7214

• UCREFRP Catalog Number: 7214
• Author: McAda, C. W. and R. S. Wydoski
• Title: Growth and Reproduction of the Flannelmouth Sucker,
• USFW Year: 1985
• Copyright Material: YES

April 1985 MCADA, WYDOSKI: FLANNELMOUTH SUCKER
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TABLE 2. Relation of total length to sexual maturity in flannelmouth stickers from the Yampa, Green, Colorado,
and Gunnison rivers, 1975-1976.
Colorado and Gunnison Rivers Yampa and Green Rivers
Total Female Male Female Male
length Number Percent Number Percent Number Percent Number Percent
r (mm) of fish mature of fish m ature of fish mature of fish mature
381-390 3 0 4 0 1 0 3 0
391-400 3 0 6 17 1 0 1 100
401-410 1 0 6 33 5 20 3 100
411-420 2 60 7 71 2 0 5 80
421-430 5 0 6 67 7 43 7 100
431-440 2 60 6 100 3 67 19 100
441-450 9 75 11 91 5 40 18 94
451-460 4 80 14 93 6 67 12 92
461-470 5 100 16 100 14 93 it 100
471-480 7 92 14 100 9 100 11 100
481-490 14 100 12 100 5 100 9 100
491-500 15 100 6 100 9 100 1 100
501-510 8 100 5 100 13 100 4 100
511-520 9 100 2 100 10 100
521-530 13 100 1 100 3 100
531-540 7 100 5 100
541-550 5 100 3 100
551-560 7 100 - -
561-570 1 100 2 100
571-580 - - 1 100
Ripe females were collected in May and
early June, but none were collected after this
period.
In the Yampa and Colorado rivers, ripe
male and female flannelmouth suckers were
collected at the upstream points of cobble
bars in water about 1 m deep, with a water
velocity of about 1 m/sec. Although spawn-
ing activity was not observed, the presence of
ripe females (collected only over the cobble
bars) suggested that spawning probably oc-
curred nearby. Flannelmouth suckers repro-
duced successfully in both 1975 and 1976 as
evidenced by the abundant young of the year
(30-40 mm TL), which we readily captured
at all study areas by midsummer.
or
DISCUSSION
The back-calculated length of flannel-
mouth suckers at the time of annulus forma-
tion for annuli I and 11 were similar to those
estimated by McDonald and Dotson (1960)
for flannelmouth suckers from the upper
Green River and by Carlson et al. (1979) for
fish from the upper Yampa River; however,
our estimates of total body length at the for-
mation of annuli III and greater were longer
than their estimates. They also observed a de-
cline in annual growth increments at age IV,
similar to this study, which probably reflects
the diversion of energy from growth to re-
production at the onset of reproductive
maturity.
Although annual growth increments did
not differ significantly between rivers, the
significant difference in the length-weight
relationships reflects heavier body weight for
a given length of fish from the Colorado and
Gunnison rivers. This observation probably
reflects a difference in the nutritional status
of the fish examined in this study. However,
the similarity between back-calculated length
at annulus formation during previous years
suggests that these differences may not al-
ways occur. Similar differences in,weight of
razorback sucker, Xyrauchen texanus, and fe-
cundity of bluehead sucker, C. discobolus,
from these study sites were observed by
McAda and Wydoski (1980, 1983 [respective-
ly]) during the same period. Although this ob-
servation probably reflects a difference in the
nutritional status of the fish examined in this
study, we cannot speculate whether this phe-
nomenon represents consistent differences
between the two study areas or merely re-
flects differences that occurred during the
study period. However, the similarity be-