Dietary overlap among native and non-native fish in Patagonian low-order streams

Abstract

-The diet composition and feeding strategy of native and exotic fish species were studied from May 2005 to February 2006 in three Patagonian low-order streams. A total of 464 fish were caught, which belonged to the exotic species Oncorhynchus mykiss (270), Salmo trutta (177) and the native species Hatcheria macraei (17). The analysis of 336 stomach contents indicated that at the individual level, the three species had a generalized feeding strategy based on benthic invertebrates (Plecoptera, Trichoptera, Coleoptera and Diptera). In the three streams, the widest population niches were observed in winter. There was, however, also a slight tendency toward an increased between-phenotype contribution to the niche width in same season, indicating that a small proportion of individuals within the fish populations specialized by predominantly feeding on a few specific prey species. Hence, the wide population niche widths observed throughout the year were partly a result of mixed individual feeding strategies within the populations. The higher diet overlaps were registered between exotics O. mykiss-S. trutta at Glyn and Carbo´n, and O. mykiss and the native H. macraei at Manguera, but it changed markedly through the year, perhaps depending on temporal changes in food availability suggesting a competitive coexistence of these species. This is mainly related to the fact that both species changed their food preferences in spring and foraged almost exclusively on Aubertoperla illiesi. This implies that in order to reduce the predation risk or the inter-specific competition for food, the fish species might partition the feeding habitats.

Feeding strategy of the non‐native rainbow trout,Oncorhynchus mykiss, in low‐orderPatagonian streams

“…As observed in other studies carried out in Patagonia (Buria et al 2009;Arismendi et al 2011;Di Prinzio & Casaux 2012), as well as in Scotland, Japan and New Zealand (Bridcut 2000;McIntosh 2000;Kawaguchi et al 2003), benthic macroinvertebrates, terrestrial insects, fish and vegetable matter were represented in the diet of rainbow trout. Except for adult dipterans, benthic macroinvertebrates predominated in the diet of trout from both streams.…”

“…; Arismendi et al . ; Di Prinzio & Casaux ), as well as in Scotland, Japan and New Zealand (Bridcut ; McIntosh ; Kawaguchi et al . ), benthic macroinvertebrates, terrestrial insects, fish and vegetable matter were represented in the diet of rainbow trout.…”

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

“…These preys contributed strongly to the diet in late summer and early autumn in NyF and in late spring and summer in CVA, decreasing their importance as prey in the remaining seasons. Despite of the overall dominance of these species, the composition of the diet varied seasonally as observed in previous studies carried out in the region (Buria et al 2009;Di Prinzio and Casaux 2012;Di Prinzio et al 2013). Rainbow trouts from both streams tended to forage on the larger individuals of each prey species.…”

“…The rainbow trout (Oncorhynchus mykiss) has been the most widely distributed species in the region (Pascual et al 2002;Baigun and Ferriz 2003;Di Prinzio et al 2009) generating a great economic resource input. Several studies focused on rainbow trouts' feeding strategies in Patagonian environments and analyzed the impact of this species on native fauna (Modenutti and Balseiro 1994;Pascual et al 2002;Buria et al 2007Buria et al , 2009Buria et al , 2010Albariño and Buria 2011;Di Prinzio and Casaux 2012;Di Prinzio et al 2013). However, the degree of prey selectivity displayed by this fish remains poorly understood.…”

Feeding habits of the alien brook trout Salvelinus fontinalis and the native brown trout Salmo trutta in Czech mountain streams

“…WFC: within-phenotype component, BPC: between-phenotype component. See also Table S5. partitioning largely depends on temporal changes in food availability and species involved (Nakano et al, 1999;Di Prinzio and Casaux, 2012).…”