7359

• UCREFRP Catalog Number: 7359
• Author: Tyus, H. M. and C. A. Karp
• Title: Spawning and Movements of Razorback Sucker,
• USFW Year: 1990
• Copyright Material: YES

I

December 1990

Tyus and Karp-Spawning and movements of Xyrauchen texanus

431

movement between the Jensen site, Island Park,
and the Yampa site (n = 4, average one-way
movement = 49.6 km, range of 30.4 to 60.8 km).
These fish passed through Split Mountain Can-
yon, a high-gradient, canyon-bound reach dom-
inated by rapids and rocky runs. Three fish were
ripe males, but sex of the fourth was not deter-
mined. One radiotagged fish made a round trip
movement between Island Park (4 May then 10
June) and the lower Yampa River (collected run-
ning ripe on 12 May) where the fish presumably
spawned.

~

DISCUSSION-Razorback suckers are rare but
widely distributed in low-gradient sections of the
Green River (including the lower 4 km of the
Duchesne River and the lower 0.8 km of Ashley
Creek; Tyus, 1987; Lanigan and Tyus, 1989)
and the lower 84.8 km of the Yampa River (E.
Wick, pers. comm.). In the spring, the fish con-
centrated in the Green River mainstream between
the confluence of the Duchesne and Yampa rivers.
This reach supports the majority of extant ra-
zorback suckers in the Green River basin (Lan-
igan and Tyus, 1989), although the species was
once abundant in the lower Green River as well
Gordan, 1891). As in other studies (e.g., Tyus,
1987), we captured no razorback suckers <405
mm TL and presumed that recruitment remained
low or nonexistent in the Green River.
Combining our information with data collected
in the Green River between 1981 and 1986 (Tyus,
1987), 58% (n = 307) of 530 adult razorback
sucker captures were captured ripe or tuberculate
(Table 1). Of these, 60% (n = 185) were breeding
males, and 24% (n = 74) were breeding females.
These data indicated a sex ratio of about 2.5
males: 1.0 female, similar to the 1.6:1.0 ratio re-
ported by Tyus (1987). Average size (total length)
of ripe razorback suckers was similar to other
accounts from the Green River basin (Tyus, 1987;
C. McAda, pers. comm.).
Ripe razorback suckers were captured from
mid-to-Iate April through May in upper Green
and lower Yampa rivers, 1987 to 1989. However,
initiation of the spawning period is no doubt ear-
lier than we observed (20 to 27 April, Table 1),
because ripe fish were captured on our first day
of sampling in 1987 and 1989. Spawning of ra-
zorback suckers extended into June in years of
high runoff (e.g., 1984 and 1986, Table 1).
Capture of ripe razorback suckers was asso-
ciated with increasing and highest spring runoff
and warming river temperatures. Spawning tem-

peratures recorded during this study (140C) of
low-to-average flow years (average flow <128
m3 Is, United States Geological data) were similar
to the 15.0 to 15.50C reported by Tyus (1987)
for the higher water period 1984 to 1986, and
we believe the lack of lowland flooding in our
study was associated with lower temperatures. In
1986, 47% (n = 20) of all ripe or tuberculate
razorback suckers (reported in Tyus, 1987) were /
captured in flooded Old Charley Wash and Stew-
art Lake Drain at water temperatures averaging
190C (range of 17 to 210C). Main channel tem-
peratures averaged only 15.80C (range of 15.0 to
16,SOC) during this period, which suggests that
razorback suckers may be seeking warmer hab-
itats in the spring. Few razorback suckers were
captured in lowlands during this study; however,
these areas were not accessible due to a lack of
widespread spring flooding.
P. Holden and L. Crist (pers. comm.) reported
capture of 56 razorback suckers in the Ashley
Creek-Jensen area from 1978 to 1980, and about
190/0 of all ripe or tuberculate razorback suckers
captured by USFWS from 1981 to 1989 (n = 57)
were taken in flooded lowlands (e.g., Old Charley j
Wash and Stewart Lake Drain) and mouths of
tributaries (e.g., Duchesne River and Ashley
Creek). Seasonal movements of some fish into
these areas suggests that flooded lowlands may
provide important habitat for razorback suckers.
Warmer temperatures and increased food avail-
ability offer plausible explanations, and Bulkley
and Pimentel (1983) reported that adult razor-
back suckers preferred temperatures of 22 to 250C
and avoided temperatures of 8 to 150C. We sug-
gest that both reproduction and recruitment in
razorback sucker in the Green River may be ad-
versely affected by loss of seasonally flooded hab-
itats due to their impoundment via dams and
dikes, loss of fish access, and alteration of the
duration and magnitude of spring flooding.
Razorback suckers exhibited a variety of local
and long-distance movements during the spring
spawning period. Spawning migrations (one-way
movements of 30.4 to 106.0 km) included move-
ment between the Jensen site and Ouray area (n
= 13), and movement between YampaandJensen
sites (n = 4). Similar movements were noted by
Tyus (1987), and historical accounts also re-
ported spring spawning movements of razorback
suckers Gordan, 1891; Hubbs and Miller, 1953;
Sigler and Miller, 1963). Other catostomids are
known to exhibit spawning migrations (Breder
and Rosen, 1966). Blockage of stream passage