over large regions. In a study conducted in the Eastern Alps, Jersabek et al. (2001)
report that the 41% of the high-altitude lakes (>0.5 ha, above 1300 m a.s.l.) present
fish fauna; in Valle d’Aosta (Western Alps), where the first documented fish
introductions date back to 1926 (Mammoliti Mochet 1995), an accurate catalogue
of all the ponds and lakes (Frezet 2003) indicate that the 43% of the lakes (>0.5 ha,
above 1000 m a.s.l.) present fish fauna and this percentage increase to the 50%
excluding those lakes above 2900 m a.s.l., where fish survival is challenged by the
extreme temperatures and glacial influence; in the Gran Paradiso National Park
(Western Alps) 35% of all the lakes (>0.5 ha) is occupied by fish (RT personal
observation). These percentages are similar to those observed in other mountain
ranges (Miró and Ventura 2013; Bahls 1992).
8.3 The Process of Species Introductions in the Pyrenees
The different fish species described to be introduced in the Pyrenees include the
salmonids S. trutta, O. mykiss and S. fontinalis, and the cyprinid Phoxinus sp. in the
southern (Spanish) Pyrenees (Miró and Ventura 2013, 2015) and these species
together with S. umbla and S. namaycush in the northern (French) Pyrenees
(Delacoste et al. 1997). At a global scale, S. trutta and O. mykiss are considered
among the 100 most invasive alien species in the world (Lowe et al. 2000). Within
Europe, O. mykiss, S. fontinalis and S. namaycush have been introduced from North
America, while S. trutta and S. umbla that are native European species have been
widely introduced beyond their native range, mostly in high mountain areas.
Therefore, they are all classified as European alien species (Hulme et al. 2009).
8.3.1 Trout Introductions
The oldest written documents describing fishing rights in high mountain lakes of
the Pyrenees date back to the fourteenth and fifteenth centuries (Miró 2011). These
initial introductions for traditional exploitation resulted in 26.5% of the lakes of the
southern slope of the Pyrenees having introduced trout by 1900 (Fig. 8.1; Miró and
Ventura 2013). Similarly, on the northern side of the Pyrenees, it has been
described that ca. 25% of the lakes had fish before the onset of widespread introductions after 1936 (Delacoste et al. 1997), which might also be attributed to
traditional fishing activities by local fishermen. Miró and Ventura (2013) findings
suggest that human exploitation of some of these lakes might have originated
further back in time, possibly back to prehistoric times, when primitive residents
already used the high-altitude pastures (Miró 2011). However, written evidence
suggests that the first major historical introductions occurred within the medieval
warm period (1000–1300 AD) when the human population in the Pyrenees was
highest (Miró 2011).
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report that the 41% of the high-altitude lakes (>0.5 ha, above 1300 m a.s.l.) present
fish fauna; in Valle d’Aosta (Western Alps), where the first documented fish
introductions date back to 1926 (Mammoliti Mochet 1995), an accurate catalogue
of all the ponds and lakes (Frezet 2003) indicate that the 43% of the lakes (>0.5 ha,
above 1000 m a.s.l.) present fish fauna and this percentage increase to the 50%
excluding those lakes above 2900 m a.s.l., where fish survival is challenged by the
extreme temperatures and glacial influence; in the Gran Paradiso National Park
(Western Alps) 35% of all the lakes (>0.5 ha) is occupied by fish (RT personal
observation). These percentages are similar to those observed in other mountain
ranges (Miró and Ventura 2013; Bahls 1992).
8.3 The Process of Species Introductions in the Pyrenees
The different fish species described to be introduced in the Pyrenees include the
salmonids S. trutta, O. mykiss and S. fontinalis, and the cyprinid Phoxinus sp. in the
southern (Spanish) Pyrenees (Miró and Ventura 2013, 2015) and these species
together with S. umbla and S. namaycush in the northern (French) Pyrenees
(Delacoste et al. 1997). At a global scale, S. trutta and O. mykiss are considered
among the 100 most invasive alien species in the world (Lowe et al. 2000). Within
Europe, O. mykiss, S. fontinalis and S. namaycush have been introduced from North
America, while S. trutta and S. umbla that are native European species have been
widely introduced beyond their native range, mostly in high mountain areas.
Therefore, they are all classified as European alien species (Hulme et al. 2009).
8.3.1 Trout Introductions
The oldest written documents describing fishing rights in high mountain lakes of
the Pyrenees date back to the fourteenth and fifteenth centuries (Miró 2011). These
initial introductions for traditional exploitation resulted in 26.5% of the lakes of the
southern slope of the Pyrenees having introduced trout by 1900 (Fig. 8.1; Miró and
Ventura 2013). Similarly, on the northern side of the Pyrenees, it has been
described that ca. 25% of the lakes had fish before the onset of widespread introductions after 1936 (Delacoste et al. 1997), which might also be attributed to
traditional fishing activities by local fishermen. Miró and Ventura (2013) findings
suggest that human exploitation of some of these lakes might have originated
further back in time, possibly back to prehistoric times, when primitive residents
already used the high-altitude pastures (Miró 2011). However, written evidence
suggests that the first major historical introductions occurred within the medieval
warm period (1000–1300 AD) when the human population in the Pyrenees was
highest (Miró 2011).
184
M. Ventura et al.