The Development and Evaluation of Methods for Quantifying Environmental Stress to Fish in Warm-Water Streams of Wisconsin Using Self-Organized Maps: Influences of Watershed and Habitat Stressors

Neal O'Reilly, Marquette University


In Section 101(a) of the federal Clean Water Act (CWA), it is stated that it's the "Congressional declaration of goals and policy" to achieve the "Restoration and maintenance of chemical, physical and biological integrity of Nation's waters..." For many decades scientist have attempted to develop tools to understand the connections between chemical and physical stresses of watershed conditions and instream habitat with biological response. To better understand the linkages between watershed and habitat conditions and biological response in warm water streams a series of multivariate statistical tools were tested using a database developed for warm water streams in the state of Wisconsin. The analysis illustrated that combination of Self-Organized Maps (SOM) with Principal Component Analysis and Analysis of Variance (ANOVA) and discriminant function analysis provided a tool that could accurately explain the effects of watershed and habitat conditions on the response by fish communities using metrics used in the Wisconsin fish Index of Biological Integrity (IBI). The results of the research illustrated that (1) unlike many water quality relations that arc linear in nature, the relations between watershed and habitat stressors and biological response are not linear and that to understand the relations nonlinear tools such as SOM are required, (2) stressors to stream environments are cumulative in nature and a multivariate approach is necessary to explain the relation, (3) different fish communities respond to different stresses in different ways, therefore strategies for watershed management need to be tailored specifically to the aquatic community that is being protected or managed.