7108

• UCREFRP Catalog Number: 7108
• Author: Johnson, J. E.
• Title: Reintroducing the Natives
• USFW Year: 1985.
• USFW - Doc Type: Colorado Squawfish and Woundfin.
• Copyright Material: YES

Status of the Razorback sucker in the Green River, Utah
Harold M. Tyus
U. S. Fish and Wildlife Serivice-CRFP
1680 W. Hwy. 40 Room 1210
Vernal, UT 84078
Abstract--The razorback sucker, once widely distributed in the
mainstem rivers of the Colorado River Basin is still found today in
riverine habitat of the Green River Basin, where it may be more numerous
than in other locations in the Upper Colorado Basin. Although historic
data prior to 1970 is scant, records from the 1890's suggest that the
fish was never as abundant in the upper basin as in the lower. Some
areas formerly supporting the razorback in the upper basin have been
altered by water development and the fish extirpated from them. The
Fish and Wi]dlife Service has studied the rare and endangered fishes in
the Green since 1979. A systematic sampling program from 1979-81 indicated
that the razorback was very rare, and was only 11% as abundant as the
endangered Colorado squawfish. However, subsequent studies from 1981-
84, including radiotelemetry, revealed that the razorback is not very
susceptible to capture except during spring spawning. Razorback spawning
was documented from 1981-84 with the capture of 47 fish in breeding
condition and tentative identification of larvae. Since no young juveniles
were collected, recruitment is apparently very low. Growth of adults
measured from the interval between capture/recapture of tagged fish
(from 16 years) averaged less than 5 mm/year, These data suggest that
the razorback should be considered endangered in the upper basin and
immediate steps should be taken to protect and recover it.