7848

• UCREFRP Catalog Number: 7848
• Author: Burdick, B. D.
• Title: Minimum Flow Recommendation For Passage Of Colorado Squawfish And Razorback Sucker In The 2.3-Mile Reach Of The Lower Gunnison River
• USFW Year: 1997.
• USFW - Doc Type: Redlands Diversion Dam To The Colorado River Confluence.
• Copyright Material: NO

recorded, equal effort was assumed for the plunge pool and downstream reach.
Therefore, the number of fish captured and sighted per trip was calculated as
well as traditional CPUE when effort was recorded.
Current Sampling. Fishery data were recorded in the field on standardized
data forms. These data were then stored in the database management system, DBASE
III+, to facilitate access and analyses as well as to provide data compatible
with the computer system and format used by the ISMP database. Computer
diskettes containing the corresponding DBASE III+ files from this study are
available upon request through the ISMP database manager, FWS, CRFP, Grand
Junction, Colorado. Hydrological data generated by the HEC-2 computer program
that predicts various surface elevations, bed profiles, velocities, and maximum
water depths with corresponding streamflows are available from the BR, Western
Colorado Area Office, Northern Division, Grand Junction.
Total CPUE was used to determine relative density of fish in el ectrofi shi ng
collections. CPUE was calculated for each fish species and hybrid collected in
the plunge pool and 2.2-mile reach. Species composition and relative abundance
(expressed as a percent) were used to describe the fish community in the plunge
pool and 2.2-mile reach. Total CPUE was plotted against flow for dates sampled
in 1994 and 1995 for four native fishes and three nonnative fishes collected in
the plunge pool and 2.2-mile reach. The four native species included bluehead
sucker, flannelmouth sucker, roundtail chub, and Colorado squawfish; the three
nonnative fishes included common carp, white sucker, and channel catfish. CPUE
was regressed against flow for sub-adult and adult Colorado squawfish collected
between 1987-1988 and 1991-1995. A combined total CPUE was also determined for
the four native fishes and for the three nonnative fishes. This combined total
CPUE for native and nonnative fishes was regressed against flow for dates sampled
in the plunge pool and 2.2-mile reach.
Discharge
Streamflow records for the Gunnison River were obtained from the USGS
stream gaging station at Whitewater, Colorado (No. 9152500). Data for flows
diverted by the Redlands Canal were obtained from the State of Colorado, Division
of Water Resources (CDWR). In this report, two different methods were used to
determine the flow in the 2.3-mile reach. The first method subtracted the
Redlands Canal flow from the streamflow at the USGS gage at Whitewater. Where
water records were not available for the canal, 750 cfs was used. A streamflow
gage installed by BR in March 1994 at RM 2.6 (CDWR No. GUNREDBCO) provided a
direct means of determining streamflows in the reach. Mean-daily streamflow was
obtained for the dates when water depth-transect data were recorded and for dates
when fish were sampled. Monthly flow exceedence was determined from mean daily
flows for the post-Aspinall water development period, 1967-1994. The mean daily
flow was the mean of 24 hourly discharge values.
Approach For Recommending Minimum Streamflow
Minimum flow recommended in this study is defined as one providing passage
for sub-adult and adult Colorado squawfish in the 2.3-mile reach. Determination
10