Ondrej Slavík

• Professor
• Professor (Full) at Czech University of Life Sciences Prague

Physiological and behavioural constraints hinder albino individuals. Albino animals are rare in the wild; this trait is associated with easy detection by predators, non-native or damaged environments, and exclusively aphotic environments in total darkness. The social aspect of albinism is reported only for human beings, and the effect is distinguis...

In addition to hypopigmentation of the skin and red iris colouration, albino animals also display distinct physiological and behavioural alterations. However, information on the social interactions of albino animals is rare and has mostly been limited to specially bred strains of albino rodents and animals from unique environments in caves. Differe...

Hormonal changes such as increased cortisol level in blood plasma in response to stress and social environmental stimuli are common among vertebrates including humans and typically accompanied by other physiological processes, such as changes in body pigmentation and/or pupil dilatation. The role of pupil size variation (PSV) as a response to stres...

Oculocutaneous albinism is the result of a combination of homozygous recessive mutations that block the synthesis of the tyrosine and melatonin hormones. This disability is associated with physiological limitations, e.g., visual impairment expressed by lower visual acuity and movement perception, and eventually leads to acrophobia and/or photophobi...

In laboratory experiments, variously colored strains of animals, including those with albino phenotypes, are commonly used. The melanocortin theory suggests, however, that coloration phenotypes alter animal physiology and behavior. Animals with the albino phenotype show photoreceptor degradation associated with lowered visual accuracy, escape react...

Differences in brain size among homeothermic vertebrates are known to have important ecological and evolutionary consequences, involving trade-offs between the cognitive benefits of larger brains and the associated energetic costs. Nonetheless, other poikilothermic vertebrate groups have been largely overlooked in this context, challenging the broa...

Parasites can change the behaviour of their hosts, but little attention has been given to the relationship between parasite effects on host behaviour and colouration. The correlation between disrupted melanin production and alterations in various physiological and behavioural traits, e.g., aggression, shoaling behaviour, stress responsiveness and s...

Domestication is a process in which animals are bred in captivity under controlled resource availability. Compared with wild-type phenotypes, animals with domesticated phenotypes exhibit reduced stress sensitivity and cognitive abilities. The pigmentation of domesticated phenotype animals is a morphological change, one of those that is considered a...

This study examined the impact of sertraline, an antidepressant common in treated wastewater, on the hostparasite dynamics between parasitic freshwater mussel (Unio tumidus, Unionidae) larvae (glochidia) and their host fish (Squalius cephalus, Cyprinidae). Employing a full-factorial design, both fish and glochidia were subjected to sertraline at th...

Biological invasions cause huge environmental and socio-economic losses worldwide. Among successful invaders, there are also several decapod crustacean species. In this study, we report the presence of an potentially invasive crab species that damages rice crops in Sumatra, Indonesia. This paddy-field crab Parathelphusa convexa DeMan, 1879 is a fre...

Animal welfare science recognizes fish as sentient beings capable of experiencing pain, stress, and various emotions. As social interactions and mutual relationships are essential for fish welfare, the social environment in aquacultures is important for fish welfare. Pigmentation influences fish social behavior, e.g., communication and/or shoaling...

An active preference for higher temperatures within a physiological optimum is ben -eficial for animal movement. For example, ascending temperatures induce an increasein cyprinid fish metabolism and swimming ability. Spring upstream migrations drivenby the search for resources may be related to these increases. Conversely, down-stream migrations in...

The pet trade is known to be one of the most important pathways of aquatic non-native species introduction and Indonesia is a significant trade partner. Popular ornamental South American river stingrays (Potamotrygon spp.) were introduced to Indonesia in the 1980s and the culture was established. Here we present a detailed Indonesian market and aqu...

Biological invasions are a major component of global change worldwide. But paradoxically, an invasive species might also have threatened populations within its native range. Designing efficient management policies is needed to prevent and mitigate range expansions of invasive alien species (IAS) in non-native areas, while protecting them within the...

Pigmentation is an important factor for the survival of organisms in different environments; in fish, it plays a key role in social communication and shoal formation. Pigmentation mediates communication among colour phenotypes, as fish may temporarily change colouring to indicate their position in a social hierarchy. Although some colour phenotypes...

Methamphetamine (METH) is a concerning drug of abuse that produces strong psychostimulant effects. The use of this substance, along with the insufficient removal in the sewage treatment plants, leads to its occurrence in the environment at low concentrations. In this study, brown trout (Salmo trutta fario) were exposed to 1 μg/L of METH as environm...

Most lotic ecosystems have been heavily modified in recent centuries to serve human needs, for example, by building dams to form reservoirs. However, reservoirs have major impacts on freshwater ecosystem functions and severely affect rheophilic fishes. The aim of this review is to gather evidence that aside from direct habitat size reductions due t...

The excessive worldwide production of plastic materials results in omnipresent microplastic pollution. Scientific studies dealing with the impacts of microplastics on aquatic ecosystems focus mainly on the marine environment, documenting the effect on the functional traits of various organisms. Polystyrene, one of the most commonly used plastics, h...

The African grey bichir Polypterus senegalus is a popular ornamental fish in Indonesia. Pet trade with this species is increasing, and aquaculture production is well established. Here we present a detailed market survey and volume of domestic trade, export and import between January 2018 and February 2021. Climate similarity between the native rang...

Reservoirs interrupt natural riverine continuity, reduce the overall diversity of the environment, and enhance the spread of non-native fish species through suitable environments. Under favourable conditions, invasive species migrate to tributaries to benefit from local resource supplies. However, the changes in physical conditions in reservoirs th...

Animal self-awareness is divided into three levels: bodily, social, and introspective self-awareness. Research has focused mainly on the introspection of so-called higher organisms such as mammals. Herein, we turn our attention to fish and provide opinions on their self-awareness based on a review of the scientific literature. Our specific aims are...

Traces of psychoactive substances have been found in freshwaters globally. Fish are chronically exposed to pollution at low concentrations. The changes of aggressive behaviour of chub (Squalius cephalus) were determined under the exposure to four psychoactive compounds (sertraline, citalopram, tramadol, methamphetamine) at environmentally relevant...

Illicit drug abuse presents pervasive adverse consequences for human societies around the world. Illicit drug consumption also plays an unexpected role in contamination of aquatic ecosystems that receive wastewater discharges. Here, we show that methamphetamine, considered as one of the most important global health threats, causes addiction and beh...

Tramadol is a widely used analgesic with additional antidepressant and anxiolytic effects. This compound has been reported in continental waters reaching concentrations of µg/L as a consequence of its inefficient removal in sewage treatment plants and increasing use over time. In this study, European chubs (Squalius cephalus) were exposed to 1 µg/L...

Farmed fish released in a native environment can display different spawning behaviour compared to their wild conspecifics. In our study, farmed and wild burbot, a species recently introduced for aqua cultural production, were equipped with electromyogram (EMG) radio tags. EMG biotelemetry allows a description of the spatial distribution of fish tog...

Reservoirs are known to alter temperature and flow regimes, shift nutrient cycles, reduce downstream species diversity and enable a predominantly upstream spread of non-native species. However, information about the seasonal dynamics of the spread of non-natives from a reservoir to its tributaries and the further consequences regarding the spatial...

Mirror tests have been used to test aggressiveness because they reduce the variability of the real opponent and allows for repeated measurements. Regular mirrors have also several disadvantages due to the inability to display a head-to-tail position during lateralization. Recently, a method using a non-reversing mirror was developed, which eliminat...

A simple and low-cost method of monitoring and collecting particulate matter detaching from (or interacting with) aquatic animals is described using a novel device based on an airlift pump principle applied to floating cages. The efficiency of the technique in particle collection is demonstrated using polyethylene microspheres interacting with a cy...

Background The aquatic environment has been contaminated with various anthropogenic pollutants, including psychoactive compounds that may alter the physiology and behavior of free-living organisms. The present study focused on the condition and related mortality of the juvenile chub ( Squalius cephalus ). The aim of the study was to test whether th...

Aggressiveness has been one of the behavioral traits most examined with various standard testing methods. We used two distinct methods (the mirror and the real opponent tests) to evaluate individual aggression and relate it to the activity and individual stress of chub (Squalius cephalus L.). Three hypotheses were formulated and tested: (a) there i...

The effect of implanting a Passive Integrated Transponder (PIT) tag on the survival, growth and condition of a small cyprinid, juvenile chub Squalius cephalus (L.) with a mean weight of 2.4 g was studied in the laboratory. During this experiment, which lasted for 31 days, 80 specimens were tagged. The changes in Fulton’s condition factor (K), speci...

Various types of micropollutants, e.g., pharmaceuticals and their metabolites and resistant strains of pathogenic microorganisms, are usually found in hospital wastewaters. The aim of this paper was to study the presence of 74 frequently used pharmaceuticals, legal and illegal drugs, and antibiotic-resistant bacteria in 5 hospital wastewaters in Sl...

The introduction of non-native species and human-altered habitats are currently the main threats to freshwater ecosystems. Due to predation and competition, biological invaders can cause extinctions and imperil the status of native species, and this phenomenon is enhanced by habitat alteration, for example, dam construction. In addition to river fr...

The home range (HR) of wild animals increases with individual body size and is smaller in high density populations in productive areas. If sufficient resources are available, animals often display sedentary behavior. The return and reuse of an environment by individuals is frequently termed “site fidelity”. Smaller HR size and high site fidelity ha...

Parasites alter their host behaviour and vice versa as a result of mutual adaptations in the evolutionary arms race. One of these adaptations involves changes in host thermoregulation, which has the potential to harm the parasite and thereby act as a defence mechanism. We used a model of the brown trout (Salmo trutta) experimentally parasitised wit...

The extreme body sizes of megafishes associated with their high commercial values and recreational interests have made them highly threatened in their native range worldwide by human-induced impacts such as overexploitation. Meanwhile, some megafishes have been introduced outside of their native range. A notable example is the European catfish (Sil...

Barriers represent one of the largest anthropogenic impacts on the ecological status of rivers, and they also potentially restrict fishes' ability to respond to future environmental changes. Thus, river management aims to restore the longitudinal connectivity of rivers to allow continuous migration and movement of water, sediments and biota. Howeve...

The future distribution of river fishes will be jointly affected by climate and land use changes forcing species to move in space. However, little is known if fish species will be able to keep pace with predicted climate and land use-driven habitat shifts, in particular in fragmented river networks. In this study, we coupled species distribution mo...

Direct and potentially damaging effects of invasive alien species can remain unnoticed or insufficiently quantified, resulting in a lack of stakeholder awareness. We report for the first time that parasitic larvae (glochidia) of the invasive freshwater mussel Sinanodonta (Anodonta) woodiana (Unionidae, Bivalvia) cause an unexpected reduction in the...

1. The effects of invasive alien species (IAS) on host-affiliate relationships are often subtle and remain unnoticed or insufficiently quantified. The global decline of freshwater unionid mussel species has been attributed to many causes, but little is known about the interactions of IAS, with their complex life cycle, which includes an obligatory...

The movement of individuals within preferred areas is reduced by a high availability of food and information about its distribution, while high number of competitors promotes increased movement. Experienced animals use information about social and physical environment to improve resources exploitation, tended to maintain positions within the prefer...

Parasitization by the larvae (glochidia) of freshwater mussels can cause harm to a fish's gills, resulting in less effective respiration and/or reduced activity by the host fish. The impact of glochidia infections on the host's physiology remains poorly understood, and no information is available concerning energy consumption in parasitized fish. H...

Quantifying patterns of prey resource use is fundamental to identify mechanisms enabling the coexistence of related fish species. Trophic interactions between the native brown trout, Salmo trutta, and the introduced brook trout, Salvelinus fontinalis, were studied monthly from May to October in three mountain streams in Central Europe (Czech Republ...

A telemetry study analysing the diel and seasonal behaviour of asp was performed weekly in the Elbe River, Czech Republic, over 12 months. Asp diel movements and home range size varied across seasons, reaching maxima in summer and autumn with diurnal and/or crepuscular peaks of activity. On the contrary, no peaks of activity occurred during spring...

Dualism in activity has been described in many fish species, including larger individuals of European catfish (Silurus glanis), which are able to switch their activities from nocturnal to diurnal in winter and spring. During the multi-year telemetry study, seasonal changes in diel activity of 45 juvenile European catfish were investigated. These ju...

Raw data for GENMOD procedures to estimate the probability of occurrence of agonistic behaviours (chasing, and lateral displays) across the duration of the experiment

Raw data for the analysis of total aggression and duration

Raw data for the analysis of duration of time that conspecifics spent at mutual distances across albino and pigmented treatments

River ecosystems are threatened by future changes in land use and climatic conditions. However, little is known of the influence of interactions of these two dominant global drivers of change on ecosystems. Does the interaction amplify (synergism) or buffer (antagonism) the impacts and does their interaction effect differ in magnitude, direction an...

When animals compete for resources, their competitive abilities and behavioural strategies can be expressed as changes in movement activity. Stress is an important predictor of activity, and the variability of this predictor reflects the impact of environmental and social factors, while the effects of stress are further influenced through individua...

This study focuses on the mechanism of density-dependent growth in a stream-dwelling landlocked population of brown trout Salmo trutta. Specifically, body growth estimated by scale reading was examined in relation to population density and recapture rate (approximation of persistence of individuals within a location associated with dispersal and mo...

Juvenile wild and hatchery-reared European grayling Thymallus thymallus were tagged with radio-transmitters and tracked in the Blanice River, River Elbe catchment, Czech Republic, to study their behavioural response to stocking and environmental variation. Both wild and hatchery-reared T. thymallus increased their diel movements and home range with...

A demogenetic analysis based on 7 years of observation (2005–2011) was conducted to examine the population structure of brown trout Salmo trutta in pristine dendritic head-waters. The value of genetic divergence (F ST) among sampling units ranged from À0.03 to 0.16. Demographic syn-chrony was low or moderate, and the average correlation coefficient...

This methodology is intended for managers of watercourses, government agencies and investors aiming to help them to assess the influence of water management constructions and other artificial fish migration barriers on freshwater ecosystems. The method is mainly focused on the evaluation of restoration actions especially fish passes. The present me...

Animals use dispersed resources within their home range (HR) during regular day-to-day activities. The high-quality area intensively used by an individual, where critical resources are concentrated, has been designated as the core area (CA). This study aimed to describe how animals utilize energy in the HR and CA assuming that changes would occur a...

In this study, we validated a scale-reading method estimating age and growth in brown trout Salmo trutta in wild, landlocked, stream-dwelling populations from mountain headwaters in the Elbe catchment area of the Czech Republic. The values estimated from scale reading were compared with measured values, collected using a mark-recapture program over...

Parasitic species can affect host behaviour in various ways. Freshwater mussels of the superfamily U nionoidea have a glochidia larva that is parasitic on fish. Our aim was to evaluate whether fish exposed to glochidia have distinct behaviour that could affect the upstream dispersal of the parasite. Many freshwater mussels are highly endangered, an...

In this study, we validated a scale-reading method estimating age and growth in brown trout Salmo trutta in wild, landlocked, stream-dwelling populations from mountain headwaters in the Elbe catchment area of the Czech Republic. The values estimated from scale reading were compared with measured values, collected using a mark-recapture program over...

The aim of this study was to test young-of-the-year (YOY) assemblage applicability for the ecological quality assessment on the basis of samples from 55 sites scattered across the entire Czech Republic. European Fish Index (EFI) values estimated with YOY and adults were positively correlated, indicating that YOY and adult sampling is comparable. YO...

The majority of stream-dwelling salmonid populations in Europe are affected by artificial stocking and the fragmentation of riverine ecosystems. The present study was performed in the unique pristine headwaters of the Otava River in the Elbe catchment area of the Czech Republic. The aim was to investigate the spatial distribution and individual gro...

Within aquaculture systems, shelters are often used to reduce cannibalism, minimise energy consumption, accelerate the start of exogenous feeding, support growth, and improve survival and welfare. However, stronger competition for shelters in aquaculture systems relative to that under wild conditions may result in a higher level of aggressiveness a...

Twenty individuals of the largest European freshwater predator, the European catfish Silurus glanis, were tagged with electromyogram (EMG) physiological telemetry sensors. The fish were observed during diel cycles during the spring and summer in the Elbe and Berounka Rivers, Czech Republic. The purpose of this study was to determine whether diel du...

River obstacles are recognised as being among the serious ecological concerns, having negative effects on biodiversity and ecosystem functions. They have been shown to affect fish community structure, which represents a fundamental component of the biological integrity of riverine ecosystems. However, a general quantitative relationship that links...

The Ponto-Caspian invader Hemimysis anomala was studied in the river Elbe, Czech Republic. The study confirmed further spread of the species: the presence of juveniles and gravid females indicated that H. anomala is established within the Elbe River. Bottom, mid-water and surface drift samples were collected during 24-h cycles from July to Septembe...

The relative performance of European grayling Thymallus thymallus reared in a hatchery on commercial dry feed or in a pond with natural food and their wild conspecifics, was assessed through recapture of tagged fish 5 months after their release into the Blanice River, Czech Republic. One-year old pond and hatchery reared fish from a resident broods...

The spawning migrations of 123 brown trout Salmo trutta were studied in six highland streams in the Elbe River catchment area, Czech Republic, in central Europe. Trout were observed by using radiotelemetry from August to November in headwater stretches isolated by artificial obstacles without fish ladders. The length of isolated headwater stretches...

Several freshwater mussel species represent some of the most problematic invasive species and have considerably altered ecosystems worldwide. Their invasion potential has been partially attributed to their free-living larvae, which have a high dispersal capability. We investigated the invasion potential of Anodonta (Sinanodonta) woodiana, a species...

The effect of water temperature and flow on the migration of fish was observed using weekly inspections of a fishpass on the lowland section of the River Elbe (Strekov, Czech Republic) from spring to fall 2003 and 2004. The effect was examined separately for immature (up to 2 years old) and adult fish and also the most abundant species (roach Rutil...

In aquaculture, fish grading is usually used to balance the resource availability for conspecifics in a stock. As a result, the social hierarchy does not limit the growth of fish in a size-homogeneous stock. However, grading also leads to the interaction of individuals without any previous contact. The interaction of these unfamiliar individuals is...

Hatchery-reared adult brown trout, Salmo trutta v. fario L., [215–335 mm standard length (LS), n = 82] were individually tagged and released into three sections of the Blanice River in May 2007. Wild populations of brown trout and grayling, Thymallus thymallus, L., in these sections and three non-stocked control sections were also tagged. The recap...

Recently, the brown trout (Salmo trutta f. fario) has been reported to be the only available native host species for the complete metamorphosis of the critically endangered freshwater mollusc pearl mussel (Margaritifera margaritifera L.) in Central Europe. Pearl mussel glochidia invade host fish in late summer, at the beginning of spawning migratio...

The Czech Republic has experienced a number of inter- and intra-continental introductions (42 introduced species total), with 29 species historically confirmed and 20 species still present in the wild. Fourteen species have become established, representing 27% of the current fish fauna. Pond aquaculture and recreational fisheries are the two major...

The EU’s Water Framework Directive (WFD) in particular makes good use of riverine biota—including fish—as ecological indicators of river integrity. However, it is also important to examine when our indicators fail to serve the purpose for which they were originally intended: to consistently and reliably describe the quality of the environment. We a...

The growth, and dispersal of stocked European grayling Thymallus thymallus, reared in a hatchery (fed dry food pellets) or in a pond (fed natural food), compared with their wild conspecifics was assessed from the recapture of individually tagged fish 168 days after their release into the Blanice River, Czech Republic. Recapture rates and site fidel...

Abstract – Electromyogram (EMG) biotelemetry allows a description of the spatial distribution of fish together with a simultaneous measurement of individual energy consumption. Using this technique, we observed behaviour of the largest European freshwater predator, Silurus glanis, in the Elbe River, Central Europe. In total, 52 diurnal cycles and 1...