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

DI PRINZIO C; CASAUX R,

ANNALES DE LIMNOLOGIE-INTERNATIONAL JOURNAL OF LIMNOLOGY

EDP SCIENCES S A

Lugar: Paris; Año: 2012 vol. 48 p. 21 - 30

0003-4088

Abstract – The diet composition and feeding strategy of native and exotic fish species were studied fromMay 2005 to February 2006 in three Patagonian low-order streams. A total of 464 fish were caught, whichbelonged to the exotic species Oncorhynchus mykiss (270), Salmo trutta (177) and the native species Hatcheriamacraei (17). The analysis of 336 stomach contents indicated that at the individual level, the three species hada generalized feeding strategy based on benthic invertebrates (Plecoptera, Trichoptera, Coleoptera andDiptera). In the three streams, the widest population niches were observed in winter. There was, however, alsoa 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 predominantlyfeeding on a few specific prey species. Hence, the wide population niche widths observed throughout the yearwere partly a result of mixed individual feeding strategies within the populations. The higher diet overlapswere registered between exotics O. mykiss–S. trutta at Glyn and Carbo´ n, and O. mykiss and the nativeH. macraei at Manguera, but it changed markedly through the year, perhaps depending on temporal changesin food availability suggesting a competitive coexistence of these species. This is mainly related to the fact thatboth 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 fishspecies might partition the feeding habitats.