The effects of trophic interaction between the Patagonian native Percichthys trucha and the invasive Oncorhynchus mykiss during the juvenile period

OTTURI, MARÍA GABRIELA; REGGI, PABLO EZEQUIEL; BATTINI, MIGUEL ÁNGEL; BARRIGA, JUAN PABLO

BIOLOGICAL INVASIONS

SPRINGER

Año: 2020

1387-3547

Introduced salmonids have invadedalmost all Patagonian freshwater environments, andyet the effect they have had on native fish populationsis difficult to evaluate due to a lack of data prior to theirintroduction. In this study we focused on evaluatingtrophic interactions during the juvenile period ofOncorhynchus mykiss, and the ecologically similarnative Percichthys trucha. For this purpose, weevaluated the diet and size range of juveniles of bothspecies in the Caleufu River over one yearly cycle.The functional response (FR: the relationship betweenprey density and consumption rate) and functionalresponse ratio (FRR = attack rate/handling time) wereestimated for each species, in mono-specific andmulti-specific trials. Comparison of the diet of thesespecies by season showed high similarity for springand summer. It was also found that juvenile sizes ofthese species overlap during early ontogeny. Additionally,both species presented a type II FR in monospecifictrials, with similar functional curves. In multispecificexperiments O. mykiss juveniles were dominant,leading to a reduction in P. trucha food intake.FRR was higher for O. mykiss than for P. trucha inmono-specific experiments, a difference whichincreased in multi-specific experiments, indicatingthe high potential ecological impact of O. mykiss. Ourresults show it is very likely that O. mykiss and nativeP. trucha compete in lotic environments, O. mykissbeing competitively superior, highlighting the potentialdetrimental effect they may have during thejuvenile period, especially in habitats and seasonswhere food resources are scarce.