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

Table 10, Species composition at Lily Park, Yampa River, 2000 to 2003,

YAMPA RIVER Lily Park Lily Park Lily Park
Spec,es 2000 2001 2003
Flannelmouth sucker 48% 68% 54,7%
Bluehead sucker 9% 7% 7.5%
Roundlail chub 0,02% 0,03% 0%
Colo, Pikeminnow 0,1% 0,0% 0,1%
White S. + hybrids 0,3% 0.2% 0,6%
Channel catfish 40% 18,0% 27.9%
Carp 2.1% 2,1% 3.4%
Smallmouth bass 0,8% 5.0% 5.0%
Northern pike 0,2% 0,2% 0,1%
Sample size 4058 2989 2129

An abundant channel catfish population was unique to the Lily Park site, Channel
catfish density and biomass estimates were highly different between years. In 2000 the
density estimate was 513 fishlha and biomass was 224 kgiha, In 2001 density was 137/ha
and biomass was 57 kgiha. In 2003 density was 276/ha (Table II) and biomass was 64 kg/ha
(Table 12), The variability in channel catfish composition between years resulted from the
presence of a large migrating population that passed through Lily Park during the summer to
upstream habitats. The low tlows in July and August 2000 could have stopped migrating
channel catfish at Cross Mountain Canyon, This increased their number at Lily Park that
year. In 200 I and 2003 either the size of the migrating population was less or it was more
dispersed,

The size and timing of the channel catfish migration wave meant their abundance can
vary greatly within and between years. Recapture rates on catfish in all three years was only
fair, with confidence intervals of20 to 40% of the estimate, Even so, widely different
population sizes were indicated between years,

Density estimates for tlannelmouth sucker, bluehead sucker and northern pike were
highest in 2000, The 2001 and 2003 estimates were lower, but similar to each other (Table
11), In contrast estimates for smallmouth bass, white sucker and carp were lowest in 2000
and highest in 2003 (Table 11), This was the same trend for the other Yampa River sites,

Biomass is a function of both density and size so when mean length is constant
biomass varies only with density, Mean length varies between years mainly due to
differences in year-class strength and growth rates. Typically mean length varies due to the
number of Age-I fish in the sample. During the study period Age-O and Age-I fish were
rarely observed in the community and very few to no Age-I bluehead sucker and
tlannelmouth sucker were observed at Lily Park in 2003 (Figures A 1- 3 and A 1-1 0),

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