As land surrounding streams becomes more urbanized, changes in stream habitat, flow, and water chemistry can affect the organisms living in the stream in many ways. Fish have long been used in assessments of streams. Data on species - their abundance and distribution, their pollution tolerance and other environmental preferences - allow computation of metrics for water quality assessment in a manner similar to that used for algae and invertebrates. Metrics computed for fish assemblages include the Index of Biotic Integrity (IBI); number of species and individuals, native taxa, predator fish; and number of fish in certain groups such as sunfishes, suckers, pollution sensitive, and pollution tolerant fish. The Wisconsin fish IBI we used was developed by the Wisconsin Dept of Natural Resources (Lyons , 1992).
As part of the USGS NAWQA program, the Western Lake Michigan Drainages (WMIC) Study Unit was one of six study units chosen to be part of the National Study on Effects of Urbanization on Stream Ecosystems. The WMIC Study was done in 2003-2004 in the Milwaukee and Green Bay Area. Methods used were nationally consistent within the USGS to allow comparison with other areas of the US. Methods are described in Moulton and others (2002). Ecological data collected included distribution and abundance of algae, invertebrates, and fish, as well as stream habitat at stream sites. As part of this Study on the effects of urbanization, we sampled fish assemblages from 30 sites during late July 2004. Sampling was done by electrofishing with either backpack or towed-barge units for a 150m reach at each site - two electrofishing passes were made for each reach. Electrofishing stuns most fish for a few seconds, allowing them to be netted and placed in a bucket or live holding well in the barge. In addition, three seine hauls were made in each reach with ¼-inch mesh nets. Fish are identified to species, counted, weighed, and measured for total length before being released back to the stream.
Data analyses for this Study are currently in progress. Raw data on fish assemblages have been reviewed and we are examining relations, if any, to environmental characteristics of the streams and their watersheds. Results will be published in 2006-7 in USGS reports and journal articles.
Moulton II, S.R., J.G. Kennen, R.M. Goldstein, and J.A. Hambrook, 2002. Revised Protocols for Sampling Algal, Invertebrate, and Fish Communities as Part of the National Water-Quality Assessment Program. U.S. Geological Survey Open-File Report 02-150, 72 pp.
Lyons, John, 1992. Using the Index of Biotic Integrity (IBI) to measure environmental quality in warmwater streams of Wisconsin : St. Paul , MN , US Dept. of Agriculture, Forest Service, North Central Forest Experiment Station, General Technical Report NC-149, 51 p.