A simple fish-based approach to assess the ecological quality of freshwater reservoirs in Central Europe

The assessment of ecological quality in freshwater ecosystems is a key issue in many countries, but conditions for the development of assessment methodologies are often country-specific. This study proposes a simple methodology for the assessment of the ecological potential of reservoirs based on fish communities using a dataset covering major environmental and pressure gradients in reservoirs in the Czech Republic. Fish data obtained by gillnet sampling were correlated with a proxy of eutrophication as a key indicator of anthropogenic pressure for selecting appropriate fish-based indicators, establishing scoring criteria and developing the index of ecological quality. Expert judgement was also used to select potential fish indicators. Nine indicators were selected for the final fish-based index, fulfilling the criteria required by the Water Framework Directive. Two steps were used to validate the fish-based index quantification of its inter annual stability and sensitivity analysis of individual indicators. Finally, the index was compared to a previously developed general index for Central and Western Europe. Our study demonstrates that a combination of expert judgement and strict validation methods can result in an informative assessment of the ecological conditions, which can help identify conservation and restoration priorities. © P. Blabolil

Long-term monitoring of fish in a freshwater reservoir: Different ways of weighting complex spatial samples

Anthropogenic activities continue to pose the greatest challenges to freshwater ecosystems. Therefore, long-term monitoring is essential for the management and conservation of these resources. Monitoring programs for freshwater bodies often use a range of indicators, including biological elements such as fish. Existing European standard provides a depth-stratified gillnet sampling approach mainly in benthic habitats and at the deepest part of lakes to account for the uneven distribution of fish. However, the commonly used CEN (European Committee for Standardization) protocol does not weight sufficiently habitat volumes and underrepresent pelagic habitats to calculate whole-lake catch and biomass per unit effort (CPUE and BPUE, respectively). Extended European standard gillnet (4 larger mesh-sizes added in the geometric series) catch data collected over 18 years (2004–2021) in Římov Reservoir (Czech Republic) were used for a method comparison on indices for relative abundance and biomass of fish: CEN protocol without volume-weighting and two volume-weighted approaches. We also evaluated changes in species composition and trends in these fish population over time. Results indicated interannual changes in species composition, relative abundance, and biomass of fish community. The CEN protocol tended to put greater emphasis on benthic habitats which generally have larger CPUE and BPUE. Consequently, the two volume-weighting approaches produced lower estimates of the two parameters, with the exception of the most dominant pelagic bleak Alburnus alburnus (L.). All approaches consistently showed an increasing trend in whole-reservoir fish abundance and a decreasing trend in biomass over the study period. Following our assessment, we put forward the volume-weighting approach that considers the Volume of the depth Stratum (VOST) for weighting as the most realistic approximation of fish populations and therefore recommend its use

Spatial distribution of fish in reservoirs and lakes

This thesis is focused on the fish spatial distribution and its changes mainly during the diel cycle. In the first part, I described the fish spatial distribution in the tropical lake ecosystem of Lake Turkana. The second part deals with the fish spatial distribution in a temperate reservoir on the different spatial scales from in/offshore habitats over the fine-scale to the level of individuals. The linkage of fish distribution patterns with selected environmental variables was also evaluated

Results of malaco-ichthyological survey of the Vltava River between 287,625-288,24 river km.

The aim of the surveys was to determine the species composition and abundance of large bivalves and fish in the 287,625-288,242 river km section of Vltava River affected by planned alluvial mining and subsequent evaluation of this impact on protective conditions of specially protected species in accordance with Decree No. 395/1992, on Nature and Landscape Protection

Monitoring of fish populations in Vltava River, quantification of fish migration from reservoir into Vltava River.

The aim of the study was to quantify fish migration activities between Lipno Reservoir body and Vltava River with special emphasis put on description of the dynamics of migratory processes, estimation of abundance of migrating fish and evaluation of the influence of migrants from reservoir on autochthonous river fish community

Ontogeny of coloration patterns in Neotropical cichlids of the Tribe Heroini (TELEOSTEI: CICHLIDAE: CICHLASOMATINAE)

We have studied the ontogeny of Cichlid fishes of the tribe Heroini, using developmental series. By observing the development of pigment patterns in larval, juvenile and adult cichlids, the homologous elements of the lateral barring pattern have been hypothesized. Although pigmentation is often disregarded as a source of characters containing historical information, the congruence of many of these characters with a recent phylogeny of heroini, suggest their utility. A common mechanism underlying pattern formation is suggested based on similarities between Neotropical and African Cichlids

Final report from the mapping of the weatherfish (Misgurnus fossilis) in the NPP Žehuňský rybník and its surroundings.

The report evaluates the results of a survey focused on weatherfish in the NPP Žehuňský rybník and the surrounding area. During the survey, a large population of weatherfish was found in the tributary part of the pond and the adjacent pool. This finding is essential for future revitalization planning and also significantly expands current knowledge of species distribution. Based on the results of the survey, the local population is one of the most important in the Central Bohemian Region

Report on the removal of fish stocks in the Jablonná nature reserve with a electrofishing device

Unwanted fish species were removed from the PP Jablonná wetland as a measure to support local amphibian populations