The fish fauna of the upper Piraí drainage , a transposed mountain river system in southeastern , Brazil

An annotated checklist of the ichthyofauna from the upper Piraí river drainage is provided. The Piraí river was a major right-bank tributary of the Paraíba do Sul river, but it has been artificially diverted to the coastal Guandu river system in southeastern Brazil to generate electric power and water for the metropolitan area of Rio de Janeiro. Based on our field sampling of 23 sites, 32 species belonging to 24 genera and 12 families were collected in 6 headwater tributaries of the Piraí river between 2009 and 2016. Phalloceros harpagos (Lucinda, 2008), Astyanax intermedius (Eigenmann, 1908), and Neoplecostomus microps (Steindachner, 1877b) were the most abundant and most widely distributed species in the samples. The sampled ichthyofauna is mostly composed by species from the Paraíba do Sul basin. Eight species are reported for the first time in the upper Piraí drainage, showing the importance of continuous ichthyofaunal surveys of fish in remaining areas of Atlantic Forest.


Introduction
The Brazilian Atlantic Forest is the second largest biome in South America, with one of the highest rates of species richness and endemism on the planet (Galindo-Leal andCâmara 2003, Ribeiro et al. 2009).Due to environmental impacts originating from human activities, only 16% of the original forest is preserved in reduced and isolated patches (Ribeiro et al. 2009(Ribeiro et al. , 2011)).Freshwater streams in southeastern Brazil are directly affected by the degradation of the Atlantic Forest, as their headwaters are located in these few remaining patches of forest, and the reduction of the riparian vegetation is one of the main sources of environmental impact in water bodies (Cetra and Ferreira 2016).Systematic surveys of fish communities that inhabit these streams are necessary to reduce knowledge gaps about biodiversity and to understand the state of conservation of the Atlantic Forest (Buckup et al. 2014).
The upper Piraí river drainage is a former tributary of the Paraíba do Sul river basin that has been artificially diverted to the Guandu river system through a complex system of tunnels and pumps to generate electric power and water for the metropolitan area of Rio de Janeiro.The Piraí river drains the Biodiversity Corridor Tinguá-Bocaina (BCTB) (Paiva and Coelho 2015).The BCTB connects Atlantic Forest fragments delimited by the Tinguá Biologic Reserve, in the central region of Rio de Janeiro, and the National Park of Serra da Bocaina, on the southern coast of the state.The BCTB is one of the most important priority areas for the preservation of the Atlantic Forest biodiversity due to its location at the most critical point of fragmentation of the largest continuous area of this biome in the Serra do Mar (Vilar et al. 2012).
In the present study, we surveyed the ichthyofauna from Upper Piraí drainage in order to provide an annotated checklist of freshwater fish species occurring in the area of study.This study is part of a long-term program to monitor the effects of forest restoration in the Guandu river system partly published by Vilar et al. (2012) andCastello Branco (2015).It includes a larger area and an updated inventory of fish species presented in previous studies (e.g.Buckup et al. 2014).

Methods
Study area.The Piraí river drainage (Fig. 1) is located within the boundaries of the municipalities of Rio Claro and Barra do Piraí, Rio de Janeiro state, southeastern Brazil.The Piraí river was a major tributary of the Paraíba do Sul river.Since the beginning of the 20th century, it has been diverted to the coastal Guandu river basin, in the Rio de Janeiro Metropolitan Region.The headwaters of the Piraí drainage are composed by streams that flow from the northern face of the mountain system of Serra do Mar.This mountain chain has an extension of 1,000 km between Rio de Janeiro state and north of Santa Catarina state (Almeida and Carneiro 1998).
Sampling.Fish were collected in 23 sampling sites along 6 streams, rio Coutinhos, rio Papudos, rio Parado, rio Passa Quatro, and Rio das Pedras, and the main channel of the upper rio Piraí (Table 1, Fig. 1) in 4 expeditions between the years of 2009 and 2016, under collecting permit 12129, issued by the Instituto Chico Mendes de Conservação da Biodiversidade.The sampling sites were selected to cover a wide range of habitats, from the alluvial plain of the streams to the high-mountain rapids.Each site was surveyed during 1 h of exhaustive sampling activity by a team of 5 ichthyologists.Fishing equipment included beach seines (2, 3, 5 and 15 m long, 4 mm nylon mesh), dip nets with metal handles (40 × 90 cm basket area, 2 mm plastic mesh), and casts nets (12 mm mesh size).An acoustic amplifier of electric signals was used to detect specimens of the order Gymnotiformes hidden in marginal vegetation and rocks.The collected specimens were preserved in 10% formalin solution and transferred to 70% ethanol after 48 h.Part of the specimens were preserved in anhydrous ethanol    for DNA-sequencing studies.The examined specimens were deposited in the ichthyological collection of the Museu Nacional, Universidade Federal do Rio de Janeiro (MNRJ) (Appendix, Table A1).Standard length, abbreviated as SL, was measured to the base of the middle caudal-fin rays.
The geographic distribution of the taxa collected in the study area and the diagnosis of the sympatric congeneric species are commented below.Although species listed here occur in other drainages, diagnostic characters described next are limited to identify the set of species that occur in the upper Piraí drainage.These diagnoses might be useful for ichthyological studies in other drainages of the Paraíba do Sul river basin, but in that case, the occurrence of other species not listed in the upper Piraí have to be considered.
Diagnosis: Characidium lauroi differs from C. vidali by the presence of small rounded dark marks below the lateral stripe, which are separated from the dorsal-lateral bars, and pigmentation bars on the caudal fin are usually absent or inconspicuous (Melo 2001b, Buckup et al. 2014).
Diagnosis: Characidium vidali can be distinguished from C. lauroi by the presence of vertical polyhedric dark marks along the medium and inferior portion of the body and by having pigmentation bars on caudal fin (Buckup et al. 2014).
Oreochromis niloticus X X
Diagnosis: Astyanax giton is distinguished from its congeners in the Piraí drainage by presenting the posterior portion of pelvic fin surpassing the urogenital opening.A gradual variation of size in dentary teeth size and higher body height (approximately 41% SL) are also distinguishable features of this species in relation to Astyanax intermedius and Astyanax sp.aff.scabripinnis (Melo 2001a).

Figure 2C
Geographic distribution: Paraíba do Sul and Doce river basins and coastal rivers of Rio de Janeiro state (Lezama et al. 2011).
Diagnosis: Astyanax intermedius differs from A. giton by body depth less than 41% of SL and abrupt reduction of tooth size posterior to the fifth dentary tooth (Melo 2001a).Also, in contrast with A. giton, the posterior portion of pelvic fin in A. intermedius does not surpass the urogenital opening in this species.Astyanax intermedius can be distinguished from Astyanax sp.aff.scabripinnis, by the presence of 5 cusps in most dentary teeth and regular sized adipose fin.Diagnosis: Trichomycterus macrophthalmus is characterized by the colour pattern consisting of transverse dark bars crossing the dorsum, which can be fused with lateral marks in this species (Barbosa and Costa 2012).Trichomycterus macrophthalmus is distinguished from T. mariamole and T. nigroauratus by the presence of 9 pairs of ribs and eye diameter 13.2% to 14.6% the size of head length (HL) (Barbosa and Costa 2012).
Diagnosis: Trichomycterus mariamole has light yellow background coloration with small circular brown marks on flanks, diameter of the eyes 9% to 11% of HL, opercular region of odontoids reduced and laterally positioned, and 7 pectoral fin rays (Barbosa and Costa 2010).Trichomycterus mariamole differs from T. claudiae, a species that occurs in the middle portion of the Piraí drainage, by the short ill-defined stripe restricted to the anterior portion of the flank (vs.well defined stripe along the whole flank) and fewer interopercular odontodes (27-34 vs. 41-46).

Harttia loricariformis Steindachner, 1877a
Figure 4B Geographic distribution: Paraíba do Sul river basin and coastal rivers from Rio de Janeiro to Espírito Santo.

Figure 4D
Geographic distribution: Paraíba do Sul river basin.
Diagnosis: Hemipsilichthys papillatus differs from H. gobio by not having plates in the dorsal midline between the base of the dorsal fin and the adipose fin, and a smaller orbital diameter (8.6-11.8%HL, Reis et al. 2006).

Hypostomus affinis (Steindachner, 1877a)
Figure 4E Geographic distribution: Paraíba do Sul and Doce river basins and coastal rivers of southeastern Brazil.
Diagnosis: Individuals of Hypostomus affinis can be distinguished H. luetkeni by the presence of 1 main postsupraoccipital plate and 4 lateral ridges on flanks (Mazzoni et al. 1994).The prevailing pigmentation pattern in adults of H. affinis comprises numerous black spots, whereas H. luetkeni has a more uniform dark pigmentation pattern.
Diagnosis: Hypostomus luetkeni can be distinguished from H. affinis by the presence of 2 or 3 plates in the main post-supraoccipital series and the absence of ridges on the flanks of the body (Mazzoni et al. 1994).Dark spots in the body, if present, are less conspicuous than in H. affinis.

Discussion
In this study, the prevalence of Siluriformes and Characiformes in the composition of the fish assemblage follows the observed composition pattern of Atlantic Forest streams (e.g.Sarmento-Soares et al. 2007, Ferreira and Petrere 2009, Camilo et al. 2015) and most Neotropical freshwater systems (Lowe-McConnell 1999, Abilhoa et al. 2011).The ichthyofauna of the upper Piraí is composed mostly by species that are widely distributed in the Paraíba do Sul basin.Scleromystax barbatus is a widespread species in coastal rivers; however, this species was collected only once, near the city of Lídice, despite our extensive sampling effort in the Piraí basin.The neotype of S. barbatus was collected in a nearby coastal river, and the species is quite abundant in the adjacent coastal plain.The city of Lidice is located less than 10 km from a recreational area in a coastal lowland river.This ichthyofaunal composition indicates that endemic species from Guandu do not live in the study area, probably because the complex system of tunnels, pumps, dams and hydropower turbines, as well as the steep altitudinal gradient across the transposition system serve as an effective barrier for upstream fish migration.
As expected, the species diversity was higher in the lowest stretches of the upper Piraí drainage than in its headwaters.According to the River Continuum Concept (Vannote et al. 1980), the composition and structure of ichthyofauna in freshwater streams is directly related to altitude.Thus, high altitude stretches with comparatively lower temperature, high dissolved oxygen and fast flowing waters tend to have lower species richness than downstream sites with decreasing slope, increasing temperature and high availability of pools.
Among the widespread species in the study area, the high number of individuals of Phalloceros harpagos present in our samples is probably correlated with the ability of poecilids to colonize a wide range of habitats and tolerate different levels of environmental quality (Araújo et al. 2009).The second most abundant species in upper Piraí drainage, Astyanax intermedius, is an opportunistic strategist, characterized by the capacity of producing rapid population turnover and colonisation (Souza et al. 2015).Regarding taxonomic representation, Astyanax and Trichomycterus were the most diverse genera in the study area, represented by 3 species each.Oddly, individuals of Trichomycterus claudiae (Barbosa and Costa 2010) were not registered in the upper Piraí drainage.This species was expected to occur in the sampled drainage due to the proximity of its type locality.
Two species collected in the upper Piraí drainage are included in the list of Brazilian fauna threatened by extinction (ICMBio 2016): Brycon opalinus, present in the lower reaches of Rio das Pedras stream, and Hemipsilichthys gobio, collected in the main channel of rio Piraí.Brycon opalinus, known as "pirapitinga", is Vulnerable due to commercial exploration and environment degradation, and its restricted distribution to preserved tributaries of the Paraíba do Sul and Doce headwaters (Gomiero andBraga 2007, ICMBio 2016).Hemipsilichthys gobio is Endangered due to habitat reduction and fragmentation (ICMBio 2016).The distribution of this species is limited to highly oxygenated cold waters of high-elevation, fast flowing tributaries of the Paraíba do Sul river basin.The presence of these 2 species indicates that preserved stretches in the upper Piraí drainage serve as natural refuge areas for threatened fish fauna.
Two non-native species were recorded in 4 sampling sites along the study area: Poecilia reticulata was captured in the lowest stretches of the Passa Quatro stream, and Oreochromis niloticus occurred in 2 sites of the main channel of upper Piraí.Poecilia reticulata is an exotic poecilid species from Venezuela, widely introduced in aquatic environments of the Americas due to its predation on mosquito larvae (Santos 1958).Oreochromis niloticus, known as Nile Tilapia, is an invasive cichlid species, originally from Africa, that is widely cultivated in tanks and net cages in Brazil, and was probably introduced by escapes from pisciculture (Orsi and Agostinho 1999).Regarding environmental conditions, invasive species are usually more successful in negatively affected systems or where native species population are depleted (Leidy et al. 2011).The introduction and population establishment of these invasive species in the mid-lower reach of the Passa Quatro stream and the main channel of upper Piraí is largely associated with areas of intense human occupation and land-use.
Among the 32 species reported in this study, the following 8 were not listed in the first survey of the Piraí headwaters (Buckup et al. 2014): Hypomasticus mormyrops, Hoplias malabaricus, Scleromystax barbatus, Hemipsilichthys gobio, Hypostomus luetkeni, Poecilia reticulata, Australoheros sp., and Crenicichla lepidota.The absence of Hypostomus luetkeni, Poecilia reticulata, Australoheros sp., and C. lepidota in the sites surveyed by Buckup et al. (2014) has been confirmed in our current survey, as these species have only been captured outside of the area of that earlier study.The single specimen of Hemipsilichthys gobio (MNRJ 36482) was misidentified by Buckup et al. (2014) as H. papillatus.In addition to the slight increase of diversity, some species were captured in significant numbers only in the recent survey (e.g.Brycon opalinus).The increase in species richness and abundance of the ichthyofauna in the upper Piraí river drainage recorded over our 7-year survey possibly correlates with the consolidation of recent conservation programs implemented in the study area to recover riparian forest (Castello-Branco 2015), although other environmental factors cannot be ruled out.Thus, the record of additional species not previously captured in the area, despite the use of standardized sampling effort, demonstrates the importance of continuous surveys in freshwater systems, in order to increase the knowledge on the distribution and impact of human activity on fish assemblages present in Atlantic Forest remnants.

Figure 1 .
Figure 1.Map of the upper Piraí river drainage, indicating the collecting sites along rio Coutinhos (C), rio Papudos (P), rio Parado (A), rio Passa Quatro (Q), Rio das Pedras (R), and the main channel of rio Piraí (I).Geographic coordinates and altitude of the sites are listed in Table1.

Astyanax
sp. aff.scabripinnis (Jenyns, 1842) Figure 2E Geographic distribution: Unknown.Diagnosis: This species was represented by a single individual and differs from A. intermedius by having 7 cusps in most dentary teeth (vs.usually 5 cusps in A. intermedius) and by having a smaller adipose fin.Astyanax sp.aff.scabripinnis differs from A. giton by the following characters: body depth smaller than 41% of SL and abrupt size reduction posterior to the fifth dentary teeth (Melo 2001a) Oligosarcus hepsetus (Cuvier, 1829) Figure 2I Geographic distribution: Coastal rivers from Santa Catarina to Rio de Janeiro state.Family Erythrinidae Hoplias malabaricus (Bloch, 1794) Figure 2D Geographic distribution: Widespread across South and Central America (Vieira et al. 2015).Order Siluriformes Family TrichomycteridaeTrichomycterus macrophthalmus Barbosa & Costa, 2012Figure3AGeographic distribution: Piraí river drainage.
Barbosa & Costa, 2008 Figure3EGeographic distribution: Upper Piraí and Barreiro river drainages in the Paraíba do Sul river basin.Diagnosis: Trichomycterus nigroauratus differs morphologically from T. mariamole and T. macrophthalmus by the presence of golden spots on the snout and body, and broad (wider than long) metapterygoid bone (Barbosa and Costa 2008).Trichomycterus nigroauratus presents ontogenetic variation of coloration, with juveniles exhibiting a black stripe along the lateral midline, and adults presenting stripes with irregular borders and dark stains that can cover the entire body in a homogeneous pattern(Buckup et al. 2014).distribution: Paraíba do Sul river basin.Diagnosis: The 2 species of Harttia that occur in the area of study can be distinguished by the distribution of plates in front of the anus: Harttia carvalhoi is distinguished from H. loricariiformis by the absence of preanal plates(Langeani et al. 2001).

Table 1 .
Geographic coordinates from the sampling sites in the Upper Piraí river drainage, Rio de Janeiro state, Brazil.

Table 2 .
List of the freshwater fishes of upper Piraí river drainage.