Competitive interaction between introduced rainbow trout and native silverside in a Chilean stream

The field experiment presented here elucidates the competitive effect of exotic trout on Chilean silverside. This is the first local experimental work that demonstrates the negative effect of trout on native fish from Chile. Interspecific competition between the Chilean Silverside Basilichthys australis and the rainbow trout Oncorhynchus mykiss was evaluated by an experimental design that used enclosures in a stream of central Chile. Nine enclosures were equally assigned to three treatments, low density, with two silversides; interspecific treatment, with two silversides and four trout; and high density treatment, with six silversides. The results indicate that silversides were weaker competitors, negatively affected by the presence of trout; they showed significant weight loss and reduction in stomach content in the presence of trout. © Springer Science + Business Media B.V. 2009