Revista Chilena de Historia Natural 80 (1): 81-98, 2007
RESEARCH ARTICLE
Establishment of Chinook salmon (Oncorhynchus tshawytscha) in Pacific basins
of southern South America and itspotential ecosystem implications
Salmon and trout species are not native to the southern hemisphere, however rainbow
and brown trout have been established a century in southern South America. Yet most attempts to introduce anadromous salmon
failed until the onset of aquaculture by 1980. Escapes of Oncorhynchus tshawytscha (Chinook salmon)
from aquaculture after 1990 have apparently produced increasingly important reproductive returns “naturalized”, to upper basins in
Chile and Argentina south of 39° S. In this paper we show data on the historic and spatial occurrence of chinook salmon in four Pacific
basins during the past decade. Our objective is to establish the progress of the settlement forecasting some ecosystem disruptions in
order to project and manage potential impacts. 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 and Pico. In Chile
and Argentina reproductive Chinooks ranged in size between 73 and 130 cm total length, being the smallest sizes those of Lake
Puyehue where the population is apparently landlocked. In Río Petrohué, the size of the runs varied from year to year reaching in the
peak season of 1996 and 2004 up to 500 kg of fish along 100 m of riverbank. Temporal distribution of juvenile Chinooks suggested
mainly a typical ocean type as they are gone to sea within the first year of age. As seen in Petrohue, reproductive populations could
import significant quantities of marine derived nutrients as they do in their original habitats thus disturbing natural cycles and balances.
Chinook establishment in these pristine watersheds in southern South America poses new challenges for decision makers and
fishermen since they may develop a fishery in the Pacific Ocean with consequences to other fishery resources. Additionally they also
become a resource for sport fishing. Therefore there is the need of developing management tools and approaches to control the
populations avoiding irreversible ecosystem disruptions and social conflicts.
Key words:
salmon invasion,
naturalized populations, nutrients uploads, sport fishing potential
