Establishment of Chinook salmon (Oncorhynchus tshawytscha)

SOTO D.; ARISMENDI I.; DI PRINZIO C.Y.; JARA F.

REVISTA CHILENA DE HISTORIA NATURAL

Lugar: Santiago de Chile; Año: 2007 p. 81 - 98

0716-078X

Salmon and trout species are not native to the southern hemisphere, however rainbow and brown trout havebeen established a century in southern South America. Yet most attempts to introduce anadromous salmonfailed until the onset of aquaculture by 1980. Escapes of Oncorhynchus tshawytscha (Chinook salmon) fromaquaculture after 1990 have apparently produced increasingly important reproductive returns “naturalized”, toupper basins in Chile and Argentina south of 39o S. In this paper we show data on the historic and spatialoccurrence of chinook salmon in four Pacific basins during the past decade. Our objective is to establish theprogress of the settlement forecasting some ecosystem disruptions in order to project and manage potentialimpacts. In Chile, sampling took place from 1995 to 2005 including rivers Petrohué, Poicas, and Río Negro-Hornopiren, and Lake Puyehue, in the X Region. In Argentina sampled rivers were Futaleufú, Carrenleufú andPico. In Chile and Argentina reproductive Chinooks ranged in size between 73 and 130 cm total length, beingthe smallest sizes those of Lake Puyehue where the population is apparently landlocked. In Río Petrohué, thesize of the runs varied from year to year reaching in the peak season of 1996 and 2004 up to 500 kg of fishalong 100 m of riverbank. Temporal distribution of juvenile Chinooks suggested mainly a typical ocean typeas they are gone to sea within the first year of age. As seen in Petrohue, reproductive populations couldimport significant quantities of marine derived nutrients as they do in their original habitats thus disturbingnatural cycles and balances. Chinook establishment in these pristine watersheds in southern South Americaposes new challenges for decision makers and fishermen since they may develop a fishery in the PacificOcean with consequences to other fishery resources. Additionally they also become a resource for sportfishing. Therefore there is the need of developing management tools and approaches to control thepopulations avoiding irreversible ecosystem disruptions and social conflicts.