Abstract
Growing to lengths and weights exceeding 1.5 m and 45 kg, the hump-backed mahseer fish of the Western Ghats biodiversity hotspot, India, is an iconic, mega-faunal species that is globally recognized as a premier freshwater game fish. Despite reports of their high extinction risk, conservation approaches are currently constrained by their lack of valid taxonomic identity. Using an integrative approach, incorporating morphology, molecular analysis and historical photographs, this fish can now be revealed to be conspecific with Tor remadevii, a species lacking a common name, that was initially, but poorly, described in 2007 from the River Pambar, a tributary of the River Cauvery in Kerala. Currently known to be endemic and restricted to the River Cauvery basin in the Western Ghats, T. remadevii is distinguished from congeners by its prominent hump originating above the pre-opercle and extending to the origin of the dorsal fin, a well-developed mandible resulting in a terminal or slightly superior mouth position, and the dorsal orientation of the eyes. While body colouration varies (silver, bronze, greenish) and is not considered a reliable diagnostic character, orange coloration of the caudal fin (sometimes extending to all fins) is considered a consistent characteristic. Having been first brought to the attention of the scientific community in 1849, and the recreational angling (game fishing) community in 1873, it has taken over 150 years to finally provide this iconic fish with a valid scientific name. This taxonomic clarity should now assist development and delivery of urgent conservation actions commensurate with their extinction risk.
Highlights
Freshwater megafauna occur in large rivers and lakes of every continent except Antarctica [1]
Given the outstanding requirement to resolve the taxonomic identity and assist the conservation of the hump-backed mahseer, the aim of this study was to 1) apply morphological and molecular analyses to test whether the hump-backed mahseer is distinct from the currently known South Indian the identity of Barbus (Tor) species, and whether it is conspecific with T. remadevii, 2) provide definitive morphological characters which can be reliably used to identify this species from congeners in the field, and 3) provide notes on current knowledge relating to distribution and habitat utilization
The results suggested that the best partition scheme was Tamura & Nei’s [34] model with invariant sites (TN+I, Bayesian Information Criterion (BIC) = 3622.967, lnL = -1580.211, df = 71) for combined partition of all three codon positions
Summary
Freshwater megafauna (defined as species with adult body weights of at least 30 kg) occur in large rivers and lakes of every continent except Antarctica [1]. Following Indian independence in 1947, the fish was largely forgotten until a resurgence in recreational angling interest and subsequent development of catch-and-release fisheries in the main River Cauvery in the early 1970s [8,9]. These fisheries subsequently became world famous for the size of mahseer they produced [8,9] and were recognized for the socio-economic benefits afforded to poor rural communities via ecotourism based employment opportunities [8]
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