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

7O NESLER ET AL.
TABLE 1.-Catches of Colorado squawfish larvae in the Yampa River, Colorado, 1980-1986.

Year Number
of
samples Capture
locations
Capture dates (river km) Number
of larvae
collected Size
range
(mme)
Seine and dip-net collections
1980 215 Aug 23-25 0.2-13.9 46 14.0-29.0
1981 423 Ju124-Aug 15 0.2-28.8 23 9.0-22.0
1982 295 Jul 7-25 0.5-19.6 20 9.9-21.0
1983 245 Jul 22-Aug 2] 1.1-]9.8 228 8.6-16.6
1984 148 Jul 7b-Aug 6 0.2-25.4 249 8.1-15.1
Drift-net co~ections
1983 ]29 Jul 22-Aug 21 3.1 102 7.3-9.3
1984 168 Jul 17-Aug 8 3.1 89 7.2-9.5
1985 204 Jul 9-Aug 16 3.1 455 7.9-10.0
1986 198 ]ul 15-Ju131 0.1 124 8.4-11.0
eTotal length.
the suspended debris load. Samples were returned
to the Larval Fish Laboratory, Colorado State
University, for processing. Colorado squawfish
larvae were measured (total length) to the nearest
0.1 mm under a binocular dissecting microscope
and assigned to a developmental phase (Snyder
1981). Further details of the sampling methodol-
ogy were described by Haynes et al. (1985) and
Nesler (1986).
Based on growth data provided by Hamman
(1981), an age-growth relationship for hatchery-
reared Colorado squawfish larvae during their first
107 d of life posthatching was developed by regres-
sion analysis (Haynes et al. 1985). These analyses
showed that the age-growth relationship for Colo-
rado squawfish larvae was best described in two
distinct phases and resulted in two predictive equa-
tions for estimating posthatching age of individual
larvae (Figure 2). The equation for larvae smaller
than 22 mm total length was the principal one used
because over 93% of the Colorado squawfish lar-
vae collected were in this size range (Table 1).
Hamman (1981) reported that the incubation time
for Colorado squawfish eggs was 3.5-6 d at water
temperatures of 20-22°C. For the purpose of pre-
dicting spawning time, 5 d were added to estimated
posthatching ages to account for incubation time.
The combined incubation time and larval post-
hatching age was used to back-calculate spawning
time from the date of capture for individual larvae.
Estimated spawning dates for individual larvae
were aggregated in a frequency distribution that
demonstrated beginning and ending dates and peak
periods of spawning.
Comparisons of Colorado squawfish spawning
periods with Yampa River flow regimes were
made for each year from 1980 through 1986. Daily
water discharge records from June 16 through
August 15 for the Yampa River were compiled for
each year from U.S. Geological Survey (USGS)
data collected at the Maybell (1934-1986) and
Deerlodge (1982-1986) gages (USGS 1934-1986;
a
C7
z_
U
Q
O
a
a
0
A= -76.7105-17.4949E
1.0555L2+0.0221 L3
L< 22mm
5 10 15 20
TOTAL LENGTH (L) IN MM
a
C7
z_
U
a
x
a
A = -26.6421 ~- 2.7798E
00
0
80
60
L=22 -47mm
40
30 40
TOTAL LENGTH (L) IN MM
FicuRe 2.-Relationships of total length (L, ± 0.1
mm) to posthatching age for young-of--the-year Colorado
squawfish. The upper curve applies to larval fish less
than 22.0 mm long; the lower curve applies [o fish of
22.0-47.0 mm.