Project Mahseer expedition to Moyar Valley

Mahseer Trust trustees Adrian Pinder and Andy Harrison recently returned from an expedition into the Moyar Valley in southern India, the last remaining stronghold of the Critically Endangered hump-backed mahseer, where they were scoping options for surveying and protecting the last remaining populations of this enigmatic species.

Under the overall umbrella of ‘Project Mahseer’, set up by conservation partnership Shoal, plans are now being put in place to conserve the few small populations of hump-backed mahseer that remain and to enhance populations within protected areas to save this iconic species from extinction.

The enigmatic hump-backed mahseer of the Cauvery catchment; a legendary fish on the brink of extinction.

Project Mahseer has been set up as a collaboration between a number of different key project partners, who are all committed to the conservation of mahseer species throughout their range countries of south and southeast Asia. Mahseer Trust is the lead project partner, working in collaboration with expert scientists from Wildlife Institute of India, WWF India, Kerala University of Fisheries and Ocean Studies and Bournemouth University. In addition, the project would not get off the ground at all without crucial support from other organisations and individuals on the ground; in particular the Tamil Nadu Forest Department, who are fully supporting the project by providing access to protected areas and helping with important logistical support.

Originally spread throughout the entire Cauvery River catchment in southern India, a combination of human impacts including illegal fishing, habitat destruction, water abstraction, pollution and, most importantly, the introduction and spread of the invasive blue-finned mahseer (Tor khudree), have decimated the hump-backed mahseer population to the extent that both its distribution range and population size have decreased by more than 90 %. This has resulted in the species being recently assessed as Critically Endangered on the IUCN Red List of Threatened Species.

The aims of Project Mahseer are to undertake scientific studies to understand the ecology of the hump-backed mahseer, with a view to A) conserving the last remaining populations in the wild within their remaining native distribution range, and B) setting up an assisted breeding programme to re-stock suitable areas of habitat to restore populations to biologically safe levels.

The distribution range and population size of the hump-backed mahseer have decreased by more than 90 %, resulting in an IUCN Red List assessment of Critically Endangered.

Before scoping and planning any proposed scientific studies, the first step was to organise a Project Mahseer start-up meeting, bringing together all the relevant project partners to discuss priorities, logistics and individual roles and responsibilities. This meeting was held in early May at the WWF India headquarters in New Delhi and it was tremendously encouraging to see the enthusiasm and commitment in the room for mahseer conservation. In particular, Ravi Singh (Secretary General and CEO of WWF India) was interested in sitting in on some of the discussion and was keen to contribute his valuable insight and experience from the perspective of wider Indian conservation initiatives.

Adrian Pinder discusses the challenges and opportunities for mahseer conservation with Ravi Singh (Secretary General and CEO of WWF India) and other key project partners at the Project Mahseer startup meeting in the WWF India headquarters, New Delhi.

The morning after the Project Mahseer start-up meeting, key members of the project team travelled 2,000 km south to Coimbatore, from where they would begin their scoping exercise of the Moyar River, one of the key remaining strongholds of the hump-backed mahseer. The first step was to meet up with the local WWF India office, who helped with logistical support for the expedition. Here, the project team discussed the logistics of the next few days and finalised arrangements for an expedition into the Moyar Valley to scope potential hump-backed mahseer survey options.

Dr Antony Johnson of the Wildlife Institute of India discusses the hump-backed mahseer conservation plans and outlines key roles and responsibilities of the different project partners.

We were all too aware that undertaking scientific studies in the Moyar Valley would pose significant logistical challenges, not least due to the fact that the area is deep within the core protected areas of Sathyamangalam and Mudumali Tiger Reserves; accessible only on foot through dense jungle landscape and steep sided valleys. Indeed, the remoteness of the location lent the author R.W. Burton in the early 1900’s to describe the Moyar as “one of the most inaccessible rivers in India, for it runs at the bottom of a tremendous ravine close upon a thousand feet deep known as ‘The Mysore Ditch’. Apart from this natural obstacle, the river there passes through forest country inhabited only by wild beasts and jungle tribes, and the steamy depths of the gorge are protected by a malaria said to be deadly even to the aboriginal people, who dare not remain on the river banks after sundown”.

The project, therefore, would not be possible without the invaluable help and logistical support of the Tamil Nadu Forest Department, who granted permissions for this scoping exercise and provided forest guards to accompany the team into the core tiger reserve areas. In an afternoon meeting, the Field Director and Chief Conservator of Forests, Dr. V. Naganathan, kindly set aside some time to meet with the project team, reaffirming his support of the project objectives and offering advice on the steps ahead.

The following morning, the team made their way to Thengumurahada, the last inhabited village on the edge of Sathyamangalam Tiger Reserve. Here, we had the opportunity to talk to local fishermen, who were keen to talk about their past and present experiences of the hump-backed mahseer – all valuable information when trying to piece together the picture of its current distribution and decline.

Adrian Pinder talks to a local fisherman about the current distribution of the hump-backed mahseer.

From Thengumurahada, we travelled on jeep along a dirt track for eight kilometres until we reached the end of the road – a Forest Department outpost, where we met up with the forest guards who would guide us on foot through the tiger reserve and up the Moyar River.

As we travelled the final section of track by jeep, we got our first tantalising glimpse of the Moyar River, home to one of the few remaining populations of hump-backed mahseer.

The project team are very grateful to the Tamil Nadu Forest Department for providing logistical support and forest guards to guide us safely on foot through the tiger reserve.

With the safe and expert guidance of the local Tamil Nadu Forest Department forest guards, we set off on foot to scope out the Moyar River.

The Moyar River is located in undisturbed forest habitat, afforded protection by being within the Sathyamangalam, Mudumali and Bandipur Tiger Reserves. Along with the fact that the downstream Bhavanisagar Dam has stopped the invasive blue-finned mahseer reaching the river, this inaccessibility has helped to ensure that a small population of the hump-backed mahseer has managed to survive within this system.

One of the key aims of Project Mahseer is to use telemetry studies (radio and/or acoustic tracking tags implanted into individual fish) to gain an understanding of hump-backed mahseer ecology. In particular, we need to know when and where they spawn, how far they migrate throughout the river system and their critical habitat requirements. This will help to inform future conservation strategies and guide the best options for an assisted breeding and restocking programme within the catchment.

The Moyar River – home to the hump-backed mahseer. An unspoilt landscape protected by its inaccessibility deep within core tiger reserve.

Telemetry studies, tracking fish movements throughout the catchment, will help inform future conservation strategies.

One of the key aspects of this scoping expedition was to understand the feasibility and logistical challenges that would be involved with undertaking a telemetry study in such an inaccessible and challenging environment. Aspects such as where we can capture fish, where we can install acoustic or radio receivers and the dangers associated with the abundant wildlife all have to be considered.

Andy Harrison, one of the lead scientists for telemetry studies, assesses options for installing receivers within the Moyar River.

One key issue with undertaking an acoustic telemetry study is that the acoustic receivers must be installed within deep pools to ensure that they do not become exposed to the air. This makes it impossible, for example, to use acoustic telemetry to track adult fish potentially migrating up ephemeral tributary streams to spawn. An alternative (or complimentary) approach may be to use radio telemetry, whereby antennae are installed on land (e.g. in a tree or other structure). However, this approach may come with its own problems, with the risk of monkeys, elephants or other wildlife damaging the antennae.

Adrian Pinder assessing what would be a deep pool in a dry river bed of one of the Moyar tributaries. Installing acoustic telemetry receivers here is not an option.

Another key factor to consider in the logistical planning of the surveys will be how to transport monitoring equipment into and out of the survey sites. There are no tracks for vehicles to access so everything will need to be carried in on foot, often through treacherous jungle terrain.

The terrain can be tough going along the Moyar Valley. All field survey equipment will need to be carried in on foot.

One of the key aspects to consider is that of the challenges of working remotely deep within the core tiger reserve, with very high densities of wild animals. In particular, elephants and tigers are abundant, along with other wildlife, including leopards, sloth bears, crocodiles and snakes.

This bull elephant spotted during the expedition is one of a large population of elephants within the protected area.

Sathyamangalam and Mudumali Tiger Reserves boast the highest densities of tigers within a single unit anywhere in the world.

The project team did not have the time nor the logistical resources to access the Moyar Gorge itself during the trip. However, we did travel to several viewpoints to gain an understanding of what is involved in accessing this area at the upstream extent of the Moyar Valley. The extreme remoteness and inaccessibility of this region may preclude ground surveys being undertaken.

Our first plans are to undertake a remote sensing survey of the gorge using drones to capture both aerial imagery of the river beneath the canopy and LIDAR to capture elevation data of the river bed itself. This will help inform the extent to which hump-backed mahseer are able to access the gorge (e.g. there may be natural barriers to upstream migration), and will also provide a first assessment of the feasibility, safety and logistical challenges associated with mounting a ground expedition to install survey equipment.

The Moyar Gorge – one of the most inaccessible areas in India.

Drone surveys will help us to understand the terrain within the gorge and also identify any barriers to upstream fish migration.

Watefalls at the upstream extent of the Moyar Gorge. A natural barrier to upstream migration of hump-backed mahseer.

After returning to civilisation, the project team are now busy raising funds and developing firm survey proposals to take forward. This is a very exciting time for mahseer conservation and with the help of all of our supporters, we are confident we can make great strides in our efforts to save the Critically Endangered hump-backed mahseer from extinction.

If you would like to support the project directly, visit the Project Mahseer page on the Shoal website and give as little or as much as you can. Alternatively, why not make a donation or become a supporter of the Mahseer Trust to help fund our ongoing conservation efforts.


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