Coupling changes in physical habitat and fish community structure in Central Texas streams with interannual variability in stream discharge.

Hydrological variability and instream habitat connectivity play predominant roles in governing fish communities in lotic ecosystems. Hydrologic extremes of drought (2006) and flood (2007) events were the backdrop for fish assemblage and physical habitat data collected during summer in 28 central Texas streams. I evaluated the correspondence between the magnitude of physical habitat and fish community composition change in stream reaches sampled in these two contrasting years using multivariate statistics and ordination techniques. Streams characterized by disconnected pools had different fish community structure and different habitat characteristics than streams that had habitats connected by flowing water. The amount of interannual change in both fish community structure and habitat characteristics was greatest between streams that had disconnected pools in 2006 and their paired samples in 2007. Indicator species analysis revealed indicator species of disconnected and connected habitat types whose life histories give us information about the biotic interactions within these habitats.