Quantifying Restoration Benefits to Native Stream Fishes

Science Center Objects

This project is a collaboration of scientists from the USGS and University of Georgia to collect and analyze data describing how small-stream fishes use habitats created through stream restoration activities.  The USFWS Region 4 requested this Science Support Partnership (SSP) project as a means to evaluate the effectiveness of stream restoration (primarily in north Georgia, and potentially in surrounding states) with respect to enhancing local species richness and densities of stream fishes.

The Challenge: Stream restoration is one of the primary tools used by natural resource managers globally to address losses of aquatic biota, particularly fishes.  In the southeast US, stream restoration is increasingly employed to mitigate for unavoidable and irreparable loss of stream habitat, such as occurs when streams are piped or buried in urban areas.  Over the last two decades, hundreds of stream restoration projects have been conducted in Georgia alone through the Corps of Engineers mitigation banking program.  Typically, these projects involve placement in streams of habitat-creating structures, such as rock vanes and J-hooks (to create pools) and artificial riffles.  Although managers commonly assume that these created habitats will support diverse and abundant populations of native fishes, published studies and syntheses have provided equivocal evidence that this is true.  Managers may thus benefit from information on how differing types of native fishes use specific types of habitats in restored compared to unrestored reaches.

The Science: We are collecting data in up to 40 stream restoration sites paired with sites in nearby unrestored sites.  At each site, we are enumerating fish and species using differing habitat types (pools and riffles) as well as hydraulic and bed sediment conditions in those habitats.  Our analyses will assess evidence that (1) stream restoration creates reaches that attract and hold more fishes than near-by unrestored reaches, (2) upstream fish movement could be impaired by particular habitat features in restored reaches or unrestored reaches, and (3) particular habitat structures contribute disproportionately to local fish diversity and fish density. Our analyses will necessarily incorporate and account for differences in fish communities that could be attributed to factors other than local habitat, including time elapsed since restoration activities, stream distance to population sources (such as larger streams), stream size, elevation and land-use history.  

The Future: This research should complement the monitoring currently conducted as part of the Corps of Engineers’ stream mitigation program, which uses total numbers of fishes of differing types captured in a standardized sample to score a restored stream reach with a respect to an Index of Biotic Integrity (IBI).  In this study, we will measure fish diversities and densities in particular habitat types within restored reaches in comparison with the habitats available in unrestored reaches. Thus, whereas standardized sampling provides a snap-shot of fish community status through an entire reach, our research may identify those habitat structures that contribute most strongly to differences between restored and unrestored reaches.