7418

• UCREFRP Catalog Number: 7418
• Author: Tyus, H. M. and C. A. Karp.
• Title: Stream Flow Needs of Rare and Endangered Fishes, Yampa River, Colorado.
• USFW Year: 1988.
• USFW - Doc Type: Vernal, Utah.
• Copyright Material: NO

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' calculated from larval size for 1981-1987. The length of optimal spawning
period in the Yampa River (Table 2), derived from Figure 8, was similar for
' each year. Spawning generally occurred earl ier in low wa ter years (1981 and,
1987) and later with higher flows (1983 and 1984) (Table 2). Dates used in
"
"
"
"
estimation of
optimal
and
total
spawning periods are provided in Table 3.
' Total spawning period included any indication of spawning activity (e.g.,
radiotagged fish, collections of ripe fish, larvae) and was about 4 to 5 weeks
' in duration. Optimum spawning periods (indicating highest spawning activity
as evidenced by simultaneous collections of radiotagged fish, ripe fish, and
' larvae) were somewhat shorter (Table 3).
' Table 3. Calculation of optimal spawning period for Colorado squawfish in

------ `Yampa River,
---
-
- 1981-1987.
---

'
Year -
-
------
----
Back 1 -----------
Ripe --------------------
Radiotagged ------------
Spawning ---------
-
Period
Calculations rFish FishZZ Total Optimum
1981 6/19-7/10 7/1-7/10 6/20-7/20 6/19-7/20 6/23-7/13
1982 7/10-7/18 7/10-8/7 7/4-8/8 7/4-8/8 7/8-8/1
' 1983 7/20-8/5 7/14-8/18 7/12-8/8 7/12-8/18 7/15-8/10
1984 7/19-8/13 7/13-8/14 7/10-8/17 7/10-8/17 7/16-8/15
1985 6/27-7/13 6/27-7/25 6/21-7/12 6/21-7/25 6/25-7/17
' 1985 6/29-8/4 7/5-7/30 N/A 6/28-8/5 7/2-8/2
1987 6/16-7/9 6/3-6/30 6/9-6/30 6/3-7/9 6/9-7/3
' 1 Larvae were separated into two size classes: <22mm and 22-47mm, for back
calculation of larval age and estimation of spawning period (equations in
Haynes and Muth 1984, Kesler 1986). An estimate of total spawning period was
' obtained by combining estimated periods for two size classes.
2 Dates (range) represent first and last appearance of radiotagged fish on
spawning grounds.
Breeding adults were most often concentrated in river reaches containing
' deep pools and/or eddies and cobble (rubble) bars. The fish moved from pools
' and/or eddies to apparently spawn on cobble bars, then returned to the former
habitat (behavior similar to that reported for spawning northern squawfish
t (Beamsderfer and Congleton 1982)). Turbid conditions in the Yampa River
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