Context: Large near-natural rivers have become rare in Europe, a fact reflected in the high conservation status of many riverine ecosystems. While the Balkan still harbors several intact river corridors, most of these are under pressure from planned hydropower constructions. Unfortunately, there is little information available on the hydromorphodynamics and biota of Balkan rivers under threat. Objectives: We present a synthesis of research on the Vjosa in Southern Albania. Here, longitudinal continuity in water flow, undisturbed sediment transport and intact fluvial dynamics are still maintained, but threatened by two large dams planned in its downstream section. We intend to provide a first multidisciplinary inventory of this river system as an example of the knowledge base required for sound water management decisions in the Balkans. Methods: Based on field work of a multidisciplinary consortium of scientists from Albania and other countries conducted from 2017 onwards, we summarize the most important findings on geomorphology of the riverine landscape, habitat turnover rates, vegetation ecology and selected animal taxa. Results: We found evidence that significant areas (86%) of the river corridor are covered by habitats listed in Annex 1 of the European Union Habitats Directive. These are associated with a high number of threatened biota. Conclusions: Our findings underscore the value of the Vjosa as one of the few remaining reference sites for dynamic floodplains in Europe and as a natural laboratory for interdisciplinary research. We emphasize that such multidisciplinary studies are a prerequisite for informed evaluation of potential impacts caused by hydropower plants.

The European eel (Anquilla anquilla) has been declining throughout its area of distribution, is addressed in several pieces of legislation, and is the target of extensive restoration efforts. Therefore, investigating and conserving natural eel habitats is urgently needed. Large, near-natural rivers have become rare in Europe but the Balkans host some of the extant examples. However, several Balkan rivers–among them the transboundary river Vjosa/Aoos of Albania and Greece–are under threat from planned hydropower constructions. This study synthesizes European eel catch data from four institutions and the results of a recent electrofishing survey. Population density and structure as well as habitat choice were studied at different spatial scales. We calculated densities for each meso-habitat (0–1303 ind./ha) and extrapolated these values across three different hydromorphological channel sections (meandering: 70 ind./ha, braided: 131 ind./ha, constrained: 334 ind./ha), resulting in an overall mean density of 168 ind./ha. Proposed hydropower plants would cut off about 80% of the catchment currently accessible and impact river sections downstream of the dams by disturbing hydrological dynamics. By linking study results to relevant legislation and literature we provide evidence-based data for water management decisions. We call for the Vjosa/Aoos to be protected in order to secure its outstanding conservation value.

The intensive utilization of tropical inland water bodies for multiple and sometimes competing activities underlines the necessity for their integrated and holistic co-management. This paper presents our synthesis on lake and reservoir fisheries in South and Southeast Asia as social–ecological systems, based on a synopsis of our research findings from a previous EU-funded research programme in Sri Lanka, Thailand and the Philippines (FISHSTRAT project). The paper attempts to merge our results with recent developments in research, policy and practice. We explore the effects of the main external and internal control mechanisms of the trophic state and pinpoint to the high production potential of traditionally unexploited small indigenous fish species. The limitations of conventional centralized management systems highlight the importance of introducing transdisciplinary approaches which integrate limnology, fish ecology and fisheries with the interests of other resource using stakeholders and decision makers in order to develop locally appropriate co-management strategies for sustainable aquatic resource use.