7399

• UCREFRP Catalog Number: 7399
• Author: Valdez, R. A., P. B. Holden and T. B. Hardy
• Title: Habitat Suitability Index Curves for Humpback Chub of the Upper Colorado River Basin
• USFW Year: 1990
• USFW - Doc Type: Rivers
• Copyright Material: YES

HUMPBACK CHUB LARVAE ('21mm)-GREEN RIVER

0.8

f (1,1.3,8.3,1.0,40.0)

n . 1498

z
o 0.8
~
N
:J
i= 0.4
:J

0.2

o
8.0

2.0 4.0 8.0
DEPTH (feel)

0.8
Z
0 0.8
~
N
:J 0.4
i=
:J
0.2

Hand Drawn
n . 1512

o
3.0

to 2.0
VELOCITY (fp8)

FIGURE 2. Raw data and interim suitability in-
dex curves for depth and velocity for larval hump-
back chub (n = number of observations or individ-
ual fish).

sympatric bony tail and roundtail chub (Gila
robusta). Following the decision/test on the
criterion of river, the experts decided to
pool the data of all three rivers. Average
depth utilized by this life stage was 2.1 feet
with a maximum of 5.1 feet, while average
velocity was 0.2 feet per second (ips) with
a range of 0 to 1.0 fps (Table 1). YOY were
found predominately over silt and sand
substrates in backwater and eddy habitats.
This curve set was applied to the Green,
Colorado, and Yampa rivers from April
through October, since no field observa-
tions had been made at other times of the
year. The experts did not recommend use
of this SI curve set at present because 49
percent of the data were taken from back-
waters.

Juveniles

The microhabitat used by juvenile
humpback chub is not well known,largely
because of the taxonomic problem of de-
finitively identifying these subadult fish
afield and the difficulty of sampling the
small fish in their turbulent habitat. Thus,
a relatively small amount of data were

I~ 38

20

HUMPBACK CHUB YOY (21-7.tmm) - GREEN RIVER
10

z
o 0.8
~
N
:J
i= 0.4
:J

16 S!
x
~
10 ffi
a
w
a:
8 ...

0.8

f (1,2.1,5.1,2.0,8.0)
n.71 8

0.2

o
0.0

1.0

2.0 3.0
DEPTH (feet)

4.0

16

0 o.a
$Z
10 X Z
~ 0 0.8
Z ~
W N
:J :J 0.4
0 i=
6 W :J
a:
...
0.2

f. GoExp(-GoX)
G . 5.000000E-OOl
n.87

o

0.0

0.2 0.4 0.8 0.8
VELOCITY (fps)

to

0.8

n.71

z
o 0.8
~
N
~ 0.4
:J

.0.2

o

CL Sl SA OR RU BO BE OT
SUBSTRATE

FIGURE 3. Raw data and interim suitability in-
dex curves for depth, velocity, and substrate for
young-of-the-year (YOY) humpback chub (n =
number of observations or individual fish).

available for curve development. Never-
theless, two curve sets were developed for
this life stage because the experts per-
ceived distinct differences in habitat, par-
ticularly depth, occupied between the
Green River, and the Colorado and Yampa
rivers. For the Green River, average water
depth used by juveniles was 2.3 feet with
a maximum of 4.4 feet, while average ve-
locity was 0.6 fps with a maximum of 2.6
fps (Table 1; Figure 4). Juvenile humpback
chub were found primarily over silt and
sand substrates in backwaters, eddies and
runs. This curve set was applied to the
Green River from July through September

Rivers. Volume I, Number 1

January 1990

~
8 Z
W
:J
o
W
4 a:
...

2

30

20~
Z
W
:J
o
w
a:
10 ...

o

HUMBACK CHUB JUV (71

0.8

z
o 0.8
~
N
~ 0.4
:J

0.2

o
0.0

0.8

z
o 0.8
~
N
~ 0.4
:J

0.8
Z
0 0.8
~
N
:J 0.4
i=
:J
0.2

o

CL Sl SA OJ
SUE

FIGURE 4. Raw data
dex curves for depth, ve
venile (JUV) humpback
= number or observatio

(confidence rating 0
available from othel
of this curve set was
29 percent of the da
backwaters.
For the Colorado
erage depth used by
with a maximum of
velocity was 0.6 fpl
2.6 fps (Table 1; Fij
the data associated
these juveniles wert
boulders and bedro<
silt substrate. This c
Colorado and Yan

I R. A. Valdez et a.