Department of Fish and Zooplankton Ecology (DFZE)



Research aim

Our research is focused on the highest trophic levels in freshwater ecosystems, zooplankton and fish. The department is divided into six research groups investigating different aspects of fish and zooplankton ecology using diverse methodological approaches and advancements.

“Ecology of early life stages of fishes” group is focused on diurnal vertical and horizontal migrations of juvenile cyprinid, percid and coregonid fishes in reservoirs and lakes, and on ecological causes as well as the consequences of these migrations. It studies the effect of ecosystem management and nutrient load on the main characteristics of fry communities in selected water bodies (species composition, abundance, distribution, growth rate etc.).

Research of “Spatio-temporal ecology of fish” group is focused on spatio-temporal distribution of fish in artificial and natural waterbodies. Main emphasis is given to enlightening the diurnal and seasonal changes of fish distribution, the effect of abiotic and biotic factors and individual as well as intra- and interspecific variability. The research of spatio-temporal distribution is linked with other aspects of fish ecology (trophic interactions, population genetics and fish physiology) and applied for broader ecological concepts explaining fish ecology and functioning in freshwater ecosystems.

“Trophic ecology of fish” group studies the structure and functioning of fish communities, food web dynamics and trophic interactions in natural and managed aquatic ecosystems. To answer its research questions, it combines both classical and novel methodological approaches (field observations, manipulative experiments, gut content analysis, stable isotope analysis etc.). The overall goal of its research is to better define and understand mechanisms governing the functioning of fish communities. Current works explore: (i) functional role of herbivorous fish in lake ecosystems; (ii) diet and feeding ecology of wels catfish, the largest European freshwater predator, in its native and introduced areas; (iii) importance of different energy pathways and carbon fluxes in food webs of novel ecosystems such as post-mining lakes and dam reservoirs; (iv) isotope composition of fish scales and its utility as an indicator of anthropogenic environmental changes.

Investigations of the “Behavioral ecology of fish” group are focused on protandry behavior in asp and individual fish strategies securing maximization of reproductive success. Further research topics include impact of climate change and predation on the fish spawning and egg survival studied in model system asp/bleak. Special emphasis is on the influence of hydropeaking under water power plants on the fish behavior and egg mortality with potential global threat to riverine biodiversity and productivity.

“Fish populations dynamics” group aims at developing ecological models to scrutinize the role played by the biotic (primary and secondary production and competition) and abiotic (water quality parameters and temperature) factors on fish survival rate, growth, reproduction and ultimately on the population dynamics of targeted species. These informations are then applied into individual-based models (IBM) that will be used to simulate the fate of economically important fish species according to the different management (stocking regimen, fishery pressure and fishing rules) and climate scenarios (temperature and water level fluctuation).

Research of the “Ecology of fish and zooplankton communities” group is aimed on monitoring and assessment of changes in the composition of fish communities of long-term monitored reservoirs and on studying succession of fish communities in newly created postmining lakes. The abiotic and biotic factors responsible for the changes are identified and particularly focus is aimed on the effect of intra- and inter-species interactions and predator-prey relationships on resulting fish community structures. Finally, the focus of the group also includes studies of eco-physio-genetic adaptations of zooplankton in the context of colonization of newly created large lakes, sharing and differentiation of ecological niches with new invasive species and studies on adaptation responses to the variable and manipulative structure of the trophic pyramid in deep valley reservoirs.

"Conservation biology" group is focused on developing novel concepts and tools in conservation biology, as well as on applying them in practice for policy and management. Research spans different topics, but mainly the fields of species extinctions and extinction risk assessments, biological invasions, population ecology, conservation culturomics, climate change, and the development of novel model-based risk assessment approaches. Research comprises various modelling tools and approaches, population viability analysis, trait-based approaches, Big Data analytical tools, time-series analysis, and the development of methods for extinction inference in species with sparse data.

We are specialist in surveying fish stocks of large inland waters

To obtain quantitative, semiquantitative and qualitative information on the abundance, biomass and composition of fish communities, we use a wide range of capturing and sampling devices.

As a basic sampling tool for qualitative and semiquantitative fish surveys, we use multi-mesh gillnets that we install in depth stratified design into all types of benthic and pelagic habitats. In addition to standardized nets with twelve mesh sizes in the range of 5 to 55 mm (net height 1.5 or 3 m, length 30 m), we also use large-mesh gillnets with mesh sizes of 70 to 135 mm (net height 1.5 or 3 m, length 40 m). In unstructured littoral habitats (the shallowest benthic habitats), we use beach seines for quantitative surveys (various mesh sizes, 10 to 200 m seine lengths). In structured littoral habitats, we apply electrofishing, when back-pack battery electroshocking devices we use for operation in smaller waters, and two special 6 m long electrofishing boats equipped with a powerful electroshocking device (output voltage up to 600 V) we use for surveying deep-waters of reservoirs and lakes. For quantitative surveys of pelagic habitats, we use trawl nets (several types of frame and frameless trawls up to 10 m height, up to 40 m width, including electrified ones) towed by one or two boats (Ota Oliva - length 8 m, engine power 64 HP, Thor Heyerdahl - length 10 m, engine power 115 HP). We also apply purse seines (various types, height up to 12 m, length up to 120 m) distributed from a special catamaran ship. In addition, we own a unique collection of ichthyoplanktonic and fry trawls and beach seines to sample young of the year fish in open water, near the flat bottom and in macrophytes.

Our hydroacoustic team has many years of experience with both acoustic estimates of abundance, biomass and fish stock composition, as well as with surveying fish spatio-temporal distribution and behavior in large water bodies (mobile and stationary hydroacoustics applying both vertical and horizontal beaming). In addition to fish and other aquatic animals, we also have experience with estimating ebullition of greenhouse gases and sediment composition and thickness. We use Simrad EK60 and wideband EK80 echosounders operating at central frequencies of 38, 120, 200 and 333 kHz (supporting chirp and continuous wave of pulse forms) and dual-frequency identification sonar (DIDSON). We also use acoustic telemetry to track fish behavior and distribution. In this case the transmitter is placed on or in a fish and its movement is recorded using a receiver system. We use Lotek Wireless Inc. system, owning 91 WHS3250 receivers operating at 76 kHz. For monitoring the environmental background, we use HOBO Pendant® temperature and light dataloggers and a mobile weather station. We also use OregonRFID passive telemetry equipment to monitor the migrations of aquatic animals. The system is suitable for monitoring the movement of fish and other organisms in smaller streams and reservoirs, in particular, it is often used to verify functionality of fish passages and for monitoring reproductive migrations. For direct visual underwater observations, we use remotely-operated cameras (Subsea Tech Observer, SplashCam Delta Vision HD), a self-operating camera systems (GoPro) and SCUBA divers.

Last but not least, we are also intensively engaged in the role of fish in the food webs of aquatic ecosystems. Here we use both, the bottom-up (food availability for fish under different conditions) and top-down (fish as predators on lower trophic levels) approaches and consequently individual (food selectivity) as well as the community-based approaches (bioenergetic modeling, food racions) are applied. Recently, in addition to generally used direct analyses of digestive tract contents, we also perform analyses based on the evaluation of stable carbon and nitrogen isotopes in various fish tissues. We are well equipped with all the instrumentation for the above mentioned analyses.


Biology Centre CAS
Institute of Hydrobiology
Na Sádkách 702/7
370 05 České Budějovice

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