Differences in fish assemblages among habitats found in the lower Willamette River, Oregon: application of and problems with multivariate analysis

Abstract Fish species assemblages and physical habitat characteristics were compared among nine sampling areas between river kilometers 0 and 27 of the Willamette River, Oregon, using data from each of three years and for all three years combined. We used cluster analysis to group sampling areas according to similarities in catch of northern squawfish ( Ptychocheilus oregonensis ), black crappie ( Pomoxis nigromaculatus ), white crappie ( Pomoxis annularis ), largemouth bass ( Micropterus salmoides ) smallmouth bass ( Micropterus dolomieui ), and walleye ( Stizostedion vitreum vitreum ). We then used canonical analysis to determine whether species assemblages were related to differences in habitat among areas caused by waterfront development. Cluster analysis revealed three clusters of sampling areas based on similarities in fish species assemblages in 1988, 1990, and for 1988–1990 combined, and four clusters in 1989. Canonical analysis results varied among years. We used our results to discuss limitations of multivariate community analysis and identify factors that may affect such analysis.