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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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Vliv přítomnosti či absence střevličky východní (Pseudorasbora parva) na produkci ryb a kvalitu vody v rybnících firmy Blatenská ryba
KOUKOLÍK, Pavel
Topmouth gudgeon (further TG) Pseudorasbora parva (Temminck & Schlegel, 1846) is a small cyprinid naturally occurring in East Asia. TG causes a lot of economic lossess on the pond culture worldwide including Czech Republic. The aim of the present B.Sc. thesis was to assess an effect of TG on fish production and water quality in the ponds of the Blatenská ryba company. The experiment was perfomed in six ponds. Three of them had a control function where two-years common carp was stocked and necessary preventive measures were taken to rule out presence of any pest species. The other three ponds were also stocked by carp, but TG was stocked as well. Water, zooplankton, zoobenthos samples collecting, water properties measurements, topmouth gudgeon sampling and morphometric-gravimetric analyses of caught carp were performed on monthly basis from March to September. From the end of September to the the first half of October all six ponds were harvested, when the overal final fish biomass, health and physical (TL, SL, W, Fulton) condition of the cultured carp were monitored. A remarkable negative influence of TG upon water quality and pond production parameters were found. The impact of TG on water quality is believed to be indirect, due to mass elimination of big size zooplankton species (Daphnia sp.). Zooplankton unavailability caused the carp's foraging shift to zoobenthos, and afterwards carp bioturbation activity when carp digged in the pond ground. This activity resulted in intensive phosphorus releasing from the sediment to the water collumn which in combination with zooplankton absence led to water quality worsening. Moreover, TG presence also had a negative impact on pond production parameters and the health status of the carp stock. Production in ponds with TG was on average 70 % lower compared to the control group. In addition, 29 % of carp suffered from tissue lesions as a consequence of facultative parasitism of TG. The conclusions of the thesis clearly proved that it is necessary to take effective measures to control TG occurrence in pond aquaculture to ensure better economic results and stability of the pond environment.
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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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Study of ecosystem impact of giant hogweed (Heracleum mantegazzianum) invasion
Hladík, Marek ; Pergl, Jan (advisor) ; Hadincová, Věroslava (referee)
The present study deals with ecological impact of giant hogweed (Heracleum mantegazzianum) invasion in Slavkovský les area. Being one of the prominent invasive species with significant impact on human health it has been subjected to a wide research. In spite of that little is known about its impact on the invaded ecosystem. My research was therefore focused on analysis of the ecosystem impact, particulary 1) microclimatic measurements of temperature and soil moisture and their comparisons between invaded and noninvaded vegetation, 2) comparison of germination and survival of model plant species sowed into invaded and noninvaded plots and 3) study of the effect of H. mantegazzianum presence on model species seed production. Results have shown significant alteration of microclimate due to H. mantegazzianum invasion. Further research is needed to resolve what impact it may pose to species in invaded communities. The effect of Heracleum mantegazzianum presence on germination and survival of model species was not significant. Similarly, seed production of model plants was not significantly affected.
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Alien species of plants and biotic resistence of invaded communities
Kubátová, Michaela ; Dostál, Petr (advisor) ; Frouz, Jan (referee)
Michaela Kubátová Alien species of plants and biotic resistence of invaded communities This study is about problems and questions of alien plants and their relation to native communities in their new range. Ecologists are increasingly aware that soil organisms may affect plant communities because they are part of the processes that affect them. The soil organisms may affect the success of alien species invasion. Each species of plants differ in interaction with soil organisms, these interactions can result in specific feedback that will influence the future growth of other plants. According to Darwin's naturalization hypothesis related species should have similar enemies. This implies less successful invasion of alien plants at home with relatives. The practical part consists of two experiments. Using plant-soil feedback I studied under controlled conditions the importance of kinship of native plants and their soil organisms on the growth of three species of alien plants Impatiens, Parviflora, Stenactis annua and Epilobium ciliatum. There were used soil samples from localities with related and unrelated species; the soil was used as inoculums for growing first-generation plants, where there were original related, unrelated and alien plants. In the second phase only alien species were grown. Part of...
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Ethics of biological invasions
Klimeš, Adam ; Komárek, Stanislav (advisor) ; Jirsa, Jakub (referee)
The Ethics of Biological Invasions Etika biologických invazí Řešitel: Adam Klimeš Vedoucí práce: prof. RNDr. Stanislav Komárek, Dr. Abstract There is a considerable attention ascribed to the phenomenon of biological invasions - to the fast spread of nonnative species in certain area. However evaluation of the biological invasions is usually limited to the calculation of damage costs and means spent on the control of nonnative species. The ethical aspect is marginalized this way, although as it conserns living orgamisms, such aspect is inevitably present. Presented study deals with identification, foundation and analysis of all values threatened by biological invasion or by its control. This can be considered as basis for establishment of an ethical approach to evaluation of biological invasions. Indentified values are instrumental value, value of individuals, species, live and esthetic value.
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Mapping of distribution of red deer and sika deer hybrids in Czechia using audio recordings - citizen science project
Nečasová, Monika ; Pipek, Pavel (advisor) ; Červený, Jaroslav (referee)
In the Czech Republic, as in other parts of Europe (e.g., British Isles), the native European red deer (Cervus elaphus) has been hybridising with sika deer (C. nippon), which was introduced from East Asia. The hybrids are fertile, and, therefore, can backcross with their parental species and threaten their genetic integrity. Offsprings of such multiple crosses are very difficult to identify according to their morphological traits, while more reliable genetic methods are financially and logistically demanding. This work follows the study of Long et al. from 1998, which showed clear differences in vocalization between red deer, sika deer and the first generation of their hybrids, and thus suggested the third way how to identify hybrids - bioacoustic analysis. We decided to test this method in the Czech Republic in a citizen science project, the aim of which was to map the distribution of parent species and their hybrids using audiorecordings of rut vocalisation. To allow more detailed analysis, we also recorded our own recordings on a professional recording device with a directional microphone. In total, 451 recordings were collected, of which only 263 with a vocalization of 162 individuals were selected for further analysis. Recordings from previous studies from Ireland (Long et al. 1998; Wyman et...
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Mapping of distribution of red deer and sika deer hybrids in Czechia using audio recordings - citizen science project
Nečasová, Monika ; Pipek, Pavel (advisor) ; Červený, Jaroslav (referee)
In the Czech Republic, as in other parts of Europe (e.g., British Isles), the native European red deer (Cervus elaphus) has been hybridising with sika deer (C. nippon), which was introduced from East Asia. The hybrids are fertile, and, therefore, can backcross with their parental species and threaten their genetic integrity. Offsprings of such multiple crosses are very difficult to identify according to their morphological traits, while more reliable genetic methods are financially and logistically demanding. This work follows the study of Long et al. from 1998, which showed clear differences in vocalization between red deer, sika deer and the first generation of their hybrids, and thus suggested the third way how to identify hybrids - bioacoustic analysis. We decided to test this method in the Czech Republic in a citizen science project, the aim of which was to map the distribution of parent species and their hybrids using audiorecordings of rut vocalisation. To allow more detailed analysis, we also recorded our own recordings on a professional recording device with a directional microphone. In total, 451 recordings were collected, of which only 263 with a vocalization of 162 individuals were selected for further analysis. Recordings from previous studies from Ireland (Long et al. 1998; Wyman et...
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Nepůvodní druhy raků na Slovensku
LIPTÁK, Boris
Human activities have largely impacted the environment and its biota to the extent that biodiversity declines can be seen worldwide. Biological invasions significantly contribute to these processes. Slovakia is a rapidly developing country stretching along the northern parts of the Pannonian basin and western Carpathian Mountains. Geological characteristics predetermine its extraordinarily high species richness thanks to largely preserved regions and habitats of high biological and conservational value. As a result, a strong population of the stone crayfish occurs in the western part of the country, while there is a countrywide distribution of the noble crayfish. On the contrary, the country's narrow-clawed crayfish is on the edge of extinction. The main reason behind the decline of this species is the expansion of the non-indigenous crayfish species transmitting the crayfish plague pathogen. Although sites of the stone and the noble crayfish occur in the upper parts of the river basins, there is a high risk of crayfish plague outbreaks, since the established spiny-cheek crayfish population are confirmed chronic carriers of the causative agent. Aquarist trade is increasingly recognized as an important pathway for the non-indigenous species introductions, out of which some may establish and become invasive. Freshwater crayfish, shrimp and crab species were recorded in the aquarist trade in Slovakia, counting altogether 26 different species. The marbled crayfish was one of the most frequently traded species. We identified several new sites of the marbled crayfish occurrence with established reproducing populations in very close vicinity of major rivers in the country. One of the newly identified flourishing spiny-cheek crayfish populations is located close behind a bank with a pumping station, i.e. critically close to a sidearm of the Danube River, with a confirmed crayfish plague infection. Marbled crayfish can become a crayfish plague carrier acquiring the pathogen from the infected spiny-cheek population in the Danube and rapidly spreading the disease along the river, thereby endangering the remaining populations of the narrow-clawed crayfish. More sites with the marbled crayfish are expected to occur in the country. Given their parthenogenetic reproduction, theoretically, a single individual is sufficient to establish a new sustaining population. Considering the high availability of the marbled crayfish in the pet trade industry and the rising numbers of established populations in the wild, research clarifying its potential impacts on the invaded ecosystems was warranted. We provide the first study investigating the trophic position and food preferences of the marbled crayfish in its well-established populations. Based on carbon 13C and nitrogen 15N stable isotopes analysis marbled crayfish were identified in the middle of the trophic chain with polyphagic diets. Marbled crayfish were found to utilize algae, allochthonous and autochthonous detritus, zoobenthos and macrophytes, thus being a strong competitor to a wide scale of organisms depended on the same food sources. The marbled crayfish transmit the energy from the bottom of the trophic pyramid to higher trophic levels as it was found to be a prey for top fish predators. This species can form dense populations and become a dominant component of the benthic fauna, thus affecting the entire invaded ecosystem. Its trophic niche width confirms high plasticity of the species, sustaining its populations in a wide range of different habitats. The marbled crayfish is thus a highly adaptable invader that can threaten not only the indigenous crayfish species by means of competition and the spread of crayfish plague, but also entire freshwater ecosystems and their biota.
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