The environmental preferences of three species of Australian freshwater fish in relation to the effects of riparian degradation

Abstract

To assess the likely effects on three coexisting species of Australian freshwater fish of riparian loss, we examined the temperature, light, and habitat preferences of each species in relation to commonly documented effects of riparian degradation on stream environments. Such effects include reduced shade, instream structure, and water depth and increased temperature and invasive instream vegetation. Xiphophorus helleri, Gambusia holbrooki, and Melanotaenia duboulayi differed significantly in mean swimming depth, preferences for light and habitat, and in their patterns of behavioural change through the day. Values of interspecific spatial overlap (25–58%) indicated that the overall environmental preferences of G. holbrooki, X. helleri, and M. duboulayi were reasonably distinct. Habitat alterations associated with riparian removal are likely to favour the exotic species G. holbrooki over the native species M. duboulayi, but the results for X. helleri suggest that not all poeciliid␣species are strong indicators of degraded conditions.