Fish Predation: A Factor Affecting the Spatial Distribution of a Stream-Breeding Salamander

Abstract

Four lines of evidence indicate that larvae of the smallmouth salamander, Ambystoma texanum, are restricted to the upper portions of breeding streams because of fish predation: 1) A strong inverse relationship exists between the spatial distribution of fish and A. texanum larvae in streams in Kentucky, Indiana, and Ohio, 2) A. texanum larvae are palatable to several fish species that commonly occur in breeding streams, 3) A. texanum larvae can survive to metamorphosis in portions of streams from which they normally are excluded so long as fish are removed, and 4) fish that are washed into pools rapidly eliminate local pool populations of A. texanum larvae. Larvae are highly susceptible to predation because they show little tendency to remain beneath cover during the day when predatory fish are active. Selection may favor diurnal activity in order to maximize growth and development and, subsequently, avoid even greater mortality from stream drying.