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rich site with high biotic integrity that drains primarily agricultural land. Canonical correspondence analysis (CCA) revealed that soil credibility was a significant predictor of species composition. Though not statistically significant, land use, soil permeability, and bedrock permeability also were indicated as predictors of fish-species composition by CCA. INTRODUCTION In 1991, the first 20 study units of the National Water-Quality Assessment (NAWQA) Program began investigations. The NAWQA study-unit design for examining surface-water quality includes the collection of ecological data, including fish community information, at all fixed sites. This report describes the fish communities at the eight wadable fixed sites and twelve comparison sites in the Western Lake Michigan Drainages NAWQA study unit. An Index of Biotic Integrity is calculated for each sample. Multivariate statistics are used to determine differences, or gradients, between stream sites, as well as to determine environmental variables that may be associated with observed patterns in species composition. The scope of this report is limited to analysis of fish-community data collected at the 8 wadable fixed sites and 12 comparison sites during 1993-95. DESCRIPTION OF THE WESTERN LAKE MICHIGAN DRAINAGES The Western Lake Michigan Drainages study area encompasses 51,540 square kilometers in eastern Wisconsin and parts of the Upper Peninsula of Michigan (fig. 1, inset map). A brief discussion of selected study-area features follows; see Robertson and Saad (1996) for a more complete discussion. The study area, which includes 10 major river systems draining to Lake Michigan, is bounded on the south by the Illinois State line and extends north to about 50 kilometers north of Escanaba, Mich. The following rivers drain directly to Green Bay: the Escanaba and Ford Rivers in the Upper Peninsula of Michigan; the Menominee River, which forms much of the border between Michigan and Wisconsin; the Oconto and Peshtigo Rivers; and the Fox/ Wolf River, the largest system in the study unit. The Manitowoc, Sheboygan, and Milwaukee Rivers all drain directly to the western side of Lake Michigan. The bedrock of the study area consists of igneous and metamorphic rocks in the northwest, sandstone in the southwest, and carbonate rocks in the east. A small area of shale underlies the East River and the North Branch of the Manitowoc River near the city of Green Bay. The overall population of the study area is 2,435,000 (U.S. Bureau of Census, 1991), with urban land use accounting for less than 4 percent of the study area. The major cities and their populations are Milwaukee, 628,000; Green Bay, 96,000; Racine, 84,000; Kenosha, 80,000; and Appleton, 66,000. About 40 percent of the study area is forested, primarily in the northwestern part. Streams and lakes abound in this area and offer excellent fishing, boating, and other recreation. Agriculture accounts for 37 percent of the land use. Cropland and pastureland used for the dairy industry are the major agricultural activities. Cropland predominates in the southern part of the study area, and most of the major urban areas are also in the southern part of the study area. Wetlands account for about 15 percent of the land use. Lake Winnebago, a 55,440-hectare lake in the Fox River Basin, is a major surface-water feature of the study area. The Milwaukee River Basin in the southeastern part of the study area has the largest human population. STUDY DESIGN AND METHODS Study Design To isolate the effects of individual factors on stream quality, the Western Lake Michigan Drainages study area was subdivided into 28 environmental settings, called relatively homogenous units (RHUs), on the basis of bedrock geology, texture of surficial deposits, and land use/land cover (Robertson and Saad, 1995; 1996). A total of eight fixed sites were established on wadable streams within the study area. Additional sites were sampled within the six largest RHUs that contained fixed sites to better understand the variation of species composition among streams of similar sizes in the same RHU. These comparison sites were located in different drainage basins and the same or, in one case, similar RHUs (fig. 1). For the two smallest RHUs with fixed sites, it was not possible to locate a comparison site in a different drainage basin. 2 Fish Communities of Fixed Sites in the Western Lake Michigan Drainages, Wisconsin and Michigan, 1993-95 V Fixed site Comparison site RHU number 14 Site number Figure 1. Locations of 8 fixed sites and 12 comparison sites in the Western Lake Michigan Drainages. STUDY DESIGN AND METHODS 3 As part of the Western Lake Michigan Drainages NAWQA study, three additional fixed sites on larger streams were established. These large-river fixed sites were sampled to characterize the water quality of a large portion of the study area. However, these largeriver fixed sites were not sampled intensively for fish communities. General characteristics of the fixed sites, including exact locations, detailed land-use information, and general water-quality characteristics, can be found in Sullivan and others (1995). The 20 fixed and comparison sites drain areas that range from 25 to 543 sq km (square kilometers), with an average of 166 sq km. Land-use/land-cover types within the 20 basins are agriculture, forest, urban, and combinations of these. Surficial deposits are either clayey, loamy, sandy, or sand and gravel. Bedrock types are either igneous/ metamorphic, shale, or carbonate. Information about the environmental settings of the 20 sites are in table 1. The 8 fixed sites were sampled once each year during 1993-95. Three of these sites were sampled at three reaches in 1994 to gain an estimate of withinstream variation. The 12 comparison sites, with the exception of the East Branch Milwaukee River, were sampled in 1993 only. Due to high flow conditions in 1993 that made obtaining a representative sample difficult, the East Branch Milwaukee River was resampled in 1995 and these data are used in this report. Habitat data were collected at the fixed sites but not at all of the comparison sites. Therefore any references to habitat data will be qualitative and limited to those sites where it was collected. The fish species composition at the 8 fixed sites and 12 comparison sites is described and characterized to provide baseline information for trends studies. An Index of Biotic Integrity is calculated for the 20 sites and the scores compared to established ranges of biotic health of streams. Species-composition data for the 20 sites are compared on the basis of RHU variables in an attempt to determine the importance of RHU variables in predicting species composition. Beyond the scope of this report, the fish data complement algal, benthicinvertebrate, and water-chemistry data and can be used in conjunction with these data in an integrated assessment of overall water quality at the fixed sites. Finally, the data will be part of a national NAWQA ecological data base. Data-Collection Methods The fish-collection protocol for the NAWQA program is detailed in Meador and others (1993). Fishcommunity samples were collected during July and August, 1993; August, 1994; and June-September, 1995. The sites were sampled using either backpackmounted or a towed barge direct-current electrofishing unit. The length of the sampling reach was determined on the basis of the following criteria: (1) at least 2 types of geomorphic units (pools, riffles, or runs) occur repetitively in the selected reach, (2) minimum reach length is the lesser of 150 m (meters) or 20 times the average stream width, and (3) maximum reach length is 300 m. An attempt was made to select reaches that were upstream from bridges to limit effects from roads and channel modifications. If upstream reaches were inaccessible or not representative of the stream, downstream reaches were selected. The multiple-reach sampling that was done at three sites in 1994 consisted of sampling three similarlength reaches that contained no major tributaries or known point sources of contamination between them. Each reach was separated from the adjacent reach(es) by sufficient stream length so that sampling in one reach did not disturb the fish in another. Data-Analysis Methods Samples were collected over multiple years at the eight fixed sites. These data, while too few to analyze for temporal trends, were analyzed by detrended correspondence analysis (DCA), an ordination procedure used to identify and describe patterns in community structure based on species composition and relative abundance at each site (Gauch, 1982). The DCA was applied by using the CANOCO computer program (Ter Braak, 1988) that plots sites and species in an ordination diagram. A plot of DCA axis 1 and axis 2 station scores (fig. 2) indicate that samples from multiple years and multiple reaches at a given site generally group more closely together than do samples from different sites. This indicates that species composition did not vary widely between sample years and reaches. Thus for simplication, all further statistical analyses will be done using 1993 data only. For the East Branch Milwaukee River, a sample collected in 1995 is used because high flow made it difficult to collect a representative sample in 1993. 4 Fish Communities of Fixed Sites in the Western Lake Michigan Drainages, Wisconsin and Michigan, 1993-95 Ta bl e 1. W at er sh ed a nd la nd sc ap e ch ar ac te ris tic s of 8 fi xe d si te s an d 12 c om pa ris on s ite s in th e W es te rn L ak e M ic hi ga n D ra in ag es [F ix ed s ite s ar e lis te d in b ol d pr in t; km 2, sq ua re k ilo m et er s; D .A ., dr ai na ge a re a; R H U , r el at iv el y ho m og en eo us u ni t; m /k m , m et er s pe r k ilo m et er ; A g, a gr ic ul tu re ] H 3 D m to & z D M ap re fe re nc e nu m be r l 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 D A Si te n am e " ^ RH U

Fish communities of fixed sites in the Western Lake Michigan Drainages, Wisconsin and Michigan, 1993-95