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 13. Mean lengths of all species collected at Lily Park, Yampa River 2000 to 2003,

YAMPA RIVER Mean length for all fish collect in cm
Lily Park 2000 2001 2003
Flannelmouth sucker 41.5 38,3 37,8
Bluehead sucker 34.2 33,5 32,5
Colorado pikeminnow 59.4 64,3 52,6
Roundtail chub 40.3 18,0 6,0
White S. + hybrids 26.6 28.0 35,8
Channel catfish 34,7 32,9 27.2
Carp 42,1 44,6 43.1
Small mouth bass 12.0 15,1 16,7
Northern pike 64,6 66,7 63,7

Channel catfish biomass was much greater in 2000, Not only was channel catfish
density and biomass highly variable between years, but length distribution was also highly
variable between years. This variability in size distribution was another aspect of a migrating
population, In 2000, 72% of the channel catfish captured at Lily Park were between 30 and
39 em in length. In 2001, 48% of the channel catfish measured from 30 to 39 em, Only 13%
were of this size in 2003, Only 13% of the channel catfish were less than 30 em in 2000, but
78% were less than 30 em in 2003. The large shift in size structure at Lily Park between
years likely indicated improved spawning and survival of small channel catfish in 200 I and
2002 compared to 1998 and 1999,

Survival of small channel catfish may be more a function of habitat conditions than
predation rates. Higher and cooler flows during the Spring and Summer of 1998 and 1999
could mean that channel catfish spawning was located further downstream. In 1998 and
1999 younger channel catfish may not have been available or capable of moving into the Lily
Park site by 2000. The presence of smaller channel catfish in 2003 would result if their
spawning and nursery habitat was much closer to Lily Park. This was indicated by the
capture of a 5 em fish (YOY) at Lily Park in 2003 and two yearling fish, 14 em and 16 em,
not observed in prior years.

The most common channel catfish size-group (mode from 30 to 40 em) in 2000 was
missing in 2003, This could be a result of poor survival in 2002 for channel catfish over 30
em. The very strong mode offish from 20 to 30 em in 2003 (Figure AI-4S) coincided with
the drought flows of 2002 which suggested habitat for channel catfish less than 30 em was
improved given those flow conditions.

White sucker and carp had their highest biomass estimates in 2003. Smallmouth bass
biomass was fairly similar for all three years in spite of the fact that bass density increased in
each year.

Age-O smallmouth bass were not collected at Lily Park in 2003 (Figure A I-52), but
were common in both 2000 and 2001, The lack ofYOY bass meant that the mean length of
smallmouth bass (Table 16) was higher in 2003 compared to prior years, By far the

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