9532

• UCREFRP Catalog Number: 9532
• Author: Anderson, R. and G. Stewart.
• Title: Riverine Fish Flow Investigations.
• USFW Year: 2000.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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In the main channel the vast majority of fish caught were over IS cm, however in

backwaters the majority offish were less than IS cm. Non-native cyprinids as a group were

the most common fish sampled in backwater and most of them were deliberately not netted.

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The next most common species in backwaters were roundtail chub (17%), carp (15%),

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tlannelmouth sucker (10%) and white sucker (9%). Largemouth bass were about 6% and

green sunfish were S% of the total in the backwaters sampled. For fish over 15 cm the most

common species were carp, flannel mouth sucker and white sucker (Table 3)

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LENGTH FREOUENCY and MEAN LENGTH

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Length frequency histograms given in Appendix C Figures .1,2 and 3 are for total fish

captured in 1998 and 1999. The length frequency histograms for bluehead sucker were very

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similar between years on the Yampa River. On theYampa river the DuffX station in 1999 had

39% bluehead sucker at 40 cm or larger, in contrast to only 2% at the Sevens. TheColorado

River had 21% of blue head sucker at and over 40 cm. Duffy als~ had the highest mean

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length in 1999 of blue head sucker at 382 mm, Sevens hadthe smallest mean length of336

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mm and it was 366 mm in the Colorado River (Table 4). Mean lengths between all sites were

statistically different at P<O.OOI in 1999 for bluehead sucker.

The length frequency histograms were also different for flannel mouth sucker between

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the three sites. Duffy in 1999 had the highest percent (44%) offish over 50 cm, and Sevens

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the lowest at 16%, and it was 28% in the IS-Mile Reach in 1999 (Figure A). The Colorado

River had the highest percent (28%) offish under 40 cm and fish under 40 cm were only 6%

for both sites on the Yampa (Appendix C Figures 4, Sand 6). Mean length oftlannelmouth

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suckerin 1999 in the Colorado River was 422 mm and it was 46S and 486 mm for Sevens and

Duffy, respectively (Table 4). The higher mean length on the Yampa River reach was a

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