. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. Figure 20. Total catch afall species (top) and 1990 dollar value of that catch (bottom) for the Illinois and Mississippi rivers from 1971 through 1991. The Mississippi River clearly supports the largest commer- cial fishery in the state, typically providing catches more than twice as large as those from the second largest fishery, the Illinois River. Mississippi River catches are variable, averaging
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. Figure 20. Total catch afall species (top) and 1990 dollar value of that catch (bottom) for the Illinois and Mississippi rivers from 1971 through 1991. The Mississippi River clearly supports the largest commer- cial fishery in the state, typically providing catches more than twice as large as those from the second largest fishery, the Illinois River. Mississippi River catches are variable, averaging around 3 million pounds per year. Catches appeared to exhibit a slow decline until 1980 ( million pounds), after which they increased steadily through the 1980s, obtaining their highest peak in 1989 ( million pounds). Illinois catches average about 650,000 pounds per year. From 1981 through 1986 catches remained relatively high, peaking at over million pounds in 1986. Illinois River catches are still small compared to historical records indicating catches of over 17 million lb in 1908 and million lb in 1950 (Starrett 1972). Mississippi catches have not varied as greatly from historical values, which ranged between approximately 3 and 4 million pounds from 1950 to 1970 (Sparks 1982). Value of catch for both rivers show less variation than total catch reflecting composition of catch and chang- ing market prices. The Mississippi River provides a relatively consistent income of approximately $950,000 /year, whereas the Illinois generates about $227,000/ year. Figure 21. Total catch of all species (top) and 1990 dollar value of that catch (bottom) for the Wabash and Kaskaskia rivers from 1971 through 1991 (breaks represent years where no catch data was obtained). Kaskaskia River catches exhibited extreme variation, ranging from 12,000 to almost 300,000 lb. Catches increased dramatically after 1978, peaking in 1982 and 1983, then declining to approximately 110,000 lb
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Keywords: ., bookcentury1900, booksubjecte, booksubjectecology, booksubjectman
