species/populations, which can be more or less planktivorous. However, larger
crustaceans have also decreased their abundance and body size, or disappeared from
some high mountain lakes with stocked fish (Fig. 8.3; Brancelj 2000; Knapp et al.
2001b; Tiberti et al. 2014b). Among salmonids, this impact has been described in
particular for S. fontinalis, which is a generalist predator and which can rely on
large zooplankton species as a temporary or seasonal resource, especially during the
winter (Knapp et al. 2001b; Schabetsberger et al. 2009; Tiberti et al. 2014b;
Dawidowicz and Gliwicz 1983).
Direct predation of more visible taxa can produce a series of indirect ecological
effects (top-down and cascading effects) which affect the entire ecosystem (Hall
et al. 1976; Schindler et al. 2001; Sarnelle and Knapp 2005; Eby et al. 2006). The
decrease of large zooplankton species can produce a competitive release of small
zooplankton species (e.g. rotifers), which are less efficient grazers (Brooks and
Dodson 1965). Therefore, a decrease in crustaceans together with enhanced nutrient
cycling have led to changes in primary producers (Sarnelle and Knapp 2005;
Magnea et al. 2013).
The effect on benthic macroinvertebrates is also important during their emergency phase, when passing through the water column, which results in a substantial
reduction or alteration of their emergency rates (Pope et al. 2009; Epanchin et al.
2010; Tiberti et al. 2016b). This is also linked with indirect effects on surrounding
habitats through resource depletion for terrestrial insectivores (Epanchin et al. 2010;
Fig. 8.2 Seasonal trend of abundance from day 0 (15 June) to day 100 (23 September) of littoral
macroinvertebrates in naturally fishless (solid line) and stocked (dashed lines) lakes. While
borrowing taxa are unaffected or even indirectly favoured by fish presence, nectonic and benthonic
taxa (non-borrowers) are very sensitive to fish predation. Modified from Tiberti et al. (2014b)
8 Why Should We Preserve Fishless High Mountain Lakes?
189
crustaceans have also decreased their abundance and body size, or disappeared from
some high mountain lakes with stocked fish (Fig. 8.3; Brancelj 2000; Knapp et al.
2001b; Tiberti et al. 2014b). Among salmonids, this impact has been described in
particular for S. fontinalis, which is a generalist predator and which can rely on
large zooplankton species as a temporary or seasonal resource, especially during the
winter (Knapp et al. 2001b; Schabetsberger et al. 2009; Tiberti et al. 2014b;
Dawidowicz and Gliwicz 1983).
Direct predation of more visible taxa can produce a series of indirect ecological
effects (top-down and cascading effects) which affect the entire ecosystem (Hall
et al. 1976; Schindler et al. 2001; Sarnelle and Knapp 2005; Eby et al. 2006). The
decrease of large zooplankton species can produce a competitive release of small
zooplankton species (e.g. rotifers), which are less efficient grazers (Brooks and
Dodson 1965). Therefore, a decrease in crustaceans together with enhanced nutrient
cycling have led to changes in primary producers (Sarnelle and Knapp 2005;
Magnea et al. 2013).
The effect on benthic macroinvertebrates is also important during their emergency phase, when passing through the water column, which results in a substantial
reduction or alteration of their emergency rates (Pope et al. 2009; Epanchin et al.
2010; Tiberti et al. 2016b). This is also linked with indirect effects on surrounding
habitats through resource depletion for terrestrial insectivores (Epanchin et al. 2010;
Fig. 8.2 Seasonal trend of abundance from day 0 (15 June) to day 100 (23 September) of littoral
macroinvertebrates in naturally fishless (solid line) and stocked (dashed lines) lakes. While
borrowing taxa are unaffected or even indirectly favoured by fish presence, nectonic and benthonic
taxa (non-borrowers) are very sensitive to fish predation. Modified from Tiberti et al. (2014b)
8 Why Should We Preserve Fishless High Mountain Lakes?
189