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Round goby (Neogobius melanostomus) in the diet of great cormorant (Phalacrocorax carbo): the role of the season and temperature
Starý, Vojtěch ; Čech, Martin (advisor) ; Adámek, Zdeněk (referee)
Round goby (Neogobius melanostomus) is invasive species, present in the Elbe river since 2015. This study The purpose of this study was to find out how piscivorous predators have adapted to its presence, using the example of the great cormorant (Phalacrocorax carbo). The research was carried out on the basis of the analysis of cormorant's pellets, collected at a locality near Velké Březno (50ř40ʹ34.2ʹʹ N, 14ř07ʹ28.5ʹʹ E) under roosting trees in the period from 1 October 2020 to 15 April 2021, during a total of 7 visits. A total of 1,775 pieces of fish, 15 species belonging to 5 families, were determined from the diagnostic bones. Of this number, 1,115 were round gobies, i.e. a total of 62.8 % of the cormorant's food consisted of these fish. However, the weight share of the total reconstructed weight of all fish caught (113.6 kg) was only very small - 6.6 %. The mean daily food intake (DFI ± S.D.) of cormorants was determined to be 423.7 ± 113.6 g. It was found that cormorants hunting only round gobies overwhelmingly do not consume the necessary prey weight to cover their energy expenditure. Furthermore, the dependence of the size of the hunted prey on the average daily temperature was tested. Linear regression did not show any significant dependence in this case. The hypothesis that at lower...
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Vliv personality proaktivní vs reaktivní u okouna říčního na náchylnost k infekci Aeromonas sp.
ČERNÝ, Jan
The existence of intra-specific differences in the life strategies of animals is described by the so-called proactive and reactive personality, where proactive individuals are characterized by a higher willingness to take risks and explore new environments compared to reactive individuals who choose a passive and inactive approach to new challenges in the environment. This concept is often defined in fish as the shy-bold continuum, with the bold individual (BI) exhibiting proactive behaviour and the shy individual (SI) typically exhibiting a reactive approach. Several studies have already been written confirming the influence of personality on fish performance traits, such as growth in three spined-sticklebacks (Gasterosteus aculeatus) or stress tolerance in Atlantic salmon (Salmo salar) or rainbow trout (Onchorhyncus mykkis). The aim of our experiment was to describe the existence of a link between personality and immunological resistance to Aeromonas sp. infection and stress tolerance in European perch. In our experiment, 1000 European perch were subjected to two behavioral tests for personality (open field, number of cm swum in 30 min; novel object, exploring zones of proximity to an unknown object). The top 20 BI fish (highest values in both tests) and the top 20 SI fish (zero values in both tests) were selected. Representatives of both behavioral groups BI and SI were then subjected to an induction stress challenge (lowering the tank level to 5 cm above the dorsal fin) and then metabolic activity values (ALT, AST, ALP, LDH, glucose, osmolytes, and cortisol) were measured, with the only significant difference shown by cortisol concentration (2.5-fold higher in SI compared to BI 30 min after stimulation and 5-fold higher in SI compared to BI in control). In immunological resistance testing, phagocytic capacity (natural immunity) was assessed first, and no significant differences were observed between SI and BI groups. Next, head kidney and peritoneal cells from representatives of the BI and SI groups were stimulated in vivo with A. salmonicida infection and then RNA was extracted to analyze gene expression of 46 immune genes 1, 3 and 7 days after stimulation to assess the adaptive immune system response. A 1.2-1.3-fold increase in the level of the ighm gene was observed in the head kidney of BI versus SI 1 day after stimulation, while the level of the identical gene showed a 2.2-fold increase in BI versus SI peritoneal cells. Furthermore, an increase in gene levels was observed in BI compared with SI for cc125 (1.2-fold in the head kidney) and Cd74 (1.3-1.5-fold in both peritoneum and head kidney). The results of this work suggest that personality has a significant effect on stress tolerance, does not affect natural immunity, but does affect the level of the adaptive immune system in European perch, with BI individuals appearing to be more resistant to both stress and infection by Aeromonas hydrophila.
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The width of diet specializations in a tropic generalist, European perch as a model example
VÁCHOVÁ, Viktorie
This bachelor thesis deals with the evolution of individual trophic specialisation and explains, what kind of consequences it might have on the aquatic ecosystems. This thesis is primarily focused on foraging generalist and its range of diet is specifically studied on European perch (Perca fluviatilis) in lakes Milada and Most. The determination of the trophic spectrum was performed through data based on gut contents analyses.
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Porovnání populací okouna říčního (Perca fluviatilis L.) z intenzivní akvakultury - vliv původu ryb na chování a kritickou rychlost plavání.
TOMÁŠEK, Ondřej
European perch is one of potential fish for breeding in conditions of intensive aquaculture. This species of fish is in relatively high demand, especially in the Alpine region, because of its very tasty meat. The relatively high price of fillets is attractive for producers. The difficulties in perch farming in conditions of European intensive aquaculture may alleviate the further domestication process of this species or its selective breeding. These pitfalls are negatively correlated with fish welfare. In this thesis, we examined morphometric (morphometry, fin damage, somatic index), behavioural (activity, aggressivity, boldness and critical swimming speed) and physiological (cortisol, glucose, enzyme activity, potassium) parameters in four populations of perch imported from different European intensive farms (France - two farms, Hungary, Denmark) engaged in their producing. Experiments performed in this thesis showed that individuals from the Danish population has the highest activity of the studied populations, including the critical swimming speed (4.24 ? 0.15 BL.sec-1). The population from Denmark also found the highest percentage (8.9 %) of bold exploratory behaviour, which subsequently increased aggressive behaviour within this population. The number of attacks on other individuals from the flock reached the highest measured values in this experiment (2.33 ? 2.31 attacks). Furthermore, experiments showed that individuals from the Danish population showed a higher tolerance for adverse environmental problems compared to other populations from Hungary or France. These differences, which have been observed in the Danish population, can be interpreted as a proactive stress mechanism that is characteristic of fast pace syndrome (fast POLS). High perivisceral fat index was found in fish from the Hungary. The morphometric characteristics of all populations were significantly different. Genomic characteristics could address this approach in the near future, in particular to streamline domestication processes and support the selective breeding of perch suitable for European intensive aquaculture.
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Analýza růstu okouna říčního \kur{Perca fluviatilis} v nádržích České republiky
KŘÍŽOVÁ, Marie
This thesis summarises published knowledge on factors affecting the growth of European perch Perca fluviatilis and evaluates its growth characteristics in five chosen reservoirs using otolith analysis. The growth differs between reservoirs and this differences are explained by reservoir characteristics applying correlation analysis followed by linear regression. Otolith analyses shows that females reach bigger sizes than males. Several reservoir characteristics are proven to effect European perch growth of age classes of 0+ to 5+ and its annual size increment.
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The influence of origin in intensively bred European perch (\kur{Perca fluviatilis}) on mass yield, chemical composition and organoleptic properties of its meat
FLOKOVIČ, Ondřej
A breeding of seven European perch (Perca fluviatilis) groups of various origin was carried out under experimental conditions at 20°C temperature since the hatching of larval fish up till the age of 278 days, with intensive feeding using BioMar Inicio plus 0,55mm fodder with 15% fat content and BioMar Inicio plus 0,1mm fodder with 18% of fat content in later initial feeding. The average final weight of fish in the individual groups ranged between 79,4g and 27,63g. Mass yield statement (mass fraction of skinless filets, on the total mass), basic chemical analysis of filets (dry matter, crude protein, lipids and ash content) and organoleptic evaluation of musculature quality were carried out in the final stage of the growth test. No influence of the fish origin on the mass yield was detected. The average values ranged between 35,41% and 32,21%, but an influence of origin on crude protein content was discovered. The lowest values were determined in the population from the north of Germany 77,5% and the highest values on the contrary were determined in the population from the Štrbské Pleso lake 80,35%. The lowest lipids content was determined again in the population from the north of Germany 7,14%, while the highest fat content was detected in the population from Slovakia 8,66%. The results of organoleptic analysis didn't show substantial differences. Overall it can be stated that the monitoring didn't prove any substantial influences of fish origin on the parameters observed, which is confirmed by results of similar observations carried out by other authors e.g. with trout and carp.
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