7640

• UCREFRP Catalog Number: 7640
• Author: Helbig, V.
• Title: Yampa River Spawning Habitat Investigations.
• USFW Year: 1984.
• USFW - Doc Type: \
• Copyright Material: NO

The results of the habitat simulations are presented in Tables 2
and 3.
Appendix 2, consistent with spawning windows (approximately June
15 - August 15) presented in Table 1, shows mean monthly flows in
June, July and August for 62 pears of record. Appendix 3 depicts
habitat availability or weighted useable area (WUA) for June,
July and August for 62 years of record.
Discussion•
As seen in Table 1, the time frame for spawning activity on the
Yampa River varies somewhat from year to year. Why this occurs
is not fully understood at this time. Whether a function of
photoperiod, flow, water tempertaure, sexual maturation or a
combination of one or more factors remains unclear. What is
evident, is the annual need for a sufficient surge or peak spring
run-off flow such that movement of fines (sand/silt) is
accomplished to maintain spawning substrates.
Colorado squawfish spawning activity is apparently composed of
two phases requiring two distinct habitat types: deposition!
fertilization and staging/resting areas. As is illustrated in
Appendix 1, each phase has different depth, velocity, and
substrate characteristics. Table 2 depicts WUA for both
functions at RM 16.5. Table 3 shows WUA for deposition/
fertilization only since little or no staging/resting habitat
occurs within the study site at RM I8.5.
As is apparent from Tables 2 and 3, WUA for deposition/
fertilization at both study-sites and WUA for staging/resting at
RM 16.5 is optimized at 700 cubic feet/second (cfs). When
compared to the historic flow of record for the Yampa River
(Appendix 2), 700 cfs is exceeded 98.4% of the time in June,
75.8% of the time in July, and 13% of the time in August.
While a flow of 700 cfs optimized WUA at 22,726 sq.f t./1000 f t.
of linear stream at RM 16.5, a 90% habitat retention level could
be attained for deposition/fertilization at an approximate range
of flows from 350-1100 cfs. For staginglresting the 90%
retention level for WUA could be maintained at approximately 300-
1500 cfs. Referring to Appendix 3 (WUA for the period of
record); at RM 16.5, 90% of optimum WUA occurred only one time in
June (limited occurrence primarily because of much higher flows),
18 times in July and 35 times in August for 62 years of record.
At the replicate site (RM 18.5), 700 cfs resulted in an optimum
WUA for deposition/fertilization of 15,230 sq.ft. /I000 ft. of
linear stream; 90% of optimum WUA could be maintained within a
range of approximately 400-1700 cfs. For the historic period of
record (Appendix 3), 90% of optimum WUA occurred at RM 18.5, one
time in June (again because of high flows), 36 times in July and
35 times in August.