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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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