Fish community structure is characterized in the NAWQA Program as part of an integrated physical, chemical, and biological assessment of water quality. The objective of the NAWQA characterization of fish community structure is to relate fish community characteristics to physical, chemical, and other biological factors to assess water-quality conditions. To accomplish this, fish community structure is described at sites representing selected environmental settings.
Fish Communities of Fixed Sites
Fish communities were surveyed at 20 wadeable stream sites during 1993-95, including 8 fixed sites. An additional 12 "comparison" sites were sampled to assess the representativeness of the fixed sites to the overall study area. The results of this work has been published in USGS Water-Resources Investigations Report 95-4211-C, Fish Communuties of Fixed Sites in the Western Lake Michigan Drainages, Wisconsin and Michigan, 1993-95, by Daniel J. Sullivan.
A total of 44 fish species from 12 families were collected at the 20 sites. The family with the most species represented were the minnows. The number of species per site ranged from one at a small urban site (Lincoln Creek at Milwaukee) to 21 at an agricultural site (North Branch Milwaukee River near Random Lake, Wisconsin). The number of individuals collected in a sampling pass ranged from 21 at a stream in the forested northwest of the study area (Peshekee River near Martins Landing, Michigan) to 498 (mostly minnows and darters) at an agricultural site (East River near Green Bay, Wisconsin). White sucker (Catostomus commersoni) were collected at the most sites, 17 of the 20. Species indicative of a coldwater environment were collected at 12 sites. In general there was more variation among fish communities of warmwater sites than among coldwater sites.
Index of Biotic Integrity (IBI) scores ranged from "Very poor" at Lincoln Creek in Milwaukee to "Excellent" at 3 sites: Silver Creek near Bowler, Wisconsin; North Branch Milwaukee River near Random Lake, Wisconsin; and Kelly Brook near Laona, Wisconsin.
Canonical correspondence analysis (CCA) indicated that soil erodibility was a significant predictor of species composition. Other factors were land use, soil permeability, and and bedrock permeability.
Fish Communities of Benchmark Streams in Agricultural Areas of Eastern Wisconsin
Fish commuties were also surveyed at 20 stream sites in agricultural areas in eastern Wisconsin in 1993 and 1995 as part of the "Benchmark Streams" study. These streams were selected for study because of their potential use as regional references for healthy streams in agricultural areas. The results of this study were published in USGS Water-Resources Investigations Report 96-4038-D Fish Communities of Benchmark Streams in Agricultural Areas of Eastern Wisconsin, by Daniel J. Sullivan and Elise M. Giddings.
Of the 20 sites, 19 are classified as trout (salmonid) streams, and fish species that require cold or cool water conditions to survive were the most commonly collected. At least one species of trout was collected at 18 sites, and trout were the single most abundant species at 13 sites. The species with the greatest collective abundance, and collected at 18 of the 20 sites, were mottled sculpin (Cottus bairdi), a coldwater species.
In all, 31 species of fish were collected at the benchmark streams. The number of species per stream ranged from 2 to 14, and the number of individuals collected at a site ranged from 19 to 264. Index of Biotic Integrity (IBI) scores indicated excellent biotic integrity at 5 sites, good at 10 sites, fair at 4, and 1 site had poor biotic integrity.