Differential piscivory of the native Percichthys trucha and exotic salmonids upon the native forage fish Galaxias maculatus in Patagonian Andean lakes

Abstract

The present paper analyses predation patterns, of Percichthys trucha and salmonid fish upon Galaxias maculatus in five lakes of northern Patagonia with differing community and environmental characteristics. Tank experiments were performed to evaluate relative efficiency of native and exotic predators of G. maculatus under treatments with and without cover (aquatic vegetation). Important differences were found between predators with regards to distribution and consumption of G. maculatus. Salmonids are more efficient than P. trucha in consuming G. maculatus in deep environments with scarcely vegetation; in contrast to native species they frequently use the pelagic environment. Although pelagic habitat might have served in the past as a refuge from native predators in the past, G maculatus now experiences intense predation in the pelagic zone by exotic salmonids. It is suggested that the widespread distribution of G. maculatus in Patagonian lakes may have facilitated the success of salmonids throughout Patagonia.

Fishes of southern South America: a story driven by temperature

“…, ecological interactions (Milano et al 2002(Milano et al , 2006, alien species (Macchi et al 1999(Macchi et al , 2007, human impacts (Pascual et al 2002;Ortubay et al 2006), phylogeography, and molecular phylogeny (Johnston et al 2003;Near et al 2004;Zattara and Premoli 2005;Ruzzante et al 2006).…”

Native and exotic fishes in a Patagonian reservoir with rainbow trout cage culture: spatial and trophic resource use

“…Diet differences between species were marked, paralleling the observed segregation by depth. However, the low piscivory-benthivory of rainbow trout and the high incidence of zooplankton consumption across all species contrasted with the usual trophic relationships observed in other lakes and reservoirs of Andean Patagonia (Macchi et al, 1999(Macchi et al, , 2007Juncos et al, 2014;Arcagni et al, 2015).…”

“…would be increased. The study of the ecology of O. hatcheri is hampered by its present low abundance (Macchi et al, 2007;Juncos et al, 2014), which we argue has been accentuated in Alicurá reservoir by the impact of fish escapees , as suggested for other species in Chilean lakes (Arismendi et al, 2009).…”

“…Therefore, these changes would reduce the low incidence of G. maculatus in rainbow trout diet, and intensify its differences with P. trucha, as it consumes greater proportions of terrestrial insects, a prey group not generally important for P. trucha (Macchi et al, 1999;Juncos et al, 2014). The abundance of P. trucha at shallow depths in Patagonian lakes seems to vary across seasons according to its breeding cycle (Buria et al, 2007;Macchi et al, 2007;Aigo, 2010;Juncos et al, 2014), with higher presence of mature individuals in shallow waters in spring and early summer. Therefore, the low relative abundance of P. trucha observed here in the littoral zone from late summer to early autumn represents the non-reproductive season, when deeper habits are more common.…”

“…However, in Patagonian lakes it has been observed that rainbow trout shares deep habitats extensively with P. trucha in autumn, with some P. trucha remaining in the littoral in nonreproductive periods, although with lower abundances (Macchi et al, 2007;Juncos et al, 2014). The strong spatial segregation between P. trucha and rainbow trout intensified in Alicurá reservoir following the onset of aquaculture 25 years ago, also characterized by the almost total absence of O. hatcheri in littoral captures .…”