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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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Influence of predator odor on the rate of evacuation of the digestive tract of the invasive black-mouthed warbler (Neogobius melanostomus)
BRYLLOVÁ, Vendula
Over the past 30 years, the round goby (Neogobius melanostomus) has colonized a significant portion of the European river system and a similar trend can be observed in the Great Lakes of North America. In parallel, however, the round goby is coming under strong predation pressure from native predators at these sites, but this appears to be negligible in destabilising its populations. However, quantification of the indirect impact of these predators on the round goby is still lacking. The aim of the present thesis was to reveal the influence of chemical signals of the original, trophically higher predator (European eel - Anguilla anguilla) on the rate of gastric evacuation of the lower predator - round goby. In the experiment, round goby was tested in the following treatments: 1) without chemical signals (control group); 2) with chemical signals originating from the European eel fed by the round goby with enrichment of the water with the conspecific alarm cues from the skin of the round goby (conspecific treatment); 3) with chemical signals originating from the European eel fed by the earthworms (heterospecific treatment). The different treatments were tested on the evacuation rate of the larvae of Chironomus sp. in the digestive tract of the round goby. The rate of gastric evacuation of the round goby was not statistically significantly different among the treatments tested. Tested food was evacuated in all treatments within 9 hours from the start of the experiment. The results obtained show that the presence of chemical signals from a higher predator (European eel), with the simultaneous presence or absence of conspecific alarm cues originating from the food (of the lower predator), does not affect the rate of gastric evacuation of the round goby, which appears to be an additional advantage of this highly invasive aquatic species when colonizing new territories.
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Rychlost evakuace trávicího traktu hlaváče černoústého (Neogobius melanostomus) v závislosti na dostupnosti a typu potravy
MIKŠOVSKÁ, Vendula
The aim of the bachelor thesis was to estimate the evacuation rate of digestive tract of Neogobius melanostomus with respect to a type and availability of food. This small benthic fish belongs to high-risk invasive alien fish species in the world. Due to direct predation, Neogobius melanostomus has impact on processes and native species in colonized ecosystem. Three types of food - Dikerogammarus villosus (Sowinsky, 1894), Pisidium sp. (hard-bodied prey) and larvae of Chironomus sp. (soft-bodied prey) were tested within the series of experiments at the temperature of 14°C. Two feeding strategies (continuous and non-continuous feeding) were tested for each kind of food. Neogobius melanostomus has had access to the tested food for 2 hours. The individuals with continuous feeding strategy then continued to be fed (other food than tested), fishes with non-continuous feeding strategy had no access to food until the end of experiment. At the time points 0,2,5,9,16,24 and 36 hours, 5 individuals from each feeding strategy were examined in order to analyse their digestive tract and calculate the evacuation rate. Evacuation rate of individuals with non-continuous feeding strategy reached statistically significant lower values (P<0,05) than the individuals with continuous feeding strategy (same outcomes were reported for all tested types of food). Among the non-continuously fed individuals was found no statistically significant difference (P<0,05) between the evacuation rate of Dikerogammarus villosus and Pisidium sp. However, within the same feeding strategy, larvae of Chironomus sp. were evacuated statistically significant slower (P<0,05) than Pisidium sp. In contrary, all three types of food statistically varied (P<0,05) from each other within the continuous feeding strategy. Neogobius melanostomus, within the continuous feeding strategy, evacuated Dikerogammarus villosus the fastest, followed by larvae of Chironomus sp. and Pisidium sp. were evacuated the slowest. Furthermore, within the continuous feeding strategy, the food was completely digested (impossible identification) in 16 hours after the beginning of experiment (Pisidium sp. were digested in 9 hours). The outcomes from the experiment with continuous feeding strategy conclude the higher ecological impact of Neogobius melanostomus on larvae Diptera and Crustacea than on Bivalvia (with hard - bodied). In comparison to the outcomes of evacuation rate of Gymnocephalus cernua (Linnaeus, 1758) (almost 3 times) or Cottus gobio (Linnaeus, 1758), stated in scientific literature, Neogobius melanostomus also achieves faster evacuating. Faster evacuation rate can also play an important role in colonisation of new territories and competitive fight with native species.
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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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Společenstvo bentických organismů na dolním toku Ohře, Labe a jejich přítocích
MUSIL, Martin
The purpose of this work was to describe the current status of benthic communities on the main stream of Elbe River and Ohře River and their tributaries affected and non-affected by biological invasions - especially by round goby (Neogobius melanostomus) and spiny - cheek crayfish (Faxonius limosus). Sampling for this research took place from April 2018 to August 2018, while morphiologic survey of waterbodies was done in November 2017. Two tributaries of the Elbe River (Milešovský brook and Ploučnice River) and one tributary of the Ohře River (Čepel) were selected for this research. Two 100 m long sections (lower stretch potentially affected by invaders and upper stretch as referential) were monitored at each tributary. At the same time a 100 m long main flow section was monitored near the mouth of the tributaries. The following parameters were monitored: morphology of the stream and basic physical and chemical parameters of water, zoobenthos community, crayfish occurrence, and fish community. The benthic communities of the upper streams were less affected by biological invasions. The biodiversity of the benthic communities in the upper sections was richer compared to the lower sections. The occurrence of the round goby seemed to be factor affecting benthic and fish communities at the sites concerned. It was an eudominant species in the Elbe section in Děčín and becoming dominant in the lower section of Ploučnice River.
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Potravní chování nepůvodních druhů hlaváčovitých ryb
GEBAUER, Radek
Global homogenisation of biota is observed at an ever-increasing rate, causing environmental and economic losses as well as emerging health risks. Ecological and economic consequences of biological invasions fuel the need for an urgent targeted and cost-effective management given the amount of invaders, vectors and pathways. We examined the effects of environmental and human-related factors on distribution of alien animal species richness in the Czech Republic (Central Europe). We compiled a set of maps showing the level of invasion of six categories of alien animal species in each of 628 grid cells (ca. 12.0 × 11.1 km) covering the Czech Republic. Relationships between alien species richness and 12 variables characterizing climatic conditions, topography, land cover, and human population size were calculated using the generalized least squares method. Species richness of all aliens, of invertebrates, and of terrestrial species showed the strongest positive relationship with mean annual temperature, while the number of black and grey (proposed prominent invaders) and aquatic species was most closely related to the presence of large rivers. Alien vertebrates showed a strong negative relationship with annual precipitation. The highest alien animal species richness was found in and near large population centres and in agricultural landscapes in warm and dry lowlands. The gateways for alien aquatic species are rather large rivers over sport fishing and aquaculture import. Two benthic fish species, round goby Neogobius melanostomus and western tubenose goby Proterorhinus semilunaris have recently expanded beyond their native ranges. Both species exert a detrimental effect on fish communities' structure directly via predation on fish eggs and indirectly via alterations of food webs. We quantified and compared the foraging behavior and efficiency of invasive N. melanostomus and alien P. semilunaris upon common carp Cyprinus carpio larvae at two temperature levels (20 and 25 °C) and in three different habitat structures (sand, cobbles, cobbles with artificial plant) using the functional response approach. Both alien predators showed type II FR in all temperature and habitat treatments. Intra-specific comparison showed no significant temperature dependency on assessed FR parameters, attack rate and handling time, suggesting broad temperature tolerance of both tested predators. The handling time did not differ between predators suggesting similar per capita ecological impact at high prey densities. Proterorhinus semilunaris showed a lower maximum feeding rate at 25 °C compared to the rest of treatments suggesting a lower temperature optima compared to N. melanostomus. Interspecific comparison showed similar values of handling time in cobble substrate and cobbles with artificial plant suggesting similar per capita ecological impacts of both aliens. Intraspecific comparison showed significantly lower values of handling time in both predators in habitat with cobbles reflecting higher maximum feeding rate. Therefore, impact of both invaders in such environment could elevate. Neogobius melanostomus showed higher attack rate in sandy habitat compared to P. semilunaris, while no significant differences were observed in other habitat treatments.
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Potravní chování hlaváčovitých ryb v závislosti na komplexitě prostředí
KOVÁŘ, Petr
Round goby Neogobius melanostomus (Pallas, 1814) and western tubenose goby Proterorhinus semilunaris (Heckel, 1837) are two benthic fish species, which have recently expanded from their native ranges of Ponto-Caspian Region to Europe and North America. While the ecological impact of round goby is widely documented, western tubenose goby receives little attention and its effect on aquatic communities has not yet been quantified. The main aims of present B.Sc. thesis are assessment and comparison of ecological impact and feeding behavior of both alien predatory fish species upon larvae of common carp (Cyprinus carpio, Linnaeus, 1758). The feeding behavior was tested in three habitats with different complexities: sandy and rocky substratum and habitat with plant. Present experiments were accomplished using comparative functional response, which has been successfully applied in assessment and comparison of ecological impact of alien species and their feeding behavior. Interspecific comparison between round goby and western tubenose goby showed similar handling times in rocky substratum and in habitat with plant suggesting similar per capita ecological impact of both predators. Intraspecific comparison showed significantly lower handling time in rocky habitats compared to others, and hence the ecological impact of both predators in such environments could elevate. Both, round goby and western tubenose goby showed type II FR in all treatments. Our results highlight the importance of complex actions in management of biological invasions, as the elimination of invasive round goby can boost the population growth of another alien species, e.g. western tubenose goby, which was not considered invasive until that time.
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