Keywords Global change Á Introduced species Á Trout Á Minnows Á Amphibians Á
Restoration Á Conservation Á High mountain lakes
8.1 Introduced Species, a Global Threat to Freshwater
Ecosystems
Among the biomes of the planet, freshwaters have suffered the strongest decline in
the number of vertebrate species during 1970–2010 (76% in freshwaters compared
to 39% in the other two biomes; McRae et al. 2014). This great decline is a result,
on a global scale, of factors related to habitat destruction, pollution, water-level
reductions and invasive species among others (Collen et al. 2014). Although these
factors are affecting all species within the habitats, amphibians are amongst the
most threatened freshwater groups (Collen et al. 2014).
In Europe, freshwater fish are one of the animal groups with a higher number of
invasive species (Hulme et al. 2009). The introduction of freshwater fish is closely
related to human activities (Gido et al. 2004; Marchetti et al. 2004) and especially to
fishing in the case of salmonids (Cambray 2003; Cowx and Gerdeaux 2004; Granek
et al. 2008). The circumstances and timing of recent arrival of some species have
been documented worldwide (FAO 2003) and in some particularly well-studied
lakes (Villwock 1994; Pringle 2005; Volta and Jepsen 2008). In other cases, it has
been possible to describe the introductions that have suffered different lakes using
historical reconstructions (Emery 1985; Garcia-Berthou and Moreno-Amich 2000;
Brancelj et al. 2000; Buchaca et al. 2011). Previous studies show that the introduction of freshwater fish can often have significant negative ecological consequences (Vitule et al. 2009).
High mountain lakes are usually isolated from lower streams by physical barriers
that have prevented natural colonisation of fish (Pechlaner 1984; Knapp et al. 2001a;
Miró and Ventura 2013). In these ecosystems, the introduction of fish species is mainly
related to recreational fishing and promoted by different administrations (Pister 2001;
Schindler and Parker 2002). There is detailed information on the historical evidences of
the spread of salmonids in some high mountain areas of the western United States
(Christenson 1977; Bahls 1992; Knapp 1996; Wiley 2003) and the Canadian Rockies
(Schindler 2000). In these areas, introductions are described chronologically from the
end of nineteenth and beginning of twentieth centuries and they were initially made by
individual fishermen, and a few decades later by the Governmental agencies
(Christenson 1977; Schindler 2000). In contrast to these areas, the information about
the stocking history in other mountain ranges is difficult to access. In particular the
information from the high mountain ranges of Asia (Petr 1999) and South America
(Vigliano and Alonso 2007; Martín-Torrijos et al. 2016) are insufficient, because of
uncontrolled stocking (Vigliano and Alonso 2007; Ortega et al. 2007).
In contrast to the American continent, in European high mountain lakes the
colonisation process has not been studied in detail (Gliwicz and Rowan 1984;
182
M. Ventura et al.
Restoration Á Conservation Á High mountain lakes
8.1 Introduced Species, a Global Threat to Freshwater
Ecosystems
Among the biomes of the planet, freshwaters have suffered the strongest decline in
the number of vertebrate species during 1970–2010 (76% in freshwaters compared
to 39% in the other two biomes; McRae et al. 2014). This great decline is a result,
on a global scale, of factors related to habitat destruction, pollution, water-level
reductions and invasive species among others (Collen et al. 2014). Although these
factors are affecting all species within the habitats, amphibians are amongst the
most threatened freshwater groups (Collen et al. 2014).
In Europe, freshwater fish are one of the animal groups with a higher number of
invasive species (Hulme et al. 2009). The introduction of freshwater fish is closely
related to human activities (Gido et al. 2004; Marchetti et al. 2004) and especially to
fishing in the case of salmonids (Cambray 2003; Cowx and Gerdeaux 2004; Granek
et al. 2008). The circumstances and timing of recent arrival of some species have
been documented worldwide (FAO 2003) and in some particularly well-studied
lakes (Villwock 1994; Pringle 2005; Volta and Jepsen 2008). In other cases, it has
been possible to describe the introductions that have suffered different lakes using
historical reconstructions (Emery 1985; Garcia-Berthou and Moreno-Amich 2000;
Brancelj et al. 2000; Buchaca et al. 2011). Previous studies show that the introduction of freshwater fish can often have significant negative ecological consequences (Vitule et al. 2009).
High mountain lakes are usually isolated from lower streams by physical barriers
that have prevented natural colonisation of fish (Pechlaner 1984; Knapp et al. 2001a;
Miró and Ventura 2013). In these ecosystems, the introduction of fish species is mainly
related to recreational fishing and promoted by different administrations (Pister 2001;
Schindler and Parker 2002). There is detailed information on the historical evidences of
the spread of salmonids in some high mountain areas of the western United States
(Christenson 1977; Bahls 1992; Knapp 1996; Wiley 2003) and the Canadian Rockies
(Schindler 2000). In these areas, introductions are described chronologically from the
end of nineteenth and beginning of twentieth centuries and they were initially made by
individual fishermen, and a few decades later by the Governmental agencies
(Christenson 1977; Schindler 2000). In contrast to these areas, the information about
the stocking history in other mountain ranges is difficult to access. In particular the
information from the high mountain ranges of Asia (Petr 1999) and South America
(Vigliano and Alonso 2007; Martín-Torrijos et al. 2016) are insufficient, because of
uncontrolled stocking (Vigliano and Alonso 2007; Ortega et al. 2007).
In contrast to the American continent, in European high mountain lakes the
colonisation process has not been studied in detail (Gliwicz and Rowan 1984;
182
M. Ventura et al.