Can satellite ponds buffer the impact of introduced fish on newts in a mountain pond network?

Fish introductions into originally fishless mountain lentic habitats can affect native amphibians at different spatial scales. Introductions are often associated with local extinctions, but they can also affect amphibian metapopulations at a landscape level, intercepting amphibians when they move into reproductive and overwintering sites, preventing these movements, or reducing the overall metapopulation abundance and diversity. 2Freshwater habitat networks are considered more resistant to biological invasions than isolated habitats, because they usually provide safe alternative sites that can buffer the impact of introduced fish. However, few studies have attempted to understand whether fish stocking also affects amphibians in surrounding fishless habitats. 3This general hypothesis was tested using distribution data of Italian crested newt (Triturus carnifex Laurenti 1768) in a mountain pond network collected over a 13-year-long study (2005-2017), encompassing the periods before (pre-2011) and after (post-2012) fish (Salmo trutta L. 1758) were introduced in the pond where most of the newts were initially observed. 4After fish introduction, visual counts dropped down close to zero in the invaded pond, but they increased in satellite ponds. This was a progressive increase not related to population size and should be regarded as a short-term consequence of the slow colonization of satellite ponds. 5These results confirm the dramatic impact of fish introductions on native amphibians at a local scale, but suggest that some amphibians can counteract their impact by moving to alternative sites, when available. 6Halting fish stocking, lake and pond recovery, and the construction of alternative sites are proposed as management and conservation actions to preserve amphibian diversity.