Inventory of the fish fauna from Laranjinha River, Paranapanema River system, Brazil

Abstract: This work is the most comprehensive survey of the Laranjinha River´s fishes, a tributary of the Cinzas River, Paranapanema River basin. Throughout its course, there is only a low-height dam, including a transposition system located 98 km from its mouth. The sampling was carried out in nine locations, from the source to the mouth, with six field incursions in each location, using different fishing gear. A total of 11,924 fish were collected, distributed in seven orders, 27 families, and 100 species. The most representative order in the number of species was Siluriformes, followed by Characiformes. As for the families, Loricariidae comprised 21% and Characidae 14% of species richness. Phalloceros harpagos was the species with the highest absolute abundance, representing 11.3% of the total, followed by Hypostomus ancistroides with 9.8%. However, considering the average abundance and frequency of occurrence, Hypostomus ancistroides was the most abundant species, followed by Hypostomus cf. paulinus, Psalidodon aff. paranae and Phalloceros harpagos. Among the collected species, the Apteronotus acidops, Brycon orbygnianus, Brycon nattereri, Crenicichla jupiaensis, and Rhinelepis aspera were classified as endangered on the most recent IUCN Red List. Also, from the total sampled fish, 9.8% are considered non-native species. Among the native species recorded, 10 species are large migratory species, which indicates that the Laranjinha River is a route for spawning and maintenance of species diversity in the middle Paranapanema River. Therefore, the Laranjinha River is a heritage of fish diversity and deserves special attention in its preservation.


Introduction
In the last few decades, human actions have caused numerous environmental changes, which emphasizes the need to know the local biodiversity, in order to reduce harmful activities. To this extend, the creation of inventories contribute to the discovery and description of new species before their extinction, also contributing to the creation of new records, to the knowledge about geographical distribution, the documentation of non-native species, the defininition of biogeographic patterns, and the establishment of suitable conservation strategies (Costello et al. 2011, Ota et al. 2015, Frota et al. 2019.
The fishes of the upper Paraná River basin are the most studied in Brazil. The basin has more than 310 fish species (Langeani et al. 2007), a number currently outdated, considering new records and the recent discovery of new species (e.g. Frota et al. 2016, Froehlich et al. 2017, Cavalli et al. 2018, Ota et al. 2018, Jarduli et al. 2020). The Paranapanema River, a major tributary of the upper Paraná River, is currently fragmented by several hydroelectric dams (Britto & Carvalho 2006), and therefore, its dam-free tributaries are of great importance for the maintenance of fish species (Hoffmann et al. 2005, Silva et al. 2017, Galindo et al. 2019, Lansac-Tôha et al. 2019. Besides, the Cinzas River is an important tributary of the Paranapanema River basin, which is the main watercourse of the region known as "Norte Pioneiro" (Pioneer North) of the Paraná state, and it is essential for maintaining ichthyofauna biodiversity of the Capivara reservoir (Vianna & Nogueira 2008, Orsi 2010. Fish inventories were carried out in the Paranapanema River tributaries, including the Cinzas, Jaguariaíva and Tibagi rivers (e.g., Shibatta et al. 2002, Castro et al. 2003, Cetra et al. 2012, Cionek et al. 2012, Costa et al. 2013, Hoffmann et al. 2005, Cetra et al. 2016, Frantine-Silva et al. 2015, Almeida et al. 2018, Jerep & Shibatta 2017, Claro-García et al. 2018, Frota et al. 2020, Jarduli et al. 2020). However, a comprehensive checklist of the Laranjinha River ichthyofauna has not been published yet, except for a small streams (e.g., Costa et al. 2013), and the scientific knowledge of its fish species remains unknown. Furthermore, projects of Small Hydropower Plants (SHPs) are being developed, which represents a potential threat to the species of this river (Galindo et al. 2019). Thus, this study aimed to provide the first inventory of the Laranjinha River fish fauna.

Study area
The Laranjinha River is entirely situated in the northeastern portion of the state of Paraná, and it is the main tributary of the left bank of the Cinzas River, which pours to the left bank of the middle Paranapanema River (Figure 1 and 2). The headwater is in the municipality of Ventania (24°14'43.43"S; 50°14'32.78"W), at 984 m of altitude, and the mouth is situated 4 km from the town of Itambaracá (23°01'03.51"S; 50°24'22.68"W), at 348 m of altitude.
The Laranjinha River, with its meanders, extends through 350 km long, and it is situated in the sedimentary basin of the state of Paraná, with its source and mouth in the second and third plateaus, respectively (Santos et al. 2006). Between the years 1956 and 1960, a Small Hydropower Plant (SHP) was built 98 km from the mouth of the river. This dam never went into operation, and in 2006, a fish pass system was built in it (Schwartz 2006; Figure 2G).

Data collection
Nine sites for sampling were distributed from the source to the mouth of the Laranjinha River (Figures 1 and 2 After the capture of the fish, the specimens were anesthetized with 10% benzocaine. This substance promotes a reduction in gill ventilation due to the depression of spinal respiratory centers, promoting a decrease in blood flow through the gills (Mattson & Riple 1989;Tytler & Hawkins 1981). After performing the opercular movements, the fish were fixed in 10% formalin and preserved in 70% ethanol in the Laboratório de Genética e Conservação of the Universidade Estadual do Norte do Paraná (GECON/UENP-CCP) and identified in species-level. The validity of the species was checked using Fricke et al. (2019), and the classification was based using Van der Laan et al. (2020). The species were identified following Ota et al. (2018), Jarduli et al. (2020), Terán et al. (2020), and in the lack of information about the species from the authors before mentioned, personal communication with specialists took place (i.e., FC Jerep, CDCM de Santana, CAM Oliveira and CH Zawadzki).  The riparian vegetation is poorly preserved on both river banks; some upstream rapids, however, a calm water segment prevails until the confluence between Laranjinha and Cinzas Rivers, including a rocky and sandy (primary) substrate; average width of approximately 48m. It is surrounded by pastureland and agriculture areas.  Table 2). Vouchers of all species were deposited in the Museu de Zoologia of the Universidade Estadual de Londrina (MZUEL). The abundances of orders, families, and species were conducted using the Statistica 7.0 software (StatSoft Inc. 2011). The Kendeigh index of abundance (1944) of each species was calculated as KI = √FO.M; where KI is the abundance index, and FO is the frequency of occurrence calculated as the number of sites where the species were captured, and divided by the total number of sites multiplied by 100, and M is the mean number of specimens of each species. The classification of species was done by sorting the values in descending order. The dominance index and evenness were calculated with the program PAST v. 2.17c (Hammer et al. 2001).

Discussion
The results presented in this study showed a high diversity of fishes (100 species) among the fish collected in the Laranjinha River. Such results follow the pattern found in the Neotropical regions, showing the dominance of Siluriformes and Characiformes (Agostinho et al. 1997, Lowe-McConnell 1999, Jarduli et al. 2020. Furthermore, among Paranapanema River tributaries, the number of species is lower if compared to the Tibagi River basin, where 158 species were registered (Lobón-Cerviá & Bennemann 2000, Bennemann et al. 2006, 2011, Shibatta & Cheida 2003, Hoffmann et al. 2005, Oliveira & Bennemann et al. 2005, Jerep et al. 2006, Sant'Anna et al. 2006, Shibatta et al. 2002, 2006a, 2006b, Galves et al. 2007, Vieira & Shibatta 2007, Orsi 2010, Raio & Bennemann 2010, Garcia et al. 2014, Frantine-Silva et al. 2015, Almeida et al. 2018, Jerep & Shibatta 2017, Claro-Garcia et al. 2018, and to the Cinzas River, with 114 species (Hoffmann et al. 2005, Vianna & Nogueira, 2008, Orsi 2010, Bennemann et al. 2011, Costa et al. 2013, Frantine-Silva et al. 2015, Almeida et al. 2018. It is noteworthy that the most frequent species of Laranjinha River was Psalidodon aff. paranae, captured in eight sites. The higher abundance were in the uppermost site A, and along the downstream, the number of specimens decreased until site H, which corroborate the hypothesis that this species has a preference regarding the headwater region (Britski 1972), but it is not restricted to that. Psalidodon aff. paranae is an insectivorous species, feeding mainly of allochthonous resources from the riparian forest. However, it can gather enough food resources from environments with different levels of degradation (Ferreira et al. 2012).
In the upper region of Laranjinha River, Phalloceros harpagos, a native species, was the most abundant one, being dominant in the site C. The value of dominance index (D=0.54) and evenness (E=0.17) of that site, reflected the disturbance in the observed environment. Biological features of P. harpagos like constant reproduction (Wolff et al. 2007), adaptability, tolerance to heat, variations in salinity (Nascimento & Gurgel 2000), and high trophic plasticity (Casatti et al. 2009, Rocha et al. 2009) may be related to the success of the species at that location. This species has a wide geographical distribution (Thomaz et al. 2019), which may also be related to its ecological plasticity.
Hypostomus ancistroides, H. cf. paulinus, and H. cf. strigaticeps were abundant and frequent from C to I sites. A factor that possibly has favored these rheophilic species is the presence of running water in the Laranjinha River (Cecilio et al. 1997;Garcia et al. 2020). Several species of Hypostomus were collected in running waters showing a substrate with pebbles and rocks Perez-Junior & Garavello 2007), but in Laranjinha River these species also occur in some places with a sand bottom. Hypostomus ancistroides, the most abundant of these species, had higher abundance in the site C, which decreased until site I, and such data demonstrates that this species is the least rheophilic one among congeners.
In general, the non-native fish species recorded in this study were introduced from other drainages in Brazil. All these species are associated with human activities like aquarium trade (possibly Aphyocharax cf. dentatus, Apteronotus albifrons, Hyphessobrycon eques and Poecilia reticulata), fish ladders (possibly Metynnis lippincottianus, Pterygoplichthys ambrosetti and Triportheus nematurus), fish farming (certainly Cyprinus carpio, Oreochromis niloticus and Sorubim lima), and control of insect larvae (possibly Poecilia reticulata). It is worth mentioning that among these non-native species, two of them are considered exotic (Cyprinus carpio and Oreochromis niloticus). These records are alarming, as C. carpio is known to promote bioturbation by continually revolving the sediment (Ritvo et al. 2004). However, only two individuals were sampled, being exclusive on site G, an area surrounded by pastures and agriculture. On the other hand, O. niloticus was more abundant and widely distributed, being sampled in five sites, which corresponds to an area surrounded by pasture and agriculture, and specifically in site B with the discharge of effluents. In addition, this species changes the environment due to the excess of nitrogen excreta, thus favoring the proliferation of algae, which decreases light and dissolved oxygen (Britton et al. 2007, Vicente & Fonseca-Alves 2013. Besides that, Poecilia reticulata was registered by Costa et al. (2013) in the study of the Penacho stream, a small tributary on the right bank of the Laranjinha River that flows into the Cinzas River. The high abundance of P. reticulata indicates an instability of the environment, including factors such as the lack of food resources for other species and the low level of dissolved oxygen (De Souza & Tozzo 2013).
The occurrence of 13 medium-to large-size migratory fishes highlights the importance of Laranjinha River for the maintenance of the diversity and viability of the ichthyofauna of the middle Paranapanema River. Other studies also highlight the Cinzas River basin and the Laranjinha River as migratory routes to the fish fauna from the Capivara dam (Dias et al. 2004, Lopes et al. 2007, Vianna & Nogueira 2008, Orsi 2010. As the Laranjinha River has only a little dam, including a fish pass system built in it, it extends a long stretch without dams, enabling migratory fish species to use its free-flowing stretches to complete their reproductive cycles. Long-distance migratory species with high commercial value have been using tributaries of rivers intensely affected by dams as migratory routes (Agostinho et al. 2008). The pressure caused by power plant dam constructions is intense in freshwater systems (Agostinho et al. 2005), because the transformation of lotic areas into lentic ones interrupts the displacement of migratory fish (Agostinho et al. 2008, Pelicice et al. 2018). The impact is not restricted to migratory species, and it also impairs the local fauna that depends on the tributaries for the viability of spawning and survival of early life stages (Oliveira et al. 2015). Studying the dynamics of eggs and larvae in the Cinzas River, Vianna & Nogueira (2008), found that the fishes of the middle Paranapanema River use this tributary to spawn. In general, biological communities are under heavy pressure due to environmental instability caused by habitat fragmentation and loss of natural environments, which affect species abundance and richness (Pusey & Arthington 2003, Di Giulio et al. 2009, Shandas & Alberti, 2009. Furthermore, the conservation of the Laranjinha River is essential to preserve the species already categorized as threatened by extinction in the IUCN's Red List (Apteronotus acidops, Brycon orbygnianus and Crenicichla jupiaensis as Endangered; Brycon nattereri as Vulnerable; and Rhinelepis aspera as Near Threatened) (ICMBio 2018). The fact that some of these fish appear on a list of endangered species is concerning and it reinforces that the focused area needs appropriate conservation strategies (Simic et al. 2007). Studies on B. nattereri reinforce the importance of Laranjinha River conservation, since this migratory and threatened species has been able to maintain a satisfactory population genetic diversity due to the quality of that environment (Galindo et al. 2019).
Finally, the Laranjinha River is a heritage of fish diversity due to the presence of large numbers of species (among migratory, threatened, and new species to science). Thus, it deserves special attention regarding its preservation.

Supplementary Material
The following online material is available for this article: Appendix 1 Appendix 2 Appendix 3 Appendix 4 Appendix 5