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<br />-13- <br /> <br />Table 6. Dolores River trout (~ 40 em) density (n/ha), 1986-1991. <br /> <br />Species 10/86 10/87 10/88 09/89 10/90 04/91 10/91 <br /> IFIM Site - Metaska Campground - River Mile 0.5 <br />Brown 2 4 0 2(2)' 9 7 0 <br />Rainbow 2 8 5 22(22) 34 22 15 <br />Cutthroat 4 7 7 8(7) 18 3 2 <br />Total trout 7 16 12 31(30) 56 30 15 <br /> Ferris Canyon Campground - River Mile 6 <br />Brown 0 2 11 29(28) 29 18 5 <br />Rainbow 2 2 13 21(18) 20 5 7 <br />Cutthroat 0 8 7 5(5) 2 24 5 <br />Total trout 2 24 24 53(48) 50 33 17 <br /> Rock Stockpile Area - River Mile 10 <br />Brown 0 5 7 4(4) 0 2 2 <br />Rainbow 0 2 6 4(4) 2 10 2 <br />Cutthroat 0 2 6 2(2) 0 0 0 <br />Total trout 0 10 18 10(10) 2 7 4 <br /> <br />'Numbers in parentheses are the lower 95% confidence limit. <br /> <br />Population Densitv and Biomass - ADril through October 1991 <br /> <br />A two stage (fall to spring and spring to late-summer) m1n1mum flow regime was <br />implemented in October 1990. This flow regime has been (for the most part) a <br />30- cfs flow from October through March with increases into the 60-70 cfs <br />range for June through August. It was hoped that this modification of the <br />downstream release pattern might facilitate a recovery in the trout <br />population. However, the trout population data strongly indicates this flow <br />regime has done nothing to improve the situation. <br /> <br />Comparison of the trout population density and biomass statistics for October <br />1991 versus the fall period for 1986-1990 reveals the October 1991 levels are <br />at a 4, 5, or 6-year low. <br /> <br />Revisiting the data contained in Tables 2-7 reveals total trout population <br />density and biomass estimates (~ 15 cm) have declined at all three (MC, FCC, <br />and RSA) sites since October 1989. The decline at the RSA site (river mile <br />10) began after its peak in October 1988 (Tables 2 and 3). Density and <br />biomass declines at the two upstream stations began after September 1989, <br />continued from October 1990 through April 1991, and reached the lowest values <br />(for the most part) in October 1991. <br />