Are There Predictable Shifts in Fish Communities Following Instream Habitat Restoration? A Multistream Analysis.

In the past two centuries, anthropogenic stressors have degraded the structure and function of streams by accelerating bank erosion, decreasing riparian buffer zones, and altering the natural flow regime. Habitat restoration has become a common mitigation strategy in response to stream degradation, though empirical research evaluating its effectiveness is lacking in the United States. This study investigated responses in fish community following habitat restoration in five restored, Illinois streams. We assigned fish species to habitat, trophic, and reproductive guilds based on their habitat preferences, feeding habits, and life history. Streams were separated into enhancement and removal groups for analysis. Shifts in functional guild composition pre- to post-restoration were investigated via non-metric multidimensional scaling (NMDS). Indicator species analysis was used to determine species significantly associated with pre- and post-restoration sampling. There were significant shifts in functional guild compositions when looking at both restoration types together, and when looking at them separately. There were 11 indicator species in enhancement streams and 29 in dam removal streams, with most of these species being indicative of post-restoration sampling. Results from this study suggest dam removal has a more pronounced impact on stream fish assemblages compared to habitat enhancement, though enhancement still has significant impact on the functional ecology of fish communities. These results are useful for managers of freshwater streams, as they can expect to see the same changes in fish communities after enhancement and dam removal are completed in their systems.