Fish diversity in streams / rivers of Kalakad-Mundanthurai Tiger Reserve , Tamil Nadu , India

This article describes fish diversity in streams and rivers of Kalakad-Mundanthurai Tiger Reserve (KMTR), Tamil Nadu. Fifty species of fishes belonging to 10 orders, 15 families, and 32 genera are recorded. Seven species, Garra joshuai, G. kalakadensis, Haludaria kannikattiensis, Hypselobarbus tamiraparaniei Mesonemachilus tambraparniensis, Neolissochilus tamiraparaniensis, and Dawkinsia tambraparniei are strictly endemic to this protected area. The minnows, Devario aequipinnatus, Garra mullya, and G. kalakadensis are widely distributed in KMTR streams. High species diversity (H’=2.81) was recorded in Gadana River, whereas low species diversity (H’=0.61) was registered in Poonkulam area. Bray-Curtis similarity analysis showed that sites along the headwater streams have similar faunal assemblage. Result of regression analysis revealed that there is a signifi ant paĀern explained between stream order and species richness (r2=0.86; p<0.05). Among 50 species, four (Garra kalakadensis, G. joshuai, Dawkinsia tambraparniei, and Tor malabaricus) are listed in threatened categories of IUCN Red List. Important threats faced by endemic species and their management strategies are discussed.


INTRODUCTION
Kalakad-Mundanthurai Tiger Reserve (KMTR) is one of the important biodiversity rich areas in southern Western Ghats forming an important watershed for the perennial east fl wing Tamiraparani River. Since this reserve has many perennial streams and rivers, this protected area is popularly known as River Sanctuary (Johnsingh & Viickram 1987). The watershed area has very rich fish fauna with notable endemic and globally threatened species. Information on fishes of this region emerged in 1950s with the description of two new species Garra joshuai and Dawkinsia tambraparniei (Silas 1953). Later, Johnsingh & Viickram (1987) provided the fi st comprehensive list of fishes (33 species) of the Mundanthurai Sanctuary with illustrations. This checklist covered the fis es from dams and associated rivers in Mundanthurai Sanctuary, and gave an insight into the ichthyological diversity of this region. Subsequently, four new species Garra kalakadensis (Remadevi 1992), and Haludaria kannikattiensis Arunachalam & Johnson 2002, Hypselobarbus tamiraparaniei Arunachalam et al. 2014 and Neolissochilus tamiraparaniensis Arunachalam et al. 2017 were described from this region. In addition to taxonomy, ecology and biology of fishes of this region have also been studied in recent years (Johnson & Arunachalam 2010Kannan et al. 2013Kannan et al. , 2014. Despite this, the diversity of fis es in KMTR is probably underestim ted, because many streams/ rivers of KMTR had not been explored in the past. Further, comprehensive information on fish in KMTR is still in an emerging stage. Hence, the present paper is an aĀempt to provide an updated status of the fish diversity and assemblage structure associated with diĀerent streams/ rivers of KMTR.

Study Area
Kalakad-Mundanthurai Tiger Reserve is located in the southern end of Western Ghats in Tirunelveli District, Tamil Nadu. This reserve comprises of four wildlife sanctuaries, namely, Kalakad, Mundanthurai, Nellai, and Kanyakumari, covering a total area of about 1,601km 2 . It lies between 8. 4166-8.8833 0 N & 77.1666 -77.9166 0 E with altitude ranging from 50m to 1,868 m at the highest point, Agasthyamalai Peak. This area represents diverse vegetation types and the core zone of the reserve is considered as one of the important rainforest areas in the country (Johnson & Kannan 2012).
The rich and dense forest types are important watershed areas for many streams and rivers. The major perennial river, Tamiraparani originates from Poonkulam at the base of Agasthyamalai (Image 1) and fl ws through the core zone of the ti er reserve. Along its course, several major tributaries such as Servalar, Manimuthar, Pachiyar, Gowthalaiar, Gadana, and Ramanadhi rivers join delete the river Tamiraparani. In the present study, 25 streams covering diĀerent streams/ rivers within the KMTR were sampled for species diversity and the survey was carried out between January 2011 and March 2012. The location of sampling sites in KMTR is presented in Figure 1.

Fish sampling
Fish sampling was performed in diĀerent habitats such as pools, riffles runs, and cascades within 100m reach based on the methods of Angermeier & Schlosser (1989) and Johnson & Arunachalam (2009). These reaches were selected based on regular paĀern of morphology such as pools and riffle and also special scales covering diĀerent stream orders. Fishes were collected using monofilame tous gill nets of diĀerent mesh sizes (8 to 32 mm), drag and scoop nets. Sampled fishes were examined, counted, photographed and released back to the system. Gill nets were also set during night along the habitat to obtain nocturnal catfishes. In addition to netti , hooks and lines were also used for collecting Anguillid and Mastacembelid fishes. Few specimens of unidentifie taxa were preserved in 10% formalin and the species were confirmed using standard taxonomic literature (Jayaram 2010). Current valid species names follow the Catalogue of Fishes (Fricke et al. 2020) and conservation status follow the IUCN Red Image 1. Poonkulam -the origin of River Tamiraparani in Kalakad-Mundanthurai Tiger Reserve, Tamil Nadu.

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List of Threatened Species (2020). At each sampling location, altitu e and GPS coordinates were recorded. In addiĀon, stream order classiĀcation was obtained for all sampling reach based on Strahlar's method (Strahlar 1957).

Data Analysis
Information on fish diversity and their distribution paĀern were extracted by adopting diĀerent univariate indices, Shannon diversity index and evenness index. Calculation of these indices followed the methods of Padhye et al. (2006). The indices were used to compare species distribution, richness, diversity, and equitability across the study streams. Quanti ati e data of species along with their abundance were used for construction of dendrogram to understand the similarity of fish assemblage structure between the streams. This was done using Bray-Curtis similarity index based on nontransformed species abundance data (Anderson 2001;Padhye et al. 2006) in PAST program. Further, the paĀerns of species distribution in KMTR streams was examined using simple linear regression model, where stream order and altitude were used as independent variables and species richness as dependant variable.

Diversity and assemblage structure
A total of 50 species of primary freshwater fishes belonging to 10 orders, 15 families, and 32 genera were recorded from the study area (Table 1 & Images 2-6). Among the species, Devario aequipinnatus, Garra mullya, Garra kalakadensis, Garra joshuai, and Rasbora dandia were commonly present across the study streams. The Malabar Mahseer Tor malabaricus was recorded from Myeelar, Pambanar, Gowthalyar, Vaalayar streams, and also in Ingikuli river. Of 50 species, seven species namely, Garra kalakadensis, G. joshuai, Haludaria kannikattiensis, Hypselobarbus tamiraparaniei, Mesonemachilus tambraparniensis, Neolissochilus tamiraparaniensis, and Dawkinsia tambraparniei are endemic to KMTR and Tamiraparani River basin. Among these endemic species, Dawkinsia tambraparniei is the only species with a wide distribution range in middle and lower reaches of Tamiraparani River basin and the rest are restricted to the headwaters of Tamiraparani (i.e., within KMTR). The exotic species Oreochromis mossambicus was recorded in the lower reach of Gadana and Tamiraparani rivers at Papanasam region.
Total number of species, Shannon diversity, and evenness index for each stream are given in Table 2. Cluster analyses of species composition in KMTR showed that two distinct clusters and two separate lines were formed based on the Bray-Curtis similarity (Figure 2). The sites along the headwater streams had more similar faunal assemblage and they were grouped together in cluster 'A'. The sites in the middle reach of the river with rich diversity sites such as Papanasam, Gadana, Servalar, Naraikkad, and Nambiyar had more similar faunal assemblages and they were grouped in cluster 'C'. The streams namely Vaalayar and Poonkulam (headwater) had distinct species assemblage and they did not cluster with other sites (line 'B' & 'D' in Figure 2). The result of regression analysis revealed that there is a strong signifi ant paĀern explained between stream order and species richness (r 2 =0.86; p<0.05). The study site with higher stream order had more species (Figure 3a). Similarly in the case of regression result on altitude vs. species richness a weak relatio ship explained between altitude and species richness (r 2 =0.19; p<0.05). Sites located at lower elevation such as Gadana, Papanasam, and Servalar had more number of species than higher elevation sites (Figure 3b).

Threatened species
Current status of KMTR fishes were compared with IUCN Red List data (IUCN 2020) and of 50 species four species are listed under threatened categories (Garra kalakadensis, G. joshuai, Dawkinsia tambraparniei, and Tor malabaricus). Apart from those, two species namely Labeo pangusia and Ompok bimaculatus are listed in the Near Threatened category. Distributions of these threatened species in KMTR are presented in Table 3. These threatened species constitu e about 8% of the species inhabiting KMTR region.

Sites
Stream order Altitude (m)  Interestingl , the record of a viable population of Malabar Mahseer in streams such as Pampanar, Gowthalaiar, Karayar, and Valayar in KMTR is additional information to this area. This mahseer was described by Jerdon (1849) as Barbus malabaricus from the mountain streams of Malabar regions of India. Menon (1992) synonymised this species with Tor khudree without any explanatio . Indra (1993), however, considered this species as a valid subspecies as Tor khudree malabaricus. Recently, Silas et al. (2005) confirmed the validity of T. malabaricus as a separate species using molecular techniques. This species is reported from rivers Balamore in Kanyakumari District, Tamil Nadu and Kallada River in Kerala (Silas et al. 2005 Arunachalam 2012), the distribution of Tor malabaricus in an east fl wing river is questionable. In this context, a separate investi ation on identity of this species using molecular techniques is in progress.

Number of Species Shannon index (H') Evenness index (E)
Moreover, recently the genus Horalabiosa was synonymised with genus Garra by Yang et al. (2012) based on molecular data without any discussion on Horalabiosa's morphological features. Other workers have also followed the same synonymy (KoĀelat 2013; Bleher 2018). We, however, strongly suspect that the chance of sampling error as juvenile Garra are morphologically similar to Horalabiosa (KoĀelat 2020). Further, combined molecular and morphological investi ation on the validity of genera Horalabiosa and

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Garra is necessary.
The paĀerns of diversity explained in the present study revealed that sites falling in the lower altitude with large stream size had high diversity of fish. The study sites Gadana, Papanasam, and Servalar are large size rivers (6 th order streams) and located at the foot-hills of Western Ghats, which had high Shannon diversity index (H'=2.81; H'=2.78; H'=2.68, respecti ely) comparted to study sites located high elevation with small stream channel (2 nd order stream). High diversity of fishes found in Gadana, Papanasam, and Servalar rivers are mainly due to the size of the channel and tributary eĀect (Horwitz 1978;Vannote et al. 1980;Minshall et al. 1985), as these are 6 th order river channel with many tributaries in the upstream. In general, main river channel will have high species richness than head waters (Schlosser 1991;Pusey et al. 1993). Similar type of paĀerns have been reported in east fl wing streams of Western Ghats (Johnson 1999;Johnson & Arunachalam 2010). Further, the regression plot fi ed with species richness vs altitude suggest that altitude is covariate for temperature, which may be a key environmental variable associated with fish species distribution in the KMTR streams. Similar observations of longitudinal gradient in species diversity and assemblage structure have been reported from other mountainous regions (Horwitz 1978;Oberdorff et al. 1993Oberdorff et al. , 1995Godinho et al. 2000;Silvano et al. 2000;Ostrand & Wilde 2002;Grenouillet et al. 2004).
An exotic fish Oreochromis mossambicus was recorded from Gadana and Tamiranaparani rivers at Papanasam. This species was introduced in south Indian reservoirs in 1950s by fishe y department (including reservoirs of KMTR) to improve reservoir fishe y producĀon (De Silva et al. 2004). Now it is well established in rivers, canals, irrigation tanks and downstream of Tamiraparani River, below the reservoirs. This species is not established in the upper reaches of KMTR (above reservoirs) due to presence of natural obstacles like high water falls and rocky cascades.
Although, the endemic fishes are present inside the protected area, there are few threats to these species.
The important threats faced by these endemic species are: habitat degradation due to tea garden operation, entry of household waste from human settleme ts in some parts of KMTR and entry of chemical contaminations from tea garden. These activitie may render the stream habitat not suitable for highly specialized fishes like Garra joshuai and G. kalakadensis, ulĀmately leading to reduction in endemic fish population. In order to conserve these threatened fishes, proper waste management mechanism should be placed in the tea garden areas. Further, the study on population status of endemic species is essential for conserving threatened species.