Complementary Indicators: Can Fully Integrating Fish and Benthic Macroinvertebrate IBI Metrics Better Reflect Stream Condition?

The US Clean Water Act requires states to monitor streams within their boundaries and report on impairment or attainment of designated uses. Preferences for stream taxa and the associated metrics chosen as indicators of biological impairment varies by state and may be influenced by allotted time and funding, regional variation (of taxa and stressors), and regional expertise. Though it has been suggested that monitoring with multiple taxa could increase the sensitivity of bioassessment, a limited number of available studies comparing the use of different stream taxa have shown inconsistent results whether there is significant concordance amongst the taxa as indicators of biological impairment when examined independently along gradients of impairment. Stream taxa do not live independently of one another and likely do not best inform us about biological impairment when assessed independently. The added utility of using multiple taxa for assessing biological impairment may be dependent upon integration of the indices and metrics. We collected community samples of fish and benthic macroinvertebrate assemblages from 50 wadeable streams representing a range of impairment in the New River watershed in North Carolina, Virginia, and West Virginia. Analyses will determine how sensitively the gradient of impairment is detected by the two assemblages separately compared with the integration of the metrics of the two assemblages. Repeatability will be explored with similar analyses of previously acquired data from the upper Wabash River watershed, Indiana. Future sampling and analyses are planned to determine the utility of integrating stream fish and benthic macroinvertebrate assemblages as complimentary indicators of stream health. Ideal results will support the creation of integrated multi-assemblage, multi-metric assessment tools.