. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. Carp () Smallmouth Buffalo () Spottail Shiner () Channel Catfish () Smallmouth Bass () Largemouth Bass () Bluegill () Carp () Bullhead Minnow () Gizzard Shad ( Green Sunfish () 1992 Other () Emerald Shiner () Bluntnose Minnow () Sand Shiner () Figure 34. Percentages of catches by species for the upper Illinois ;ay, for 1963 a
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. Carp () Smallmouth Buffalo () Spottail Shiner () Channel Catfish () Smallmouth Bass () Largemouth Bass () Bluegill () Carp () Bullhead Minnow () Gizzard Shad ( Green Sunfish () 1992 Other () Emerald Shiner () Bluntnose Minnow () Sand Shiner () Figure 34. Percentages of catches by species for the upper Illinois ;ay, for 1963 and J 992, based on number of individuals collected per hour ofelectrofishing. In 1963, goldfish, a non-native species, accounted for almost one- third of all fish collected per hour, followed by carp (also a non-native), emerald shiner, and gizzard shad. In 1963, these four pollution-tolerant species accounted for of all individuals collected per hour. In contrast, in 1992. 13 species accounted for approximately of all fish collected per hour, and goldfish were collected in insignifi- cant numbers, while carp were reduced to a minor component. In 1992, pollution-sensitive centrarchid species (, largemouth and smallmouth bass, bluegill) made up substantial portions of catches; in addition, minnow species (, emerald shiner, sand shiner, bluntnose minnow), important as a forage base for piscivorous fishes, showed a higher diversity than in 1963. 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. well (Vinyard and O'Brien 1976, Buck 1956). The centrarchids also have complex reproductive and social behaviors that depend on visual cues, and their eggs and larvae are susceptible to smothering with sediment or predation if the guardian male cannot see and defend them. The recovery of many other species (, yellow bass, northern pike, black buffalo, and se
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