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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adjustments" and that "structural characteristics" of stream communities conform to the
location of the river i'llong the continuum. As! a result, streams of a similar classification
can be expected to have many physical aspects similar to other streams of the same
classification, "As stream order, the classificati~n scheme, increased...total combined fish
increased per length of stream..." Upstream o~ Cripple Creek, Fourmile Creek is a fourth-
order stream and as the creek flows downstream" .11 becomes a fifth-order stream,
Fourmile Creek fish distribution reflected the continuum of changing physical parameters
and structural characteristics as expected,

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As subtle physical habitat changes oCCU:r from montane to a mixture of montane and
plains to plains, fish populations respond. ! For example, trout dominate the higher,
narrower, steeper colder reaches. As gradient :decreases, volume increases and so forth,
trout and minnows are equally present. Eventl!ially physical conditions suit minnows over
trout, and they dominate the fish assemblag$. Fourmile Creek is unique in that it flows
north to south along the Front Range prolonging a complete transition from cold to warm
water. Most streams on the Front Range floW west to east and change from the habitat
features of mountain streams to the plains, asiwell as from cold to warm water. Fourmile
Creek has characteristics and aquatic fauna \:If both mountain and plains streams.
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The amount of fishery data available f\:lr Fourmile Creek is limited, However, the
fisheries in the stream appeared extremely dynamic in 1994 and 1995. The number of
brown trout and long nose dace decreased in '1995 compared to 1994 in Fourmile Creek
downstream of Cripple Creek and downstream of the Carlton Tunnel. The decrease in
brown trout numbers was significant. White suckers disappeared from Fourmile Creek
downstream of the Carlton Tunnel in 1995, !

The r~ason(s) for these changes in the! Fourmile Creek fish community from 1994
to 1995 can not be identified at this time, the lack of fishery data in Fourmile Creek
upstream of Cripple Creek in 1994 confoundedlthe interpretation of 1995 data. Conditions
in Fourmile Creek upstream of Cripple Cree~ or in Cripple Creek could have resulted in
decreased fish numbers downstream of these two waters. The possibility that Cripple
Creek was the cause of decreased numbers \:If fish in Fourmile Creek was supported by
the change in the population dynamics of the s(onefly Hesperoperla pacifica upstream and
downstream of Cripple Creek. '
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Any of the variations in Fourmile C~eek macroinvertebrates or fish observed
singulary would not be considered unusual.: There is a high degree of variability that
occurs when man attempts to ennumerate a natural system. For example, the DOW has
documented a single instance where there was, a significant annual increase in brown trout
numbers at two control sites on the Eagle iRiver. The chance that all the changes
observed in 1995 in Fourmile Creek were due to chance events is fairly low. The numbers
of fish in Fourmile Creek downstream of Crippl~ Creek in 1995 appeared to decrease from
1994. Cause of the decrease is unknown. T~ese changes in the fish of Fourmile Creek
could be a function of natural variation, human or naturally induced environmental
disturbances, sampling techniques or sampling error. The existing data base is not