8105

• UCREFRP Catalog Number: 8105
• Author: Haines, G. B., D. W. Beyers and T. Modde.
• Title: Estimation of Winter Survival, Movement and Dispersal of Young Colorado Squawfish in the Green River, Utah.
• USFW Year: 1998.
• USFW - Doc Type: Recovery Program Project 36,
• Copyright Material: YES

SUBADULT HUMPBACK CHUB IN THE COLORADO RIVER

275

Table VI. Results of generalized, randomized block MANOV A for mean depth, veloc-
ity and cover among shoreline types and reaches (for reaches I and 2 only). DF, degrees
of freedom

Source

DF

F

Shoreline (S)
Reach (R)
RxS

15, 152
3,55
15,152

Wilks' ).

P

<0.001
<0.001
0.003

0.198
0.611
0.554

8.09
11.68
2.42

Relationships between subadult humphack chub and geomorphology

Fish densities did not monotonically decline from upstream to downstream or show any other
recognizable pattern; however, mean relative density varied substantially among shoreline types (Figure
4). In addition, other species, such as speckled dace, not reported here, differed in habitat use and relative
abundance from that of subadult humpback suggesting that sampling efficiency bias among shoreline
types was minimal (Valdez and Ryel, 1995). These results imply that subadults were quickly dispersing
and then preferentially using specific shoreline types along the river corridor while avoiding others.
Discriminant functions analysis showed that subadult humpback chub used locations that were physically
different than unoccupied areas (Table VII). Areas with fish had more cover (p < 0.001) and lower
velocity (p = 0.10) than those without but did not differ significantly in depth (p = 0.84).
Estimates of overall fish abundance, based on shoreline availability and shoreline use, were highest in
reach 3 (82 fish caught per 10 h of fishing), intermediate in reach I (50 fish caught per 10 h fishing) and
lowest in reach 2 (33 fish caught per 10 h fishing). However, a GRB ANOV A showed a significant
interaction between reach and shoreline type, suggesting that the pattern of shoreline selection varied
between reaches (Table VIII).
Overall, densities were highest in vegetated shorelines, followed by talus and debris fan shorelines.
Bedrock, cobble and sand shorelines had low densities of subadults. However, when considering the
interaction with reach, relative densities in bedrock shorelines in reach 2 were high compared with
bedrock shorelines in reaches I and 3, whereas relative densities in talus shorelines in reach 2 were low

:

3
2

Depth (m)

o
0.60
Velocity (m/s)
0.45
0.30
0.15
0.0
100
80
60
40
20
o

Cover (%) Reach 1
. Reach 2

BE CB OF SA TS VG
Shoreline type

Figure 3. Physical differences in depth, velocity and cover among shoreline types and between Reaches I and 2. Be, bedrock; CB,
cobble; DF, debris fan; SA, sand; TS, talus; and VG, vegetation

<<:J 1998 John Wiley & Sons, Ltd.

Regul. Rivers: Res. Mf(mt. 14: 267-284 (1998)