Milan Říha

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Verified

Milan verified their affiliation via an institutional email.

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• PhD
• Reasercher at Czech Academy of Sciences, Biology Centre

The availability and spatial distribution of prey determine the energetic costs of predators foraging and largely drive their space use, activity level and foraging timing. Consequently, predators in ecosystems with different prey availability and distribution should adjust their movement patterns to optimise their foraging success in order to maxi...

Fish are an important component of aquatic ecosystems, thus representative and reliable assessments of their population variables are essential for a variety of ecological applications, management and conservation. Determining Fish Density per actual Spatial Unit (volume or area, FDSU) as a measure of absolute fish quantity is of particular interes...

To understand the spatiotemporal overlap in the habitat use of sympatric predators, we studied longitudinal activity and reservoir section and depth use of pike (Esox lucius), pikeperch (Sander lucioperca) and catfish (Silurus glanis) in the Římov Reservoir, using an autonomous telemetry system for 11 months. We found significant differences among...

Understanding animal movement is essential to elucidate how animals interact, survive, and thrive in a changing world. Recent technological advances in data collection and management have transformed our understanding of animal “movement ecology” (the integrated study of organismal movement), creating a big-data discipline that benefits from rapid,...

The common carp (Cyprinus carpio) is an important species in global aquaculture. To optimize its production, it is necessary to understand its behaviour in relation to environmental and management factors. This study investigated the spatial and temporal dynamics of carp behaviour in a semi-intensive aquaculture pond under controlled feeding regime...

Animals move in three spatial dimensions, but many animal movement tools have only focused on the use of 2D coordinates for modelling space use, habitat selection, behavioural classification, social interactions and movement. Here, we submit that many common movement ecology analyses can and should be extended to consider all three spatial dimensio...

Pikeperch ( Sander Lucioperca ) belongs to main predatory fish species in freshwater bodies throughout Europe playing the key role by reducing planktivorous fish abundance. Two size classes of the young‐of‐the‐year (YOY) pikeperch are known in Europe and North America. Our long‐term fish survey elucidates late‐summer size distribution of YOY pikepe...

Gillnets are widely used in research and commercial fishery activities. As passive gear, gillnets can be selective and dependent on the diel migration of fish. In areas with limited littoral extent, inshore–offshore migration may cause bias in the gillnet catch. Our hypothesis was that some factors, such as gillnet saturation, fish depletion, or ch...

The availability and spatial distribution of prey determines the energetic costs of predators foraging and largely drives their space use, activity level and foraging timing. Consequently, predators in ecosystems with different prey availability and distribution should adjust their movement patterns to optimise their foraging success in order to ma...

Understanding inter-annual variation in the density of young-of-the-year fish is an important tool for assessing stock status and guiding management decisions. We analyzed data spanning from 2003 to 2022 collected at Lipno Reservoir in Czechia. The study aimed to identify factors influencing the density of pikeperch (Sander lucioperca), a valuable...

Acoustic telemetry (AT) has emerged as a valuable tool for monitoring aquatic animals in both European inland and marine waters over the past two decades. The European Tracking Network (ETN) initiative has played a pivotal role in promoting collaboration among AT researchers in Europe and has led to a significant increase in the number of tagged an...

Despite great promise for understanding the impacts and extent of climate change and extreme weather events on aquatic animals, their species, and ecological communities, it is surprising that electronic tagging and tracking tools, like biotelemetry and biologging, have not been extensively used to understand climate change or develop and evaluate...

Biogeochemical fluxes and water masses transport in thermally stratified lakes are often dominated by internal waves. These phenomena are triggered by baroclinic forces generated by the interaction of wind-driven flows and temperature variation along the water column. Although this mechanism is well documented, the complexity of the mathematical to...

Geolocating aquatic animals with acoustic tags has been ongoing for decades, relying on the detection of acoustic signals at multiple receivers with known positions to calculate a 2D or 3D position, and ultimately recreate the path of an aquatic animal from detections at fixed stations. This method of underwater geolocation is evolving with new sof...

Global climate change has been altering freshwater ecosystems by impacting many ecological processes, including individual fish growth. Predictions of responses of local fish populations to future environmental change can draw inferences from past long-term biochronological data. In this study, we reconstructed individual growth pattern of one of t...

Freshwater protected areas are designated parts of the inland waters that restrict human activities. They were created as a mechanism to combat the decline of fauna and flora of the world. Some authors have questioned their actual effectiveness in terms of the purpose of protecting endangered fauna and flora. We conducted an experiment in Lipno res...

Hydric recultivation—flooding of abandoned mining pits—creates a completely new, underexplored habitat for a wide range of aquatic organisms. Periphyton, dominated by algae and cyanobacteria, is frequently a key component of newly established aquatic ecosystems. Periphyton and its response to abiotic factors were studied in the littoral zone of thr...

Hydric recultivation—flooding of abandoned mining pits—creates a completely new, underexplored habitat for a wide range of aquatic organisms. Periphyton, dominated by algae and cyanobacteria, is frequently a key component of newly established aquatic ecosystems. Periphyton and its response to abiotic factors were studied in the littoral zone of thr...

Anthropogenic activities continue to pose the greatest challenges to freshwater ecosystems. Therefore, long-term monitoring is essential for the management and conservation of these resources. Monitoring programs for freshwater bodies often use a range of indicators, including biological elements such as fish. Existing European standard provides a...

To examine the suitability of fish scales as potential tracers of nutrient pollution, we analysed the nitrogen and carbon stable isotope values (δ15N and δ13C) in scales of a generalist fish species, roach Rutilus rutilus, collected from 22 Czech reservoirs covering wide gradients of catchment land use and nutrient enrichment. Using generalised add...

Ligula intestinalis (Linnaeus, 1758) is a tapeworm parasite with a worldwide distribution that uses a wide variety of fish species as its second intermediate host. In the present study, we investigated the prevalence and population genetic structure of plerocercoids of L. intestinalis in five common cyprinoid species, roach Rutilus rutilus (Linnaeu...

The book contains the overview and the description of the methods for the monitoring of qualitative and quantitative composition of the fish stock of lakes and reservoirs. It gives thorough description of the fieldwork and primary processing of information collected. Template field protocols to accompany every sample are attached. Use of multi-mesh...

Gillnetting is a technique commonly used in relative abundance and biomass estimates of fish. However, due to its passive nature, the direct recalculation of the catch to reservoir volume or area is not trivial. This issue is often solved by using hydroacoustics, which provides information about fish density, though without the ability to distingui...

It is difficult to understand the composition and diversity of biological communities in complex and heterogeneous environments using traditional sampling methods. Recently, developments in environmental DNA metabarcoding have emerged as a powerful, non-invasive method for comprehensive community characterization and biodiversity monitoring in diff...

Internal seiches are common in stratified lakes, with significant effects on stratification patterns, hydrodynamics and vertical nutrient transport. In particular, seiches can change the vertical distribution of the thermocline and the cold hypolimnetic and warm epilimnetic water masses by several metres on a timescale of a few hours, leading to ra...

Many fish species exhibit female-biased size dimorphism that may lead to spatial segregation of sexes. We selected two common European percids (Percidae, European perch Perca fluviatilis and ruffe Gymnocephalus cernua) differing in total body size, reproduction mode, habitat use and diurnal activity, to test whether they display size dimorphism and...

Models of animal distribution predict dispersion of animals over their environment and are an important aspect of theoretical ecology. In this article, we focus on fitness-based distribution models of individual animals (DM) that also incorporate species interactions and the effect of distribution on ecosystem processes. These models have evolved f...

To understand the conditions of coexistence in multiple-species predator community, we studied longitudinal and vertical movement of pike (Esox lucius), pikeperch (Sander lucioperca) and catfish (Silurus glanis) in the Rimov Reservoir, using an autonomous telemetry system for 11 months. We found significant differences among these three species in...

Fish communities differ significantly between the littoral and the pelagic habitats. This paper attempts to define the shift in communities between the two habitats based on the European standard gillnet catch. We sampled the benthic and pelagic habitats from shore to shore in Lake Most and Římov Reservoir (Czech Republic). The 3 m deep pelagic net...

Epilithon contributes to phosphorus (P) cycling in lakes, but its P uptake traits have been rarely studied. We measured the chemical composition of epilithon and its inorganic P uptake kinetics using isotope ³³ P in three deep oligo- to mesotrophic post-mining lakes in April, July, and October 2019. Over the sampling period, epilithon biomass doubl...

Structural complexity is known to influence prey behaviour, mortality and population structure, but the effects on predators have received less attention. We tested whether contrasting structural complexity in two newly colonised lakes (low structural complexity lake—LSC; high structural complexity—HSC) was associated with contrasting behaviour in...

Internal seiches are common in stratified lakes, with significant effects on stratification patterns, hydrodynamics and vertical nutrient transport. In particular, seiche can change the vertical distribution of the thermocline and the cold hypolimnetic and warm epilimnetic water masses by several meters on a timescale of a few hours. The results ar...

Obtaining a representative sample is fundamental to the assessment of fish communities. In this study we used data from 99 different surveys of 29 artificial lakes in the Czech Republic to evaluate the precision of fish community indicator estimates based on reduced gillnet scenarios derived from triplet gillnets installed in each particular locali...

Movement ecology is increasingly relying on experimental approaches and hypothesis testing to reveal how, when, where, why, and which animals move. Movement of megafauna is inherently interesting but many of the fundamental questions of movement ecology can be efficiently tested in study systems with high degrees of control. Lakes can be seen as mi...

Succession of submerged vegetation was monitored from the early stages for a period of 10 years by Self‐Contained Underwater Breathing Apparatus (SCUBA) divers in Milada Lake. Milada Lake is the result of a flooded surface coal mine, the first large‐scale hydrological recultivation in the Czech Republic. The main focus was on apparent changes in th...

Information about fish distribution and abundance in the upper part of the water column are often fundamental for both research and management. However, this information is extremely hard to obtain using conventional hydroacoustic methods. For this reason, the mobile hydroacoustic upward-looking system (38 kHz split-beam echosounder) in combination...

Epilithon contributes to phosphorus (P) cycling in lakes, but its P uptake traits have been rarely studied. We measured the chemical composition of epilithon and its inorganic P uptake kinetics using isotope 33P in three deep oligo- to mesotrophic post-mining lakes in April, July, and October 2019. Over the sampling period, epilithon biomass double...

Structural complexity is known to influence prey behaviour, mortality and population structure, but the effects on predators has received less attention. We tested whether contrasting structural complexity in two newly colonised lakes (low structural complexity lake – LSC; high structural complexity - HSC) was associated with contrasting behaviour...

Using archived fish scale samples together with long-term monitoring data, this study investigates the potential of fish scales to record historical changes in the aquatic environment. We analysed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in the scales of two planktivorous cyprinid species collected from the meso-eutrophic Římov Reservoir,...

Repeat spawners constitute an important component of Atlantic salmon populations, but survival of post-spawning individuals (kelts) are often compromised by anthropogenic structures such as hydropower plants (HPPs). Potential effects of HPPs include migration delays and associated increased energy depletion, which potentially results in increased o...

Temporal and spatial heterogeneity in the distribution of cladocerans in lakes could be caused by abiotic (wind, water currents) and biotic factors (reproduction, food resources, predation). Diel horizontal and vertical distribution of cladoceran assemblages was studied in two deep lakes (Milada and Most Lakes, Czech Republic) in early (June) and l...

Fish otoliths are conservative structures that are widely used on fishery science for multiple purposes. Despite its relevance in the research field, little is known about the ontogeny and inter-population effects on the otolith of freshwater fish. In this study we used otoliths from 1800 European perch (Perca fluviatilis) individuals from 9 differ...

Wildlife monitoring using passive telemetry has become a robust method for investigating animal migration. With increased use, this method progressively pollutes the environment with technological waste represented by so called ghost tags (PIT tags ending in the environment due to reproductive expulsions, shedding or animal mortality). However, the...

Fish respond to predation threat by size/cohort-dependent presence in particular habitats and this may contribute to sexual segregation between habitats in species with sexual size dimorphism (SSD). The present study examines the validity of the “predation risk hypothesis” and importance of SSD on habitat (pelagic/inshore) segregation and dietary d...

The higher proportion of males of the invasive round goby Neogobius melanostomus in samples from two activity selective passive fishing gears compared with one activity non‐selective fishing gear in three Dutch lakes is related to higher male locomotory activity and is a sex‐dependent trait. This difference in activity reflects the different ecolog...

Spatial distribution of young-of-the-year (YOY) and older roach, rudd, perch and ruffe was compared in two artificial lakes with macrophytes present and absent, and a valley reservoir, using gillnets. Almost all species of interest and both age categories preferred benthic habitats. The depth distribution in benthic habitats was relatively consiste...

We investigated the change in benthic fish communities in three artificial lakes of the Biesbosch area in the Netherlands between two time periods: before and after the invasion of round goby (Neogobius melanostomus). Native ruffe (Gymnocephalus cernua), the dominant species in benthic gillnet and littoral beach seining catches before the invasion,...

Sampling of benthic fish is complicated, especially in deep inland water bodies with a structured bottom. The catches were compared of rapidly spreading round goby (Neogobius melanostomus) using small fykes nets and benthic gillnets in three artificial lakes in The Netherlands over a two year period. Round gobies were captured at all depth layers i...

Differential use of habitat and prey resources is an important mechanism that may allow coexistence of sympatric species. Unlike interactions between smaller cyprinid and percid fishes, the resource use by coexisting predatory asp (Leuciscus aspius) and pikeperch (Sander lucioperca) is relatively unknown. Here, gut content and stable isotope analys...

A novel sampling scheme, using a combination of electrofishing, visual exploration by scuba divers, two types of fyke nets and longlines, was tested in four reservoirs (including their inlets and outlets) to monitor a population of burbot Lota lota. This was supplemented by fry trawling and vertical hydro‐acoustics, to detect L. lota larvae in two...

Supplementary Table (Appendix S1) and Figures (Appendixes S2 - S5) to the paper written by Sajdlová et al. (2018) - Freshwater Biology.

1. Diel vertical migrations (DVMs) belong among the most pronounced movements in the aquatic environment. A general pattern of DVMs has been well described, particularly in European perch (Perca fluviatilis), but whether the migrations are directly controlled by light and what is the ultimate cause of the diel vertical shifts, remains poorly unders...

The condition and feeding behaviour of burbot, a widespread potamodromous species in riverine and lacustrine environments, were compared in order to evaluate the importance of both in three artificial systems. Subadult burbot were sampled in three temperate reservoirs in spring, and one of them also in summer and autumn. Standardised abundance and...

The European Water Framework Directive (WFD) requires the national classifications of good ecological status to be harmonised through an intercalibration exercise. In this exercise, significant differences in status classification among Member States are harmonized by comparing and, if necessary, adjusting the good status boundaries of the national...

Oligotrophication of Lake Ontario has led to increased water clarity and an increased proportion of zooplankton residing in the metalimnion during the day, which may affect the utilization of different depth regions for planktivorous fish. We investigated day and night distributions of fish using hydroacoustics and suspended vertical gillnets durin...

Monitoring of biota in heterogeneous ecosystems requires sampling in different habitats and across environmental gradients. The resulting multivariate community data are typically aggregated into one or several indicator values for the entire ecosystem, but the relationship between the robustness of such indicators and sampling effort, including th...

The European Water Framework Directive (WFD) requires the national classifications of good ecological status to be harmonised through an intercalibration exercise. In this exercise, significant differences in status classification among Member States are harmonized by comparing and, if necessary, adjusting the good status boundaries of the national...

The European Water Framework Directive (WFD) requires the national classifications of good ecological status to be harmonised through an intercalibration exercise. In this exercise, significant differences in status classification among Member States are harmonized by comparing and, if necessary, adjusting the good status boundaries of the national...

The assessment of ecological quality in freshwater ecosystems is a key issue in many countries, but conditions for the development of assessment methodologies are often country-specific. This study proposes a simple methodology for the assessment of the ecological potential of reservoirs based on fish communities using a dataset covering major envi...

Sexual dimorphism is common across the animal kingdom, but the contribution of environmental factors shaping differences between the sexes remains controversial. In ectotherms, life-history traits are known to correlate with latitude, but sex-specific responses are not well understood. We analyzed life-history trait variation between the sexes of E...

Freshwater reservoirs are water bodies of special interest, as they provide various ecosystem services such as the supply of drinking water, agricultural irrigation, industrial and cooling water supplies, power generation, flood control and recreation. Reservoirs share many features with natural lakes but differ from them in several important aspec...

Piscivory in cyprinids (Cyprinidae) is extremely rare. Specifically, common bream (Abramis brama) and common carp (Cyprinus carpio) are zooplanktivorous fish in deep lentic waters. Nevertheless, we observed predation by these two cyprinids under natural conditions in the Vír Reservoir, Czech Republic. We conducted diet analysis for cyprinids caught...

Data file. Spreadsheet containing basic data required to reproduce the analyses, figures and table presented in the manuscript. (XLS)

Perch (Perca fluviatilis, L.) is usually believed to spawn in a shallow water of rivers, lakes and reservoirs where majority of egg strands is deposited to a maximum depth of 2 m. We studied the depth distribution of egg strands of perch in Chabařovice Lake, Czech Republic, in spring 2007, 2008, 2009, 2010 and 2012 (Fig. 1). In total, three SCUBA...

Ecological quality assessment of non-natural water bodies is, in contrast to natural systems, less developed and requires determining biological indicators that reliably reflect environmental conditions and anthropogenic pressures. This study was motivated to propose fish indicators appropriate for assessment of reservoir ecosystems in central Euro...

Juvenile perch ( Perca fluviatilis ) often inhabit deep zones of lakes or reservoirs (metalimnion to hypolimnion). Using fry trawling and hydroacoustic measurements, we studied perch distribution to determine if juveniles are using deep hypoxic waters (oxygen concentration ≤3.5 mg L ⁻¹ ) as a refuge from predation. We found a heterogeneous depth di...

This study addresses fish behaviour at the mouth of a midwater trawl in two temperate reservoirs. Fish distribution and behaviour were monitored using a SIMRAD EK60 (38. kHz) split-beam echosounder with the transducer deployed at the water surface, attached to the surface trawl headrope. We were able to describe day and night patterns of vertical d...

Fish recruitment in riverine reservoirs is not fully understood because the long-term data series required for standard stock-recruitment models are often lacking. In this study, two unrelated piscivorous species with different ecologies, asp (Leuciscus aspius) and pikeperch (Sander lucioperca), were investigated over a 14-year period in a reservoi...

Data from nine reservoirs in the Czech Republic were used to investigate density and size distribution patterns for dominant fish species of the juvenile pelagic community at night. Clear trends of increasing density along the longitudinal gradient for bream, roach, bleak, and pikeperch were observed in long (>5 km) reservoirs but were absent in sh...

The European Standard EN 14757 recommends gillnet mesh sizes that range from 5 to 55mm (knot-to-knot) for the standard monitoring of fish assemblages and suggests adding gillnets with larger mesh sizes if necessary. Our research showed that the recommended range of mesh sizes did not provide a representative picture of fish sizes for larger species...

The following information is missing from the Funding section: This study received institutional support from the Czech Academy of Sciences (RVO:60077344, http://www.avcr.cz/) and the CEKOPOT project (CZ.1.07/2.3.00/20.0204), co-financed by the European Social Fund and the state budget of the Czech Republic. Additionally, this study was supported b...

We investigated diel habitat use of fish covering the littoral and pelagic zones of the Římov Reservoir (Czech Republic) and analyzed the influence of predator presence and of shifting feeding habitats in all dominant species and age groups. Our sampling revealed distinctive diel changes of fish distribution in the reservoir, which were age- and sp...

The European Standard EN 14757 (“Water quality – sampling of fish with multimesh gillnets”, 2005) recommends gillnet mesh sizes that range from 5 to 55 mm (knot-to-knot) for standard monitoring of fish assemblages and suggests adding gillnets with larger mesh sizes if necessary. Our research showed that the recommended range does not provide a repr...

Disruptions to the forage base in Lakes Huron and Michigan have had drastic effects on salmon fisheries. Despite similarities between these systems and Lake Ontario, patterns in population metrics observed in these lakes for alewife Alosa pseudoharengus, the dominant forage species, are not apparent for Lake Ontario. Alewife age- and size-structure...

Fish associations with different types of littoral habitats were studied in four canyon-shaped reservoirs in the Czech Republic in years 2010 and 2011 by gillnets. Two to three habitats per reservoir–beaches (former meadows), stump fields (former forest) and rubble slopes–were defined and sampled along the longitudinal axis of reservoirs. Effects o...

Large year-to-year variability in different fish species recruitment has been confirmed by previous studies while diurnal patterns of occupation in two basic reservoir habitats (pelagic and littoral) by different age-0 fish species in late summer are still unclear. Data collected over an 11-year period regarding late-summer age-0 fish assemblages i...

Fish avoidance behaviour in the trawl mouth at night was investigated in the extremely shallow and turbid Lake Neusiedl in Austria. To evaluate fish reactions, a fixed frame benthic trawl with three electricity modes (without electricity, with continuous electricity and with interrupted electricity) was used and the captured fish abundances, biomas...

Environmental gradients influence the distribution and taxonomic composition of planktonic taxa, including Daphnia. In canyon-shaped reservoirs with pronounced horizontal gradients of food supply, predation pressure and other factors, not only species and interspecific hybrids but also clones within these taxa are non-randomly distributed. Using a...

The diel horizontal migration (DHM) of fish between the inshore and offshore zones of the Římov Reservoir (Czech Republic, deep, stratified, meso-eutrophic) was investigated by a combination of horizontal and vertical hydroacoustic surveys at 3-h intervals over 48 h and day/night purse seining in August 2007. An overwhelming majority of fish were a...

This study investigated the post-spawning dispersal of seven species occurring in a tributary of the Římov Reservoir during the years 2000-2004. Fish were captured during spawning migration to the tributary, marked and released. The subsequent distribution of marked fish was followed in the reservoir and tributary during three successive periods 1)...