Response of Rainbow Trout to Different Food Web Structures in Northern Patagonia: Implications for Growth, Bioenergetics, and Invasiveness

Abstract

Rainbow trout Oncorhynchus mykiss have successfully colonized almost all available water bodies in Patagonia. Introduction and restocking practices have taken place since the beginning of the 20th century without prior consideration of differences between environments in terms of fish community composition and trophic food web structure. We assessed how observed growth, growth efficiency, production, and biomass of rainbow trout populations from four Patagonian lakes were influenced by food web structure and prey quality, and we evaluated the growth strategies adopted by this species in response to environmental differences. Fish communities vary in terms of species composition and dominance. Bioenergetics simulations showed that size and growth patterns of rainbow trout varied between lakes, mainly owing to dietary differences. Fewer and lower-quality food items led to low growth efficiency and stunted growth, while a more diverse and higher-energy diet base led to higher growth efficiency and larger sizes. Rainbow trout density, production, and biomass were higher in the larger, more structurally complex lakes, although rainbow trout production values in the smallest lake were comparable with those in a lake twice its size. This study provides comparative evidence of the high plasticity of rainbow trout, for which the adoption of different growth strategies facilitates the successful colonization of environments where diet bases range widely in quality.

Received August 8, 2010; accepted November 9, 2010

ACKNOWLEDGMENTS

This paper was partially supported by Universidad Nacional del Comahue (Centro Regional Universitario Bariloche, B001) and Agencia Nacional de Promoción Científica y Tecnológica (25722). We thank David Beauchamp for suggestions and advice in relation to bioenergetics modeling and Audrey Shaw for the revision of the written English. This manuscript was greatly improved by the comments of the anonymous reviewers.