The establishment of exotic Chinook salmon (Oncorhynchus

DI PRINZIO C.Y.; PASCUAL M.A.

Ann. Limnol. - Int. J. Lim.

Año: 2008 vol. 44 p. 25 - 32

The aim of this paper is to report the colonization process of three headwater rivers of two large trans-national Pacific riverbasins shared by Chile and Argentina, by exotic Chinook salmon (Oncorhynchus tshawytscha). To characterize the populations atthe sites, fish were analyzed in terms of length, weight, age, and stream residency patterns. Fishermen familiar with the area wereinterviewed to establish the seasonal occurrence of fish and to reconstruct the history of the colonization process. Records ofsalmon production in Chile by regions were examined to evaluate the potential origin of fish in coastal net pen aquaculture. Theregularity of spawning runs in our study sites indicates that Chinook salmon have established spawning populations in theserivers. While spawning was verified in all three rivers, only one seems to serve as a holding area for pre-spawning salmon early inspring. The correlation in the historical occurrence of Chinook salmon in the three rivers suggests that they have been colonizedas part of the same introduction event. Moreover, the temporal correlation with the development of ocean net pen production forthis species in the Chiloé region suggests that the fish may originate from escapes from these enterprises. As in all previousreports of exotic Chinook salmon in Patagonia and New Zealand, populations in the three rivers have a combination of streamand ocean ecotypes. We discuss the importance of plasticity in critical life history characteristics for the success of Chinooksalmon in Patagonia, compared to other species of anadromous salmonids.