2005; Peters and Lodge 2009). A similar situation exists on the southern slope of
the Pyrenees, where the release of any organism to the environment without government authorization is also strictly prohibited (Miró 2011). Nevertheless, similar
to the findings from the southern valleys of the Pyrenees, in some regions of North
America a large proportion of anglers appear to be unaware of, or choose to ignore,
the current regulation forbidding the release of live organisms because they believe
their actions are compassionate and that the released unused bait is a suitable food
for angling fishes (Kerr et al. 2005; Kilian et al. 2012). The results described above
strongly suggest the need to intensify preventive actions by giving accurate
information of the potentially adverse effects on the local environment of the release
of non-native organisms to fisheries boards and local communities. These actions
are one of the best guiding principles to prevent the spread of invasive species
together with regulation and legislation (Simberloff et al. 2013).
8.4 Ecological Consequences
The implications of stocking into high mountain lakes derive primarily from the
fact that fish occupy a higher trophic level that was previously inexistent leading to
profound ecological changes. Their introduction in fishless lakes is commonly
associated with extirpation or reduction of native aquatic species (e.g. invertebrates
and amphibians) and can have indirect effects on the whole ecosystem, and on its
linkage with the surrounding terrestrial habitats (Eby et al. 2006). From high altitude lakes, fish can colonise otherwise inaccessible downstream aquatic habitats
often propagating the ecological impact at a whole basin scale (Adams et al. 2001).
The studies concerning the ecological impact of introduced fish in high-altitude
lakes are strongly biased towards the impact of salmonids, even if minnows and
other small species are likely to become—or already are—a serious conservation
problem in the near future. Since trout are visual predators, most of the direct
impacts are attributable to their size selective predation strategy, affecting only
larger non-fossorial taxa (Knapp et al. 2001b; Tiberti et al. 2014a, b). Published
studies from different mountain regions of the world have focused mainly on the
effects of trout introductions that produce a drastic reduction or elimination of those
autochthonous animal groups of bigger size. Threatened groups live mostly in the
littoral and benthic zones and include amphibians (Knapp 2005; Orizaola and Braa
2006; Pope 2008; Pope et al. 2008; Pilliod et al. 2010; Tiberti and von Hardenberg
2012; Bosch et al. 2006; in particular those with aquatic larval stages; Bradford
et al. 1993; Martinez-Solano et al. 2003; Tiberti et al. 2014b) and conspicuous
macroinvertebrates (Knapp et al. 2001b; Pope et al. 2009; de Mendoza et al. 2012;
Pope and Hannelly 2013; Tiberti et al. 2014b; Fig. 8.2). The effects on amphibians
are of special concern, since they are one of the most threatened animal groups
worldwide (Beebee and Griffiths 2005).
The effects of trout on the plankton are less predictable, basically due to the
smaller size of the planktonic animals, and the biology of the introduced
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M. Ventura et al.
the Pyrenees, where the release of any organism to the environment without government authorization is also strictly prohibited (Miró 2011). Nevertheless, similar
to the findings from the southern valleys of the Pyrenees, in some regions of North
America a large proportion of anglers appear to be unaware of, or choose to ignore,
the current regulation forbidding the release of live organisms because they believe
their actions are compassionate and that the released unused bait is a suitable food
for angling fishes (Kerr et al. 2005; Kilian et al. 2012). The results described above
strongly suggest the need to intensify preventive actions by giving accurate
information of the potentially adverse effects on the local environment of the release
of non-native organisms to fisheries boards and local communities. These actions
are one of the best guiding principles to prevent the spread of invasive species
together with regulation and legislation (Simberloff et al. 2013).
8.4 Ecological Consequences
The implications of stocking into high mountain lakes derive primarily from the
fact that fish occupy a higher trophic level that was previously inexistent leading to
profound ecological changes. Their introduction in fishless lakes is commonly
associated with extirpation or reduction of native aquatic species (e.g. invertebrates
and amphibians) and can have indirect effects on the whole ecosystem, and on its
linkage with the surrounding terrestrial habitats (Eby et al. 2006). From high altitude lakes, fish can colonise otherwise inaccessible downstream aquatic habitats
often propagating the ecological impact at a whole basin scale (Adams et al. 2001).
The studies concerning the ecological impact of introduced fish in high-altitude
lakes are strongly biased towards the impact of salmonids, even if minnows and
other small species are likely to become—or already are—a serious conservation
problem in the near future. Since trout are visual predators, most of the direct
impacts are attributable to their size selective predation strategy, affecting only
larger non-fossorial taxa (Knapp et al. 2001b; Tiberti et al. 2014a, b). Published
studies from different mountain regions of the world have focused mainly on the
effects of trout introductions that produce a drastic reduction or elimination of those
autochthonous animal groups of bigger size. Threatened groups live mostly in the
littoral and benthic zones and include amphibians (Knapp 2005; Orizaola and Braa
2006; Pope 2008; Pope et al. 2008; Pilliod et al. 2010; Tiberti and von Hardenberg
2012; Bosch et al. 2006; in particular those with aquatic larval stages; Bradford
et al. 1993; Martinez-Solano et al. 2003; Tiberti et al. 2014b) and conspicuous
macroinvertebrates (Knapp et al. 2001b; Pope et al. 2009; de Mendoza et al. 2012;
Pope and Hannelly 2013; Tiberti et al. 2014b; Fig. 8.2). The effects on amphibians
are of special concern, since they are one of the most threatened animal groups
worldwide (Beebee and Griffiths 2005).
The effects of trout on the plankton are less predictable, basically due to the
smaller size of the planktonic animals, and the biology of the introduced
188
M. Ventura et al.