Fishes from the Jaru Biological Reserve , Machado River drainage , Madeira River basin , Rondônia State , northern Brazil

This work assessed freshwater fishes collected at 12 stations located along the Tarumã River, middle Machado River, Madeira River basin. The fieldwork took place in May and September 2015 during the high and low water seasons, respectively. We gathered 1,482 specimens representing seven orders, 30 families, 54 genera and 74 species using seine, gill, and hand nets. The family Characidae was the most representative, exhibiting the highest number of species captured. The species with the greatest abundance were Hemigrammus vorderwinkleri, Hyphessobrycon bentosi, Hemigrammus cf. bellottii, Bryconella pallidifrons, and Apistogramma resticulosa. Two species that remained unidentified are probably a new species. This study represents the third fish survey totally conducted at a Conservation Unit in the Rondônia State, and will certainly provide valuable information for future investigations on biodiversity conservation in the Machado River.


Introduction
Among the 33,984 fish species described around the world (Eschmeyer & Fong 2016), at least 13,000 varieties are unique to freshwater environments (Nelson et al. 2016).The Neotropical realm (South and Central America) encompasses more than 4,000 valid fish species (Reis 2013), with the Amazon River basin harboring the world's greatest diversity of freshwater fish (Freitas et al. 2010, Winemiller et al. 2016, Reis et al. 2016).To date, most studies of the Amazonian ichthyofaunal diversity have concentrated in the floodplains adjacent to large rivers (cf.Lowe-McConnell 1999) and next to urban areas (Mendonça et al. 2005, Souza et al. 2016).Notwithstanding, there are few reports on the ichthyofauna inhabiting environmental areas of high conservation value (Camargo & Giarrizzo 2007, Oliveira et al. 2009, Pedroza et al. 2012, Vieira et al. 2016).
Despite concerns about the effectiveness of conservation units in the tropics, there is growing evidence that they have been surprisingly useful tools for curbing deforestation (e.g.Jaru Biological Reserve) (Bruner et al. 2001) or conservation of fish species (Frederico et al. 2016).Historically, the majority of the current protected areas in Brazil were created with disregard for the aquatic environment (Agostinho et al. 2005, Abell et al. 2007).Nevertheless, it is uncontestable that they can protect many water bodies and, thus, play a highly important role in the conservation of freshwater organisms (Agostinho et al. 2005).
This study presents a survey of the ichthyofauna of the Tarumã River, a right-bank tributary of the Machado River, located within the Jaru Biological Reserve.This area displays virtually unchanged habitats in respect to its external environment.As the Tarumã River flows within a legally protected area, the objective of this study is to provide a first

Study area
The Jaru Biological Reserve (Rebio Jaru) was established on July 11, 1979, under Federal Decree-law number 83,716, and is managed by the Instituto Chico Mendes de Conservação da Biodiversidade/Ministério do Meio Ambiente (ICMBio/MMA).Marked by the high degree of conservation, the rain forest of the Rebio Jaru is practically intact.The reserve has a humid tropical climate with temperatures varying between 23°C and 26 o C, and the average annual rainfall ranges from 1,700 to 2,400 mm.The dry season occurs between May and October (Justina 2009).
The Rebio Jaru hydrographic network is part of the Machado River Basin located in eastern Rondônia State, northern Brazil.The Tarumã River, the main sub-basin of the Rebio Jaru, runs almost entirely (99%) within the Rebio Jaru.The average depth of the Tarumã River during the dry season was 2.8 ± 0.9 m; the average width, 32.8 ± 7.8 m; and the average water speed, 0.4 ms -1 .On the other hand, the average depth, width, and water flow values are 5.6 ± 1.2 m; 41.9 ± 4.0 m; and 0.3 ± 0.1 ms -1 during the wet season, respectively.The Tarumã River has many rapids flowing across the granitic formation of the Serra da Providência and Jamari complex (Justina 2009).The high transparency of the water (average transparency Dry = 1.2 ± 2.1 m; and average transparency Wet = 1.1 ± 0.4 m) due to the low amount of sediment, characterizes the Tarumã as a clear water river.

Data collection
We performed collections of freshwater fish in the Tarumã River in May and September 2015.Each expedition lasted four days.Our samplings comprised 12 sites in two different aquatic environments: five in the main channel and seven in the small stream channels (igarapés) of the Tarumã River (Table 1, Figure 1).
The physical conditions of some sampling stations in the Tarumã River basin are shown in Figure 2.
River 1 (R1) -stretch, 112 m wide and 6.2 m deep located near the mouth of the Tarumã River, preserved riparian vegetation and slow current (Figure 2c).
River 4 (R4) -stretch, 30 m wide and 4.5 m deep located near the head of the Tarumã River, preserved riparian vegetation, slow current (Figure 2f).
We accomplished the collections in the river channels using a total of eight gill nets with standard size meshes of 2 x 20 m, and fishing nets with mesh sizes varying from 30 to 100 mm (between opposite knots).The fishing nets were set at each sampling site during the morning, from 8:00 am to 12:00 pm, and at night, from 8:00 pm to 5:00 am.For the same period, we used a trotline with four 5/0 hooks with ends tied either to the bank vegetation or to mooring spikes.We used some pieces of piranha, Serrasalmus rhombeus Linnaeus 1766, as baits attached to the trotline hooks.
In small streams, the fish collection in a stretch of 80 m lasted one hour during the daytime.Three collectors used hand gathering techniques with a seine net (1.5 × 2 m, 2 mm mesh) and a hand net (0.5 × 0.8 m, 2 mm mesh) along the entire stretch, selecting the best technique for each environment.Before the collections, the ends of the sampling sections were blocked with fine-mesh nets (5 mm between opposite knots) to prevent fish escapes, regardless of the capture method used.Abiotic data, such as depth, width, and soil were observed in situ.We sacrificed the specimens in a solution of clove oil (Eugenol, 2 drops per liter; cf.American Veterinary Medical Association 2001).After that, the fish were fixed in 10% formalin solution and then preserved in 70% ethanol.For species identifications, we consulted the most currently accepted taxonomic literature and identification keys (Queiroz et al. 2013b).The classification followed Nelson et al. (2016).The specimens were deposited in the Coleção de Peixes, Universidade Federal do Mato Grosso, Cuiabá, MT, Brazil (CPUFMT); Laboratório de Ictiologia de Ribeirão Preto da Universidade de São Paulo, Ribeirão Preto, SP, Brazil (LIRP) and Museu de Zoologia da Universidade de São Paulo, São Paulo, SP, Brazil (MZUSP) (Appendix 1).The fish sampling was authorized by the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio, License: 48723-2/2015).

Discussion
Most of the several studies conducted in different portions of the Madeira River Basin in the Brazilian territory have focused either on a relatively small area or on specific tributaries.These investigations identified 122 species from the Jamari River (Santos 1996), 133 from the Marmelos River (Camargo & Giarrizzo 2007), 447 from the Aripuanã and middle Madeira rivers (Py-Daniel et al. 2007), 74 from the Belmont Stream (Araújo et al. 2009), 160 from the Guariba and Roosevelt Rivers (Pedroza et al. 2012), 189 from the Cuniã Lake (Queiroz et al. 2013a), and 174 from the middle Madeira River (Torrente-Vilara et al. 2011).A more comprehensive inventory identified 820 species along the Madeira River Basin (Queiroz et al. 2013b).More specifically, in the Machado River Basin, 48 species were recorded near the urban area of the Cacoal town (Perin et al. 2007), and 140 species in different tributaries (Casatti et al. 2013).However, contrary to the previously mentioned works, only the present study and the assays of Queiroz et al. (2013a) and Vieira et al. (2016) were conducted entirely in a Conservation Unit in the Rondônia State, resulting in the identification of 74, 189, and 141 species, respectively.The current work contributed 24 species to the general inventory of the Machado River and 26 species to the inventory conducted in Conservation Units in the Rondônia State.Additionally, the material deposited in the Brazilian collections enabled the accomplishment of recent taxonomic studies, which contributed to enhancing the knowledge of the ichthyofauna of both the Madeira River (Rocha et al. 2008a, Rocha et al. 2008b, Zanata & Ohara 2009, Ribeiro et al. 2011, Ohara 2012, Marinho & Ohara 2013, Zanata & Ohara 2015, Ohara & Lima 2015a, Tencatt & Ohara 2016a, Ohara & Neuhaus 2016, Tencatt & Ohara 2016b, Ohara et al. 2016a, Pastana & Ohara 2016), and the Machado River (Ohara & Lima 2015b, Ohara & Marinho 2016, Ohara et al. 2016b).
Among the sampled species from the Tarumã River, almost 44% (35 species) appear on the list of ornamental fish (Brasil 2012).Some of those species, such as Apistogramma resticulosa, Hemigrammus ocellifer, Hemmigramus vorderwinkleri, Hemmigramus cf.bellottii, Hyphessobrycon bentosi, H. copelandi, Elachocharax pulcher, and Serrasalmus rhombeus (Table 2) were well represented in our survey, suggesting a relatively high local abundance.However, according to the Environmental Crimes Law number 9605, of February 12, 1998, the capture of ornamental fish in the Rebio Jaru is prohibited (ICMBio 2010).Several species were discriminated with the use of "cf" or "aff", indicating that the number of new species may be higher.For example, the species identified herein as Brycon cf.pesu Müller & Troschel 1845 belongs to a complex of species, where new species are undergoing a description process (Zanata & Lima pers. comm.).Several species, namely, Hemigrammus cf.bellottii, Phenacogaster cf.retropinnus Lucena & Malabarba 2010, Characidium cf.pellucidum Eigenmann 1909, Characidium aff.zebra Eigenmann 1909, Corydoras cf.armatus Günther 1868, and Corydoras cf.trilineatus Cope 1872, belong either to poorly known taxonomic groups or represent still undescribed species, meaning that further taxonomic studies will be necessary.
Our work highlights the importance of conducting studies within protected areas and strengthens the role of territorial spaces with relevant environmental characteristics in a context where only three inventories within 14 Conservation Units in Rondônia have taken place.The presence of protected areas may help mitigate environmental impacts and maintain the biological integrity of a region surrounded by a long history of anthropogenic

Figure 1 .
Figure 1.Map of the study area showing the collection stations in the drainage systems in the Jaru Biological Reserve (shaded area), Rondônia, Brazil.Triangles represent streams and circles represent collection points in the river channels of the Tarumã River.

Figure 3 .
Figure 3. Number of individuals and richness of species of the fish orders collected in the Tarumã River Basin, Rondônia, Brazil.

Figure 4 .
Figure 4. Number of individuals and richness of species of the fish families collected in the Tarumã River Basin, Rondônia, Brazil.

Table 1 .
Sampling sites in the Tarumã River basin with environmental classification, geographic coordinates, and altitude.