Native and exotic fishes in a Patagonian reservoir with rainbow trout cage culture: spatial and trophic resource use

BLASETTI, GUILLERMO; NABAES JODAR, DIEGO N.; CORDERO, PEDRO; CUSSAC, VÍCTOR E.; BECKER, LEANDRO A.

KNOWLEDGE AND MANAGEMENT OF AQUATIC ECOSYSTEMS

EDP SCIENCES S A

Año: 2017 p. 1 - 14

1961-9502

Although the interactions of exotic salmonids with native Patagonian fishes are well known,little is known about the ecology and impact of farmed fish escapees. Salmonid production in Argentina islargely concentrated in the Alicurá reservoir in north Patagonia, where fish community studies have beenscarce. Here, we assess and compare the spatial distribution, body size?condition and diet of the differentfish species in this reservoir. Strong vertical segregation was observed between exotic rainbow troutOncorhynchus mykiss (both escapees and wild), dominating the littoral zone, and native Percichthys truchawhich dominate the medium and deep strata. Low piscivory?benthivory and high zooplanktivory wereobserved for rainbow trout, both traits being uncommon at a regional scale. Escaped farmed rainbow trout(ERT) diet included abundant indigestible items along with wild prey. Higher body condition of P. truchaclose to farms, as well as the regionally unprecedented high incidence of Daphnia sp. in the guts of all thespecies suggest that farm nutrient discharges have had significant impacts. Finally, the high body conditionof ERT, together with their wild food diet and the long dispersal distance observed, demonstrate post-escapesuccess, drawing our attention to potential upstream dispersion affecting the biodiversity and fisheries ofPatagonian rivers and lakes.