7157

• UCREFRP Catalog Number: 7157
• Author: Haynes, C. M., et al.
• Title: Larval Colorado Squawfish ‎(
• USFW Year: 1984
• Copyright Material: YES

~ti The Sultthwr..~tenz Naturalist vol. 29. IlO. I
TABu: 3.-Summary u/larval Coloradu squaw/ish cullectiuns, Yampa River. 1980-8J.
t:slimaled Age [slimaled Spawning
Oal.. I Ax-aIiIY (River kill) Number TUlal Lenglh (mm) (Oays) Period
J980
8/23 13.9 16 16.0-29.0
15.3 1 15.0
10.8 3 14.0-17.5
7.9 2 19.0-22.0
8/24 3.9 2 17.0-18.0
3.5 I 27.0
2.4 12 18.0-28.0
8/25 0.3 6 24.0-28.0
0.2 3 22.0-29.0
46 14.0-29.0 22-71 6/16-8/2, 1980
J981
7/21 19.6 2 11.0
7/25 17.4 1 9.0
14.2 I 11.0
9.6 2 11.0-12.0
8.8 I 12.0
7/26 5.2 1 11.0
0.2 2 12.0-13.0
to 9.0-13.0 8-26 7/1-7118. 1981
8/B 28.8 4 10.5-13.0
14.6 2 11.0-14.0
8/15 8.5 6 12.0-16.5
8.4 1 22.0
13 10.5-22.0 12-52 6/25-8/3. 1981

DISCUSSION.-Based upon extensive field collection in the Upper Colorado
Ri ver basin in 1979-1981, it appears that reproduction of Colorado
squawfish is limited to the lower reaches of the Colorado River in Mesa
County and the Yampa River in Moffat County. However, since considera-
bly fewer collections were made in the White and Gunnison rivers, it is
conceivable that spawning also might have occurred in these rivers and
larvae were simply not captured during our survey. Squawfish with
breeding tubercles were reported in the White and Gunnison rivers during
1979-1981 (Miller et aI., 1980; Wick et al. 1981; Wick, unpublished). Since
mature Colorado squawfish can apparently undergo long-distance spawn-
ing migrations (Sigler and Miller, 1963; Holden and Stalnaker, 1975;
Steelhaler, 1978; Tyus et al.; 1981) it is conceivable that adults reported in
the White and Gunnison rivers migrated elsewhere to spawn. Radioteleme-
try studies, similar to those conducted by Tyus et al. (1981) in the Yampa,
would be useful for evaluating this possibility.
Hamman (1981) reported that squawfish larvae began swimming to the
surface 72-96 hours after hatching. Under field conditions. it is reasonable
to assume that swim-up larvae would be likely to drift downstream from the
areas in which they hatched, but the extent of drift has not been
investigated in this species. Therefore, it is conceivable that the low-velocity
shoreline embayments in which we captured larvae were some distance
downstream fro,m actual spawning areas. Given that ripe adults have been
reported in these reaches of the Colorado River (1979-1981) (Tyus et aI.,