JoTT PAPER 1(10): 507-513 Diversity, distribution and assemblage structure of fishes in streams of southern Western Ghats, India J.A. Johnson 1 & M. Arunachalam 2 1 Wildlife Institute of India, P.Box No. 18, Chandrabani, Dehradun, Uttarakhand 248001, India 2 Sri Paramakalyani Centre for Environmental Sciences, Manonmaniam Sundaranar University, Alwarkurichi, Tamil Nadu 627412, India Email: 1 [email protected] Abstract: Diversity, distribution and assemblage structure of fishes were studied in 10 selected streams of southern Western Ghats. The sampling was performed between April 2001 and March 2002. Sixty species of primary freshwater fishes belonging to four orders, 13 families and 27 genera were recorded from the study area. Cyprinids were the most dominant assemblage members in all study streams. Maximum number of species, number of individuals and cyprinids were recorded from Thalayanai stream. More specialized forms Homaloptera santhamparaiensis, Glyptothorax madraspatanum, Noemacheilus guentheri, N. keralensis, N. semiarmatus and N. triangularis were recorded in Panniyar stream. High diversity was observed in Achankoil stream. Evenness index of similarity was uniform in all study streams. Similarity cluster analysis showed streams from nearby basins had similar faunal assemblages. Principal Component Analysis was performed to study the similarity of fish assemblages between the study streams. The analysis described clear pattern of segregation between Thalayanai and Karaiyar (east flowing) and Kallar and Achankoil (west flowing) streams. Thirty-nine Western Ghats endemic fishes were recorded from the study area. Current distribution and threats to endemic fishes are discussed. Keywords: Assemblage structure, endemic fishes, fish diversity, species richness, Western Ghats. Date of publication (online): 26 October 2009 INTRODUCTION Date of publication (print): 26 October 2009 ISSN 0974-7907 (online) | 0974-7893 (print) Freshwater habitats in rivers, streams, springs and headwaters are heterogeneous Editor: Neelesh Dahanukar due to variations in altitude, flow rates, dissolved oxygen, physical substrate and the riparian zones that provide food, shade and cover (Armantrout 1990). As a result, Manuscript details: freshwater habitats harbour diverse fauna, with fish serving as prime indicators of Ms # o2146 Received 13 February 2009 ecosystem status (Karr et al. 1986). Riverine fauna show a high degree of endemism, Final received 16 October 2009 with most endemic fish species living in headwater streams and/or short stretches of Finally accepted 17 October 2009 river (Groombridge 1992; Kottelat & Whitten 1997). Thus riverine freshwater habitats Citation: Johnson, J.A. & M. Arunachalam (2009). are among the least studied, and likely many species still await discovery (Kottelat & Diversity, distribution and assemblage structure Whitten 1997). of fishes in streams of southern Western Ghats, The Western Ghats biogeographic region of India is home to a highly diverse fish India. Journal of Threatened Taxa 1(10): 507-513. fauna, consisting of 288 known species belonging to 12 orders, 41 families and 109 Copyright: © J.A. Johnson & M. Arunachalam genera (Dahanukar et al. 2004), of which 116 (53%) species are endemic to this region 2009. Creative Commons Attribution 3.0 Unported (Daniels 2001). Until recently few details on abundance and assemblage organization License. JoTT allows unrestricted use of this ar- ticle in any medium for non-profit purposes, re- were available for streams and rivers (Silas 1951; 1953; Rajan 1963; Johnsingh & production and distribution by providing adequate Vickram 1987; Devi 1992; Devi & Menon 1994; Devi et al. 1997; Easa & Shaji 1997; credit to the authors and the source of publica- tion. Johnson & Soranam 1999; Arunachalam & Johnson 2002; Arunachalam et al. 2002), however, recent studies have examined diversity distribution and assemblage Author Details: see end of this article. organization. Arunachalam (2000) studied association of microhabitat variables to Author Contributions: see end of this article. species diversity and habitat usage, and diversity, endemism and distribution patterns of fishes have been studied in the central (Bhat, 2003; 2004; Dahanukar et al. 2004) Acknowledgements: JAJ is grateful to the and Kerala regions (Raghavan et al. 2008). While reports on the fish assemblage and Department of Science and Technology, New Delhi for the financial support under Fast Track Young distribution patterns seem to cover the Western Ghats fairly well, gaps remain with Scientist scheme. Critical comments from an regard to assemblage structure of the southern region. Thus the main objective of this anonymous reviewer in improving the quality of study is to describe fish assemblage structure in streams of the southern Western the manuscript are sincerely appreciated. Ghats, assess species diversity and similarity of faunal assemblage between streams and evaluate endemism and current conservation status of Western Ghats fish populations. MATERIALS AND METHODS Study Area: The southern Western Ghats lie between 80-120N & 760-780E. The region covers about 500km of mountain valleys shared by Tamil Nadu and Kerala. The important ecoregions of this area are Agasthyamalai, Anamalai, Cardamom hills and Nilgiris. This hill chain is interrupted in the north by the 30km wide Palghat gap at around 110N, and south of this gap lies the Anamalai range of hills with its highest peak Anaimudi at 2695m. This area receives precipitation from both southwest (June to September) and northeast (October to November) monsoons and the average annual OPEN ACCESS | FREE DOWNLOAD precipitation exceeds 2,800mm. Many torrential and perennial hill streams of this Journal of Threatened Taxa | www.threatenedtaxa.org | October 2009 | 1(10): 507-513 507 Assemblage of southern Western Ghats fishes J.A. Johnson & M. Arunachalam 7700’0”E 7800’0”E 7900’0”E Analysis: Information about structure of assemblages was extracted by adopting different univariate indices, namely Margalef s species richness index, Shannon diversity index and Shannon evenness index. The calculation of these indices was followed by the methods of Magurran (1988) and 15’0”N 15’0”N 0 0 Padhye et al. (2006). Margalef s species 11 11 richness is calculated using the equation R = (S-1)/ln N, where S is the number of species, N is the total number of individuals. The Shannon index of diversity is obtained by the following equation H = 6 pi. In pi, where pi = ni/ N; ni is the number of individuals of ith species and N = 6 ni. Evenness index is calculated by E = H/lnS, where S is the number of species. The indices were 0’0”N 0’0”N 0 0 used to compare the species richness, 10 10 diversity and equitability across the study streams. The quantitative data of species along with the number of individuals belonging to each species were used to calculate percent similarity index using Bray-Curtis similarity index based on Padhye et al. (2006). Dendrograms were constructed to understand the similarity between the sampling sites. This was done using 45’0”N 45’0”N 0 0 8 8 Bray-Curtis similarity index using non- transformed species abundance data (Anderson 2001). Further, Principal Component Analysis (PCA) was performed to study the similarity of fish assemblage between the study streams 7700’0”E 7800’0”E 7900’0”E and understand which species Figure 1. Map indicating sampling sites in southern Western Ghats. contributed to the difference in fish S1 - Samikuchi; S2 - Thalayanai; S3 - Karaiyar; S4 - Hanumannadhi; S5 - Gogalthurai; assemblage between east and west S6 - Kallar; S7 - Achankoil; S8 - Panniyar; S9 - Thalipuzha; S10 - Bavalipuzha. flowing streams. region are the main source of major west made in different habitats such as pools, RESULTS and east flowing rivers. The western riffles, runs and cascades using portion is drained by the Vamanapuram, monofilament gill nets of different mesh Fish assemblage structure, species Pamba, Periyar, Bharathapuzha and sizes (10 to 34 mm), drag, scoop and cast diversity and similarity: Chaliyar. In addition to major rivers, nets. Fish sampling followed the method During the study a total of 60 species number of quick flowing streams of Arunachalam (2000). After collection of primary freshwater fishes belonging originate and quickly discharge into fishes were examined, counted and to four orders, 13 families and 27 genera Arabian Sea. The eastern portion is released. A few specimens (5-10) of were recorded from the study streams drained by the Tamiraparani, Vaigai, unidentified species were preserved in (Table 2). Number of species, total Moyar, Bhavani and Cauvery rivers. In buffered formalin (10%) and transported abundance, cyprinid abundance and their the present study ten streams covering to the laboratory for analysis. Species percentage, richness index, Shannon major river basins in Tamil Nadu and identification and confirmation were diversity and evenness index for study Kerala states were selected (Fig. 1) and carried out using standard fish taxonomy streams are given in Table 3. Maximum the sampling was carried out between textbooks (Talwar & Jhingran 1991; numbers of species and individuals were April 2001 and March 2002. The study Jayaram 1999). Data on current recorded in Thalayanai stream, while low streams and their general features are conservation status was obtained from number of species and individuals were given in Table 1. reports of the Conservation Assessment recorded in Hanumannadhi stream. In the Data collection: