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<br />Table 6. A comparison of pre and post-impoundment aquatic insect data <br />collected from Dunn Creek site. Preimpoundment data are four <br />year averages from 1968 through 1971, while post-impoundment <br />data are annual mean of monthly means from October 1979 through <br />September, 1980. <br /> <br />Orde r <br /> <br />pre-impoundmentt~ <br />(n = 57 samples)- <br />Dens i ti es Bi omass <br />(x2?o/m3! (am/m2) <br />x- (s)- X ( s ) <br /> <br />539(434) 2.0(1.4) <br />570(320) 5.8(3.5) <br />732(215) 11.3(5.5) <br />4(5) trace <br />1,030(466) 4.0(1.8) <br /> <br />2,876(1,197) 23.1(10.2) <br /> <br />Ephemeroptera <br />Plecoptera <br />Tri choptera <br />Co 1 eoptera <br />Di ptera <br /> <br />TOTAL <br /> <br />Pas t-i mpoundmen t <br />(n =n 63 samples) __ <br />Densities Biomass <br />ex no/m2J (cc/m2) <br />xes} xes) <br /> <br />8,797 (7,778) <br />6 (6) <br />62(32) <br />7 (6) <br />17,363(8,322) <br />26,235 (6 ,779) <br /> <br />16.4 (12.4) <br />0.01(0.03) <br />1.1(0.7) <br />trace <br />12.5(8.0) <br />30.0(16.0) <br /> <br />Percent Composition <br />Ephemeroptera 18.7 8.7 33.5 54.7 <br />Pl ecoptera 19.8 25.1 0.02 .03 <br />Tri chop tera 25.5 48.9 0.2 3.7 <br />Co 1 eoptera 0.1 0.03 <br />Di ptera 35.8 17.3 66.2 41.7 <br /> <br />1/ Bonde and Bush (1975) <br />Ii x is mean number of grams (pre-impoundment) or cubic centimeters (post- <br />impoundment) . <br />1/ S is one standard deviation. <br /> <br />-20- <br />