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Key-words:invasive species, Gobiidae, Proterorhinus semilunaris, diet, site-effect, sex-differencesThe tubenose goby, Proterorhinus semilunaris, has expanded its range throughout Europe. Comprehensive studies to identify its impact on native riverine ecosystems, however, are relatively scarce. Here, we evaluate dietary preferences of P. semilunaris on a non-native river to reveal any such impacts. Fish were sampled monthly over 2011-2012 from three sites along the River Dyje (Czech Republic; Danube basin) with differing population levels and food availability. Both the amount of food consumed and dietary composition varied seasonally, with site having a strong effect. Food consumed differed between males and females, but not dietary composition; while diet differed between age classes, but not food consumed. In general, Trichoptera, Chironomidae and zooplankton dominated the diet at all sites, with Trichoptera taken more often earlier in the year and zooplankton later. Mussels were always avoided, despite high abundance, while less preferred prey were occasionally taken in high numbers in response to increased availability or energy demand (e.g. spawning). Fish eggs and fry (all P. semilunaris) were only taken in high numbers at one site, being related to high population level and fry drift from a reservoir. Male feeding declined over the breeding season, presumably due to nest guarding, while female feeding declined over winter, possibly resulting in high mortality. Proterorhinus semilunaris is a feeding opportunist, which may facilitate colonisation in habitats with poor prey availability. No predation pressure on native species was observed through consumption of eggs or fry, though small/young indigenous fish may be affected through diet competition. RÉSUMÉLes gobies demi-lune, non autochtones, Proterorhinus semilunaris, montrent des diffé-rences dans le régime alimentaire liées au site, au sexe et à l'âge. Mots-clés :espèces envahissantes, Gobiidae, Proterorhinus semilunaris Le gobie demi-lune, Proterorhinus semilunaris, a élargi son aire de répartition à travers l'Europe. Cependant, les études approfondies afin d'identifier son impact sur les écosystèmes lotiques indigènes, sont relativement rares. Ici, nous évaluons les préférences alimentaires de P. semilunaris dans une rivière où il n'est pas autochtone pour révéler ces impacts. Les poissons ont été échantillonnés mensuellement sur 2011−2012 à partir de trois sites le long de la rivière Dyje (République tchèque ; bassin du Danube) avec différents niveaux de population et de disponibilité de la nourriture. À la fois la quantité de nourriture consommée et la composition régime alimentaire, effet site, différences sexuelles alimentaire variaient saisonnièrement, le site ayant un effet important. La quantité d'aliments consommés différait entre les sexes, mais pas la composition alimentaire ; le régime alimentaire différait entre les classes d'âge. En général, les trichoptères, les larves de chironomes et le zooplancton ont dominé le régime à tous ...

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Všetičková L., Adámek Z., Rozkošný M., Sedláček P. 2012. Effects of semi-intensive carp pond farming on discharged water quality. Acta Ichthyol. Piscat. 42 (3): 223-231.Background. Fish pond management can substantially modify the hydrological regime and ecological quality of receiving waters (usually rivers, canals, and ponds downstream in an interconnected system) with potentially positive or negative impacts on watershed functioning. To evaluate these effects with respect to carp pond management, the environmental impacts of semi-intensive farming on discharged water quality were monitored at four differently managed carp ponds, differing in trophic status (two eutrophic and two hypertrophic ponds). Materials and methods. Fundamental determinants of pond inflow and outflow water quality were monitored monthly from April to October 2009. Water temperature, pH, and dissolved oxygen concentration and saturation were measured in situ whilst hydrochemical and microbiological parameters were assessed in the laboratory.Results. Compared to the inflow water, in the effluents there was a significant decline in numbers of bacterial loading indicators (Escherichia coli, enterococci, faecal coliform and mesophilic bacteria) in the outflow water. In ponds with the poor quality inflow water (downstream of water treatment plant discharges), a significant decrease was also registered in nutrients (N-NH 4 , N-NO 3 , total nitrogen, P-PO 4 , and total phosphorus) and organic loads? (five-day biological oxygen demand, chemical oxygen demand) of pond effluents. At the pond supplied with good quality river water, however, the same determinants showed that effluent water quality worsened significantly. Total organic carbon and suspended solids increased in effluents of ponds with high fish biomass stocked.Conclusion. The results demonstrate that, during the growing season, properly managed carp ponds represent ecosystems with high self-cleaning ability. They may play an important role in the nutrient balance, storage and trapping in agricultural landscape with high population density.