7305

• UCREFRP Catalog Number: 7305
• Author: Tyus, H. M. and W. B. Harned.
• Title: Distribution, Spawning and Habitat Use of the Razorback Sucker in the Green River Basin, Colorado and Utah, 1979-84.
• USFW Year: 1985.
• USFW - Doc Type: \
• Copyright Material: YES

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The recaptures of 30 razorback sucker, of which three were recaptured twice, have
aided in understanding their distribution and spawning behavior. A total of
16 fish were local recaptures, tagged and recaptured within about one
month's time (11 in 1984 and 5 in 1981). With some exceptions, these
fish remained near the original capture locations. An additional 14 recaptures
were recovered after a year or more and included recaptures of up to 6 years
duration (lable 2). The distances moved by these fish over the years ranged
from 0 to 129 miles. The data were then partitioned to separate recaptures
within three time periods: breeding, nonbreeding, and combination breeding and
nonbreeding periods. This was accomplished by segregating May and June as
breeding months. Fish tagged and recaptured during the breeding season (9)
averaged only 7 miles movement and one fish tagged and recaptured during the
nonbreeding season travelled only about 1 mile. However, 5 fish tagged in
the nonbreeding and recaptured in the breeding season (or vice versa) averaged
51.4 miles distance between captures. The preceding indicates that the
razorback is sedentary during most of the year, perhaps making only local
movements, but may travel longer distances to reach suitable spawning grounds.
These local movements are demonstrated by one razorback sucker implanted with
a radiotransmitter in 1980 (Tyus, et al. 1981). This fish moved about 3.8 miles
downstream of its capture location and into the Duchesne River. It remained
less than 1 mile inside the Duchesne River until flooding occurred in early
June when it moved into the Green at the mixing zone of the two rivers and was
lost and presumably spawned at some unknown location. The sucker then was
relocated in July near the same area and slowly moved upstream in the Green
River about 7 miles, when contact was lost August 13.

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HABITAT USE

Microhabitats and specific physical conditions required by the razorback
for spawning are still somewhat of a mystery and the fish appear to stage
and spawn in different habitats. A large concentration of razorbacks discovered >
by Vernal Dialogists in 1981 at the junction of the Green River and Ashley
Creek (Tyus et al. 1982) prompted many collecting trips up Ashley Creek in
search of spawning areas. 10 date, none have been discovered in Ashley Creek
and no razorback has been captured further upstream in the creek than 0.3
miles, habitat that does not appear suitable for spawning because of the
silty substrate. It is possible that the large shallow eddy produced at this
location makes it desirable for a staging area. Fish tagged early in May at
the mouth of Ashley Creek and recaptured further upstream in the Green River
in ripe spawning condition tend to support this hypothesis. Most ripe
razorbacks were collected over coarse sand substrate; however, some were
collected near gravel and cobble bars. Temperatures at the point of capture
for the ripe fish ranged from 10.5 C (May 10) to 18 C (June 14) in the Green
River during 1984 collections, averaging about 15 C. The USGS records for
Jensen indicate that the river flow during this time period varied from
13,800 to 38,500 cfs, and averaged 26,100 cfs. The river peaked on May 18,

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