Predation relationships between introduced salmonids and the native fish fauna in lakes and reservoirs in northern Patagonia

Abstract

Abstract– A few native and exotic fish species are caught frequently in Andean lakes and reservoirs of northwestern Patagonia. Puyen (Galaxias maculatus) prey on zooplankton and benthos. Percichthys trucha has a wide range of prey, mainly benthos, while P. colhuapiensis become piscivorous when grown. Pejerrey (Odonthestes hatcheri) is omnivorous and large size individuals can be piscivorous. A siluroid, Diplomystes viedmensis, preys on benthos, insects, and fishes. Introduced salmonids are potential piscivorous. The puyen is the major prey category among fishes. Salmonids and perchichtids seem to partially overlap their diets but predation on Diplomystes appears to be restricted to salmonids. Present abundance of puyen, pejerrey and Percichthys spp. does not indicate a strong salmonid effect. However, the low abundance of D. viedmensis does. We studied present predation relationships among native and introduced fishes and postulated possible effects upon native fish fauna.

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

“…However, our results showed an intense vertical segregation that suggests strong (Barriga et al, 2002(Barriga et al, , 2007Juncos et al, 2014), and more abundant terrestrial insects are expected in spring and summer (Juncos et al, 2014). 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.…”

“…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).…”

“…Along with ERT, the native puyen Galaxias maculatus (Jenyns), big puyen Galaxias platei Steindachner, the catfishes Hatcheria macraei (Girard) and Diplomystes viedmensis MacDonagh (Muñoz-Ramírez et al, 2014), O. hatcheri, P. trucha (including, according to Ruzzante et al, 2006Ruzzante et al, , 2011 several nominal forms considered by López-Albarello, 2004), and the exotic rainbow trout, Atlantic salmon Salmo salar Linnaeus, brown trout Salmo trutta Linnaeus, and brook trout Salvelinus fontinalis (Mitchill), have been reported in the reservoir (Cussac et al, 1998;Macchi et al, 1999;Aigo et al, 2008). O. hatcheri, P. trucha, rainbow trout, and S. trutta are the most frequently captured species.…”

“…Previous reports on trophic relationships studied only the shallow littoral of the reservoir (Cussac et al, 1998;Macchi et al, 1999), and ERT were not discriminated from wild rainbow trout (WRT). Studies of the ecology of ERT are also lacking from other farmed lakes and reservoirs of Argentina.…”

Feeding habits and their implications for the conservation of the endangered semiaquatic frog Atelognathus patagonicus (Anura, Neobatrachia) in a northwestern Patagonian pond

“…Studies on the feeding habits of this species in North Patagonian lakes and reservoirs classify it as a voracious carnivore (Ferriz 1989, Cussac et al 1998, Macchi et al 1999) that includes in its diet animal organisms from benthos, nekton and macrophytia, and becomes piscivorous with growth and increase in size.…”