Diversity and distribution of ichthyofauna in streams of the middle and lower Tibagi river basin , Paraná , Brazil

This study investigates the distribution and structure of the assemblages of fishes in tributaries of middle and lower sections of Tibagi river basin. The samples were conducted quarterly from December 2013 through December 2014, in 24 sampling sites of 8 tributaries. A total of 5643 individuals belonging to 44 species distributed in 13 families and 5 orders are reported. The families Characidae, Loricariidae, and Heptapteridae were predominant; Astyanax paranae, Phalloceros harpagos, Piabina argentea, Astyanax bockmanni, and Trichomycterus davisi were the most abundant species. Four non-native species were collected: Coptodon rendalli, Poecilia reticulata, Xiphophorus hellerii, and Oreochromis niloticus. The fish fauna of the middle and lower sections of Tibagi river basin has previously been threatened by human activities such as urbanization, industry, agriculture, and currently with dam construction.


Introduction
Freshwater fishes in the Neotropical region are remarkably diverse, especially in Brazil, representing an estimate between 8000 and 9000 species, possibly because of the presence of the largest and independent river basins in the world (Reis et al. 2016), as for example, the Amazonas and Paraná rivers.Many of these basins are isolated and mainly composed of small tributaries, with a large percentage of ichthyofauna understudied (Stevaux et al. 1997).
Despite this great diversity, Brazilian water systems are under strong human pressure (e.g.agriculture, dambuilding, urbanization), causing strong alterations in the landscape (Allan et al. 1997).These alterations can cause loss of diversity and simplification of ecosystems (Matson et al. 1997, Tscharntke et al. 2005), mainly in small streams, because the impacts on terrestrial ecosystems are strongly reflected in aquatic environments (Lee 2000).
The ichthyofauna of the Tibagi River, according to Shibatta et al. (2007), has been studied since the 1980s; however, most of these studies were directed to the main channel of the river and larger tributaries, as evidenced by the studies of Bennemann et al. (1995), Shibatta et al. (2002), Shibatta et al. (2006), Galves et al. (2007), and Shibatta et al. (2007).On the other hand, studies aimed at inventorying the fish fauna of small tributaries have intensified in recent years (Shibatta and Cheida 2003, Oliveira and Bennemann 2005, Vieira and Shibatta 2007, Shibatta et al. 2008, Silva et al. 2013, Hoffmann et al. 2015.This study was conducted as a survey of ichthyofauna in streams of middle and lower Tibagi River, which are areas influenced by human activities such as urbanization (Mandaçaia, Uvaranal, and Engenho de Ferro streams) and agriculture (Saltinho, Tigre, and Água Branca streams), as well as in preserved areas (Lambedor and Varanal streams).Due to the incomplete knowledge of the diversity of fish fauna in small tributaries, and their vulnerability to the accelerated process of transformation, this study aims to investigate the distribution and structure of the assemblages of fishes in tributaries of middle and lower sections of Tibagi river basin.

Methods
Study site.The headwaters of the Tibagi River are located in the Palmeira region in Paraná State, at 1060 m altitude, and run 550 km until joining the Paranapanema river basin.The Tibagi river basin has an annual rainfall varying from 1400-1700 mm, and a temperature varying between 13-28 °C (Medri et al. 2002, Pinese 2002, De França 2002).Fish were collected in streams from middle and lower Tibagi river basin, in the municipalities of Telêmaco Borba (Mandaçaia, Uvaranal, Lambedor, and Varanal streams), Assaí (Saltinho, Tigre, and Água Branca) and Ibiporã (Engenho de Ferro streams) (Fig. 1), in the Paraná State, Brazil.We selected 3 sites (headwaters, middle, and mouth) for each studied stream (Table 1).
Data collection.Fish were collected quarterly from December 2013 through December 2014.For the sampling we used standard ichthyological gear based on active capture with sieves, seine nets, and casting net.The fish were anesthetized with eugenol (3 g/L) (Vidal et al. 2008, Lucena et al. 2013), fixed in 10% formalin solution and after 48 hrs transferred to 70% ethanol.Species were identified up to the lowest possible taxonomic level, using available literature (Shibatta et al. 2002, Fernandes et al. 2005, Jerep et al. 2006, Graça and Pavanelli 2007, Bennemann et al. 2008, Lucinda 2008, Richer-de-Forges et al. 2009, Calegari et al. 2013, Lucena and Soares 2016).The taxonomic classification follows Eschmeyer et al. (2017).To evaluate the relationships between fish assemblages in streams we calculated the Bray-Curtis similarity index (Bray and Curtis 1957).Voucher specimens were deposited in the fish collection of the Museu de Zoologia da Universidade Estadual de Londrina (MZUEL), Londrina, Paraná State, Brazil (Table 2).Collections were authorized by ICMBio (collecting permit number 12120-1); and approved by Ethics Committee on Animal Use of the Universidade Estadual de Londrina, Londrina (permit number 22201.2013.21).
In the middle streams of the Tibagi, a total of 2581 individuals were collected, belonging to 22 species.In the lower section were registered a higher abundance and species richness, with 3,061 individuals of 36 species.From the 44 species collected in this study, 14 were common to both sections.The streams Saltinho, Tigre, and Engenho de Ferro reported the highest species richness with 22, 25, and 29 species, respectively.The highest abundance was registered in the Uvaranal stream, with 1,008 individuals; followed by Saltinho with 857 individuals, Engenho de Ferro with 808 individuals and Água Branca stream with 728 individuals, all from the lower Tibagi.The Bray-Curtis similarity analysis showed differences among the fish assemblages from the middle and lower portions of the Rio Tibagi (Fig. 6).

Discussion
In this study, the composition of fish assemblage was dominated mainly by Characiformes and Siluriformes, with more than 70% of total collected fish species; in particular, the predominance of families Characidae, Loricariidae, and Heptapteridae, represented more than 50% of the species.This dominance can be influenced Table 1.Geographic coordinates and mean values of the physical-chemical water parameters from the collecting sites in the Tibagi river basin, Paraná state, Brazil.Alt: altitude (m), Wid: width (m), Dep: depth (m), WS: water speed (m•s -1 ), DO: dissolved oxygen (mg•L -1 ), Con: conductivity (µS•cm -1 ), Tem: temperature (°C), Sub: substrate, Rip: riparian forest (%).by the high number of species contained in these orders (Characiformes and Siluriformes with approximately 2100 and 3700 species respectively, Eschmeyer and Fong 2017).Moreover, a large variety of specializations and adaptations, ecological, morphological, and physiological, allows them to survive in a wide variety of environments (Bruton 1996, Ortí 1997, Reis 2013).
According to Shibatta et al. (2002) and Vazzoler (1996), all specimens collected are small sized (200 mm or less) reflecting the expected pattern for streams of upper Paraná river basin, where more than 65% of all fish species described for this kind of environment are of small size (Langeani et al. 2007).According to Castro (1999) and Shibatta and Cheida (2003), one of the factors that can influence the small size of the species is the instability of the environmental conditions of the streams.
We do not find any species in the red book of Brazil-ian fauna threatened by extinction (ICMBIO, 2017).On the other hand, some of the species collected in this study, as Astyanax bockmanni, Isbrueckerichthys cf.calvus, Neoplecostomus yapo, and Trichomycterus davisi are associated with more pristine environments (Casatti et al. 2009, Jerep et al. 2006) and can be affected by changes in habitat complexity, water quality and hydromorphological aspects, influenced by common activities in the basin, such as agriculture and urbanization (Walsh et al. 2005, McKinney 2006, Alexandre et al. 2010).
We registered 4 non-native species, collected in the Uvaranal, Mandaçaia, and Engenho de Ferro streams; streams characterized for filing a degree of environmental degradation influenced by urbanization (municipalities of Telêmaco Borba and Ibiporã, Paraná).The degradation of aquatic environments influenced by urbanization can be associated with the invasion of non-native species and with increased pollution-tolerant species (Vieira and Shibatta 2007, Cunico et al. 2009, Leidy et al. 2011).
Astyanax was important in relation to species richness (5 species), distribution and abundance.The success of this genus can be influenced by high phenotypic plasticity and ability to adapt to diverse environments, a result of a series of ecological and morphological specializations, allowing access to most environments, mainly small streams (Ornelas-García et al. 2008, Matoso et al. 2013).
Bray-Curtis analysis showed the existence of similarity patterns in fish assemblages in streams sampled in each section (middle and lower); thus, the geographically closest streams have higher affinity among their ichthyofaunas.This pattern of similarity in relation to abundance and composition of fish assemblages between streams can be influenced by factors such as the physicochemical conditions of water and structural conditions such as substrate types.The streams of the middle and lower portions of the Rio Tibagi showed differences in variables like temperature, conductivity and dissolved oxygen, and proportion substrates like sand, gravel, clay, pebbles, and rocks (personal observation).Another factor that can influence the pattern of similarity between fish assemblages is the riparian forest, through the regulation of primary production and input of allochthonous resource (Vannote et al. 1980, Allan 2004).The riparian forest in Varanal and Lambedor streams is well preserved, while in others was affected by anthropic activities such as urbanization (Mandaçaia, Uvaranal, and Engenho de Ferro streams) or agriculture (Água Branca, Tigre and, Saltinho streams) (Table 1).There are other important factors such as water velocity, water flow, and the presence or absence of physical barriers such as waterfalls or rapids (Vannote et al. 1980, Araújo et al. 2009).
In general, the fish fauna of the middle section of Tibagi river basin has been threatened by human activities as urbanization, industry, agriculture, and currently with the construction of the hydroelectric plants.The Varanal, Uvaranal, Lambedor, and Mandaçaia streams will be influenced directly by the dams, isolation, or flooding.Thus, the Lambedor stream and part of private reserve of natural heritage in the Klabin S.A will be severely affected.