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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

EXECUTIVE SUMMARY

This report describes the findings of a fishery study conducted to monitor the Lake Powell inflow of the
Colorado River before and after spring runoff to determine if significant numbers of age-O Colorado squawfish
(Ptvchocheilus lucius) and larval razorback suckers (Xvrauchen texanus) are being transported into the area.

Eighty two Colorado squawfish, including 73 age-O, 8 juvenile and 1 adult were captured during pre and pot-
runoff sampling in the Lake Powell inflow in 1994. One adult and one juvenile squawfish were captured
electrofishing, all other squawfish were captured with seines. The adult squawfish was captured in the Palmer
Canyon area (RM 195.0) during pre-runoff sampling on 4120/94. This fish was a female of 349 mm Tl.., and
weight of 240 g, it was implanted with PIT-tag number 1F1F793COD.

During pre-runoff sampling a total of 69 age-O and 7 juvenile (> 70 mm TI..) Colorado squawfish were captured
seining. resulting in a geometric mean CPE of 1.12 (S.D. 3.86) fish/100m2. Average length ofage-O squawfish
captured during pre-runoff was 47.5 mm TL (range 31 - 68 m.m TI..). The seven juvenile squawfish ranged
from 71 to 83 mm TL. During post-runoff sampling four age-O Colorado squawfish were captured seining.
resulting in a geometric mean CPE of 0.08 (S.D. 1.34) fish/100m2. These fish ranged from 29 to 52 m.m TL.
No juvenile squawfish were captured during posHunoff sampling.

As percentage of total catch, the most common species captured in the inflow region were red shiner (28.5).
sand shiner (25.1). and fathead 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 ~. and
speckled dace. All these species combined comprised only 0.2% of the total catch.

Use of larval light traps increased sampling efficiency in the lentic habitat of the inflow region. This sampling
device proved very successful in capturing young fish in areas unsuitable for conventional sampling gear (Le.
seines and gill nets). However. no native species were captured with light traps in 1994.

ill