Diversity and risk patterns of freshwater megafauna: A global perspective Inaugural-Dissertation to obtain the academic degree Doctor of Philosophy (Ph.D.) in River Science Submitted to the Department of Biology, Chemistry and Pharmacy of Freie Universität Berlin By FENGZHI HE 2019 This thesis work was conducted between October 2015 and April 2019, under the supervision of Dr. Sonja C. Jähnig (Leibniz-Institute of Freshwater Ecology and Inland Fisheries), Jun.-Prof. Dr. Christiane Zarfl (Eberhard Karls Universität Tübingen), Dr. Alex Henshaw (Queen Mary University of London) and Prof. Dr. Klement Tockner (Freie Universität Berlin and Leibniz-Institute of Freshwater Ecology and Inland Fisheries). The work was carried out at Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Germany, Freie Universität Berlin, Germany and Queen Mary University of London, UK. 1st Reviewer: Dr. Sonja C. Jähnig 2nd Reviewer: Prof. Dr. Klement Tockner Date of defense: 27.06. 2019 The SMART Joint Doctorate Programme Research for this thesis was conducted with the support of the Erasmus Mundus Programme, within the framework of the Erasmus Mundus Joint Doctorate (EMJD) SMART (Science for MAnagement of Rivers and their Tidal systems). EMJDs aim to foster cooperation between higher education institutions and academic staff in Europe and third countries with a view to creating centres of excellence and providing a highly skilled 21st century workforce enabled to lead social, cultural and economic developments. All EMJDs involve mandatory mobility between the universities in the consortia and lead to the award of recognised joint, double or multiple degrees. The SMART programme represents a collaboration among the University of Trento, Queen Mary University of London and Freie Universität Berlin. Each doctoral candidate within the SMART programme has conformed to the following during their 3 years of study: (i) Supervision by a minimum of two supervisors in two institutions (their primary and secondary institutions). (ii) Study for a minimum period of 6 months at their secondary institution (iii) Successful completion of a minimum of 30 ECTS of taught courses (iv) Collaboration with an associate partner to develop a particular component / application of their research that is of mutual interest. (v) Submission of a thesis within 3 years of commencing the programme. This project has been funded with support from the European Commission. This publication reflects the views only of the author and the Commission cannot be held responsible for any use which may be made of the information contained therein. Table of contents Table of contents Summary ................................................................................................................................................ I Zusammenfassung.............................................................................................................................. III Thesis outline .......................................................................................................................................VI List of figures .......................................................................................................................................IX List of tables...................................................................................................................................... XIV 1. General introduction ........................................................................................................................ 1 1.1 Freshwater biodiversity crisis ................................................................................................. 1 1.2 Overlooked freshwater biodiversity in current conservation schemes .................................... 3 1.3 Megafauna: ecological roles, extinction risks and their potential in advancing biodiversity conservation .................................................................................................................................... 5 1.4 Research gaps, aims and thesis structure ................................................................................ 9 1.5 References (Chapter 1).......................................................................................................... 12 2. Freshwater megafauna diversity: Patterns, status, and threats ................................................. 23 2.1 Abstract ................................................................................................................................... 24 2.2 Introduction ............................................................................................................................. 25 2.3 Methods ................................................................................................................................... 26 2.3.1 Species distribution mapping ............................................................................................... 26 2.3.2 Population trends and conservation status ........................................................................... 27 2.3.3 Human pressure on freshwater megafauna .......................................................................... 28 2.4 Results ..................................................................................................................................... 29 2.4.1 Distribution and status of freshwater megafauna ................................................................. 29 2.4.2 Human pressure on freshwater megafauna .......................................................................... 30 2.5 Discussion ............................................................................................................................... 33 2.5.1 Current status of freshwater megafauna ............................................................................... 33 2.5.2 Human pressure throughout distribution ranges of freshwater megafauna .......................... 34 2.5.3 Future challenges for freshwater megafauna conservation .................................................. 36 2.6 Acknowledgements ................................................................................................................. 38 2.7 References (Chapter 2)............................................................................................................ 39 Table of contents 3 Disappearing giants: A review of threats to freshwater megafauna ........................................... 46 3.1 Abstract ................................................................................................................................... 47 3.2 Introduction ............................................................................................................................. 47 3.3 Threats to freshwater megafauna ............................................................................................ 51 3.3.1 Overexploitation................................................................................................................... 53 3.3.2 Dam construction ................................................................................................................. 55 3.3.3 Habitat degradation .............................................................................................................. 57 3.3.4 Pollution ............................................................................................................................... 59 3.3.5 Species invasion ................................................................................................................... 60 3.4 Outlook: Filling the freshwater megafauna information gap .................................................. 62 3.5 Acknowledgements ................................................................................................................. 63 3.6 References (Chapter 3)............................................................................................................ 64 4. The global decline of freshwater megafauna ................................................................................ 79 4.1 Abstract ................................................................................................................................... 80 4.2 Introduction ............................................................................................................................. 80 4.3 Methods ................................................................................................................................... 83 4.3.1 Population abundance .......................................................................................................... 83 4.3.2 Distribution range ................................................................................................................ 84 4.4 Results ..................................................................................................................................... 85 4.5 Discussion ............................................................................................................................... 89 4.5.1 The loss of freshwater megafauna........................................................................................ 89 4.5.2 Uncertainty in population data of freshwater megafauna .................................................... 90 4.5.3 Implications for freshwater biodiversity conservation. .......................................................