Thursday, June 7, 2007 - 10:15 AM
395

Channel stability or habitat quality? which drives fish IBI in midwestern streams?

Brenda J. Asmus1, Joseph A. Magner2, Bruce Vondracek3, and James A. Perry1. (1) Fisheries, Wildlife, and Conservation Biology, University of Minnesota, 200 Hodson Hall, 1980 Folwell Ave, St Paul, MN 55108, (2) Fisheries, Wildlife, and Conservation Biology; Forest Resources, University of Minnesota, 200 Hodson Hall, 1980 Folwell Ave, St Paul, MN 55108, (3) USGS, Minnesota Cooperative Fish and Wildlife Research Unit, 200 Hodson Hall, 1980 Folwell Ave, St Paul, MN 55108

We investigated relationships among fish communities, channel stability and habitat quality in two contrasting river basins in Minnesota.  Biological monitoring programs in the United States often assess aquatic habitat; it is uncommon to quantify channel geomorphic stability.  Stream beds and banks are major sources of sediment in disturbed Midwestern streams.  Excess sediment in streams is linked to chemical and biological impairments that require Total Maximum Daily Load (TMDL) investigations.  We examined whether channel stability (Pfankuch’s Stream Reach Inventory and Channel Stability Evaluation, PSI) or habitat quality (a modified Qualitative Habitat Evaluation Index, QHEI) was more able to predict the fish Index of Biotic Integrity (IBI).  We found that IBI was correlated with PSI in the Snake River, a wooded gravel-bed basin (n=14, ρ=0.49, p=0.07), whereas QHEI was not (ρ=0.34, p=0.23).  In contrast, IBI was correlated with QHEI in the Redwood River, a row crop dominated sand-bed basin (n=14, ρ=0.59, p=0.03), whereas PSI was not (ρ=0.06, p=0.83).  Both channel stability and habitat quality are important drivers of fish IBI, but their effects appear to be basin specific.  We recommend that both physical indices be assessed during biological monitoring to aid TMDL investigations of chemical and biological impairments.


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