Research Paper

Habitat-based variation in the trophic ecology of the world’s highest-altitude self-sustaining population of invasive rainbow trout

¹ Doctorado en Ciencias Aplicadas mención Sistemas Acuáticos, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de Antofagasta, Antofagasta, Chile
² Fish and Stable Isotope Ecology Laboratory, Instituto de Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile
³ Millenium Nucleus of Austral Invasive Salmonids (INVASAL), Concepción, Chile
⁴ Universidad de Antofagasta Stable Isotope Facility (UASIF), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
⁵ Genomics in Ecology, Evolution and Conservation Laboratory, Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Casilla 160-C, Universidad de Concepción, Concepción, Chile
⁶ Scottish Centre for Ecology and the Natural Environment, University of Glasgow, Glasgow, UK

^* Corresponding author: karina.gonzalez.flores@ua.cl; karinabe.gf@gmail.com

Received: 9 May 2024
Accepted: 27 August 2024

Abstract

Rainbow trout (Oncorhynchus mykiss) have been widely introduced outside of their natural range and are one of the World’s most invasive species. Illegally introduced into the isolated, high-altitude (4520 m) Chungará catchment of northern Chile, rainbow trout have now been present in the system for ∼30 years and to our knowledge are the World’s highest known self-sustaining population. However, nothing is known about the status and impacts of these trout in the system. We analysed stomach contents and stable isotopes (δ¹³C, δ¹⁵N, δ³⁴S) from liver and muscle to study the trophic ecology of rainbow trout from lake, river mouth and riverine habitats in the Chungará catchment to understand their basic ecology and to characterise their potential trophic interactions with native taxa. Both stomach contents and stable isotope values showed spatial differences in diet and habitat use, but also revealed that diet varied temporally within habitats. The trophic position of rainbow trout was similar in the three habitats examined and was constant over time, apart from the riverine population. Predation by rainbow trout had different potential effects across pelagic, benthic, and riverine habitats in the Chungará catchment, through the consumption of zooplankton, native amphipods, aquatic insects, and the endemic cypriniodontid fish Orestias chungarensis.