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Dolph, C. L., D. D. Huff, C. J. Chizinski, and B. Vondracek. 2011. Implications of community concordance for assessing stream health at three nested spatial scales in Minnesota, USA. Freshwater Biology 56(8):1652-1699.


1. Fish and invertebrate assemblage data collected from 670 stream sites in Minnesota
(USA) were used to calculate concordance across three nested spatial scales (statewide,
ecoregion and catchment). Predictive taxa richness models, calibrated using the same
data, were used to evaluate whether concordant communities exhibited similar trends in
human-induced taxa loss across all three scales. Finally, we evaluated the strength of the
relationship between selected environmental variables and the composition of both
assemblages at all three spatial scales.
2. Significant concordance between fish and invertebrate communities occurred at the
statewide scale as well as in six of seven ecoregions and 17 of the 21 major catchments.
However, concordance was not consistently indicative of significant relationships
between rates of fish and invertebrate taxa loss at those same scales.
3. Fish and invertebrate communities were largely associated with different environmental
variables, although the composition of both communities was strongly correlated to
stream size across all three scales.
4. Predictive taxa-loss models for fish assemblages were less sensitive and precise than
models for invertebrate assemblages, likely because of the relatively low number of
common fish taxa in our dataset. Both models, however, distinguished reference from
non-reference sites.
5. The importance of concordance, geographic context and scale are discussed in relation to
the design and interpretation of stream integrity indicators. In particular, our findings
suggest that community concordance should not be viewed as a substitute for an
evaluation of how assemblages respond to environmental stressors.


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July (3rd Quarter/Summer) 2011

Unit Authors

  • Bruce Vondracek

Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey