1	Development of Fish Biological Criteria for Streams of the Western Corn Belt Plains Ecoregion R.W. Bouchard Jr. & D.G. Huggins Central Plains Center for Bioassessment, Kansas Biological Survey, University of Kansas 2021 Constant Ave, Lawrence, KS 66047, bouchard@ku.edu
2	Introduction Fish bioassessment techniques were standardized to facilitate comparison of biological stream data among states in the Western Corn Belt Plains (WCBP) ecoregion using methods outlined in the Environmental Protection Agency’s (EPA) manual, Biological Criteria: Technical Guidance for Streams and Small Rivers (Gibson 1996). In this study we used existing fish data to determine and compare a number of fish metrics to watershed and macroinvertebrate conditions. Comparisons of watershed, macroinvertebrate and fish metrics and rankings were accomplished through the use of both graphic and statistical techniques.
3	Description of Ecoregion The WCBP ecoregion encompasses most of Iowa as well as parts of Kansas, Nebraska, Missouri, Minnesota and South Dakota (Figure 1). The region was once covered with bluestem prairies and oak-hickory forests, but this fertile region is now dominated by corn, soybeans, feed grains and livestock forage (Griffith et al. 1994). Agricultural runoff, removal of riparian corridors and stream channelization has impacted and modified the lotic systems in this region extensively (Donley 1999).
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5	Data Collection Sixteen 4^th order streams were sampled seasonally for 2 ½ years for a total of ten collection events (Figure 1). Five sites on each stream were sampled during each collection event. Habitat, periphyton, chemistry, macroinvertebrate and fish were sampled using methods outlined in Higgens (1994), Lary (1997) & Wang (1997). Fish were sampled with electrofishing and exhaustive seining.
6	Metric Selection Forty-six candidate metrics were calculated for reference and impacted sites from the fish samples. Metrics were selected on the basis of two criteria: Separation between reference and impacted box plots. Low variability. Based on these criteria, 26 metrics were potentially useful, but there were redundancies. A correlation matrix eliminated some redundancies and the list of metrics was reduced to 11 (Table 1).
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9	Index of Biotic Integrity (IBI) An IBI similar to Environmental Protection Agency’s Rapid Bioassessment Protocol (Barbour et al. 1999 & OEPA 1987) IBI was used with the 11 selected metrics. Upper, middle and lower divisions were selected for each metric using natural breaks or by dividing the chart into thirds when the data was scattered. A score of 1, 3 or 5 was assigned to lower, middle and upper values respectively (Table 2). The score from each metric was summed to produce a value between 11 and 55 (55 = Best possible conditions & 11 = Worst possible conditions).
10	Table 2: Scoring for WCBP IBI metrics.
11	Results There is some separation between reference and impacted box plots using the WCBP IBI and a higher than ideal level of variability (Figure 3). Several intermediate sites ranked lower than the impacted watershed Four Mile (Figure 4). In general, there was a direct relationship between fish community metrics and the overall assessed condition of the watershed, but this relationship tended to break down at the more impacted sites.
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13	Figure 4: WCBP IBI scores for the sixteen watersheds.
14	Discussion The WCBP IBI is capable of identifying relationships between fish communities and stream health, but the limited, tolerant fish communities of small watersheds in the WCBP ecoregion limits their usefulness in evaluating watershed and/or water quality changes. Due to the high levels of anthropomorphic impact in this region, most of these streams are moderately impacted, decreasing the effectiveness of fish metrics. In order to overcome the constraints of this ecoregion and accurately determine stream health, a multivariate approach incorporating habitat, chemistry, periphyton, benthic macroinvertebrates and fish parameters should be utilized.
15	References Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999. Rapid bioassessment protocols for use in streams and wadeable rivers: Periphyton, benthic macroinvertebrates and fish, Second edition. EPA 841-B-99-002. U.S. Environmental Protection Agency; Office of Water; Washington D.C. Donley, S.R. 1999. Development of biological criteria for macroinvertebrates for streams of the Western Corn Belt Plains ecoregion. M.S. Thesis, University of Kansas. 82 pp. Higgins, K.H. 1994. An assessment of the cumulative effects of watershed structure on stream water quality in agricultural landscapes. M.S. Thesis, University of Kansas. 226 pp. Gibson, G., M.T. Barbour, J.B. Stribling, J. Gerritsen and J.R. Karr. 1996. Biological criteria: technical guidance for streams and small rivers. EPA/822-B-96-001. Office of Water, U.S. Environmental Protection Agency, Washington, D.C. Griffith, G.E., J.M. Omernik, T.F. Wilton and S.M. Pierson. 1994. Ecoregions and subregions of Iowa: a framework for water quality assessment and management. Journal of Iowa Academy of Science. 10(1): 5-13. Lary, M.R. 1997. Investigation of the impacts of agricultural nonpoint pollution on aquatic macroinvertebrate communities in small streams of the Western Plains Corn Belt ecoregion. M.S. Thesis, University of Kansas. 186 pp. OEPA (Ohio Environmental Protection Agency). 1987. Biological criteria for the protection of aquatic life: Volume II. Users Manual for biological field assessment of Ohio surface waters. WQMA-SWS-6. Division of Water Quality Monitoring and Assessment, Ohio Environmental Protection Agency, Columbus, OH. Wang, S. 1997. Nitrate dynamics in small agricultural streams of the Western Corn Belt Plains ecoregion. Doctoral Thesis, University of Kansas. 229 pp.