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The round goby (Neogobius melanostomus) is a well-known invasive fish. Knowledge of its feeding habits and means of food processing is key in understanding its impact on aquatic food webs. The present study assessed the gut evacuation rate of round gobies feeding on three different types of prey occurring naturally in the diet of this species (small native freshwater clams, an invasive amphipod and chironomid larvae), at two different temperatures (14 and 20 °C) and under different food availability scenarios (continuous and non-continuous feeding). Gut evacuation rates varied significantly between the prey availability scenarios and, specifically, round gobies processed prey significantly faster in the continuous feeding mode when food was regularly available than when fed only once. The highest evacuation rates were detected for individuals fed with clams, in which complete gut clearance was observed within 16 h, compared to within 24 h and 36 h for chironomid larvae and amphipods, respectively. Our study shows that round gobies evacuate chironomid and mollusc prey most rapidly, which suggests that potentially the highest predatory pressure will be exerted on these prey types, assuming that all three prey species are locally present. The slower processing and digestion of amphipods may be due to their bulkier shape, which makes them more difficult to swallow. The relatively high evacuation efficiency of the round goby observed in the continuous feeding mode suggests overall increased pressure on food resources, thereby potentially reducing availability for other consumers and accelerating resource depletion, mainly driven by the high local densities of the round goby populations. [ABSTRACT FROM AUTHOR]

Simple Summary: The round goby is considered one of the most widespread Ponto-Caspian invasive species, which poses a threat to ecosystems and food web alterations. While it is known for direct predation, its interactions with native higher predators and its feeding behaviour upon their presence remain unclear. Therefore, we investigated how the exposure to chemical alarm cues emitted by conspecifics and the odour of a native predator, the European eel, affects the round goby's feeding activity. Surprisingly, the gobies did not exhibit any pronounced threat sensitivity to both types of chemical stimuli, which was observed in unchanged food consumption probability and gut evacuation rates. The obtained outcomes suggest boldness, great efficiency in food processing, and a potential competitive advantage over native counterparts when colonising new ecosystems, irrespective of local higher predator presence. The round goby Neogobius melanostomus is a notoriously invasive fish originating from the Ponto-Caspian region that in recent decades has successfully spread across the globe. One of its primary impacts is direct predation; in addition, when entering new ecosystems, the round goby is likely to become a food resource for many higher native predators. However, little is known either about the indirect effects of predators on the round goby as prey or its feeding behaviour and activity. The non-consumptive effect of the presence of higher native predators presumably plays an important role in mitigating the impact of non-native round gobies as mesopredators on benthic invertebrate communities, especially when both higher- and mesopredators occupy the same habitat. We tested the food consumption probability and gut evacuation rates in round gobies in response to chemical signals from a higher predator, the European eel Anguilla anguilla. Gobies were placed individually in experimental arenas equipped with shelters and exposed to water from a tank in which (a) the higher predator had actively preyed on a heterospecific prey, earthworms Lumbricus sp. (the heterospecific treatment; HS); (b) the higher predator had fed on round gobies (the conspecific treatment; CS); or (c) the water was provided as a control treatment (C). To ensure exposure to the chemical stimuli, this study incorporated the application of skin extracts containing damaged-released alarm cues from the CS treatment; distilled water was used for the remaining treatments. No significant differences were observed in either the food consumption probability or gut evacuation rate in the tested treatments. Despite the lack of reaction to the chemical stimuli, round gobies did exhibit high evacuation rates (R = 0.2323 ± 0.011 h−1; mean ± SE) in which complete gut clearance occurred within 16 h regardless of the applied treatment. This rapid food processing suggests high efficiency and great pressure on resources regardless of the presence or not of a higher predator. These findings hint at the boldness of round gobies, which did not exhibit any pronounced threat sensitivity. This would seem to suggest great efficiency in food processing and a potential competitive advantage over local native species when colonising new ecosystems, irrespective of the presence of native predators. Our study did not detect any non-consumptive effect attributable to the higher predator, given that the feeding activity of the invasive round goby was not altered. [ABSTRACT FROM AUTHOR]

This study presents the findings of a faunistic survey conducted on aquatic beetles and bugs in nine protected areas in South Bohemia. For sampling, baited funnel traps, aquatic light traps, and kitchen strainers were utilised. In total, 75 beetle species from ten families and thirteen heteropteran species from nine families were identified. Additionally, eight beetle species and one hemipteran species that were found are listed in the national red list. A notable discovery was the identification of a new locality of the protected diving beetle Graphoderus bilineatus in Horní Lužnice. [ABSTRACT FROM AUTHOR]

Abundance and per-capita foraging efficiency are essential factors for predicting and quantifying an invasive predator impact on prey, i.e., the impact potential (IP). However, population structure is not included in the calculation, and IP accuracy might be improved by incorporating predator body size. The population structure of the round goby Neogobius melanostomus, a highly invasive predator, was surveyed in the Elbe River. We determined the functional response (FR, per capita foraging) of the three most abundant size classes of N. melanostomus on the water louse Asellus aquaticus. We then calculated the IP for each size class and for the entire population with (the actual impact potential -- IPA) and without (the impact potential for limit size rage -- IPLSR) population body size structure (based on FR of the medium size class). All three size classes of the predator showed type II FR with respect to A. aquaticus. The estimated FR parameters, attack rate and handling time, as well as the maximum feeding rate, were size dependent. Despite the lowest per capita foraging efficiency, small individuals displayed the highest IP among the tested size classes because of their high abundance. Conversely, medium and large individuals, although showing highest per capita foraging efficiency, displayed lower IP. Hence, IPA showed more precise IP calculations compared to IPLSR. Overestimation of the potential impact as a consequence of omitting predator population size structure was negligible at the investigated locality. The IP of the N. melanostomus population five years post-invasion can be accurately calculated based on the FR of medium-sized fish. [ABSTRACT FROM AUTHOR]

Optical measurements of transmittance in the far infrared region performed on crystalline silicon wafers exhibit partially coherent interference effects appropriate for the determination of thicknesses of the wafers. The knowledge of accurate spectral and temperature dependencies of the optical constants of crystalline silicon in this spectral region is crucial for the determination of its thickness and vice versa. The recently published temperature dependent dispersion model of crystalline silicon is suitable for this purpose. Because the linear thermal expansion of crystalline silicon is known, the temperatures of the wafers can be determined with high precision from the evolution of the interference patterns at elevated temperatures. [ABSTRACT FROM AUTHOR]

Communities of aquatic beetles and heteropterans were surveyed in 13 protected areas in South Bohemia. We used baited funnel traps, subaquatic light traps and a kitchen strainer for sampling. Overall, the occurrence of 84 species of aquatic beetles from 9 families and 17 species of aquatic heteropterans from 9 families were recorded in the surveyed localities. Moreover, during the survey we recorded 14 species of aquatic beetles and two species of aquatic heteropterans listed in the Red List of Endangered Species of the Czech Republic. The most interesting records are Bidessus grossepunctatus at two localities, Hydroporus scalesinaus at one locality and Notonecta lutea at three localities. Our results point to relatively high biodiversity in some protected areas and their crucial importance as refuges for these insect communities. [ABSTRACT FROM AUTHOR]

In this study we report the results of a faunistic survey on aquatic beetles and heteropterans in 12 selected protected areas in South Bohemia. For sampling, we used baited funnel traps, subaquatic light traps, and a kitchen strainer. In total, we found 92 species of aquatic beetles from 10 families and 12 species of aquatic heteropterans from 6 families. We also found 16 species of aquatic beetles and 2 species of aquatic heteropterans listed in the national Red list including interesting records of Graphoderus bilineatus at 3 sites, Bidessus grossepunctatus at 2 sites and Hydroporus scalesianus at 1 site. [ABSTRACT FROM AUTHOR]

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Sterlet (Acipenser ruthenus), one of the last sturgeons in the Danube basin, is regularly stocked in national and international restoration programs, but the efficacy of stocking has not yet been evaluated. Effectiveness of stocking should involve marking and evaluating growth and survival of juveniles. Chemical marking with alizarin red S (ARS) was evaluated to establish optimal ARS staining approaches for juvenile sterlet. Bathing in a 100–200 mg l−1 ARS concentration for 12 h had no affect on fish mortality or growth. Use of a green laser on the upper five external structures (dorsal, lateral, and ventral scutes and rostral and anal plates) allowed easy detection for at least a year. Simultaneous use of multiple external structures was effective for distinguishing stocked from wild fish without harm or sacrifice. We conclude that ARS staining enabled a cost‐effective, quick, and labour‐nonintensive way to mark sterlet, with a high‐field detectability and minimal previous experience required. [ABSTRACT FROM AUTHOR]