Prairie Stream Fish Community Structure and Related Effects of Semi-Permeable Barriers

Fish community structure within stream networks is influenced by species-specific movement patterns from adjacent streams.  However, fragmentation caused by barrier construction disrupts fish movement within networks and contributes to altered community structure.  Here we consider how community composition varied among stream networks with differential levels of fragmentation imposed by semi-permeable barriers (e.g., road crossings).  We sampled three sites within 12 stream networks (36 total sites) of Kansas during summer and fall of 2010.  We computed the Dendritic Connectivity Index (DCI) for each network and considered community similarities (Percent Similarity Index) among sites within networks across a gradient of DCI values.  Preliminary results suggested crossings with perches (waterfalls) occurring at their outflows were associated with differences in upstream community structure and selectively excluded some potamodromous species (e.g., Catostomidae).  However, the flashy nature of prairie streams may act to mitigate effects of fragmentation because of inundation of perched outflows.  Potential conservation approaches include crossing designs that maintain natural substrates and do not eventually develop perches at their outflows.