Food consumption by Eurasian perch (Perca fluviatilis L.) and ruffe (Gymnocephalus cernuus [L.]) was studied in single and mixedspecies treatments in the laboratory, where alternative food resources, chironomids and zooplankton, were offered simultaneously. The effects of structural complexity, which was represented by substrate grain size, and of feeding level on food consumption were analysed...

Trading between conflicting demands is a fundamental part in how animals interact with its environment and social surrounding. Knowledge of what factors shaping trade-off decisions is central in our understanding of animal adaptation and ecology. This thesis summarizes a series of behavioural experiments investigating how animals compromise behaviours depending on environmental background and c...

Trait combinations that lead to a higher efficiency in resource utilization are important drivers of divergent natural selection and adaptive radiation. However, variation in environmental features might constrain foraging in complex ways and therefore impede the exploitation of critical resources. We tested the effect of water transparency on intra-population divergence in morphology of Eurasi...

One of the keys for an optimal Eurasian perch aquaculture broodstock management is being able to determine sex individuals. For perch, compared with other methods identification fish and according 3R principle (replacement, reduction refinement), ultrasonography a rapid, non-lethal, non-invasive accurate method. During two successive experiments, we used ultrasound identify gender immature broo...

It is widely accepted that sex steroid hormones play an important and a specific role during the process of sex differentiation in fish. In order to describe the role of the three main sex steroid hormones (testosterone--T, 17beta-estradiol--E2 and 11keto-testosterone--11KT) during embryogenesis and sex differentiation in Eurasian perch, Perca fluviatilis, eggs, larvae and juveniles originating...

Due to altered biogeochemical processes related to climate change, highly colored dissolved organic carbon (DOC) from terrestrial sources will lead to a water "brownification" in many freshwater systems of the Northern Hemisphere. This will create deteriorated visual conditions that have been found to affect habitat-specific morphological variations in Eurasian perch (Perca fluviatilis) in a pr...

Adapting to fluctuating predation conditions is a challenge for prey. By learning through experience, animals may adjust their anti-predator behavior to better reflect current predation risk. Although many studies show experience of predation to alter prey behavior, little is known about how prey rely on such experience over time. By comparing boldness over different temporal scales between ind...

The importance of overwinter mortality of 0+ perch (Perm fluviatilis L.) in central European lakes was estimated using a stochastic simulation model. The probability of overwinter mortality of a perch co­ hort was calculated by using a model developed for yellow perch (P. flavescens Mitchill). Winter duration from a long-term data set and the length of perch at the end of the first year from fi...