. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. 1992 White Bass () O^6' <46%) Smallmouth Buffalo ()^ Channel Catfish ()^ Black Crappie ()/ Bigmouth Buffalo ()/ River Carpsucker / () Largemouth Bass () Freshwater Drum () Green Sunfish () Bluegill (). Gizzard Shad () Carp () Emerald Shiner () Carp () Figure 36. Percentages of catches by species for the middle Illinois Waterway, for 1963
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. 1992 White Bass () O^6' <46%) Smallmouth Buffalo ()^ Channel Catfish ()^ Black Crappie ()/ Bigmouth Buffalo ()/ River Carpsucker / () Largemouth Bass () Freshwater Drum () Green Sunfish () Bluegill (). Gizzard Shad () Carp () Emerald Shiner () Carp () Figure 36. Percentages of catches by species for the middle Illinois Waterway, for 1963 and 1992, based on number of individuals collected per hour of electrofishing. In 1963, 10 species accounted for 95% of all fish collected per hour, and catches were dominated by gizzard shad, carp, and emerald shiner. In 1992, 13 species accounted for of all fish collected per hour, with bluegill being the most abundant, while gizzard shad, carp, and emerald shiner were reduced in numbers in comparison to 1963. Overall, percentages for each species in 1992 were more evenly distributed than in 1963, indicating no single species overwhelmingly dominated catches. Species are arranged in descending order of relative abundance in a clockwise direction and are labeled separately until approximately 95% of the pie is filled. sored among others by the National Science Founda- tion and the National Research Council, have focused on possible causes of decline and on strategies for obtaining relevant scientific documentation. Much of the decline is attributable to obvious destruction or degradation of natural habitats. Acid precipitation, pesticide release, agricultural practices, and exotic species introductions also have been implicated. In addition, amphibians are suspected to be particularly sensitive bioindicators of widespread, subtle ecological hazards such as increased ultraviolet radiation. Distin- guishing the effects of these factors from natural fluctuations in populat
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