Trophic interactions between a native Catfish (Trichomycteridae) and a non-native species, the Rainbow Trout, in an Andean stream, San Juan, Argentina

Abstract

The trophic relationship between Torrent Catfish (Hatcheria macraei) and Rainbow Trout (Oncorhynchus mykiss) was studied in a lotic Andean system of Argentina to examine whether these fish compete for the same food resources. Fishes were sampled seasonally, in autumn, spring, and summer. Hatcheria macraei and O. mykiss presented a carnivorous generalist feeding strategy. Trout diet was dominated by aquatic macroinvertebrates, and terrestrial invertebrates were an important component in summer. Large-sized Rainbow Trout fed on Catfish, which in turn preyed mainly on Chironomidae and Elmidae larvae. During flood periods, the Trout diet, as well as that of the Catfish, was mainly composed of clingers (Elmidae and Chironomidae) and particularly in the case of Catfish, burrowers (Oligochaeta) were found. We found an elevated dietary overlap between Trout and Catfish with seasonal changes. Our results suggest that coexistence of Trout and Catfish depends on input of terrestrial invertebrates, and the feeding of Catfish on small prey.

Keywords:

• non-native salmonids
• terrestrial and aquatic prey
• competition
• diet

Acknowledgements

We thank the two anonymous reviewers for their comments and improvements to the manuscript. We are also grateful for the field trip assistance we received from Rodrigo Acosta, Gustavo Fava, Alejandro Laspiur and Lucas Corrales.

Funding

This study was partially funded by the Consejo de Investigaciones Científicas y Técnicas y de Creación Artística (CICITCA – UNSJ, RES. 1531 JCA).

The corresponding catch permit granted by the Dirección de Conservación y Áreas Naturales Protegidas (Bureau of Conservation and Natural Protected Areas) was received from the Subsecretaría de Medio Ambiente (Department of Environmental Affairs) (Resolution No. 002 dated 12/03/08, processed by File No. 1204-1593-I-08).