of São Paulo State; its source is in the municipality of Cedral, SP and it runs across nearly 25 km until the urban area of São José do Rio Preto, SP, where it becomes highly modified by stream flow channelization, impoundments, and lack of riparian forest (ComiteTG 2009).There are two dams and in the end of the second, the river has a spillway with circa four meters.After that, it runs for approximately 150 km until its confluence with the Turvo River, in municipality of Pontes Gestal, SP, Grande River drainage in the upper Paraná River basin.
The Northwest of São Paulo State has only 4% of its native vegetation, which has been replaced by agricultural crops since the beginning of the XIX century (Nalon et al. 2008).One of the remaining native riparian forest along Preto River is on the "Cachoeira de São Roberto", a tourist and recreational area with a series of small riffles situated approximately five km from its mouth, in the municipality of Pontes Gestal, SP.The area shows a tropical semi-humid climate, with temperature around 24ºC and pluviosity around 1,418 mm annual (PMPONTESGESTAL 2015).
Two sites in the lower Preto River basin were sampled (Figure 1): Reach 1 (R1), "Cachoeira de São Roberto" located approximately five km upstream from its mouth into the Turvo River (20°11'S 49°41'W), which is characterized by high water velocity with some declivity, substrate composed primarily by slab and basaltic boulders, besides the presence of sparse riparian forest composed by few trees (width of the riparian strip is approximately 10 m from each bank); Reach 2 (R2), located almost two km upstream from R1 (river distance), near to the mouth of the Botelho Stream (20°11'S 49º41'W).It is characterized by lower water velocity than R1, sandy substrate with some pebbles, and marginal vegetation composed mainly by grasses (Poaceae) (Figure 2).These two different reaches (R1 and R2) were selected aiming to know the ichthyofauna that could be affected by the Small Hydroelectric Plant.
Sampling was conducted bimonthly during one year (April 2013 to February 2014) in both reaches.A total of six sample collections were made, three in the dry season (April to August) (the period of low rainfall, 307 mm precipitation) and three in the wet season (October to February) (a period of high rainfall, 605 mm total).Pluviometric data was obtained by "Coordenadoria de Assistência Técnica Integral (CATI)ˮ from the municipality of Votuporanga, SP.
Fishes were sampled using a small net (2.0 x 0.95 m, 2 mm mesh size) and a dip net (0.8 x 0.4 m, 2 mm mesh size).Standardized sampling effort (involving three people) was performed for two hours over approximately 150 m in each reach.Fishes were fixed in 10% formalin for 72 hours and after transferred to 70% alcohol to final preservation.Specimens were identified and vouchered at the fish collection of the "Departamento de Zoologia e Botânica do Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista 'Júlio de Mesquita Filho', câmpus de São José do Rio Preto, SPˮ (DZSJRP) (Figures 3, 4).Species abundance in R1 and R2 reaches was grouped and randomized as a function of the sampling effort, i.e., the number of sampling events (12 events, six from R1 and six from R2), to generate an accumulation curve.The Chao 1 index (with 100 permutations), which is a function of the ratio of the number of species with only one specimen in a sample (singletons) by the number of species with two specimens (doubletons) was used to estimate fish richness in the area (R1 plus R2).
Historical records from lower Preto River basin were composed by fish species sampled downstream of spillway of the dam in the municipality of São José do Rio Preto, SP, using the database of fish collection of DZSJRP.These data were compiled to the fish checklist of lower Preto River, excluding its abundances (Table 1).

Results
A total of 3,662 individuals were recorded in the sampling for both reaches, belonged to 53 species, 16 families, and seven orders.Characiformes represented the richest order, with 58.5% of the sampled species, followed Table 1.Fishes of the lower Preto River basin: abundance (N) of the fish species (Orders and Families) in each reach (R1 and R2).Fish classification to families follows Reis et al. (2003), except to Serrasalmidae, according to Calcagnotto et al. (2005).* indicates threatened species; hyphen (-) indicates absence of quantitative data because are occurrence of species according to historical records.

Species
Reach  (Eigenmann), and 'Cheirodon' stenodon Eigenmann were the most abundant ones in the R2.
The estimated richness of the sampled reaches was 65 species (±8).This result was supported by the species accumulation curve, which was increasing without reaching an asymptote (Figure 5).
In addition to the current sampled ichthyofauna (53 species), 16 additional species were added to this inventory by the historical records in the lower Preto River basin (downstream of spillway in municipality of the São José do Rio Preto, SP) (Figure 6).The origin of ichthyofauna in the lower Preto River was predominantly by native species (88.4%) with eight non-native

Discussion
Higher abundance of Characiformes and Siluriformes in the lower Preto River basin, upper Paraná River basin was already expected, since they are commonly found in the Neotropical region (Britski 1992, Lowe-McConnell 1999, Reis et al. 2003, 2016, Eschmeyer et al. 2016).The richness recorded in the sampled area (53 species) was similar to others studies performed in the Northwest of São Paulo State (Garutti 1988, Casatti et al. 2009, Ferreira & Casatti 2012), although these studies had been performed in streams using different methodologies.
In addition to the 53 sampled species, 16 species were regained from historical records, comprising a total of 69 species to the lower Preto River.These data are, probably, underestimated, due to the fact they are the first ones for the area.
The higher abundance of Astyanax fasciatus, Bryconamericus stramineus, and Planaltina britskii in R1 than in R2 is, probably, because these species are drift feeders (Casatti & Castro 1998) that can obtain the maximum food intake at sites with an uninterrupted and lotic water flow.Nonetheless, Parodontidae and Hypostomus spp.were also more abundant in this reach.These species have low body depth, ventral mouth, and pectoral fins used to deflect high water flow and cling to the rocky substrate (Garavello & Garavello 2004), the predominant substrate type in riffle areas like R1.In R2, where grasses were present in the river bank, the highest abundance was assigned to H. eques and S. notomelas.The presence of grass in the river bank can provide an increase of food resources availability, such as aquatic insects, often associated with marginal grasses (Ceneviva-Bastos & Casatti 2014, Zeni & Casatti 2014).Moreover, this condition can be important to the establishment and growth of Aphyocheirodon hemigrammus and Myleus tiete, threatened species in Brazil, since grasses leaves and roots can be used as refuges from predators, acting as a nursery for large-bodied species (Araújo & Garutti 2003).In fact, the juvenile specimen of Myleus tiete (23.8 mm SL) recorded in this study was sampled in R2.According to Zeni et al. (2015), juvenile specimens from others species [Acestrorhynchus lacustris (Lütken), Erythrinus erythrinus, Galeocharax gulo (Cope), Hoplias cf.malabaricus (Bloch), and Pterygoplichthys ambrosettii (Holmberg)] were found associated to this area during reproductive period.
Myleus tiete is a migratory fish and, currently, considered as an endangered species (EN) (ICMBio 2015), since few and small populations are geographically fragmented and isolated, specially due to the numerous dam-buildings in the drainages of upper Paraná River basin.Modification of lotic to lentic system can jeopardize this migratory species by preventing the life cycle to be completed, since some stages can occur only in lotic environments.Furthermore, the suppression of riparian vegetation mainly caused by agriculture practices can directly affect M. tiete feeding habits as well as A. hemigrammus.Aphyocheirodon hemigrammus occurs, preferentially, in lentic and floodplain environments and it has been considered vulnerable to extinction (VU) (ICMBio 2015), mainly due meso-and microhabitat homogenization associated to siltation, which has been decreasing this species' population.Although both species can be found in different habitats (lotic and lentic environment), in the lower Preto River they were found only in the lentic reach (R2).As a conclusion, this type of environment can be important to the occurrence of lentic-adapted species, as A. hemigrammus, and juvenile of rheophilic species, as M. tiete.
Large rheophilic fishes previously reported from the "Cachoeira de São Roberto", such as Megaleporinus obtusidens (Valenciennes) ('piapara'), Brycon sp.('piracanjuba'), and Salminus brasiliensis (Cuvier) ('dourado') (Borges 2007) were not found during more than one year of sampling.The absence of these species, even juvenile specimens, may be due to the failure in the sampled methods used in this study or result of the human impacts on the Preto River.Land use changes, removal of riparian vegetation, physical habitat homogenization due to the invasion of grass from pastures, organic pollution, and more recently, dam-building in the urban sections of the river, and the presence of non-native species can affect the occurrence of large rheophilic species (Agostinho et al. 2005).Besides these species, local fishermen have recognized Prochilodus lineatus (Valenciennes) ('corimba') and Salminus hilarii Valenciennes ('tabarana') in the area, but not recorded in this study.
The occurrence of fishes in the lower Preto River comprised 11.6% of non-native species introduced in the upper Paraná River from different vias (Langeani et al. 2007, Azevedo-Santos et al. 2015).Pisciculture and aquarism are probable the principal causes of fish introduction observed in the lower Preto River basin and in others Brazilian river basins (Alves et al. 2007, Vitule 2009;Azevedo-Santos et al. 2015).Megaleporinus macrocephalus, Coptodon rendalli, and Oreochromis niloticus were both introduced by pisciculture (Langeani et al. 2007), whereas Laetacara araguaiae was probably introduced via upper rio Araguaia basin (pers.obs.), and Poecilia reticulata could had been introduced by aquarism or mosquito control (Deacon et al. 2011).Erythrinus erythrinus was probable introduced by sport fishing, whereas Triportheus nematurus was probably distributed in the upper Paraná after the Itaipu dam construction (Langeani et al. 2007).Metynnis lippincottianus had probably been accidentally introduced in the upper Paraná River basin (Ota 2015).
In the historical records in the lower Preto River basin there are three non-native species (Triportheus nematurus, Oreochromis niloticus, and Coptodon rendalli), whereas two of them are Perciformes.Cichlidae was one of the most diverse families in these records and maybe this was caused by their association with lentic environment, since the sampling site of these records was marginal lagoons of the Preto River, near the District of Macaúbas, municipality of Mirassolândia, SP.Perciformes has showed high occurrence in the upper Paraná River basin through natural (Langeani et al. 2007) and artificial environments, as the dam in the upper portion of the Preto River, in São José do Rio Preto, SP (Andrade 2003).
Dam-building could have affected lower Preto River if the SHPs projects in Turvo River had been approved.Physical homogenization caused by dam-building and the introduction of non-native species are synergistic processes responsible for biotic homogenization of communities (Rahel 2002).Fortunately, these projects were denied by the "Companhia Ambiental do Estado de São Paulo" (CETESB), as long as the alterations caused by them are environmentally impracticable by jeopardizing hydrological flow and leading to the suppression of more than 60% of the remaining forest fragments.The final decision of CETESB (2012) concluded that "Cachoeira de São Roberto" is situated in the future reservoir area, being affected by changes in water dynamic of the Preto River.In fact, dam-building change lotic into lentic environment and this can affect species with specific adaptations to survive in high flow environments and not only decreasing native species richness (Agostinho et al. 2007, Agostinho et al. 2008, Winemiller et al. 2016), but also increasing the abundance of non-native species (Hoeinghaus et al. 2009).Thus, the suppression of "Cachoeira de São Roberto" would affect the occurrence and abundance of several native species, such as Hypostomus spp., Parodontidae, and rheophilic species, as Myleus tiete, that could not resist to habitat alterations, besides increase the occurrence of non-native species, such O. niloticus and C. rendalli.In this context, ichthyofaunistic inventory is important not only to know fish richness, which can include new and threatened species, but also to

Figure 1 .
Figure 1.Location of the two reaches (R1 and R2) in the lower Preto River in the Northwest of São Paulo State, Brazil.Modified from Zeni et al. (2015).

Figure 5 .
Figure 5. Species accumulation curve based on sampling efforts in the two reaches.