Ecological impact of introduced fish in high altitude lakes: a case of study from the European Alps
Fish introduction is a major threat to alpine lake biota leading to the loss of native species and to the degeneration of natural food-webs. This study provides an extensive investigation on the impact of the introduced fish Salvelinus fontinalis on the native communities of alpine lakes in the Gran Paradiso National Park. We compared the macroinvertebrate and zooplankton communities of six stocked and nine fishless lakes with a repeated sampling approach during the summers 2006–2009. The impact of fish presence on alpine lake fauna is often mediated by the strong seasonality governing these ecosystems, and it dramatically affects the faunal assemblage of littoral macroinvertebrates and the size, structure, and composition of the pelagic zooplankton community with a strong selective predation of the more visible taxa. Direct ecological impacts include a decrease or extinction of non-burrower macroinvertebrates and of large zooplankton species, while small zooplankton species and burrower macroinvertebrates were indirectly advantaged by fish presence. Due to the existence of a compensation between rotifers and crustaceans, fish presence does not affect total zooplankton biomass and diversity even if fish are a factor of ecological exclusion for large crustaceans. These compensatory mechanisms are a key process surrounding the impact of introduced fish in alpine lakes.
KeywordsSalvelinus fontinalis Zooplankton Macroinvertebrates Top-down effect Bayesian MCMC approach
We would like to thank all the students and field assistants who made this research possible: Francesca Ercoli, Gianluca Roncalli, Stefano Brighenti, Mattia Barbieri, Valentina Anello, Emanuele Acerbi, and Claudia Canedoli. We wish to extend a special thanks to Bruno Bassano (Gran Paradiso National Park) for the support and contribution to the research program. Funding and logistic support for this research was provided by the Gran Paradiso National Park within the framework of the FP7 ACQWA Project (Assessment of Climatic Change and Impacts on the Quantity and Quality of Water), Grant Agreement No. 212250. Supplemental funding for the chemical analyses was provided by ISE-CNR, Pallanza.
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