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Schaufler G.,University of Salzburg | Stogner C.,University of Salzburg | Gassner H.,Federal Agency of Water Management | Kaiser R.,University of Salzburg | Schabetsberger R.,University of Salzburg
International Review of Hydrobiology

Half a century after introducing the final host Northern pike (Esox lucius L. 1758) into Lake Grundlsee in Austria, a sudden massive infection with the pike tapeworm Triaenophorus crassus Forel 1868 was noticed in the population of the intermediate host Arctic charr (Salvelinus umbla (L. 1758)) and led to the closure of this famous fishery. In an effort to contain the epidemic, a total of 1163 pike were removed over a period of three years (2008-2010). The efficiencies of gill and fyke netting as well as electro and spear fishing were assessed. All four methods were costly with EUR 37-371 to catch a single fish. During intensive fishing, catch per unit effort and fish lengths of pike declined. Fyke netting coupled with electro fishing turned out to be the most practicable strategy to reduce the pike stock. After another three years, prevalence of T. crassus in Arctic charr could be reduced by 40% in 2013. However, it will be impossible to completely eradicate pike and its parasite in the lake. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Poikane S.,European Commission - Joint Research Center Ispra | Birk S.,University of Duisburg - Essen | Bohmer J.,Bioforum GmbH | Carvalho L.,UK Center for Ecology and Hydrology | And 16 more authors.
Ecological Indicators

The Water Framework Directive is the first international legislation to require European countries to establish comparable ecological assessment schemes for their freshwaters. A key element in harmonising quality classification within and between Europe's river basins is an "Intercalibration" exercise, stipulated by the WFD, to ensure that the good status boundaries in all of the biological assessment methods correspond to similar levels of anthropogenic pressure. In this article, we provide a comprehensive overview of this international comparison, focusing on the assessment schemes developed for freshwater lakes. Out of 82 lake ecological assessment methods reported for the comparison, 62 were successfully intercalibrated and included in the EC Decision on intercalibration, with a high proportion of phytoplankton (18), macrophyte (17) and benthic fauna (13) assessment methods. All the lake assessment methods are reviewed in this article, including the results of intercalibration. Furthermore, the current gaps and way forward to reach consistent management objectives for European lakes are discussed. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND. Source

Sichrowsky U.,University of Innsbruck | Schabetsberger R.,University of Salzburg | Gassner H.,Federal Agency of Water Management | Kaiser R.,University of Salzburg | And 2 more authors.

Cestode-infested copepods (Cyclops abyssorum) are strongly attracted to illuminated cages used for rearing juvenile whitefish (Coregonus sp.) in Lake Fuschlsee, Austria. In the submersed cages, artificial light at night concentrated zooplanktonic organisms about 40-fold compared to normal abundances outside cages, thus ensuring a sufficient food supply for planktivorous fish. However, inside the cage the average prevalence of Triaenophorus spp. and Proteocephalus spp. within C. abyssorum was 5.4 and 5.1 times higher than in the pelagic zone of the lake. In absolute numbers 3.83Ind.L-1 within the cage hosted a procercoid compared to 0.04Ind.L-1 in the open water. After three months in the cage, 90% of the coregonids harboured on average 5 plerocercoids of Triaenophorus crassus and 100% were parasitized by Proteocephalus exiguus. Total length and weight of whitefish with T. crassus plerocercoids were lower than of those without the parasite. Rearing fish for stocking purposes in illuminated cages increases the risk of cestode accumulation in fish populations. We discourage from using this method in lakes with cestode-problems or suggest to at least release fish before procercoids of Triaenophorus spp. occur in the zooplankton to prevent massive infestations inside the cage. © 2013 Elsevier B.V. Source

Schaufler G.,University of Salzburg | Stogner C.,University of Salzburg | Achleitner D.,Federal Agency of Water Management | Gassner H.,Federal Agency of Water Management | And 3 more authors.
International Review of Hydrobiology

In 2005, an epidemic of the pike tapeworm Triaenophorus crassus Forel, 1868 broke out in the Arctic charr (Salvelinus umbla (L. 1758)) stock of Lake Grundlsee, Austria. Besides the definitive host Northern pike (Esox lucius L. 1758), which was introduced into the lake in the 1960s, the cestode requires copepods as first and salmonid fish as second intermediate hosts. Within 2 years, the prevalence of the cestode in medium sized Arctic charr increased to almost 100% and the abundance reached a maximum of 55 cysts per fish, leading to the closure of the fishery. Such a massive infection of Arctic charr has never been reported. High pike abundance and the occurrence of a suitable copepod host facilitated the outbreak. The only first intermediate host Cyclops abyssorum praealpinus Kiefer, 1933 predominated the zooplankton community during May, when cestode coracidia hatch from eggs. Only during this infectious period, C. abyssorum praealpinus was eaten by Arctic charr (2-50% of prey organisms). Low fishing pressure on pike enabled the development of a large population that served as reservoir for T. crassus with up to 687 cestodes per fish. To contain the epidemic, 1671 pike were removed between 2008 and 2013. Infection of Arctic charr decreased to 60% and a maximum number of 16 cysts in 2013. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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