9375

• UCREFRP Catalog Number: 9375
• Author: Kimball, J. F.
• Title: Flow Effects on Humpback Chub ‎(Gila cypha)‎ in Westwater Canyon.
• USFW Year: 1999.
• USFW - Doc Type: Salt Lake City.
• Copyright Material: NO

Table 14. Pearson correlation coefficients (PC) and associated levels of significance (p) for August
catch rates (fish/ m2) vs. peak flow as recorded at the State Line, Utah, USGS gage station;
1992 -1996.
Species Above Canyon Canyon
Fathead PC= -.88 PC= -.63
minnow p = .048 p = .26
Red PC= -.63 PC= -.42
Shiner p = .26 p = .48
Sand PC= -.49 PC= -.59
Shiner p = .40 p = .29
Speckled PC= .O1 PC= .42
dace p = .98 p = .48
Bluehead PC= .51 PC= .48
sucker p = .38 p = .41
Age 1 and Age 2 Gila spp Catch rates. - an index of recruitment
Relative abundance of juvenile chubs was tracked annually within Westwater Canyon beginning
in 1993. Juvenile chubs were collected most effectively by electrofishing shoreline azeas after dazk.
The greatest catch rates occurred between RK 193.6 and 192. Juvenile chub habitat is characterized by
moderate depth (.3 - 1.Om) and areas of complex flow, e.g., swift runs, chutes, shoreline pour overs, and
the associated pool habitats immediately upstream and downstream. Habitats with boulder and cobble
substrates or debris piles were preferred as were shallow shoreline benches. Juvenile chubs were often
collected in the presence of adult roundtails as well as bluehead sucker, common carp, channel catfish,
adult humpback chub and flannelmouth sucker in order of decreasing abundance.
Age 1 and Age 2 Gila spp. cohorts (Table 15) could be distinguished in a length frequency
analysis (Appendix Table 4). By September, of most years, the Age 2+ fish had grown large enough that
it became difficult to distinguish them from the conglomeration of adult fish (many year classes) which
were 200 mm TL and larger. Chubs less than 175 mm TL were not PIT tagged in this study and
therefore an analysis of recruitment is limited to a comparison of catch rates .
Table 15. Three cohorts of Gila spp. that were tracked through their third growing season. Lengths
refer to the modal peaks as identified in length frequency analyses (Appendix Table 4). All
fish were collected in Westwater Canyon (Colorado River miles 199.2 - 119); 1992-1996.
Dates refer to fish community monitoring trips.
Sep, 93 Oct, 93 July, 94 Sep, 94 Sep, 95 Oct, 95 July, 96 Sep, 96
1992 l+ 1+ 2+
110mm 110mm 135mm
1993 1+ 1+ 2+
80mm 120mm 160mm
1994 1+ 1+ 2+ 2+
110mm 120mm 140mm 170mm
15