Invasive rainbow trout Oncorhynchus mykiss preying on the endangered naked characin Gymnocharacinus bergii at its thermal limits

Abstract

The expansion of the invasive rainbow trout Oncorhynchus mykiss into the thermal headwaters of Valcheta Stream (Patagonia, Argentina) and new predation records on the endangered endemic naked characin Gymnocharacinus bergii are presented here. These findings are discussed in relation to the contemporary evolution and thermal refuges hypothesis. This study has immediate implications for the conservation of G. bergii.

Status and population dynamics of the Critically Endangered Valcheta frog Pleurodema somuncurense on the Patagonian Somuncura Plateau

“…In contrast, the local populations of the Rama Fría were small and restricted to stream sections located up to 1 km away from the hot springs (Velasco et al 2016). These differences might be due to the presence of a high number of threats at Rama Fría, including a higher number of sites occupied by the invasive rainbow trout Onchorynchus mykiss (Quiroga et al 2017), which is a well-known predator of native am phibians worldwide (e.g. Gillespie 2001, Matthews et al 2001, Pilliod & Peterson 2001, Martín-Torrijos et al 2016.…”

Gymnocharacinus bergii: Cussac, V., Quiroga, S., Kacoliris, F., Povedano, H., Crichigno, S., Becker, L. & Baigún, C.

“…This decline is in coincidence with the increasing expansion in range of the exotic salmonid, the Rainbow Trout (Oncorhynchus mykiss), towards the headwaters of the stream since its introduction at the beginning of the 20th century (Macchi and Vigliano 2014). Such behaviour could be related to a rapid local adaptation and heritability for higher temperatures in juveniles of this population of Rainbow Trout (Crichigno et al 2015, Quiroga et al 2017. The Naked Characin is considered to occur in one threat-defined location, based on the ubiquitous presence of introduced salmonids in the basin that predate on this endemic fish (Quiroga et al 2017), and a recently introduced species of characid (Cheirodon interruptus) that is thriving in the stream and is assumed to be a strong competitor for food and space with the Naked Characin (Perez et al 2015).…”

Predation by invasive rainbow trout on the critically endangered Pehuenche spiny‐chest frog

“…This salmonid is a voracious predator and considered to be one of the 100 most harmful invasive exotic species in the world (Global Invasive Species Database, 2020). In Argentina, there are many examples of the adverse effects of exotic fish on native amphibian and endemic fish (Cuello et al, 2009;Ortubay et al, 2006;Quiroga et al, 2017;Velasco et al, 2018). Corbalán et al (2010) This stream flows into the Pehuenche Stream (Figure 1) which, at this time, showed a very low flow compared to previous years.…”