Parasitism, life history traits and immune defence in cyprinid fish from Central Europe

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The diet of reservoir perch before, during and after establishment of non-native tubenose goby

In recent decades, gobiid species have increased their distribution throughout Europe and now often represent the dominant genus along many rivers and canals. In this study, we assessed the role of tubenose goby (Proterorhinus semilunaris) as a prey species of native perch (Perca fluviatilis) in a lowland reservoir soon after their initial introduction in 1994 (sampling started 1998) and 17 years after establishment (2011–2012). We compare these data with perch diet composition from before introduction (1981–1982). Our data indicate that tubenose gobies quickly became the dominant species along the reservoir bankside, making them an attractive prey for ≥1 + perch. There was a clear increasing trend in the numbers of larger perch caught along the rip-rap, with the largest fish clearly specialising on gobies. As such, introduction of tubenose gobies has had a pronounced effect on food web and population dynamics along the littoral zone. While goby numbers appear to have dropped significantly in recent years, apparently due to predation pressure, further studies are needed to assess whether such changes have had any general impact on population and food web dynamics within the reservoir

La Prospección de placeres del oro y otros minerales densos

[eng] Alluvial prospecting is the most widely used method in heavy mineral exploration. Heavy minerals are resistant to meteoric agents. Economically, the most important heavy minerals are: precious metals (gold, silver and platinum group minerals), gems (diamonds, rubies, sapphires, emeralds, etc), the tin base metal group (cassiterite), technologic metals such as titanium (ilmenite and rutile), tungsten (wolframite and scheelite), zirconium (zircon) and the rare earths. The most usual techniques used in alluvial prospecting and the different criteria employed in exploration, mineral benefit and evaluation of alluvial ore deposits known as placers are presented.[cat] La prospecció al.luvionar es un mètode excepcional per la recerca de minerals de interès econòmic, com los minerals densos d'elevada resistència física i química. Entre ells son d' interès els metalls preciosos (or, plata i platí), gemmes (diamant, rubí, zèfirs, maragdes, aigua-marina, etc.), metalls de base com l'estany (cassiterites), minerals tecnològics com el titani (ilmenites i rutils), wolfram (volframita i scheelita), zirconi (zircó), de terres rares (monacites), etc.. En aquest text, és presenten las tècniques mas usuals en Prospecció al.luvionar com la batea, així com els distints criteris a seguir per dur a termini una prospecció, un benefici i una avaluació dels seus jaciments que es coneixen com ¿placeres¿.[spa] La prospección aluvionar es un método excepcional para la búsqueda de minerales de interés económico, como los minerales densos de elevada resistencia físico-química. Entre ellos son de interés los metales preciosos (oro, plata y platinoides), gemas (diamante, rubíes, zafiros, esmeraldas, aguamarinas, etc.), metales de base como el estaño (casiteritas), minerales tecnológicos como el titanio (ilmenitas y rutilos), wólfram (volframita y scheelita), circonio (circón), de tierras raras (monacitas), etc.. En este texto, se presentan las técnicas mas usuales en prospección aluvionar como la batea, así como los distintos criterios a seguir para llevar a cabo una prospección, un beneficio y una evaluación de sus yacimientos que se conocen como ¿placeres¿

Biomanipulation measures at the Hamry water supply reservoir - poor reaction of phytoplankton to planctivorous fish reduction

One measure commonly used for improving water quality in open waters is biomanipulation of fish stock. Previous studies in shallow lakes confirm the importance of reducing cyprinid populations for increasing zooplankton. Empirical results from reservoirs, however, are scarce. The aim of this study was to evaluate the effect of an intensive reduction of cyprinid fishes and perch fry density between 2009 and 2013 on water quality in the Hamry drinking water reservoir. The abundance of common bream broodstock decreased by around 12 000 individuals over the five years, and biomass dropped below 20 kg.ha-1. Stocking with pike and zander proved less effective. In reservoirs similar to Hamry, reduction of bream biomass can be a highly effective means of increasing filtering zooplankton biomass. Phytoplankton dynamics, however, appear to depend on additional factors, with nutrient loading (especially phosphorus) probably playing the primary role

Assessment of species composition and abundance of juvenile fish communities in relation to the assessment of good water status at specified profiles along the River Oder

The aim of this report is to evaluate species composition and abundance of juvenile fish communities along specified profiles along the Oder in relation to the assessment of good water status, as a basis for updating the "Plan for the Upper Odra River sub-basin" in accordance with appropriate methodologies laid down by the Ministry of the Environment

The standpoint on the importance of the Nové Mlýny Reservoir fish pass

The subject of this contract is an assessment of the importance of the Nové Mlýny dam fish pass on the River Dyje as regards its importance for the fish community

Monitoring of fish fry as an indicator of river habitat quality

The aim of the study was to analyse the 0+ juvenile fish community at designated river localities selected according to the state network of the water quality control