. Critical trends assessment Program 2002 report. Critical Trends Assessment Project; Ecosystem management; Environmental monitoring; Natural resources surveys. 25 20 15 10 - 5 - Sowbug MKJge. Macroinvertebrate Taxa Figure /. Mean ahimdance of the most common taxa identified statewide 2002 (N=234) Taxa Richness, Percent Composition of Indicator Organisms & MBI The number of taxa identified ranged from 1 to 21. Twenty-eight percent of the monitored sites identified five or fewer indicator taxa, 55% had six to 10 taxa, and 29% had 11 or more taxa. EPT taxa comprised, on average, 22% of the o
. Critical trends assessment Program 2002 report. Critical Trends Assessment Project; Ecosystem management; Environmental monitoring; Natural resources surveys. 25 20 15 10 - 5 - Sowbug MKJge. Macroinvertebrate Taxa Figure /. Mean ahimdance of the most common taxa identified statewide 2002 (N=234) Taxa Richness, Percent Composition of Indicator Organisms & MBI The number of taxa identified ranged from 1 to 21. Twenty-eight percent of the monitored sites identified five or fewer indicator taxa, 55% had six to 10 taxa, and 29% had 11 or more taxa. EPT taxa comprised, on average, 22% of the organisms sampled while worm taxa made up less than 5% of the organisms. However, volunteers arc most likely to sample riffle habitats, the preferred habitat for EPT taxa, rather than undercut banks and sediment where worm (aquatic worm and bloodworm midge) taxa predominate. The most common taxa were neither EPT nor worm taxa, but sowbugs and midges. The average MBI score for monitored streams was The poorest MBI score was and the best score was Less than 6% of sites have MBI scores above According to the MBI few Illinois streams monitored by RiverWatch are in poor health. Macroinvertebrates of Special Interest Fingernail clams, a native species, are the most common taxa of special interest reported and occurred at 29% of the monitored sites. Volunteers reported no Chinese mystery snails or Zebra mussels this year. This most likely indicates these invasive species have not yet spread from larger rivers to the smaller streams monitored by volunteers. Volunteers noted the presence of native mussels at 12% of the sites and Asiatic clams at 10% of the sites (Table 2). These results are consistent with previous years, indicating native mussels are occurring at the same levels as reported previously. Number of Monitored Sites RiverWatch volunteers monitored 234 sites statewide in 2002. Another 18 could not be monitored due to reported flooding or low water. The n
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