. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. WETLANDS increase in the numbers stopping on Pool 19 in the central Mississippi River region since 1948 are apparent (Figure 51) (Havera 1992). The crash in the peak numbers of lesser scaups, primarily on renowned Upper Peoria Lake, occurred in the 1950s. The peak numbers of lesser scaups recorded in the Illinois River region from Peoria northward were 585,100 in 1954, 73,650 in 1955, 34,250 in 1956
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. WETLANDS increase in the numbers stopping on Pool 19 in the central Mississippi River region since 1948 are apparent (Figure 51) (Havera 1992). The crash in the peak numbers of lesser scaups, primarily on renowned Upper Peoria Lake, occurred in the 1950s. The peak numbers of lesser scaups recorded in the Illinois River region from Peoria northward were 585,100 in 1954, 73,650 in 1955, 34,250 in 1956, and 10,075 in 1957. Subsequently, the numbers of lesser scaups stopping in this stretch of the Illinois River have never recovered. On Pool 19 in the central Mississippi River region, however, numbers of lesser scaups began to increase steadily after 1950 and reached a zenith of 686,500 in 1969. Unfortunately, the trend in lesser scaup numbers has been downward since then. In 1991, only 19,050 lesser scaups were observed on the Mississippi River from Keokuk, Iowa, to Rock Island, Illinois—the lowest number since the aerial inventories were begun in 1948 (Havera 1992). The highest number of canvasbacks inventoried in the Illinois River region occurred on the beds of aquatic vegetation on Upper Peoria Lake, where 95,000 were present in November 1953 and 85,000 were recorded in October 1952 (Havera 1992). The peak number of canvasbacks recorded in the Illinois River region north of Peoria was 105,160 in 1952 and 103,500 in 1953; in 1971, a maximum of 120 were observed there (Figure 52). Similar to the numbers of lesser scaups, the numbers of canvasbacks crashed in the Illinois River region in the mid-1950s. The numbers of canvasbacks had not recovered to any reasonable levels by 1991. In the central Mississippi River region, the numbers of canvasbacks began to increase in 1963, mainly on Pool 19, and, after a downturn in the mid-1970s, reached their maximum number of 188,150 i
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Keywords: ., bookcentury1900, booksubjecte, booksubjectecology, booksubjectman
