52 research outputs found

    Quantification of Chaoborus and small fish by mobile upward-looking echosounding

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    Chaoborus larvae inhabit frequently the water column of lakes, when they can be mistaken for small fish. Because larvae ascend up to the blind zone of downward-looking echo sounding at night, quantitative acoustic estimation of them is possible only with upward-looking approach. For this reason, the mobile hydroacoustic upward-looking system (120 and 38 kHz split-beam echosounder) in combination with a direct catch method (trawling) was tested to investigate the night community of invertebrates and juvenile fish in the surface layer of the Římov reservoir (Czech Republic). In the target strength range of invertebrates (smaller than -59 dB), the 38 kHz echosounder recorded only a small proportion of targets while the 120 kHz echosounder recorded distinct peaks corresponding to high densities of Chaoborus (target strength, TS range -70 to -60 dB, average TS -66 to -64 dB). At 120 kHz frequency, the TS distribution of smaller cohort of juvenile fish ( 1.5 ind.m-3.

    Seasonal habitat use of three predatory fishes in a freshwater ecosystem

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    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 lucioerca) and catfsh (Silurus glanis) in the Římov Reservoir, using an autonomous telemetry system for 11 months. We found signifcant diferences among these species in studied parameters that varied considerably over tracked period. Pike consistently used the same sections of the reservoir, while pikeperch and catfsh frequently visited a tributary during the warm season (late spring and early autumn), and moved closer to the dam during the cold season (late autumn to early spring). Pike longitudinal activity was highest in the cold season, pikeperch in the warm season, and catfsh activity peaked in both seasons. Overlap in the depth use among species was higher in the warm season, when all species used the upper layer of the water column, and lower in the cold season, when pikeperch and catfsh used deeper areas. These results demonstrated overlay and temporal variation of habitat use among these predators, as well as potential spatiotemporal space for their direct ecological interactions. Acoustic telemetry · Predators · Habitat use · Movement ecology · Winter ecologypublishedVersio

    Long-term monitoring of fish in a freshwater reservoir: Different ways of weighting complex spatial samples

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    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 depth-stratified gillnet sampling approach mainly in benthic habitats and at the deepest part of lakes to account for the uneven distribution of fish. However, the commonly used CEN (European Committee for Standardization) protocol does not weight sufficiently habitat volumes and underrepresent pelagic habitats to calculate whole-lake catch and biomass per unit effort (CPUE and BPUE, respectively). Extended European standard gillnet (4 larger mesh-sizes added in the geometric series) catch data collected over 18 years (2004–2021) in Římov Reservoir (Czech Republic) were used for a method comparison on indices for relative abundance and biomass of fish: CEN protocol without volume-weighting and two volume-weighted approaches. We also evaluated changes in species composition and trends in these fish population over time. Results indicated interannual changes in species composition, relative abundance, and biomass of fish community. The CEN protocol tended to put greater emphasis on benthic habitats which generally have larger CPUE and BPUE. Consequently, the two volume-weighting approaches produced lower estimates of the two parameters, with the exception of the most dominant pelagic bleak Alburnus alburnus (L.). All approaches consistently showed an increasing trend in whole-reservoir fish abundance and a decreasing trend in biomass over the study period. Following our assessment, we put forward the volume-weighting approach that considers the Volume of the depth Stratum (VOST) for weighting as the most realistic approximation of fish populations and therefore recommend its use

    Transportation of excess sports equipment by air travel

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    This work describes the transportation of excess sports equipment by air travel in particular with regard to the liability of air carriers in case of destruction, loss, damage or delay. Increased attention is paid to transportation to specific surf destinations, e.g. Canary Islands and island of Bali in Indonesia. The aim is to confirm or refute the unsatisfactory situation in the field of transportation of excess sports equipment by air travel, own survey was carried out for this purpose

    Monitoring of fish stock in Bolevecky pond in 2023

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    The report summarizes results of fish monitoring in Bolevecky pond using electrofishing device. Simoutaneously, the abundance of unfavorable fish species in terms of water quality were decreased. Futher recommendation for fish management and the need for future surveys were stated

    Complex survey of fish community of Kamýk reservoir in 2012

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    The report summarizes results of complex ichthyological survey of Kamýk reservoir in 2012, which purpose was to evaluate possible influence of considered building of pumping hydroelectric power station (increased daily water level fluctuations) on ichthyofauna of Orlík and Kamýr water bodies

    Odklon v českém trestním procesu (de lega lata)

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    S ohledem na poměrně krátkou dobu která uplynula od poslední novelizace trestního řádu, bylo by zřejmé předčasné posuzovat efektivnost nové úpravy zejména ve vztahu k institutu v procesu aplikace institutu PZTS podaří naplnit zákonodárcem sledovaný záměr a zda tento institut nezůstane bezobsažným méně problematickým se jeví uplatňování institutu TP. Zdá se, že významná část věcí náležejících do kompetence samosoudce nebude projednávána v hlavním líčení, nýbrž vyřízena vydáním TP
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