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Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, “Each year at the season of the falling of the waters, the people living in the vicinity of the Golden Basin, the home of the Pla Buk [Mekong giant catfish, Pangasianodon gigas], join together for the purpose of catching these fish…..The ceremonies connected with the taking of these fish are ancient and have been performed from time immemorial, and carried out once a year.” - F.H. Giles, 1935 This thesis was undertaken to test the potential of the relatively new survey technique of analyzing water samples which contain DNA that has been shed by organisms (environmental DNA) for the study of diversity and distributions of fishes inhabiting tropical and subtropical rivers. The purpose was to gain information on species richness, assemblages, and distributions; with the ultimate aim of improving conservation management of rare and endangered freshwater fishes. The limitations of conventional (observation-based) survey methods to study rare and threatened fishes in large tropical rivers motivated the choice of testing environmental DNA (eDNA) analysis approaches. Specifically, challenges encountered during prior work to conserve the Mekong giant catfish and other rare species fostered the goal of testing eDNA analysis methods. The Mekong giant catfish was once part of a fishery with substantial cultural and socioeconomic import, as described by Giles (1935). However; today the fishery and ceremony surrounding it no longer exists, as the species has become so rare that the capture of wild individuals is banned and it has been assessed as Critically Endangered by the IUCN Red List. The case of the Mekong River and giant catfish represents an archetypical example of the challenges and limitations of using conventional methods to study and conserve rare fishes in large tropical rivers. These rivers host the highest species diversity of any freshwater environment, yet are facing the highest rates of extinction. This dire situation is partially due to the difficulty of gainin

“Each year at the season of the falling of the waters, the people living in the vicinity of the Golden Basin, the home of the Pla Buk [Mekong giant catfish, Pangasianodon gigas], join together for the purpose of catching these fish…..The ceremonies connected with the taking of these fish are ancient and have been performed from time immemorial, and carried out once a year.” - F.H. Giles, 1935 This thesis was undertaken to test the potential of the relatively new survey technique of analyzing water samples which contain DNA that has been shed by organisms (environmental DNA) for the study of diversity and distributions of fishes inhabiting tropical and subtropical rivers. The purpose was to gain information on species richness, assemblages, and distributions; with the ultimate aim of improving conservation management of rare and endangered freshwater fishes. The limitations of conventional (observation-based) survey methods to study rare and threatened fishes in large tropical rivers motivated the choice of testing environmental DNA (eDNA) analysis approaches. Specifically, challenges encountered during prior work to conserve the Mekong giant catfish and other rare species fostered the goal of testing eDNA analysis methods. The Mekong giant catfish was once part of a fishery with substantial cultural and socioeconomic import, as described by Giles (1935). However; today the fishery and ceremony surrounding it no longer exists, as the species has become so rare that the capture of wild individuals is banned and it has been assessed as Critically Endangered by the IUCN Red List. The case of the Mekong River and giant catfish represents an archetypical example of the challenges and limitations of using conventional methods to study and conserve rare fishes in large tropical rivers. These rivers host the highest species diversity of any freshwater environment, yet are facing the highest rates of extinction. This dire situation is partially due to the difficulty of gainin, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

A critical requirement in assessing progress towards global biodiversity targets is improving our capacity to measure changes in biodiversity. Global biodiversity declined between 2000 and 2010, and there are indications that the decline was greater in freshwater than in terrestrial or marine systems. However, the data, tools and methods available during that decade were inadequate to reliably quantify this decline. Recent advances in freshwater monitoring make a global assessment now close to becoming feasible. Here we identify priorities for freshwater biodiversity assessment for 2020 and 2030, based on the Essential Biodiversity Variables (EBV) framework. We identify 22 priority activities for 2020 under three of the EBV classes (species populations, community composition, and ecosystem structure), which include: a globally systematic approach to collecting and assessing species data, collating existing and new data within global platforms, coordinated effort towards mapping wetland extent at high spatial resolution, linking in-situ data to modelling across regions, and mobilising citizen science for the collection and verification of data. Accomplishing these will allow the state of global biodiversity to be assessed according to a Red List Index with expanded geographic and taxonomic cover, an improved freshwater Living Planet Index with a greater number and phylogenetic range of species, measures of alpha and beta diversity, and globally-consistent estimates of wetland extent. To assess variables in the other EBV classes (genetic composition, species traits, and ecosystem function) we identify 15 priorities, which include development of environmental DNA methods, species-traits databases, eco-informatics and modelling over the next 15 years.