Long-term dynamics in fish populations

This project is the first comprehensive study of the long term development of riverine fish communities from the late Middle ages onwards until present. It will be done within the framework of a bilateral cooperation between interdisciplinary research teams of river and fish ecologists, environmental historians and archaeologist from Austria and Russia. The spatial focus will be on representative Alpine catchments (Salzach) and rivers from the Russian North as well as on rivers in urban environments (Vienna on the Danube, St. Petersburg on the Neva, Pskov on the Velikaya). The case studies will offer the possibility to analyse different natural but also different societal conditions. Our research is motivated by several research questions addressing methodological issues relevant for the reconstruction of past ecological conditions on the one hand and particular societal and natural conditions investigated in case studies on the other hand. The project will consist of three main research topics. The first one will define a comprehensive methodology for analysing long-term changes of riverine fish populations. This methodology will use existing studies providing approaches for particular issues. It will also build on existing fish ecological knowledge of species traits and habitat-fish relationships. The second research topic will be dedicated to the case studies. Each case study will reconstruct long-term changes of fish communities and populations, climate and in particular temperature change as well as the societal alterations of fish communities and the riverine habitat. These three elements will enable us to interpret long-term fish ecological changes against the background of dominating natural and human driving forces. In the third research topic we will elaborate spatial differences in the historical development of fish communities through a cross national comparison. We will draw general conclusions on how different environmental and societal processes shaped fish populations and establish a final conceptual framework. The methodology and the conceptual framework for analysing the historical development of riverine fish population will be main outputs of the project. They can be applied to other historical ecological studies of river fish communities. The results can be also relevant for effective future river management and contribute to the crucial task of defining restoration targets by highlighting historical legacies acting in present riverine landscapes and by showing patterns of the long-term evolution of river ecosystems. Our study will produce a multitude of results related to fish ecology, climate change and societal modifications of river systems and the interaction between them as well as to methodological issues. They will be synthesized in scientific papers addressed to different target groups and be presented in various scientific conferences.

The bilateral Austrian-Russian research project DYNAFISH systematically investigated written historical sources and archaeological fish remains to reconstruct historical changes of riverine fish communities. The results produced by the interdisciplinary team of fish ecologists, environmental historians and ichthyo-archaeologists have advanced the historical ecology of riverine fish, a still underdeveloped research field compared with the marine environment. The project output improves ecology-oriented long-term reconstructions of fish communities and populations, which currently focus mostly on the 19th century as a reference situation. The DYNAFISH results go back earlier and show how much riverine fish communities had already at this time been altered by different human interventions and how they were influenced by past climate changes. The research findings will contribute to answering applied fish ecological questions such as the definition of ecological assessment targets based on historical conditions. They can also help identify trajectories of riverine fish communities. The project team developed a typology of written historical sources taking into account early biological records, fishery, fish trading, fish consumption and fish in culture. Most of these sources have a societal filter which masks ecological information. This hinders taking them directly at face value and we have developed methods to investigate them. Often, different source types had to be combined to produce meaningful outputs. The methods developed were tested for two Austrian case study sites, the Danube with a special focus on the Vienna Basin and the Salzach River system. For both study sites fishery statistics for longer periods were not available. Among the written sources which proved to be most useful for the Austrian rivers were fishing laws, yearly and monthly historical fish market statistics, historical fish distribution maps and fishery surveys providing at least verbal abundance information. By using historical and future air temperature we were able to demonstrate the influence of past climate changes on fish, to predict the effect of future climate change and to evaluate how much future fluctuations are outside the historical range. The latter was particularly evident for some cold-water species such as brown trout (Salmo trutta fario) and warm-water species such as barbel (Barbus barbus). Methodological advancements were made in the use of archaeological fish remains, in particular for identifying some cyprinid species and reconstructing fish lengths and their changes from Roman times until the early modern period. The results of DYNAFISH will be made available to the scientific community via publications in peer-reviewed international journals and edited volumes. Five papers are already published, eleven manuscripts are in review or will be submitted in the next weeks. The main project results were presented at an international workshop organized by the Institute of Hydrobiology, BOKU, in September 2013. As an output of this workshop a special issue of Aquatic Sciences is in preparation. Among the 11 contributions in this volume, six are from the DYNAFISH project. Altogether 26 presentations were given at scientific workshops and conferences. A virtual exhibition to be published on the Environment and Society portal of the Rachel Carson Center, Munich, Germany, in summer 2014, will be the main output for the broader public.