7195

• UCREFRP Catalog Number: 7195
• Author: Nesler, T. P., R. T. Muth and A. F. Wasowicz
• Title: Evidence for Baseline Flow Spikes as Spawning Cues for Colorado Squawfish in the Yampa River, Colorado
• USFW Year: 1988
• USFW - Doc Type: American Fisheries Society Symposium
• Copyright Material: YES

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FtcutsF, 4.-Relationships of estimated Colorado
squawfish spawning dates (vertical bars) to Yampa River
flow regimes (curves) at the U.S. Geological Survey's
Maybell and Deerlodge gages for 1980-1982. Number of
fish represents number sampled and distributed accord-
ing to estimated spawning date.
spike events, whereas in 1982, the flow spike
occurred in the middle of the spawning period.
Comparison of the Deerlodge and Maybell hy-
drographs for the Yampa River each year from
1982 through 1986 (Figures 3 and 4) indicated that
flow fluctuations were regional in their occur-
rence. The two USGS gages are 65 km apart, and
it is presumed from this that similar flow fluctua-
tions would also be evident at the Colorado
squawfish spawning area 47 km downstream from
Deerlodge. During 1982-1986, the flow spikes of
interest began simultaneously at both sites but
NESLER ET AL.
their peaks were simultaneous at both sites only in
1984. In 1983, 1985, and 1986, the flow spike peak
occurred at the Deerlodge site 1 d later than at the
Maybell site. Therefore, date of occurrence of a
flow spike at the primary Colorado squawfish
spawning area at km 24-30 was considered tem-
porally proximal to its occurrence at the upstream
gage stations. Flow spikes were associated with
major rainstorms in the area of Dinosaur National
Monument. In each yeaz from 1980 to 1986, rain-
storms representing 17-89% of the month's precip-
itation occurred immediately preceding the flow
spikes related to Colorado squawfish spawning.
Examination of daily flow hydrographs for the
Yampa River during the June 16-August 15 period
from 1934 through 1986 suggested that baseline flow
spikes might qualify as a recurring environmental
variable for along-lived, riverine fish species such
as Colorado squawfish. Sixty-eight flow spikes were
recorded during this season over the 53-yeaz period
(Table 2). Flow spikes similar to those observed for
1983-1986 (25.5 mils or greater) represented 34% of
the number documented and occurred in 19 of 53
yeazs. The mean interval between these flow spikes
was 1.7 years. The maximum interval was 8 years.
The minimum magnitude of a flow spike needed to
act as a spawning cue is unknown, so smaller flow
spikes than those observed in 1983-1986 may be
sufficient. Flow spikes of 14.2 m'/s or greater rep-
resented 60% of the total number, and occurred in
32 of 53 years. The mean interval between occur-
renceswas 0.6 years and the maximum interval was
5 years. The duration of these baseline flow spikes
from beginning to peak was predominately 4 d or
less (Table 3). Eighty-two percent of the 68 spikes
peaked within this time frame. For flow spikes 25.5
m3/s or greater, 74% peaked in 4 d or less. For flow
spikes ranging from 14.2 to 22.7 m3/s, 89% peaked in
4 d or less.
A relationship was also noted between flow
level and cessation of notable spawning activity
(Figure 3). Spawning activity in 1986 dropped
markedly on July 14 when flow decreased to 66.3
m'/s, and ceased when flow reached 58.4 m'/s.
Spawning activity during the first peak in 1985
appeared to drop to a negligible level by July 5,
when river flow decreased to 57 m3/s. During the
second spawning peak in 1985, substantial spawn-
ing started on July 23, when flow reached 62.6 m3/
s after increasing from a low of 27.7 m3/s. Spawn-
ing activity dropped off again after July 26 as flow
decreased to 57.5 m3/s. In 1984, peak spawning
activity dropped off by July 19 when flow was at
95.8 m3/s and spawning activity became negligible
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