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Rybí společenstva toků VÚ Boletice
PETRÁŇOVÁ, Karolína
The aim of the thesis was to monitor a population status of fish communities in two water catchments in SAC Boletice. The monitoring was performed in 2021 in five localities in the Blanice river catchment and in five localities in the Křemžský stream sector. The fish was caught with a help of electric current in a 100m long fishing sector. After setting the basic ichthyologic characteristics and evaluation the condition and health condition, the fish was returned back to their original habitat. There were four kinds of fish obtained (European bullhead, river trout, common minnow and European perch) and one kind of lamprey (brook lamprey). The locality with the highest diversity was locality No.3 (the Blanice - 3rd locality). On the other hand, there was no fish obtained in locality No.7 (Chlumanský stream below the pond) and there was only European perch obtained in locality No.8 (Chlumanský stream above the pond). The discussion of this thesis is focused on the links between the characteristics of individual localities and fish species occurrence as well as on a comparison of the results of the monitored flows with those from the previous years. Also the authors, who performed a SAC Boletice monitoring in previous years, had similar conclusions.
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Denní a noční aktivita hlaváče černoústého a vranky obecné
POLÍVKA, Zdeněk
This Bachelor thesis is about comparison of the day and night activity of the round goby and the European bullhead under controlled conditions with shelter and positive stimuli (food) provided. 15 European bullheads and 15 round gobies were observed for this experiment - in three separated artificial systems with a simulated water flow. Each system consisted of storage tank, pumps and experimental channel. In the experimental channel (length 2 m, width 0.15 m, water depth max. 0.1 m) was possible to change the water flow up to 40 l per second and was equipped with a barrier to prevent fish to escape. The light regime was set for 12 hours of day light and 12 hours of dark. That was similar to natural ambient light regime in natural conditions during experimental work (from 22.5. to 8.6.2019). Fish were observed for 28 hours and obtained video-recordings were analysed by program EthoVision?XT and visually. Activity and spatial preferences of above-mentioned species were monitored. In accordance to our results we can conclude that there are not big differences between studied species. The main differences were stress induced behavioural fluctuations after deployment, reflected by different activity and environmental preferences. During the stress period, the round goby was more active than the European bullhead and spent a longer time in the escape zone. The next difference occurred with the stress after putting fish into the tanks. There was seen steady decline of activity in the round goby and the step-like decline of activity in the European bullhead after acclimatization period. Our results also confirmed preferences of the round goby rather for slow running water areas while in the European bullhead the opposite pattern i.e. prefer faster running water. Round Goby was more active outside of the shelter during the light acclimatization. Round goby moved more frequently with only slight decreases between light and dark acclimatization compared to European bullhead. There was not big difference in the food acquisition, which reflects that both species are able to cope with high water velocities exceeding 0.7 m. s-1. Our results also evidently provided information that fish need for behavioural stabilization relatively long acclimatization period.
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Koktejl invazivních druhů ve vnitrozemských vodách - ekologická charakteristika, vzájemné působení a následky
ROJE, Sara
This thesis combines four main chapters: 1) a general summary of the current knowledge of the impact of aquatic invasive species in Europe, ecological characteristics, main representatives, their interaction and the consequences of spread; 2-3) two studies addressing mutual species impacts between invaders co-occurring together in the same habitat; and 4) investigating the differences between the behaviour of native and alien fish species. Chapter 1 looks at the theoretical concept and impacts of aquatic invasive species and in particular, four chosen groups of invaders with a review on specifically chosen high-profile aquatic invasive species in freshwaters, their associated impacts and detailed descriptions of the species used in experiments. Chapter 2 focuses on the predatory impact of killer shrimp on the early developmental stages of marbled and signal crayfish, concluding that killer shrimp are almost unstoppable. They were able to feed on different developmental stages of larger freshwater crustaceans even if they were protected by their mothers. Chapter 3 observes the interactions of two invaders: the round goby and the marbled crayfish. The round goby showed dominant aggressiveness consuming all the juvenile crayfish sizes offered. The study also confirmed that the round goby was able to predate on, attack and take shelters from crayfishes. The only limiting factor in this interaction was the larger size of the crayfish. When interacting, both tested species negatively influenced each other, which can mean mutual consequences for both species. In Chapter 4, the individual behaviour during day and night activity under laboratory conditions in a flow simulator was studied. Both species showed very similar behaviour, with only slight differences towards adaptability and stress-related activity. Despite the similarities, the round goby was confirmed to be an aggressive, bottom-dwelling predator sharing a habitat with a lot of other benthic animals like amphipods, crayfish, and other fish - native or other aliens. In general, all alien species are present a threat to all populations sharing similar characteristics in their habitat, taking their shelters, attacking them, and predating on them with invasive amphipods and crayfish being no exception. One species can limit the other, or the outcompeted species can be displaced forcing it to find an alternative niche and therefore increase the overall pressure on the ecosystem. The presented thesis is submitting some new findings mainly about the interactions between invaders and also represents a baseline for future experimental work focused on more complex setups that will enable us to increase our understanding of invasive species.
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Effect of the revitalization adjustments of small stream on fish society
ANTONÍN, Petr
The objective of my work was to consider the effect of the Mlýnský potok revitalization on its fish society. My work is based on the ichtyological researches made before and after the revitalization. The brook is situated at the Šumava mountain between the Lipno reservoir and the border with Austria. The revitalisation had a positive effect on biodiversity, abundance and fish biomass. At the same time are here described individual requirements for successful revitalization water stream and in particular fisches, to the these streams. In my work compare achieved results of postponements fishes of the three tracked brooks Horský, Bukový and Mlýnský
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