9443

• UCREFRP Catalog Number: 9443
• Author: Bestgen, K. R., G. B. Haines, R. Brunson, T. Chart, M. Trammell, R. T. Muth, G. Birchell, K. Chrisopherson and J. M. Bundy.
• Title: Status of Wild Razorback Sucker in the Green River Basin, Utah and Colorado, Determined From Basinwide Monitoring and Other Sampling Programs.
• USFW Year: 2002.
• USFW - Doc Type: Project Number 22D,
• Copyright Material: NO

The length-frequency distribution of stocked razorback suckers captured in Basinwide

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and other sampling programs from 1996 to 1999 suggested the presence of fish from 280 to 460
mm TL (Fig. 4). Recaptures of hatchery fish released since 1995 suggested that few or none of
the relatively small razorback suckers stocked in 1995 survived but some larger fish stocked in
1996, 1998, and 1999 survived and grew (Table 2). The average change in length for fish
stocked in 1996 and recaptured in 1997 and 1998 was 99 and 130 mm TL, respectively.
Razorback suckers stocked in 1998 and recaptured in 1999 grew an average of 66 mm TL. Even
fish stocked and recaptured in 1999 exhibited an average positive change in length of 19 mm TL.
Inferences about individual growth rates are impossible to make because only a mean length was
taken for batches of hatchery fish released from 1996 to 1999. Several hatchery fish captured
were in spawning condition and four of those were found with wild fish on or near the Green
River spawning bars near Escalante Ranch.
Middle Green River sampling, adults, 1980 to 1999.-A total of 593 individual razorback
suckers were captured from 1980 to 1999 (Table 3). A total of 184 recaptures were recorded, for
a total of 777 capture events. Length frequency distributions of wild fish captured since 1980
reflected the preponderance of large fish in samples, and fish 440 mm TL or less were absent in
most years (Fig. 5). Selective sampling for larger fish during Basinwide sampling was
discounted because the sampling gear captured stocked fish that were 300 to 440 mm TL (Fig. 4).
Sampling in Basinwide and other programs was also conducted in a variety of main stem and
flood plain areas, so it seems unlikely, especially in the middle Green River, that concentrations
offish went undetected. The mean size and size range of fish also changed little over time, with
the exception of 1994 and 1995 (Fig. 6). Most of the small fish captured in 1994 and 1995 were
from a managed wetland, Old Charlie Wash, that was drained in autumn (Modde 1996). Only
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