7224

• UCREFRP Catalog Number: 7224
• Author: Kaeding, L. R., B. D. Burdick, P. A. Schrader and C. McAda
• Title: Temporal and Spatial Relations between the Spawning of Humpback Chub and Roundtail Chub in the Upper Colorado River
• USFW Year: 1990
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

30
20
10
0
X
w
~ 6
Z
U
~= 4
Q
O 2
O
~ 0
Q
Z
~ 30
20
SPAWNING OF HUMPBACK AND ROUNDTAIL CHUBS
FEMALE
ROUNDTAIL
CHUB
5
_~

4
~ 6 3 ~ 2
~ - - - -
- MALE
_ ROUNDTAIL
CHUB
_ 12 5
- 4 11
-~ ~ ~
- FEMALE
_ HUMPBACK
CHUB
10
0
10 -
13 14 10 -
1 4 g 5 -
2-
3
3 19
10 13 5 9
3
2
2
2 2
m
139
AriliL nnAY JUNE JULY
MONTH
FIGURE 3. -Seasonal changes in the gonadosomatic index (100 x gonad weight whole-body weight) for male and
female roundtail chub of mature size in the Colorado River at Black Rocks, Colorado, 1983 and 1984, and for
female humpback chub in 1983. Means (crosses), standard error of means (vertical boxes), ranges (vertical lines),
and sample sizes (numbers} aze given.
correlated with the occurrence of expressible ova
in both species (Figures 2, 3). The index of female
roundtail chub increased during early June and
decreased as spawning progressed in July (Figure
3). The pattern of seasonal change in the gonad-
osomatic index of the male roundtail chub was
generally like that of females. Female humpback
chub were examined internally beginning in early
July 1983, when their external characteristics sug-
gested that spawning might be occurring. Their
indices declined as spawning occurred during the
subsequent 3 weeks (Figure 3).
The fish spawned when river discharge was near
its seasonal high or was receding, and when river
temperatures were 14-24°C (Figure 4). Relatively
high seasonal runoff flows (two of the highest on
record) in 1983 and 1984 delayed the seasonal
warming of the Colorado River (compare to Val-
dez and Clemmer 1982).
Fish Movement
We implanted 33 humpback chub and 17
roundtail chub with radio transmitters; for each
of these fish, the principal component analysis
supported the taxonomic classification made in
the field. We found no differences in movement
either between sexes or among years within species.
Humpback chub moved relatively little from Black
Rocks and had a mean maximum displacement
of 1.4 km from the release site; in contrast, round-
tail chub moved extensively and had a mean max-
imum displacement of 33.9 km (Table 3). During