Pavel Horký

Host compatibility as a critical factor in management unit recognition: population‐level differences in mussel–fish relationships

Summary 1. The recognition of management units (MUs) that respect interpopulation distinctions in management needs is central to many biological applications addressing species conservation, biological invasions and ecosystem processes. 2. We present a methodological approach for the evaluation of population-level differences in the host compatibility of natural populations of affiliate (dependent) species. Two experiments were performed to diagnose the sources of variability in the relationships between an endangered freshwater mussel Unio crassus and its host fish species in a fragmented river system in Central Europe. 3. Despite the common approach applied to the conservation of U. crassus throughout the study area, we identified differences in the ability of U. crassus to infest particular host fish species between nearby and recently isolated mussel populations. These differences could strongly influence their reproductive success under a constant conservation regime. 4. The observed differences were accompanied by genetic and morphometric distinctions, as revealed by microsatellite, mtDNA and elliptic Fourier descriptor analyses. The genetic data indicated substantial reproductive isolation, which could have resulted in adaptive or random changes responsible for the differences in host compatibility. 5. We showed that experimental testing of physiological host compatibility can be effectively used for the detection of different MUs of U. crassus, with direct implications for the management of host populations. In combination with traditional genetic and morphometric techniques, this approach may provide a general framework for the recognition and care of management units of affiliate species. 6. Synthesis and applications. Population-level evaluations of host compatibility should be utilized in management unit recognition and the formulation of management targets for affiliate species. We demonstrated that small-scale cross-compatibility testing can be effectively used to diagnose the sources of variability in host relationships with direct management implications. This approach can enhance the targeting of management actions in many biological applications addressing species conservation, biological invasions and ecosystem processes.

Factors influencing movement behaviour and home range size in ide Leuciscus idus

Seventeen individuals of ide Leuciscus idus were radio-tracked weekly from September 2003 to September 2004 in the River Elbe, Czech Republic, to examine migration patterns and the influence of environmental factors on their diurnal behaviour. Of the 10 environmental factors measured, L. idus were significantly influenced by turbidity, which increased diurnal movement and the home range size of the species. The peak of longitudinal movement occurred in the spring, indicating pre-spawning migration. Migrating fish moved downstream and later returned upstream to the vicinity of their original locations, displaying a homing behaviour.

Influence of Increased Dietary Selenium on Glutathione Peroxidase Activity and Glutathione Concentration in Erythrocytes of Lactating Sows

Abstract We studied the influence of different selenium (Se) levels on some parameters of the antioxidant potential of lactating sows. The experiment involved 15 sows of the Large White breed divided into 3 equal groups. The addition of Se (from Se-enriched yeast) amounted to 0.0, 0.25 and 0.50 mg per kg of diet in the control, Se1 and Se2 groups, respectively. Erythrocyte Se concentration, glutathione peroxidase (GPx) activity and reduced/oxygenated glutathione ratio were measured as some of the indicators of the sow’s antioxidant status. Supplementation of Se at 0.25 mg/kg of diet increased Se concentration (by 50.0%; P<0.01), GPx activity (by 17.0%: P<0.05) and reduced/ oxygenated glutathione ratio (by 29.7%; P<0.05). Addition of Se at 0.50 mg/kg of diet increased Se concentration (by 63.6%; P<0.01), GPx activity (by 34.7%; P<0.01) and reduced/oxygenated glutathione ratio (by 64.0%; P<0.01). A significant relationship (P<0.01) was found between the Se concentrations and activity of GPx in erythrocytes from sows in the Se1 and Se2 groups (r=0.76 and 0.77, respectively). Percentage of piglets weaned/born was higher (P>0.05) in the Se2 than in the Se1 and control groups. In summary, addition of 0.25 or 0.50 mg Se/kg of diet can improve antioxidant status of lactating sows, but addition of 0.25 mg Se/kg may be also sufficient.

Brown Trout Spawning Migration in Fragmented Central European Headwaters: Effect of Isolation by Artificial Obstacles and the Moon Phase

Abstract The spawning migrations of 123 brown trout Salmo trutta were studied in six highland streams in the Elbe River catchment area, Czech Republic, in central Europe. Trout were observed by using radiotelemetry from August to November in headwater stretches isolated by artificial obstacles without fish ladders. The length of isolated headwater stretches ranged between 5.7 and 16.1 km. Migration distance per day and total migration length over the study period (total migration) were analyzed. In total, 1,957 individual fish positions were recorded. In general, the brown trout spawning migration reflected the seasonality with respect to temperature. Migration distance per day was low in August, reached a maximum in October, and then decreased in November. In isolated headwaters, trout adapted their migrations to the length of available free migration stretches, as both migration descriptors (migration distance per day and total migration) increased according to this variable. Moon phase appeared to be t...

Post-release growth and dispersal of pond and hatchery-reared European grayling Thymallus thymallus compared with their wild conspecifics in a small stream.

The growth, and dispersal of stocked European grayling Thymallus thymallus, reared in a hatchery (fed dry food pellets) or in a pond (fed natural food), compared with their wild conspecifics was assessed from the recapture of individually tagged fish 168 days after their release into the Blanice River, Czech Republic. Recapture rates and site fidelity were higher for wild T. thymallus than for artificially reared fish. Specific growth rate and upstream or downstream dispersal did not significantly differ between any of the groups of fish. An influence of rearing conditions (pond v. hatchery) on the overall performance of stocked fish was not demonstrated. Initially, lower condition factors of reared T. thymallus were equal to wild fish after recapture, suggesting adaptation of artificially reared fish that remained in the sections studied.

Distribution and growth of brown trout in pristine headwaters of Central Europe

The majority of stream-dwelling salmonid populations in Europe are affected by artificial stocking and the fragmentation of riverine ecosystems. The present study was performed in the unique pristine headwaters of the Otava River in the Elbe catchment area of the Czech Republic. The aim was to investigate the spatial distribution and individual growth pattern of brown trout, Salmo trutta, populations. Twenty sites in two main streams and their tributaries were sampled twice a year (spring and autumn) during the period 2005–2011. The sampling sites were grouped into fourteen so-called synchronised population units within the boundaries of three populations, according to analyses of synchrony in population abundance. The individual growth of juveniles (age-0, age-1) varied between all three spatial units (sampling sites, synchronised population units and populations), while the individual growth of adults (age-2 and older) did not. The distinctiveness regarding individual growth and demographic independence among the synchronised population units and populations indicates their suitability for use as population units for management purposes.

Occurrence of cyprinids in fish ladders in relation to flow

To analyse the relationship between spawning migrations and flow, cyprinids from ten fish ladders of the Elbe River (Czech Republic) were collected during the period of spawning migrations (April–June) in 1996, 2000 and 2001. Number of species and individuals in the fish ladders increased with increasing flow up to medium values, followed by further decrease during high flows, whilst length of individuals increased with increasing flow. Moreover, occurrence of four the most numerous species (bleak, roach, silver bream and barbel) showed species specific differences in response to flow variability. In early spring, the highest number of bleak in fish ladders occurred during the low flow, whilst later increased with increasing flow. Occurrence of roach and silver bream achieved the maximum during the medium flow values across the whole studied period. In opposite, occurrence of barbel increased with increasing flows during the whole period. Furthermore, it can be assumed that occurrence of fish in ladders was associated not only with spawning migrations but also reflected shifts in local fish distribution in response to flow variability in the main channel.

Validation of scale-reading estimates of age and growth in a brown trout Salmo trutta population

In this study, we validated a scale-reading method estimating age and growth in brown trout Salmo trutta in wild, landlocked, stream-dwelling populations from mountain headwaters in the Elbe catchment area of the Czech Republic. The values estimated from scale reading were compared with measured values, collected using a mark-recapture program over eight consecutive years. The age-corrected absolute percentage error was 10.71%, primarily because the ages of the oldest individuals according to scale reading were underestimated, and the ages of juvenile individuals were slightly overestimated. The back-calculated length was slightly underestimated (the mean error was −4.60 mm), but it was not significantly different from the real measured length. This study suggests that in cold mountain headwaters, scale reading is a sufficiently accurate method for age and growth estimation in juvenile brown trout; however, the results for adult individuals must be taken with caution.

Ostracism of an Albino Individual by a Group of Pigmented Catfish

Physiological and behavioural constraints hinder albino individuals. Albino animals are rare in the wild; this trait is associated with easy detection by predators, non-native or damaged environments, and exclusively aphotic environments in total darkness. The social aspect of albinism is reported only for human beings, and the effect is distinguishable in time and space when social benefits, are used to a limited the extent. Thus far, the social consequences of albinism for animals remain unknown. We used socially established groups of the pigmented catfish, (Silurus glanis), to observe space and temporal distance detachment of albino specimens in laboratory conditions. The albino fish were separated at larger distances from the group than pigmented individuals with the same social status determined by familiarity, and this asymmetry also varied in time. Albinism-related ostracism results in a solitary existence, usually followed by enhanced predation risk. The motivation for an individual’s exclusion from a group appears to be the avoidance of the predation risk that increases not only for an odd individual but also for conspecifics within a group. Our findings indicate a role for albinism in behavioural processes related to sociality in a group of conspecifics.

Effect of Protein Concentrate Supplement on the Qualitative and Quantitative Parameters of Milk from Dairy Cows in Organic Farming

Abstract In our experiment, we studied the effects of protein concentrate addition on the qualitative and quantitative composition of milk in organically farmed dairy cows. A total number of 40 Holstein cows were divided into two groups. Live weight of dairy cows was around 625±25 kg. Average production efficiency of animals was 7600±50 kg milk for the lactation period. Animals of both groups received identical basal feed ration. The first experimental group of cows (n=20) received in the feed ration a protein concentrate from organic production (soybean cake 60%, sunflower cake 20%, linseed cake 20%) at 1 kg per head and day. The second group served as a control (n=20) without the addition of protein concentrate. The experiment lasted 30 days. The goal of the experiment was to investigate whether the addition of protein concentrate can affect individual milk components. The measured values show that the experimental group of dairy cows with the addition of protein concentrate exhibited increases in fat content by 7.4% (P≤0.05), in urea content by 83.1% (P≤0.001) and in citric acid content by 18.6% (P≤0.01), and decreases in free fatty acids by 54.9% (P≤0.001), in ECM by 5.5% (P≤0.05) and in FCM by 6.1% (P≤0.05). The control group of cows exhibited the citric acid content in milk increased by 20.0% (P≤0.05). The results indicate that the protein concentrate composed of soybean, sunflower and linseed cakes can affect the composition of milk from organically farmed dairy cows