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 ANGEL; BARRIGA, JUAN PABLO

BIOLOGICAL INVASIONS

SPRINGER

Lugar: Berlin; Año: 2020 vol. 22 p. 3293 - 3305

1387-3547

Introduced salmonids have invaded almost all Patagonian freshwater environments,and yet the effect they have had on native fish populations is difficult to evaluate due toa lack of data prior to their introduction. In this study we focused on evaluating trophicinteractions during the juvenile period of Oncorhynchus mykiss, and the ecologicallysimilar native Percichthys trucha . For this purpose, we evaluated the diet and sizerange of juveniles of both species in the Caleufu River over one yearly cycle. Thefunctional response (FR: the relationship between prey density and consumption rate)and functional response ratio (FRR= attack rate/handling time) were estimated for eachspecies, in mono-specific and multi-specific trials. Comparison of the diet of thesespecies by season showed high similarity for spring and summer. It was also found thatjuvenile sizes of these species overlap during early ontogeny. Additionally, bothspecies presented a type II FR in mono-specific trials, with similar functional curves. Inmulti-specific experiments O. mykiss juveniles were dominant, leading to a reductionin P. trucha food intake. FRR was higher for O. mykiss than for P. trucha in monospecificexperiments, a difference which increased in multi-specific experiments,indicating the high potential ecological impact of O. mykiss . Our results show it isvery likely that O. mykiss and native P. trucha compete in lotic environments, O.mykiss being competitively superior, highlighting the potential detrimental effect theymay have during the juvenile period, especially in habitats and seasons where foodresources are scarce.