ISFAPPC04246

• Case Number: 00CW0101
• Stream Name: Fourmile Creek
• Watershed: Fourmile Creek
• Water Division: 2
• Water District: 12
• County: Fremont
• Instream Flow App - Doc Type: Supplemental Data

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7

3.3 Fish

3.3.1 Species Composition and Distribution in Fourmile Creek
The fish community of Fourmile Creek was typical of a Colorado mountain stream.
As the stream flowed from its headwaters to the confluence with the Arkansas River. the
number and types of fish fluctuated. In the headwaters of Fourmile Creek upstream of
Wright's Reservoir, brook trout (Sa/velinus tontina/is) dominated with few minnows,
long nose dace (Rhinichthys cataractae) and white sucker (Catostomus commersom)
present. As the creek flowed downstream increasing in volume, size and nutrients, more
minnow and sucker species appeared but did not dominate, Brown trout (Sa/mo truffa)
replaced brook trout in this area upstream and downstream of Cripple Creek and the
Carlton Tunnel. Rainbow trout (Oncorhynchus mykiss) were infrequently collected in this
portion of Fourmile Creek, These rainbow trout may have originated from Wright's
Reservoir from DOW stocking. In the lowest stretch of river near Canon City, minnows and
suckers became dominant although brown trout were still present. Community composition
is illustrated in Figures 2, 3, and 4,

3.3.1.1 Trout
A population of 72 brook trout per acre was found in Fourmile Creek upstream of
Cripple Creek in 1995 (Table 10), Only a few brook trout were found at any sampling site
downstream of Cripple Creek in 1994 and 1995. Downstream of Cripple Creek, the
numbers of brook trout in Fourmile Creek were so low that populations estimates could not
be calculated, Low numbers of rainbow trout were collected at some sites upstream of the
Carlton Tunnel in 1994 and 1995 (Table 11),

Brown trout were the dominant salmonid in Fourmile Creek from Cripple Creek to
the downstream control site (Fourmile at Lion's Restoration), The number of brown trout
collected varied for the two years for which data are available (Table 11). In 1995, fewer
brown trout (164/acre) were found in Fourmile Creek upstream of Cripple Creek than
downstream (Table 11), Population estimates were 274/acre and 603/acre downstream of
Cripple Creek and the Carlton Tunnel, respectively. As Fourmile Creek flowed farther
downstream toward Canon City, the number of brown trout declined at Lion's Restoration
Park (259/acre), In 1994, the same pattern was found with fewer brown trout at the low-
elevation site near Canon City (Lion's Restoration) compared to the sites downstream of
Cripple Creek and downstream of the Carlton Tunnel. No upstream control site (Fourmile
Creek upstream of Cripple Creek) WFls sampled in 1994,

Calculation of 95 percent confidence intervals for brown trout population estimates
allowed for a more rigorous comparison of numbers of fish present among sites and
between years, If confidence intervals for two different sites overlap, there probably was
no difference in the number offish at the sites. If the confidence intervals do not overlap,
there was a difference in numbers of fish at the sites. Comparison of 1994 brown trout
population estimate confidence intervals (Table 11) indicated that the same number of
brown trout per acre was in Fourmile Creek downstream of Cripple Creek (768/acre-
850lacre) compared to the site downstream of the Carlton Tunnel (740/acre-838/acre,).