7125 ‎(2)‎

• UCREFRP Catalog Number: 7125
• Author: McAda, C. W.
• Title: Aspects of the Life History of Three Catostomids Native to the Upper Colorado River Basin.
• USFW Year: 1977.
• USFW - Doc Type: Utah State University,
• Copyright Material: YES

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Poor reproductive success has also been reported in the upper
basin [Banks, 1964; Vanicek, Kramer and Franklin, 1970; Holden and
Stalnaker, 1975a and 1975b]. The apparent lack of young of the year
and juveniles in collections can probably be attributed, at least in
part, to their close resemblance to young flannelmouth suckers. The
few young-of-the-year and age I razorback suckers that might have
been collected could easily have been overlooked among large numbers
of juvenile flannelmouth suckers. Conversely, sub-adult razorback
suckers should have been easily recognized by the bony nape if they
had been collected. Holden [unpublished data] collected a few sub-
adult fish, but none were collected during 1974-76.
During this study, razorback suckers were observed spawning over
gravel bars in the Yampa and Colorado Rivers. Three spawning sites
were located, although most spawning razorback suckers were collected
from a bar located 400 m upstream from the mouth of the Yampa River
(Figure 7, site A; Figure 8). The fish were collected from water
approximately 1 m deep at the upstream point of the gravel bar. The
substrate was predominantly cobble (ranging in size from 20 to 50 mm
in diameter) and the water velocity was approximately 1 m/sec (Table 8).
During a two week period, 14 razorback suckers (2 females and 12 males)
were captured over this bar. Females captured in nearby locations
were not yet ripe (i.e., exuding eggs) but female razorback suckers
collected from the water column over the bar were ripe, indicating
that they were spawning in the immediate vicinity. Males captured
over the bar and in nearby locations were all ripe (i.e., exuding
sperm).
Spawning may have been attempted in the gravel pit at the Walter