8087

• UCREFRP Catalog Number: 8087
• Author: Valdez, R. A. and B. R. Cowdell.
• Title: Lake Powell Inflow Study. Annual Summary Report - 1994.
• USFW Year: 1994.
• USFW - Doc Type: 453-1,
• Copyright Material: NO

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3.4 DATA COLLECTION AND STORAGE

All data collected in the field were recorded on standard forms using codes consistent with the Upper
Colorado River Basin Database Codes (UFWS 1987). The data forms used and a list of field codes were
provided with the 1993 Annual Report (Valdez and Cowdell 1994). The data were stored in the database
management system dBase IV 1.1.

4.0 RIVER FLOWS AND WATER TEMPERATURES

Fish habitat in the study area was largely determined by the surface elevation of Lake Powell. During pre-
runoff sampling (April 18-22, 1994) lake level was approximately 3,660 it creating riverine habitat to
Clearwater Canyon (RM 189). Cataract Canyon flows during this trip averaged 7500 cfs. During post-runoff
sampling (August 22-24, 1994) lake level was 3,658 ft (similar to pre-runoff sampling) with the Colorado River
entering Lake Powell just below Cle3rwater Canyon at RM 190. Cataract Canyon flows during post-runoff
sampling averaged 5000 cfs (range 4800 - 5100 cis).

During pre-runoff sampling Colorado River mainchannel temperatures ranged from 17.0 to 19.0 oc, Lake
Powell surface temperatures ranged from 18.0 to 21.00C. During post-runoff sampling Colorado River
temperatures ranged from 24.0 to 27.0 oC, and Lake Powell surface temperatures ranged from 25.0 to 27.00C.

5.0 RESULTS

5.1 SUMMARY OF FISH COLLECTIONS

A total of 19 species of fish representing 7 families, were captured in the Lake Powell inflow in 1994 (Table
2). This list is similar, though not as extensive, as that reponed for collections in the region in 1985-1988
(Valdez 1990).

As percentage of total catch, the most common species captured in the inflow region were red shiner (28.5),
sand shiner (25.1), and fathe3d minnow (17.3). These 3 non-native species comprised 96.1% of total catch
(percentage includes unidentified shiners which comprised 25.2% of the catch).

Native fish species captured in the Lake Powell inflow included: bluehead sucker, flannelmouth sucker,
Colorado squawfish, Gila m. and speckled dace. All these species combined comprised only 0.2% of the total
catch.

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