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Introduction - <br />Biotic integrity and health of the <br />environment are not new concepts (Karr, <br />1993). Monitoring of the environmental <br />health of freshwater systems has progressed <br />from the near universal measurement of <br />BOD earlier in this century, to measurement <br />of a broader spectrum of chemical and <br />physical quantities, to incorporation of biota <br />into indices that are reflective, at least to <br />some extent, of environmental health (e.g., <br />Karr, 1981; Hilsenhoff, 1982). In spite of <br />this progression, and even with the <br />acknowledgment that biota provide better <br />interpretability than chemical parameters <br />(Steedman and Haider, 1993), there is much <br />to be learned. Indeed, the "agony of <br />community ecology" (Lewontin, 1974) is <br />that we often do not know which variables <br />are important and we lack simple <br />quantitative models to describe <br />environmental variation and its effect on the <br />biota (Keddy et al., 1993). <br />Biotic integrity can be defined as the <br />condition in which the biota of a given <br />system have an organizing, self-correcting <br />capability to recover from disturbance and <br />regain an end-state that is normal and good <br />for that system (Regier, 1993). "Normal <br />and good" can be something other than <br />pristine or naturally whole. Ecological <br />health, or integrity of the ecosystem, has <br />been attained when chemical, physical, and <br />biological integrity occur simultaneously. <br />Much research has been focused recently on <br />development of indices of biotic integrity <br />(IBn. To be effective, an IBI must be <br />applied to a geographical set of waters that <br />have similar ecological features (Stewart <br />and Loar, 1994). The concept of <br />ecoregions has been developed as a means <br />of stratifying the landscape (Omernik, 1986, <br />1987; Hughes and Larson, 1988). <br />Ecoregions group naturally similar <br />ecosystems and therefore group sites that <br />have potential to be similar in aquatic <br />chemistry, physical features, and biota <br />(Hughes and Larson, 1988). The use of <br />ecoregions can enhance the effectiveness of <br />an ecological monitoring program because <br />.-ecoregional-division of "sites caia control <br />variance which in turn makes it easier to <br />detect potential problems (Stewart and Loar, <br />1994). <br />The present study seeks to find meaningful <br />patterns of variation in the organization of <br />biological communities. Through study of <br />the aquatic biota and the chemical, physical, <br />and climatic features of their environment; <br />we hope to identify factors responsible for <br />the distribution and/or abundance of aquatic <br />biota in New Mexico. Information about <br />community stumm, and how it is affected <br />by underlying physical, chemical, and <br />climatic processes, will enable us to <br />determine expected biotic community <br />structure for . an aquatic ecoregion. <br />Expected community structure then provides <br />a baseline against which sites can be <br />compared. The ability to compare sites <br />within an aquatic ecoregion will facilitate <br />development of an IBI that is protective of <br />aquatic biota and that facilitates remedial or <br />mitigative action. <br />Over the past four years, sampling has been <br />conducted at 142 aquatic sites representing <br />the major river drainages in New Mexico <br />(Appendix 1). Specimen collection and <br />processing is still underway. This report <br />describes the results of statistical analyses <br />on environmental, fish, benthic <br />macroinvertebrate, and chironomid data <br />