Saving the iconic hump-backed mahseer from extinction

 The hump-backed mahseer population has decreased by 90% in the last 15 years. But due to a case of mistaken identity, the fish disappeared unnoticed from South India's River Cauvery until research led by Adrian Pinder, director of Bournemouth University's Global Environmental Solutions and director of The Mahseer Trust, highlighted the giant carp's plight.

Now on the brink of extinction, the humpback's hopes rely on actions such as its inclusion as Critically Endangered on the IUCN's (International Union for Conservation of Nature's) Red List, to which it was added in November 2018. "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'," Adrian says. "However, with the hump-backed mahseer, we are talking about a creature which is actually more imperilled than these better-known icons."

Fisherman's friend
The hump-backed mahseer earned itself the title as 'one of the world's hardest fighting freshwater game fish' after appearing in the 1873 classic angling book The Rod In India. This reputation, combined the fact that the freshwater giant, which qualifies as megafauna, is capable of growing up to 1.5 metres in length and 54kg in weight, became a prize catch for avid anglers across the globe, until it was believed to have become extinct due to destructive fishing methods after India gained its independence.

Global interest reignited in 1978 when the Trans World Fishing Team rediscovered the fish and recorded impressive catches. Local villages prospered as catch-and-release anglers arrived in their droves, and patrols were set up to protect the fish from poachers, and the ecology of the river temporarily thrived.

A list of enemies

Pollution, dam construction, water abstraction, sand and gravel extraction, poaching, destructive fishing and deforestation have all contributed to the humped-back's downfall, but perhaps more significantly was a non-native invader. "As a boy, I read about this great fish," says Adrian "In 2010, I made my first trip the River Cauvery, where I realised the fish I was catching did not match the appearance of the iconic specimens I'd seen in historic photos."

On returning to the UK, Adrian reached out to Dr Rajeev Raghavan at Kerala University of Fisheries and Ocean studies in Kochi. "Comparing photographs over the internet opened a can of worms and confirmed that very little was known about all of the mahseer species found throughout South and Southeast Asia," he says. "I suspected that it was not correctly recognised as a species."

Adrian studied extensive angler logs to demonstrate the humped-backed mahseer had been pushed to the edge of extinction. "I discovered that the Galibore Fishing Camp, one of three former angling camps in the Karnataka jungle, had kept detailed angler catch records. This not only allowed us to analyse the temporal trends in population size over the previous 15 years but also form a detailed understanding of how the type and species of mahseer had changed over time."

The bluefin invader

The angler data showed that in 1998 for every one hump-backed mahseer caught there were four blue-finned mahseer being caught, yet by 2012, for every one humpback there were over 273 blue-fins. Upon further investigation, Adrian on behalf of Bournemouth University's Centre for Ecology, Environment, and Sustainability in collaboration with Professor Robert Britton, discovered that non-native, hatchery-reared Blue-finned mahseer had been introduced to the river in the name of species conservation. "Despite the positive intention of conservationists, this is clearly a conservation programme which has backfired," Adrian remarks. "They are now one of the most abundant fish in the river. Without a doubt, their success has been at the expense of the humped-backed mahseer."

Citizen science
This wasn't the first time Adrian encountered a non-native species, after publishing a number of papers with colleagues highlighting the invasive potential and ecological threats posed by Asia's topmouth gudgeon and other emerging non-native fishes such as sunbleak, on UK waterways.

By working with the angling press, Adrian and his colleagues educated anglers about the threats these fish posed and how to identify them. The feedback the team received helped identify populations which were eradicated by the Environment Agency, vastly reducing the risk that they posed to native fish species.

This model of research (identifying a problem, researching to better understand the issue, and working with members of the public and industry bodies) is one Adrian has continued to use and refine through his career, including his approach in establishing The Mahseer Trust, with Dr Rajeev Raghavan in 2013.

What's in a name?

The few humpbacks plucky enough to survive the formidable gauntlet of adversaries have found their procreation attempts thwarted, as dozens of newly created hydroelectric dams have altered their habitat and restricted the river's flow, preventing the fish from migrating to their spawning grounds.

The result is no young and an ageing population hurtling towards extinction. Ordinarily, activists would have pressed for the fish's insertion on the IUCN Red List list; however, despite being the most imperilled of all the mahseer species until recently, it couldn't be considered for inclusion because it lacked a formal taxonomic name, which required DNA evidence.

Only after three years of expeditions were Adrian and his team were successful in finding a small population of humpbacks in a remote jungle section of the River Moyar, where Indian colleagues were then able to collect specimens for genetic and morphometric analysis.

Introducing Tor remadevii... again
In July 2018 the humped-backed mahseer was finally demonstrated to be the same species as Tor remadevii; first 'described' as a new species by scientists in 2007 who didn't realise that the juveniles they found in the most southerly tributary of the Cauvery were the same as the giant hump-backed mahseer of the main River Cauvery.

Now, with a formal scientific name, growing research data and robust conservation strategy in play, Adrian and colleagues have revised the entire genus as part of a coming paper and has reassessed each species for the IUCN Red List. "This will reset the genus at 16 species," he says. "Eight are data deficient, three are near threatened, one is vulnerable, three are endangered and one, the Tor remadevii, the first mahseer to be assessed as Critically Endangered."

A brighter future?
With only two small isolated self-sustaining populations of the humped-backed mahseer left on the planet, the fish's fate is said to rest in the unified will of the governments across the three Southern states of Karnataka, Tamil Nadu and Kerala. This is why, Bournemouth University and the Mahseer Trust spearheaded a historic two-day summit in 2017, attended by stakeholders from the regions and other invested organisations, resulting in multiple viable conservation suggestions and pledges of support.

In the short term, however, Adrian is in no doubt that inclusion on the Red List is an important milestone: "Being included affords formal recognition of a) the species and b) the imperilled conservation status. This will also afford the species protection from river engineering projects (dams/reservoirs etc.) and assist with securing conservation grants to protect remaining populations and develop a species conservation plan. I think that without action, one decade from now, the species will be extinc

https://www.bournemouth.ac.uk/research/projects/saving-iconic-hump-backed-mahseer-extinction