A Fish Index of Biotic Integrity for South Dakota's Northern Glaciated Plains Ecoregion

Ecosystem goods and services are impaired when stream biotic communities are degraded by anthropogenic stressors.  An Index of Biotic Integrity (IBI) translates community structure into a standardized ecoregion-specific score of stream health.  Our main objectives were to (1) develop a fish IBI for streams of the Northern Glaciated Plains (NGP) Ecoregion and (2) validate candidate reference sites against streams of known condition.  The screening of fish metrics for wadeable, perennial streams required  the sampling of 8 sites of known condition and 15 random sites twice during the summers of 2010 and 2011.  Twenty-eight reference sites were sampled by the South Dakota Department of Environment and Natural Resources during the summers of 2006 - 2011.  Candidate metrics were tested using metric range, signal-to-noise ratios, responsiveness to disturbance, and redundancy.  Least disturbed sites were more similar to reference sites than targeted disturbed sites and the average rank of least disturbed sites was higher for screened metrics than disturbed sites.  Ultimately, these fish metrics will be combined with periphyton and macroinvertebrate metrics to form an Integrated IBI that will be used to compare stream scores across the NGP to provide valuable insights into the influence of changes to stream ecosystem services.