Lorestan University Press Journal of Animal Diversity 2676-685X 8 2 2026 06 01 Diversity of ichthyofauna in headwater streams of Pamba River Basin, Southern Western Ghats, Kerala, India 1 12 738743 10.22034/JAD.2026.8.2.1 EN Ruby Thomas Department of Zoology, St. Berchmans College (Autonomous), Changanassery, Kottayam, Kerala, India 0000-0003-2271-9705 Raju K. Thomas Post Graduate and Research Department of Zoology, Mar Thoma College, Tiruvalla, Kerala, India 0009-0007-1991-6640 Journal Article 2026 03 08 This study investigates the diversity of ichthyofauna in the upstream tributaries of the Pamba River Basin in the Western Ghats of Kerala, India. A total of 45 fish species, representing 26 genera, 10 families, and five orders, were recorded from five sampling sites: Nilackal–Kaduvappara (S1), Karimthookku (S2), Veluthodu (S3), Chorakakki (S4), and Chekuthanthodu (S5). The family Cyprinidae was the most species-rich family, with 21 species. Species recorded from all five study streams included Haludaria melanampyx (Day, 1865), Opsarius bakeri (Day, 1865), Opsarius barna (Hamilton, 1822), Devario aequipinnatus (McClelland, 1839), Devario malabaricus (Jerdon, 1849), Rasbora dandia (Valenciennes, 1844), and Garra mullya Sykes, 1839, indicating their broad ecological tolerance. Species richness was highest at Chorakakki (S4), as indicated by the highest Margalef’s species richness index (DMg = 2.853), whereas Karimthookku (S2) exhibited the highest species dominance. Endemic species constituted 60.00% of the total recorded ichthyofauna (27 of 45 species). Among these, 13 species (28.89% of the total ichthyofauna) were categorized as Western Ghats endemics (EN-WG), while the remaining endemic species belonged to other endemicity categories, including the Southern Western Ghats (EN-SWG), Kerala (EN-K), Peninsular India (EN-PI), India (EN-I), the Nilgiri Hills (EN-NI), and the Anamalai landscape (EN-AL). Endemism was assessed following Gopalakrishnan and Ponniah (2000), and no exotic species were recorded. Conservation status was assessed according to the IUCN Red List, which classified eight species as Endangered (EN) and two as Vulnerable (VU), while the remaining taxa were classified as Near Threatened, Least Concern, or Data Deficient. The Jaccard similarity analysis indicated that Veluthodu (S3) and Chorakakki (S4) shared the highest degree of species similarity among the five study streams. This relationship was also reflected in the UPGMA dendrogram. The findings highlight the high conservation value of the headwater stream ecosystems of the Pamba River Basin and emphasize the need for targeted conservation efforts to protect endemic fish species.

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