8003

• UCREFRP Catalog Number: 8003
• Author: Haynes, C. M. and R. T. Muth.
• Title: Identification of Habitat Requirements and Limiting Factors for Colorado Squawfish and Humpback Chubs ‎(January 1, 1981 to June 30, 1982)‎.
• USFW Year: 1982.
• USFW - Doc Type: SE-3-4,
• Copyright Material: NO

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storage been completed. During April - June, 1982, 114 sein samples and
approximately 20 one-hour drift net samples were collected. These samples
will be processed and placed in computer storage during fall-winter, 1982-83.
A total of 17 species have been identified from the Colorado River study
area in 1981, of which only six were native to the drainage. As in the
case for the Yampa data, YOY chubs were not distinguishable as either
roundtails or humpbacks and were all grouped as Gila spp. for the purposes
of this progress report.
For the Colorado River study area as a whole, 48,901 fishes were processed
in 1981. Of these, red shiners were the most numerous (24,353 individuals)
followed by another exotic, fathead minnows (Pimephales promelas), with
16,019 individuals. Gila spp. was the most abundant native group with
3,488 individuals. Spawning periods for the eight most abundant species
in this study area during I98I have been determined (Figure 3) based upon
length-frequency analyses (Appendix C). Comparisons of spawning-
related data for Colorado - Yampa River species by other researchers are
presented in Table 4. Species-habitat associations will be conducted
utilizing the MANAGE program.
On 2 May 1981, 11 redside shiners (Richardsonius balteatus) were collected
48 km west of Grand Junction at km 230.4 - 243.4 (mi 143.1 - 151.2).
This species, while relatively common in the Yampa River study area, had
not been previously documented in the mainstem Colorado River in either
the upper or lower basin. This observation was published in The Southwestern
Naturalist (Haynes, et al., 1982).
Colorado Squawfish
In 1981, 23 larval Squawfish were collected. in the Yampa River study area,
while only one was collected in the Colorado River study area. Yampa
squawfish collected on 7/22-26/1981 were captured by NW Regional personnel
and submitted to Nongame Research staff for length-frequency analysis.
Squawfish collected on 8/11-18/1981 were captured by Nongame Research
personnel, as was the single Colorado River specimen. Collection data
for both 1981 Yampa and Colorado River squawfish larvae are presented in
Table 5. Estimated 1981 spawning periods in the Yampa River based upon
maximum and minimum size per collection and estimated growth rates ranged
from 25 June to 3 August. The earliest Yampa data correlates closely with
both dates and locations when ripe radiotagged adults were observed over
apparent spawning gravels in the same area by FWS personnel (Tyus et al.,
1981) i.e., 26 June - 10 July, lan 19.6 - 0.2.Juvenile (age-class I)
squawfish were not collected.
_ In July 1981, seven of the Yampa squawfish larvae were collected in main
channel embayments, two were collected in side channel backwaters, while the
remaining individual was collected in a side channel isolated pool.
Eight were captured over a predominantly silt substrate whereas the
remaining two were associated with a substrate that was predominantly
sand. For all individuals, velocity could not be detected and was
recorded as 0.0 m/sec. Depth varied from 0.1 - 0.3 meters. In August,
all 13 YOY squawfish were associated with main channel embayments with