7157

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

Man'h 198'1

Haynes et aJ.-Larval Colorado Squawfish

25

TABLE 2.-Summary of larval Colorado squawfishcollections, Colorado River, 1979-81.

Dale

Localily (River km)

N limber

Eslimated Age ESlimated Spawning
TOIaI Lenglh (mm) (Days) Period

1979
8/2'1
8/26

2211.6
217.7

11 17.0-J9.5
5 15.0-24.5
8 15.0-24.5
2 111.0-14.0
11 11I.0-J5.0
46 12.0-19.0
I 14.0
I 14.0
2 20.0-21.0
11 111.0-21.0
1 18.0
67 111.0-21.0
5 110.0-115.0
1 110.0
4 112.0-118.0
10 110.0-118.0

25-58 6/29-8/2. J979

1980
8/ 111

245.7
244.J
2411.9
241.9
2119.7
2111.7
218.2
212.2

8/14
8/15
8/16

19-49 6/28-7/26, 1980

10/111
1I/J
JI/2

2119.4
217.7
217.7

67-95 7/111-8/26. 1980

1981
7/27 2411.6 1 18.0 114-40 6/18-6/24. 1981
/' I

individuals, km 243.9, 13 Aug 1980) was taken in Horsethief Canyon near
the mouth of an ephemeral tributary in Rattlesnake Canyon. A collection of
II larval squawfish was taken approximately 27.5 km downriver in Ruby
Canyon (km 218.2, 15 Aug 1980). Sizes ranged from 12.0 mm (km 243.9, 13
Aug 1980) to 38.0 mm TL (km 217.7, 2 Nov 1980).
In the YaI;llpa, larval squawfish were found near the confluence with the
Green River upstream to km 28.8 (14 Aug 1981) ip lower Yampa Canyon
(Table 3). Number per sample ranged 'from 16 individuals (km 13.9, 23 Aug
1980) to a single larva in 7 samples in 1980 and 1981 combined. Sizes
ranged (rom 9.0 mm total length (km 17.4, 25 July 1981) to 29.0 mm (km
0.2,25 Aug 1980).
Estimated spawning periods in the Colorado River based upon maximum
and minimum size per collection and estimated growth rate ranged (rom 18
June (1981) to as late as 26 August (1980) (Fig. 2). In the Yampa, we
estimate that spawning occurred as early as 16 June (1980) and as late as 3
August (1981) (Fig: 3). In 1981, we estimate that spawning occurred in the
lower Yampa as early as 25 June, which correlates closely with the dates
and locations of ripe radio tagged adults observed over apparent spawning
gravels in the same area by Tyus et al. (1981) i.e., 26 June - 10 July, km
19.6-0.2. However, since fish growth rate is temperature-dependent (De
Vlaming, 1972), lower temperatures in late-August would probably decrease
the rate at which larvae grow. Therefore, these late-summer spawning dates
should probably be adjusted forward. Since growth rate-temperature data
for young Colorado squawfish are lacking, it is not possible to state to what
extent estimated late-season spawning periods should be corrected.