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

SPAWNING CUES FOR COLORADO SQUAWFTSH
73
TABLE 2.-Magnitude and relative frequency of baseline flow spikes in the Yampa River (Maybell gage) during
June 16-August 15, 1934-1986.
Cumulative
Flow Number of frequency
(m'!s) occasions (%)
Frequency
(number/53 yeazs)
Mean
interval
(Years)
Maxi-
mum
interval
(years)
28.3+ 18 26
25.5+ 23 34
22.7+ 25 37
19.8+ 30 44
17.0+ 36 53
14.2+ 41 60
11.3+ 50 74
8.5+ 59 87
5.7+ 67 99
2.8+ 68 100
17
19
19
23
28
32
2.1
1.7
1.7
1.2
0.8
0.6
by July 28 when flow decreased to 79.6 m3/s. In
1983, major spawning activity ceased by August 1
when river flow dropped below 62.9 m3/s.
Discussion
Our hypothesis formed from these comparisons
of flow spikes and spawning periods is that a flow
spike near baseline in the Yampa River acts as a
recurring environmental cue to adult Colorado
squawfish to initiate the spawning process of egg
deposition and fertilization. The flow spike repre-
sents the observable physical event we have as-
sociated with Colorado squawfish spawning, but
we do not exclude the possibility that, in reality,
one or more environmental variables coincidental
to the flow spike may be serving as the actual cue
perceived by the adult fish. Prior to a discussion
of the role the flow spike cue might play in the
reproductive ecology of this species, an evalua-
tion of the approach used to establish the above
hypothesis is necessary. The limited population
size associated with an endangered species, the
difficulties of representative sampling in the
aquatic environment, and the indirect methods
used complicate interpretations of the biological
significance of Yampa River flow spikes in the
spawning ecology of the Colorado squawfish.
Although the cumulative affect of these sources of
variation upon the alignment of the flow spike
with peak spawning by Colorado squawfish is
unpredictable, these uncertainties are considered
to be responsible for the noise evident in the
alignments and do not detract from an otherwise
remarkably consistent relationship. The strength
of the flow-cue hypothesis is based on the close
association noted between flow spikes and peak
spawning activity in 4 consecutive years.
Potential Sources of Error
Use of different sampling gear may be respon-
sible for differences in the total catch of larvae
between 1983-1986 and 1980-1982. The inclusion
of drift-net sampling in 1983-1986 and the poten-
tial inadequacy of seine sampling for representa-
tively sampling drifting Colorado squawfish larvae
may account for the observed differences rather
than a biological change signifying increased
spawning success. Drift-net data from Haynes et
al. (1985) and Nesler (1986) demonstrated that
larval Colorado squawfish were transported
downstream and out of the Yampa River within 3-
15 dafter hatching. The majority of Colorado
squawfish larvae produced in the Yampa River in
a given year may be transported downriver as a
discrete group that is present in any 6-km segment
of the river for only 1-2 d (Nesler 1986). Drift-net
sampling over time at a permanent station would
ultimately pickup this concentration of larvae and
TABLE 3.-Frequency distribution of flow spikes according to duration in number of days to peak.
Number of spikes of duration
Flow (m3/s) l d 2 d 3 d 4 d 5 d 6 d 7 d
25.5+ 2 5 5 5 1 3 2
14.2-22.7+ 4 6 5 1 1 0 1
Total 6 11 10 6 2 3 3
All flows 8 21 16 11 4 5 3