Fish Assemblage Use of Constructed Woody Microhabitats in Sand-Bed Streams of the Upper Gulf Coastal Plain

We investigated fish use of standardized, constructed woody microhabitats (cane bundles) in four north Mississippi sand-bed streams with different degrees of channel degradation and natural instream woody cover. The streams described a disturbance gradient: Lee Creek (deeply incised, least depth and wood), Cypress Creek (channelized, low depth and wood), Puskus Creek (natural channel, moderate depth and wood) and Chewalla Creek (natural channel, deepest, highest wood).  We deployed replicate cane bundles over one year (six samples).  We focused on three measures of microhabitat use: fish occupancy, abundance, and assemblage structure.  Across all streams, we captured 30 fish species representing eight families.  Fishes used bundles least in the most disturbed stream (7% occupancy) but showed similar occupancy in the others (20-27%).  Mean fish abundance in bundles differed greatly between the two most disturbed streams but was intermediate and similar in the least disturbed streams.  Fish assemblages in bundles were distinct among streams.  Pairwise effect sizes in assemblage similarity described a gradient from the most to least disturbed stream.  Small wood in these sand-bed streams is obviously an important but dynamic component of fish habitat, but responses of fishes to that habitat are mediated largely by the disturbance history of the stream.