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• UCREFRP Catalog Number: 7300
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes, Yampa River, Colorado.
• USFW Year: 1989.
• USFW - Doc Type: Biological Report 89‎(14)‎,
• Copyright Material: NO

Colorado squawfish. Service data from 1981 to 1988
indicated that spawning occurs with declining flows
(following spring runoff) and increasing temperatures
(Fig. 10) -about 26 days (range: 17-33 days) after
migration. Regression analyses and multiple regression
techniques were used to investigate possible
cause-effect relations between spawning period,
discharge, and temperature for 1981-88. Peak discharge
preceding spawn, and mean minimum temperatures
during spawn, were highly correlated with the spawning
period (r = 0.84 and r = 0.88, respectively; P < 0.05),
ostensibly because discharge, temperature, and
spawning period are correlates. We do not presume the
above relations represent all conditions necessary for
successful spawn-rather, spawning of Colorado
squawfish is a result of complex environmental and
biological influences and is not triggered by a single flow
or temperature event. For example, Nesler et al. (1988)
hypothesized that flow spikes from rainstorms during
spring runoff may be important influences on ovulation
and spawning in Colorado squawfish.
Colorado squawfish spawn in the lower 51.2 km of the
Yampa River, particularly in a reach extending from
Warm Springs Rapid (RK6.56) to the vicinity of Harding
Hole (RK 32; Tyus et al. 1982b, 1987; Wick et al. 1983;
Haynes et al. 1984; McAda and Tyus 1984). Numerous
captures of ripe fish in a 6.4 km reach near Mathers Hole
(RK 28.3) suggest that egg deposition and fertilization
may be concentrated in this area (Fig. 4), where large,
deep pools and eddies are intermingled with runs and
cobble bars of gravel, cobble, and boulder substrates.
Spawning behavior of Colorado squawfish was
divided into two phases: (1) cresting-staging phase in
pools or large shoreline eddies, where the fish may find
suitable resting and feeding habitat between spawning
forays or where males aggregate until females are ripe;
and (2) adeposition-fertilization phase on cobble bars,
where actual spawning occurs (Archer and Tyus 1984).
Breeding adults occupied pools or eddies having an
average depth and velocity of 2 m and 0.2 m/s,
respectively, and cobble bars with an average depth and
velocity of 1 m and 0.5 m/s (Table 4).
Breeding adults were most often concentrated in
river reaches containing deep pools, eddies, and cobble
(rubble) bars. Radio-tagged fish moved from pools or
eddies to cobble-gravel bars (where they presumably
spawned). This behavior is similar to that of spawning
northern squawfish (Beamesderfer and Congleton
1981). Turbid conditions in the Yampa River have
precluded direct observations of egg deposition;
however, cobbles removed from the substrate during
that time of year are clean of sediment and algae
Table 4. Depths and velocities taken at location of radio-tagged Colorado squawfish o~i Yampa River spawning
grounds, 1981, 1983, 1984, 1985, 1987, and 1988.
Depth (m) Velocity (m/s)
Number Number of
Yeara of fish contactsb Mean Range Mean Range
Resting-Stagingc
1981 7 74 1.80 (0.76-2.68) 0.39 (0.03-1.19)
1983 7 46 2.36 (1.07-5.79) 0.47 (0.09-1.46)
1984 5 261 1.70 (0.76-3.05) 0.17 (0.00-0.40)
1985 3 77 3.30 (0.76.27) 0.22 (0.00-0.30)
1987 4 22 1.97 (1.28-2.74) 0.14 (0.06-0.18)
1988 2 8 2.86 (2.74-3.05) 0.06 (0.06)
Weighted Mean 2.06 0.24
Deposition-Fertilizationd
1981 7 65 1.16 (0.61-1.68) 0.59 (0.36-1.20)
1983 4 21 1.02 (0.55-1.22) 0.79 (0.27-1.04)
1984 6 82 0.89 (0.61-1.52) 0.40 (0.09-1.01)
1985 1 1 1.52 - 0.15 -
1988 3 12 0.87 (0.46-1.22) 0.48 (0.15-0.92)
Weighted Mean 1.01 0.52
a No fish located in deposition-fertilization habitat in 1987.
b One contact =one 15-min period of observation.
c Includes eddy and pool habitat.
d Includes riffle and shallow run habitat over cobble and boulder substrate.
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