EFFECT OF INTRODUCED FISH ON AMPHIBIAN ASSEMBLAGES IN MOUNTAIN LAKES OF NORTHERN SPAIN

We have analyzed the effect of introduced fish on amphibian assemblage s in mountain lakes of the Cantabrian range (Asturias and Leon; northe rn Spain), by comparing amphibian species richness, abundance and dive rsity in lakes occupied by introduced fish and in those without fish. Amphibian species numbers were significantly lower in lakes inhabited by fish, both considering the absolute mumber and the values corrected for the effect of the main correlates of the species richness (shore extent and altitude). Amphibian abundance (all species and stages pool ed) and diversity also tended to be lower in lakes inhabited by fish a s compared with the fishless ones. Direct predation by fish, for which we present evidence in our studied lakes, is likely to be the main ca use for the reported amphibian depletion, although recognition by adul t amphibians of chemical cues from predatory fish and subsequent avoid ance of habitats with fish for reproduction could also be contributory .