WSP12249

• File Number: 8240.200.10.B
• Description: UCRBRIP - Riverine Fish Flow Investigations
• Basin: Colorado Mainstem
• Date: 6/1/2004
• Author: CDOW
• Title: Riverine Fish Flow Investigations 2004
• Water Supply Pro - Doc Type: Publication

Species composition, density and biomass data presented in the results section was
for fish over 15 cm in length, Length data are inclusive for all fish captured at the site,

YAMPA RIVER

Duffv

Native fish species were uncommon to rare at Duffy during all years of sampling,
averaging only 14% of fish over 15 cm for first three years, 10% in 200 I and 7% in 2003
(Table 2). Flannelmouth sucker and bluehead sucker both hybridized with non native white
sucker. White-tlannelmouth and white-bluehead hybrids comprised about 50% of the
suckers captured during the study period, Pure native sucker represented about 10% of the
catch in the baseline years and only 5% in 2003. Roundtail chub were near 3% of the catch
during the study period. Colorado pikeminnow were uncommon at Duffy comprising
between \.5% to 0.6% of the total catch from 1998 and 2001. None were caught in 2003.

Table 2, Species composition (fish> 15 cm) at Duffy, Yampa River 1998 to 2003.

YAMPA -REACH DUFFY DUFFY DUFFY DUFFY DUFFY
Species 1998 1999 2000 2001 2003
Flannelmouth sucker 5% 5% 5% 2% 4%
Bluehead sucker 4% 6% 4% 4% 1%
Roundtail chub 3% 3% 4% 3% 2%
Colo, Pikeminnow 1.5% 0,6% 0,8% 0,6% 0%
White S, + hybrids 69% 72% 73% 50% 66%
Channel catfish 3% 4% 3% 4% 4%
Carp 3% 1% 1% 2% 0.3%
Smallmouth bass 8% 6% 10% 33% 18,2%
Northern pike 2.8% 2,3% 0,9% 1,1% 0.7%
Black bullhead 2%
Black crappie 2%
Sample size 1653 2092 1294 856 584

The total fish density estimates at Duffy were highest in the baseline years and lowest
in 2003, The highest total density occurred in 200 I due to a higher estimate of smallmouth
bass for that year (Table 3). Densities estimates for tlannelmouth sucker, bluehead sucker,
Colorado pikeminnow and roundtail chub were highest in the baseline years of 1998 and
1999, but lowest in 2003 (Table 3). The same trend was also found for the non-native
species of white sucker, carp and northern pike. Smallmouth bass was the only species to
display a strong increase in abundance during the dry years of 200 I and 2003,

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