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Vol. 54, 2015
Selective foraging
by non-native rainbow trout on invertebrates in Patagonian streams in
Argentina
Cecilia
Yanina Di Prinzio1,2,3*, Guillermo Omad1,2,3,
María Laura Miserendino1,2,3 and Ricardo Casaux1,2,3,4
1Consejo
Nacional de Investigación en Ciencia y Tecnología (CONICET), Rivadavia
1917, 1033 Buenos Aires, Argentina
2Centro de Investigaciones Esquel de Montaña y Estepa
Patagónica (CIEMEP), Sarmiento 890, 9200
Esquel, Argentina
3Laboratorio de Investigación en Ecología y
Sistemática Animal (LIESA), Universidad Nacional de la Patagonia,
Sarmiento 890, 9200 Esquel, Argentina
4Instituto Antártico Argentino, Cerrito 1248, 1010
Buenos Aires, 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.
Key words:
Selective predation; Non-native fish; Stream; Patagonia.
*Correspondence: E-mail: laracar@posgradouatx.com.mx
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