The latest update of the IUCN Red List of Threatened Species, led by BUG in collaboration with the Mahseer Trust, has confirmed one of the world’s largest and most iconic freshwater fish, the hump-backed mahseer, is now Critically Endangered and on the brink of extinction.
It is perhaps hard to believe that a freshwater fish of sufficient international notoriety to earn the title ‘the tiger of the water’ due to its size and sporting reputation, could have avoided formal study by ichthyologists since first being popularised 150 years ago by the publication of HS Thomas’s classic A Rod in India, published in 1873. However, it was not until June 2018 that a team of researchers, led by BUG’s Adrian Pinder, published a paper in the international journal Plos One, which afforded the iconic hump-backed mahseer of South India its first valid scientific name – Tor remadevii, also highlighting serious conservation concern for the survival of the species. This represented a significant breakthrough in an attempt to protect the hump-backed mahseer, as without a scientific name, the fish did not previously qualify for inclusion in the IUCN Red List of Threatened Species.
Updated today, the IUCN Red List, designed to highlight the extinction risk of individual species, has published the first assessment of the hump-backed mahseer T. remadevii, as the only species of mahseer (Tor spp.) to be listed as ‘Critically Endangered’. Pinder said “When we think of endangered species, we often think of ‘flagship’ species such as the Giant Panda and Bengal tiger, which are currently and respectively assessed on the IUCN Red List as ‘Vulnerable’ and ‘Endangered, here we are talking about an equally charismatic animal, but due to living beneath the water, it has remained out of sight and out of mind. We hope that this assessment has not come too late and that there is still sufficient time to save this fish before it’s lost forever”.
The hump-backed mahseer is one of 16 currently valid species of mahseer which represent an iconic group of cyprinid fishes found throughout the fast-flowing rivers of South and Southeast Asia. Characterised by their very large scales, mahseer have long been afforded saintly status as God’s fishes and revered amongst isolated tribal societies across India and beyond. Their international reputation as premier sport fishes targeted by catch-and-release anglers, their nutritional value to poor rural communities and the critical role they play in maintaining natural ecosystem function and biodiversity, mean that they are of considerable cultural, recreational and conservation significance.
Today all mahseers and their habitats are under unprecedented anthropogenic pressure due to extensive deforestation, massive abstractions to service rapidly growing cities, and a penchant for damming rivers for power production which prevent mahseer from migrating to their spawning grounds. Where populations have managed to survive against these odds, the remaining fish have to run a daily gauntlet of an unsporting bombardment of illegal and unsustainable fishing methods such as small mesh nets, plant based poisons and dynamite fishing.
“We knew something needed to be done to support the survival of this amazing group of fishes” said Pinder. “When we started working on mahseer back in 2011, it quickly became apparent that there was still widespread confusion about their taxonomy and the distribution ranges of individual species; this, of course, is a fundamental requirement to assess population status and conservation needs”.
To address these issues and work towards a better understanding of the mahseers, in 2012 Pinder enlisted the help of Dr Rajeev Raghavan, Assistant Professor at the Kerala University of Fisheries and Ocean Studies (KUFOS), and IUCN’s Freshwater Fish Red List Authority Coordinator for Asia and Oceania. Supported by a wider team of researchers from Bournemouth University, KUFOS, the Bombay Natural History Society (BNHS) and the Indian Institute of Science and Education (IISER, Pune), Pinder and Raghavan have worked together to disentangle many of the published and propagated errors regarding the taxonomy of the mahseers.
As a result, in May 2019 BU | BUG and Mahseer Trust hosted an international Red Listing workshop to develop assessments across the 16 species they have identified as currently valid, inclusive of the hump-backed mahseer, Tor remadevii, and a further three species that had no previous assessment or formal conservation status. Despite eight species being assessed as ‘Data Deficient’, the new assessments identify the specific knowledge gaps that require addressing. Of the remaining eight species, one is now assessed as ‘Critically Endangered’ (T. remadevii), three as ‘Endangered’, one as ‘Vulnerable’ and three as Near Threatened’.
Dr Raghavan said, “The assessments published today have confirmed the hump-backed mahseer is the most threatened of all mahseer species. It only occurs in the River Cauvery basin and requires immediate conservation attention, both in-situ and ex-situ. Securing the future of the hump-backed mahseer will depend on the strong willingness and cooperation of a range of stakeholders from three southern Indian States; Kerala, Tamil Nadu and Karnataka, in one of India’s most contested rivers – the Cauvery.”
Adrian Pinder concluded, “These assessments were long overdue, but we now have a much clearer idea as to the species of greatest conservation priority, the sites that require immediate protection, actions which need to be fed into individual species conservation plans and an appreciation of the further field exploration required to fill remaining knowledge gaps. We also hope that this new baseline of knowledge will encourage other researchers to both challenge and build on the current state of knowledge and inspire stakeholders to apply pressure to governments to invest in the protection of these freshwater icons”.
The research team will be presenting their findings at the International Mahseer Conference organized by the WWF-Bhutan in Paro, Bhutan in December, with a view to identifying and pursuing conservation goals.
The IUCN Red List popularly called the ‘Barometer of Life’, is a comprehensive inventory of the conservation status of the world’s flora and fauna. The Red List estimates the ‘risk of extinction’ of an organism. This widely accepted conservation prioritisation tool determines the likelihood of a species going extinct in the near future given current knowledge about its population trends, distribution range, as well as recent, current and predicted threats. The assessments of all listed species can be downloaded at https://www.iucnredlist.org/
In a previous scientific paper published in the international journal Endangered Species Research in 2015, Pinder’s team identified the stocking of non-indigenous mahseer species into the main River Cauvery as a major biodiversity threat and a key reason for the collapse of the endemic hump-backed mahseer. This paper is available ‘open access’ at https://www.int-res.com/articles/esr2015/28/n028p011.pdf
The paper naming the hump-backed mahseer as Tor remadevii is Open access and available to read at https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0199328