Selective foraging by non-native rainbow trout on invertebrates in Patagonian streams in Argentina

Abstract

Background It is well known that fish predation alters ecosystem processes by top-down effects. Salmonids are described as aggressive, visually and size-selective predators. Thus, prey selection by the non-native rainbow trout was examined on a seasonal basis at two streams: Nant y Fall (NyF) and Cabeza de Vaca (CVA) at Patagonia, a region where this kind of information is lacking. Results The benthos density at NyF was higher than that at CVA, and at both streams, riffles supported higher macroinvertebrate densities than pools. The diet of trouts from both streams was dominated by aquatic macroinvertebrates, was diverse, and was varied seasonally. The individuals represented in the stomach contents were among the largest available at the streams. Diet diversity peaked during spring at NyF and during summer at CVA, whereas at both streams, the niche width peaked during spring. Prey selectivity varied seasonally. The selected preys included both aquatic (Gasteropoda, Crustacea, Plecoptera, Trichoptera, Ephemeroptera, Coleoptera, Diptera, and Odonata) and terrestrial organisms (adult dipterans, Oligochaeta, Araneae, Homoptera, Hymenoptera, Orthoptera, and Hemiptera). Some infaunal invertebrates like oligochaetes and some small Coleoptera and Diptera larvae (mainly Chironomidae) were not selected by trouts. Conclusions Despite of the overall dominance of trichopteran species, the composition of the diet of the rainbow trout varied seasonally. This fish positively selected both aquatic and terrestrial organisms. We observed that in both streams, trouts consumed the larger individuals available in those environments.Fil: Di Prinzio, Cecilia Yanina. Universidad Nacional de la Patagonia "san Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones En Ecología y Sistemática Animal; ArgentinaFil: Omad, Guillermo Hugo. Universidad Nacional de la Patagonia "san Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones En Ecología y Sistemática Animal; ArgentinaFil: Miserendino, Maria Laura. Universidad Nacional de la Patagonia "san Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones En Ecología y Sistemática Animal; ArgentinaFil: Casaux, Ricardo Jorge. Universidad Nacional de la Patagonia "san Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones En Ecología y Sistemática Animal; Argentin

The effects of trophic interaction between the Patagonian native Percichthys trucha and the invasive Oncorhynchus mykiss during the juvenile period

“…Meridialaris chiloeensis nymphs (Ephemeroptera) were collected manually from the Gutie ´rrez stream, and used as prey. These nymphs are very abundant in lotic environments (Albarin ˜o and Buria 2011) and fish species consumed them readily (present study; Di Prinzio et al 2015;Navone 2006). Prey size did not differ significantly between fish species trials (Mann-Whitney, P [ 0.05).…”

“…Ephemeroptera nymphs and Chironomidae larvae represent a significant part of the total biomass of macroinvertebrates found in Andean Patagonian rivers (Miserendino 2001), and are commonly eaten by fishes in rivers. It is known that O. mykiss juveniles have a generalist feeding strategy, and are capable of feeding on any peak of prey (Arismendi et al 2011;Di Prinzio et al 2015). In the same way, P. trucha juveniles in lentic environments have been described as generalized benthic invertebrate predators (Lattuca et al 2008).…”

Quantifying the Foodscape for Stream‐Dwelling Cutthroat Trout Reveals Spatial and Temporal Ranges of Resource Exploitation and Energy Intake

“…While many species of salmonids have terminally oriented mouths, perhaps making benthic foraging difficult, behavioral observations indicate a shift towards benthic foraging under experimentally reduced levels of drift abundance (Fausch et al 1997). In addition, salmonids are typically viewed as diurnal foragers, feeding during daylight hours when drift can be observed and targeted in the water column (Kreivi et al 1999;Neuswanger et al 2014;Di Prinzio et al 2015) and because they have a reduced detection and capture success of invertebrates in darkness (Fraser and Metcalfe 1997;Rader 1997;Miyasaka and Nakano 1999;Elliott 2011). Although food availability has long been thought to be one of the main limits of salmonid abundance in streams (Chapman 1966;Grant and Kramer 1990;Allen and Castillo 2007;Railsback and Harvey 2011), and departures from diurnal drift-foraging behavior are acknowledged in the literature, the extent and importance to which benthic and nocturnal foraging contribute to food intake are largely unknown (Harvey and Railsback 2014).…”

“…2014; Di Prinzio et al. 2015) and because they have a reduced detection and capture success of invertebrates in darkness (Fraser and Metcalfe 1997; Rader 1997; Miyasaka and Nakano 1999; Elliott 2011). Although food availability has long been thought to be one of the main limits of salmonid abundance in streams (Chapman 1966; Grant and Kramer 1990; Allen and Castillo 2007; Railsback and Harvey 2011), and departures from diurnal drift‐foraging behavior are acknowledged in the literature, the extent and importance to which benthic and nocturnal foraging contribute to food intake are largely unknown (Harvey and Railsback 2014).…”

Seasonal changes in abundance and feeding ecology of an endemic, keystone predator following the introduction of large rainbow troutOncorhynchus mykiss

“…Outside of warmwater stream introductions, salmonid and smallmouth bass interactions have been primarily focused on negative effects of invasive smallmouth bass on salmonids in western North America (Fritts & Pearsons, 2004;Vigg et al, 1991;Zimmerman, 1999). Moreover, effects of introduced trout on keystone predators have generally been studied in reference to other native trout (Dunham et al, 2002;Krueger & May, 1991;Peterson et al, 2004) or effects of non-native trout on prey communities (Di Prinzio et al, 2015;Shelton et al, 2015aShelton et al, , 2015bYard et al, 2011).…”