. Critical trends in Illinois ecosystems. Ecological assessment (Biology); Environmental impact analysis; Nature; Pollution; Conservation of natural resources; Environmental quality. Rock River Watershed 39 ECOSYSTEM MONITORING CTAP biologists assessed eight streams in this watershed. The region had the worst average HBI score of all watersheds, indicating that its streams were the most organically enriched. Since the watershed is heavily grazed by livestock, the HBI average is not surprising. The Rock also had lower than average EPT richness, fish richness, and habitat quality-. While histori
. Critical trends in Illinois ecosystems. Ecological assessment (Biology); Environmental impact analysis; Nature; Pollution; Conservation of natural resources; Environmental quality. Rock River Watershed 39 ECOSYSTEM MONITORING CTAP biologists assessed eight streams in this watershed. The region had the worst average HBI score of all watersheds, indicating that its streams were the most organically enriched. Since the watershed is heavily grazed by livestock, the HBI average is not surprising. The Rock also had lower than average EPT richness, fish richness, and habitat quality-. While historically it was one of the richest watersheds in EPT and native fish species, the loss of vegetated riparian zones, stream channelization, siltation, and livestock grazing have taken their toll. The best stream sampled was Elkhorn Creek near Milledgeville. It had a habitat score well above the state and basin average, but it also had a rela- tively low native fish richness. The worst site was Coal Creek near Mineral in Bureau County. It had recently been dredged, so the bottom was mostl) clay overlain by loose sand and silt. It yielded just two EPT taxa and habitat quality' was ver>' poor due to channelization, lack of variation in depth, and lack of canopy. However, native fish richness was relatively high for such a monotonous habitat. RiverWatch collected 179 samples at 75 sites on 50 streams between 1995 and 1999. Its bio- logical indicator data also suggest that the Rock River watershed is of slightly below-average Table 16. Watershed Indiccitor Scorecard Indicator Watershed Value Statewide Value Watershed Ranking Macminvertebrates HBI 10 MBI 4 EPT richness 7 EPT taxa (RW) 6 Taxa richness 7 Taxa dominance 8().2% 6 Fish Native fish 6 Darter richness 8 Exotic species 10 Habitat Habitat score 8 ecological quality' (Table l6).The watershed ranked near the median in MBI and EPT taxa, both indicato
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