Conserving the Iconic and Highly Threatened Mahseer Fishes of South and Southeast Asia
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CONSERVING THE ICONIC AND HIGHLY THREATENED MAHSEER FISHES OF SOUTH AND SOUTHEAST ASIA ADRIAN C. PINDER A Thesis submitted in partial fulfilment of the requirements of Bournemouth University for the Degree of Doctor of Philosophy Bournemouth University March 2020 The copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and due acknowledgement must always be made of the use of any material contained in, or derived from, this thesis CONSERVING THE ICONIC AND HIGHLY THREATENED MAHSEER FISHES OF SOUTH AND SOUTHEAST ASIA Adrian C. Pinder ABSTRACT This thesis and supporting papers constitute the submission for an award of a PhD research degree by publication and consists of a cohesive synthesis linking a total of eight published papers across seven peer review journals and an IUCN Red List assessment. The mahseers (Tor spp.) represent an iconic group of large-bodied cyprinid fishes found throughout the fast-flowing rivers of South and Southeast Asia. Due to the considerable religious, cultural and recreational significance of these fishes, and the anthropogenic pressures they face, they are of high conservation concern and represent flagship and umbrella focal species for the sustainable management of river systems throughout their biogeographic range. Based on research conducted since 2012, considerable advances in the taxonomic and human dimension aspects of mahseer conservation have been acheived. Engagement with the recreational angling community has demonstrated the high value, and future potential for this rapidly expanding stakeholder group to impact positively on the conservation of mahseer and rivers more generally. This has been evidenced through the development of economic incentivised community habitat protection initiatives. Specifically, community level recognition that a live fish captured and released by paying anglers has a renewable value over the single revenue value of a harvested fish, has been shown to offer employment opportunities and support the sustainable stewardship of aquatic ecosystems. Where such i incentives are lacking however, fisheries continue to be subject to high levels of exploitation, due to limited alternative livelihood opportunities available within impoverished rural communities. Further, and due to a combined lack of political will and the difficulties associated with sampling large fishes in large and remote monsoonal rivers, records from catch-and- release angler logs have provided the only available insight to the temporal performance of mahseer populations. Over a 12 year period, angler derived data not only revealed a collapse (>90% reduction) in the River Cauvery’s endemic mahseer population, but also evidenced the establishment and rapid invasion of the non-indigenous blue-finned mahseer, thus highlighting the previously under-appreciated risks of stocking mahseer species into novel systems beyond their natural distribution range. With particular focus on the mahseers of South India’s River Cauvery, this work has afforded the largest of all mahseer species, the hump-backed mahseer, with a valid scientific name (Tor remadevii) and, through extensive analysis of angler catch data, has highlighted its high extinction risk, with it now assessed as ‘Critically Endangered’ on the IUCN Red List of Threatened Species. This has in turn impacted on regional and national fishery and wildlife policy and affected a concerted international effort to apply a multidisciplinary and multiple stakeholder approach to saving this iconic species of megafauna from extinction. In the absence of these works, it is highly probable that the species would have remained on a trajectory towards rapid extinction. Instead, the first major steps to safeguarding its future have been taken. In achieving these research highlights, this work has also resulted in an extensive gap analyses to identify and address some of the many knowledge gaps which have been constraining the effective direction and efficacy of international efforts to conserve species across the genus. With specific reference to previous taxonomic uncertainties, a comprehensive synthesises and critique of species descriptions and subsequent morphological and molecular focused literature, has resulted in the previously listed 24 species of Tor, being revised to just 16 valid species. Additional collation of ii available data to inform distribution ranges, population trends and threats across the genus, has facilitated the revision of IUCN Red List assessments, with one species now ‘Critically Endangered’, three as ‘Endangered’ one as ‘Vulnerable’, three as ‘Near Threatened’, and eight remaining ‘Data Deficient’. In discussing residual uncertainties, population threats, conservation prospects and the role of stakeholders across the region, this submission concludes with an overarching synthesis of the current knowledge base pertaining to the genus Tor. In discussing taxonomic clarifications, emerging research priorities and potential mechanisms to effect species conservation, this also represents a first point of reference for researchers, while encouraging further research to challenge and enhance the knowledge base necessary to conserve and promote these freshwater icons as focal species to support the ecological integrity of South Asian rivers. Acknowledgements In addition to the many names and organisations acknowledged within the ten papers which constitute this thesis, there are a few unsung heroes worthy of special mention. Rewinding to the beginning of my career, I remain indebted to Dr RHK Mann for the opportunity to work as his assistant and for nurturing my early enthusiasm for fisheries research. Working with Rudy Gozlan in the early 2000’s was a pivotal time in my career and I thank him for his encouragement to publish my first papers and for the many laughs we’ve had along the way. In recent years my colleague Dr Andy Harrison has been a constant source of sound technical advice and provided the day-to-day cover which has allowed me to undertake multiple trips to India during work time. My supervisor Professor Rob Britton has been a great source of inspiration and I am incredibly grateful for his support and encouragement. iii With specific reference to my mahseer research journey, I thank my main partner in crime Dr Rajeev Raghavan and other members of Team Mahseer not already mentioned above; Shannon Bower, Steve Cooke, Steve Lockett, Sascha Clarke-Danylchuk, Andy Danylchuk, Derek D’souza and Unmesh Katwate. Working with these incredibly talented professionals has not only been an education, but also exceptional fun, despite some of the challenging environments and circumstances that we have had to work together. I thank the growing numbers of global supporters of the Mahseer Trust who have attended our conferences, assisted our research, facilitated site access, provided hospitality or just shown an intereser and support for mahseer conservation. Closer to home, my family have all had a role in making this happen. I’m indebted to my Mum and Dad for their ongoing support and encouragement since day one. Furthermore, the extensive travel required to complete this submission would not have been possible without the full support of my wife Claire and our kids Jasmine, Harry and Rudi. I dedicate this body of work to my family. x iv Contents 1. Chapter 1: THESIS OVERVIEW ........................................................... 1 1.1 Rationale .......................................................................................... 1 1.2 Main Research Themes ................................................................... 1 1.3 Publications Submitted for Examination ......................................... 2 1.4 The Structure of the Supporting Document..................................... 5 2. CHAPTER 2: A VERY FISHY CAREER ............................................. 7 2.1 Centre for Ecology and Hydrology ................................................. 7 2.2 Consultancy ..................................................................................... 9 2.3 The Mahseer Trust ......................................................................... 11 3. CHAPTER 3: INTRODUCTION ......................................................... 13 3.1 Cultural significance of mahseer ................................................... 13 3.2 My introduction to India and the mahseer ..................................... 16 3.3 Specific research objectives .......................................................... 18 3.4 References ..................................................................................... 19 4. CHAPTER 4: EXPLORING THE ROLE OF RECREATIONAL ANGLERS IN MAHSEER CONSERVATION .......................................... 22 4.1 Prelude to Submission 1 ................................................................ 22 4.1.1 References .............................................................................. 25 4.2 Submission 1 ................................................................................. 27 5. CHAPTER 5: STAKEHOLDER ENGAGEMENT ............................. 40 5.1 Prelude to Submissions 2 & 3: ...................................................... 40 5.1.1 References .............................................................................. 44 5.2 Submission 2 ................................................................................. 47 5.3 Submission 3 ................................................................................