8178

• UCREFRP Catalog Number: 8178
• Author: Anderson, R. and G. Stewart.
• Title: Riverine Fish Flow Investigations.
• USFW Year: 1999.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

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River reaches with higher rime/run ratios may have higher potential for
invertebrate production and therefore may be associated with higher fish biomass. Total
rime habitat is to be determined at the two study sites based on surveys made in 1998.
Results of these collections suggest a relationship between invertebrate community
dynamics and depths and velocities in rimes. If so, invertebrate productivity may be a
function of quantity and quality of available rime habitat. The rimes at Sevens and
Duffy are scheduled for sampling depending on budgeting in September 1999. These
and the 1998 samples will be evaluated for assigning suitable indices for invertebrates
based on water depth.

HABITAT COMPOSITION

The bulk of the hydraulic modeling and habitat quantification is still in process,
therefore, no analysis could be completed for comparing habitat availability to fish
population characteristics. The main deterrent to successful model runs is apparently
related to the low energy grade line or slope of the water surface and the steep banks of
the Yampa River. This meant that the elevation of the channel bed had to be very
precise and a lot of mesh refinement was required. The model is expected to perform
better in higher gradient rivers such as the Colorado River in the IS-mile reach.

SUMMARY AND CONCLUSIONS

. Large differences were found in species composition between the two surveyed sites
(Sevens and Duffy).

. Non-significant differences in fish density and biomass were found for the two
surveyed sites (Sevens and Duffy).

. Significant difference in density and biomass were found between the two
representative reach areas.

. The surveyed sites were not representative of the longer river reaches at both sites.
The riffle-run sequence selected for habitat analysis contained a larger and deeper
run than was typical of the river reach.

. Traditional surveying equipment used in 1998, total station and prism, was time
consumptive and not practical for long river reaches.

. Differences were identified between Seven and Duffy for gradient, substrate and
percent wetted perimeter at flows of 200 and 600 cfs. Mean channel widths were
similar for the two sites.

· The I-D flow model (BEC RAS) identified differences between the Sevens and
Duffy surveyed sites with higher depth diversity and a higher amount of deep areas
in Duffy compared to Sevens.

· The I-D flow model (BEC RAS) did not provide a velocity attribute needed to
define habitat types for habitat mapping and diversity analysis.

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