7354

• UCREFRP Catalog Number: 7354
• Author: Wydoski, R. S.
• Title: Biological Review of Endangered or Imperiled Fish in the Upper Colorado River Basin.
• USFW Year: 1985.
• USFW - Doc Type: Washington, D. C.
• Copyright Material: NO

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Table 2. Biological Summary of Rare Colorado River Fish
Item Colorado Squawfish
Ptychocheilus Lucius
Status/Distribution Endangered; Absent from much of its historic range;
Fewer fish in present range; See Figure 1 for summary
of distribution and identification of sensitive areas.
Colorado River Yampa-Green River
n-68 n¦63
Age and Growth I 44* _ 44*
(TL in mm) II 106 71
III 198 172
IV 285 269
V 355 342
VI 411 480
VII 453 449
VIII 495 486
IX 531 518
X 570 556
XI 619 600
* Imperical data
Maximum Size to 2 m; 27-36 kg
Maximum Age Unknown; growth practically stops with maturity;
largest fish could have been 60 years or older.
Reproduction
Size/Age at Maturity About 428 mm TL; Age 6
Fecundity wild; n-25; average 77.436 (25.241/lb.)
hatchery; n-18; average 60.676 (31.094/lb.)
Maximum 242.981 for wild fish
Spawning Period late Jung - early Septelber
Temperature at Spawning about 20 C (12.5 - 28.5 C)
Streamflow at Spawning Descending Hydrograph
Green River 10-20.000 cfs -- 5.700 cfs
Yampa River 5.900 cfs -- 1-2.000 cfs
Food Habits Young - zooplankton and invertebrates switching to fish
at 50 mm TL; feed entirely on fish when 200 mm TL.
Adults - primarily fish; also terrestrial insects when
available; reports of feeding on small mammals
during high water (floods).
Anglers catch this species easily on live bait and lures.
Habitat
.Young - Inhabit quiet, warm backwaters with some flushing
action.
Adults - Inhabit deeper areas of river channels and move into
quiet, shallow water to feed at night during the
sumner. Probably use deep reaches of river with slaw
velocity during the winter. During high flows in late
spring and early summer. adults will move into quiet,
flooded areas. Require bars with rubble or gravel
substrate for spawning; 3.4-5.0 feet deep with water
velocity 1.6-5.0 feet/sec. Also apeear to require
pools next to the spawning bars as staging- areas that
are 5 or more feet deep with water velocity 0.5-26
feet/sec.
Movement Squawfish save long distances in the Green and Yampa Rivers to
spawn in the spring (up to 90 miles with many moving over 60
miles). In the Colorado River squawfish tend to move less
distance (under 20 miles for most fish).
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