Dominance and size affect foraging position choice by Arctic grayling (Thymallus arcticus).

Salmonid fishes are a widespread and economically important group of fishes that are strongly affected by anthropogenic environmental degradation. Consequently, studies on their behavior and ecology are essential for their conservation. Wild Arctic grayling (Thymallus arcticus) were observed in an unimpacted Alaskan river using underwater video observations for two consecutive summers (2015 and 2016).

Long-lines for research monitoring and efficient population regulation of an invasive apex predator, European catfish ().

European catfish is a large-bodied apex predator, a key species in native areas, but invasive in others where it negatively impacts local aquatic fauna necessitates catfish regulation. However, traditional ichthyological methods face challenges in capturing it. The study presents a detailed description of the efficient long-line method, refined through 48 sampling campaigns across twelve European water bodies.

A non-lethal stable isotope analysis of valued freshwater predatory fish using blood and fin tissues as alternatives to muscle tissue.

Stable isotope analysis (SIA) is widely used to study trophic ecology and food webs in aquatic ecosystems. In the case of fish, muscle tissue is generally preferred for SIA, and the method is lethal in most cases. We tested whether blood and fin clips can be used as non-lethal alternatives to muscle tissue for examining the isotopic composition of two freshwater predatory fish, European catfish (Silurus glanis) and Northern pike (Esox lucius), species of high value for many freshwater systems as well as invasive species in many others.

Trophic Position of the Species and Site Trophic State Affect Diet Niche and Individual Specialization: From Apex Predator to Herbivore.

Intra-species variability in isotopic niches, specifically isotopic total niche width (ITNW), isotopic individual niche width (IINW), and isotopic individual specialization (IIS), was studied using an innovative approach without sacrificing the vertebrates. Stable isotopes (C, N) in four body tissues differing in isotopic half-life were analyzed from four freshwater fish species representing different trophic positions. ITNW was widest for the apex predator (European catfish) and narrowest for the obligate predator (Northern pike).

Standalone Sensors System for Real-Time Monitoring of Cutting Emulsion Properties with Adaptive Integration in Machine Tool Operation.

This paper presents a novel cutting fluid monitoring sensor system and a description of an algorithm framework to monitor the state of the cutting emulsion in the machine tool sump. One of the most frequently used coolants in metal machining is cutting emulsion. Contamination and gradual degradation of the fluid is a common occurrence, and unless certain maintenance steps are undertaken, the fluid needs to be completely replaced, which is both un-economical and non-ecological.

A comparative study of three fishery methods for sampling the invasive topmouth gudgeon (Pseudorasbora parva) in ponds.

Invasive fish threaten ponds' ecological status and their ecosystem services, therefore obtaining a representative sample of fish community composition is fundamental to fishery management, research and nature conservation. Estimates of the size distribution, density and biomass of the topmouth gudgeon (Pseudorasbora parva) model species of invasive fish in three ponds were compared among three sampling methods: electrofishing, fish-trapping and throw-netting. The study illustrates that the invasive fish, P.

Fish scale stable isotopes as potential indicators of nutrient pollution: Exploring the response of roach (Rutilus rutilus) scale δN and δC to a gradient of land use disturbance.

To examine the suitability of fish scales as potential tracers of nutrient pollution, we analysed the nitrogen and carbon stable isotope values (δN and δC) 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 additive mixed models in the first step and generalised linear mixed models in the second step, we evaluated the response of roach scale stable isotope values to catchment land use variables (percentage of agricultural land and human population density) and in-reservoir water quality variables. Roach scale δN values varied by 15 ‰ among the reservoirs and were strongly, linearly, and positively associated with the percentage of agricultural land in the reservoir catchments, pointing to agriculture as the dominant source of nitrogen pollution in the investigated systems.

Different hosts in different lakes: prevalence and population genetic structure of plerocercoids of Ligula intestinalis (Cestoda) in Czech water bodies.

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 (Linnaeus), freshwater bream Abramis brama (Linnaeus), white bream Blicca bjoerkna (Linnaeus), bleak Alburnus alburnus (Linnaeus), and rudd Scardinius erythrophthalmus (Linnaeus), collected in six water bodies of the Czech Republic (Milada, Most, Medard, Jordán, Římov and Lipno).

Application of ANN for Analysis of Hole Accuracy and Drilling Temperature When Drilling CFRP/Ti Alloy Stacks.

Drilling of Carbon Fiber-Reinforced Plastic/Titanium alloy (CFRP/Ti) stacks represents one of the most widely used machining methods for making holes to fasten assemblies in civil aircraft. However, poor machinability of CFRP/Ti stacks in combination with the inhomogeneous behavior of CFRP and Ti alloy face manufacturing and scientific community with a problem of defining significant factors and conditions for ensuring hole quality in the CFRP/Ti alloy stacks. Herein, we investigate the effects of drilling parameters on drilling temperature and hole quality in CFRP/Ti alloy stacks by applying an artificial neuron network (ANN).

The Influence of Cutting Parameters on Plastic Deformation and Chip Compression during the Turning of C45 Medium Carbon Steel and 62SiMnCr4 Tool Steel.

The paper deals with the issue of cutting zone and chip compression. The aim was to analyse the microstructure transverse section of the cutting zone on a metallographic cut, due to determined values of chip compression and plastic deformation, which affect the cutting process efficiency. The tested cutting tool material was coated with cemented carbide.

Contrasting structural complexity differentiate hunting strategy in an ambush apex predator.

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 an aquatic apex predator, Northern pike (Esox lucius; hereafter pike) present in the lakes. Behaviour of pike was studied with whole-lake acoustic telemetry tracking, supplemented by stable isotope analysis of pike prey utilization and survey fishing data on the prey fish community.

Nanobody-siRNA Conjugates for Targeted Delivery of siRNA to Cancer Cells.

Targeted extrahepatic delivery of siRNA remains a challenging task in the field of nucleic acid therapeutics. An ideal delivery tool must internalize siRNA exclusively into the cells of interest without affecting the silencing activity of siRNA. Here, we report the use of anti-EGFR Nanobodies (trademark of Ablynx N.

Fluctuations in pelagic fish density linked to ambient conditions.

Animal behaviour has been broadly studied for its social or functional aspects but less often for understanding the interactions between organisms and their ambient conditions. A pilot observational study was performed by means of underwater camera to investigate the correlation between environmental factors and the density of fish in the epipelagic habitat of a European temperate reservoir. Explored factors confirmed a positive correlation between water temperature and all observed categories: nonpredatory, predatory, single nonpredatory and schooling fish, as well as freshwater bream and roach.

Diel changes in vertical and horizontal distribution of cladocerans in two deep lakes during early and late summer.

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 late (September) summer. The objective was to study diel vertical migration (DVM) and diel horizontal migration (DHM) of cladocerans under conditions of different macrophyte cover in littoral areas (rich in Milada Lake, poor in Most Lake) and fish assemblages (non-specialised planktivorous species in Milada Lake, and abundant planktivorous fish - maraena whitefish, Coregonus maraena - in open water habitats in Most Lake).

Logical-Linguistic Model of Diagnostics of Electric Drives with Sensors Support.

The presented paper scientifically discusses the progressive diagnostics of electrical drives in robots with sensor support. The AI (artificial intelligence) model proposed by the authors contains the technical conditions of fuzzy inference rule descriptions for the identification of a robot drive's technical condition and a source for the description of linguistic variables. The parameter of drive diagnostics for a robotized workplace that is proposed here is original and composed of the sum of vibration acceleration amplitudes ranging from a frequency of 6.

Experimental Study of Drilling Temperature, Geometrical Errors and Thermal Expansion of Drill on Hole Accuracy When Drilling CFRP/Ti Alloy Stacks.

The drilling of holes in CFRP/Ti (Carbon Fiber-Reinforced Plastic/Titanium alloy) alloy stacks is one of the frequently used mechanical operations during the manufacturing of fastening assemblies in temporary civil aircraft. A combination of inhomogeneous behavior and poor machinability of CFRP/Ti alloy stacks in one short drilling brought challenges to the manufacturing community. The impact of the drilling temperature and time delay factor under various cutting conditions on hole accuracy when machining CFRP/Ti alloy stacks is poorly studied.

Modeling of Boring Mandrel Working Process with Vibration Damper.

The article considers the issue of modeling the oscillations of a boring mandrel with vibration damper connected to the mandrel with a viscoelastic coupling. A mathematical model of the boring mandrel oscillations, machine support and inertial body (damper) is developed in the form of a differential equations system. The model is made in the form of a four-mass system of connected bodies.

Species-specific schooling behaviour of fish in the freshwater pelagic habitat: an observational study.

Social living of animals is a broadly occurring phenomenon, although poorly studied in freshwater systems, fish schooling behaviour is an excellent example. The composition of fish schools, species-specific schooling tendencies and preferences of adult fish were studied in the pelagic habitat of the Římov Reservoir, Czech Republic. Video recordings captured over a total of 34 days (16 h per day) in the clear water period of three seasons were analysed.

The pros and cons of the invasive freshwater apex predator, European catfish Silurus glanis, and powerful angling technique for its population control.

Catfish have spread across Europe and several countries out of this region within the last decades. Basic knowledge of this apex predator has revealed concerns of invasive behaviour and questions regarding its utilization as a biomanipulation species. However, a method enabling its regulation to a required level has not yet been developed.

Density dependent attributes of fish aggregative behaviour.

Grouping behaviour, as fascinating as it is unclear, has lately drawn the attention of numerous researchers. While most of the authors focused their work on a mechanistic approach to the matter of schooling, this study explores the issue from a population point of view. Present camera observation study on the fish community carried out in the epipelagic habitat of a European temperate reservoir in the Czech Republic explored the relationship between density and aggregative features of predominantly cyprinid fish stock.

Impact of herbivory and competition on lake ecosystem structure: underwater experimental manipulation.

Two basic ecological relationships, herbivory and competition, distinctively influence terrestrial ecosystem characteristics, such as plant cover, species richness and species composition. We conducted a cage experiment under natural conditions in an aquatic ecosystem to test the impacts of two treatments combined in a factorial manner: (i) a pulse treatment - removal of dominant competitors among primary producers (macroalgae Chara sp. and Vaucheria sp.

Can species-specific prey responses to chemical cues explain prey susceptibility to predation?

The perception of danger represents an essential ability of prey for gaining an informational advantage over their natural enemies. Especially in complex environments or at night, animals strongly rely on chemoreception to avoid predators. The ability to recognize danger by chemical cues and subsequent adaptive responses to predation threats should generally increase prey survival.

Assessment of burbot Lota lota (L. 1758) population sustainability in central European reservoirs.

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 deep reservoirs that have had a long-term stocking programme.

European catfish (Silurus glanis) as a freshwater apex predator drives ecosystem via its diet adaptability.

Apex predators play a key role in ecosystem stability across environments but their numbers in general are decreasing. By contrast, European catfish (Silurus glanis), the European freshwater apex predator, is on the increase. However, studies concerning apex predators in freshwaters are scarce in comparison to those in terrestrial and marine ecosystems.

Macrophytes shape trophic niche variation among generalist fishes.

Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.