1108

• UCREFRP Catalog Number: 1108
• Author: Valdez, R. A.
• Title: Fisheries Biology And Rafting Annual Summary Report - 1987
• USFW Year: 1988.
• USFW - Doc Type: ‎(Contract no. 6-CS-40-03980)‎.
• Copyright Material: NO

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Objective 2: Determine whether humpback chub populations exist in Cataract.

1. Recommendation #1 for Objective 1 above is essential to addressing this
'. objective as well. Since sample conditions in Cataract Canyon vary greatly,
and can be very difficult at times, ongoing efforts must be maintained to
capture a cross section of the morphotypes that represent the Gila complex
in Cataract Canyon.

2. Biochemical, meristic, and morphological examination of chubs from Cataract
Canyon are needed to ascertain the true classification of the different
morphotypes encountered in the region. Sacrifice of any chubs from the
study area should be kept to a minimum, and done only with sufficient
justification and throughdocurnentation of the analyses to be performed.

3. The two additional "confluence trips" (one in April and one in September),
as conducted in 1987, are also recommended for 1988, wi th the stated
objective of surveying the Colorado and Green Rivers above the confluence
for the presence of reproducing populations of chubs. A second objective
that should be added to the April trip is seining of backwaters to determine
CPE for the previous year class in an attempt to assess overwinter mortality
of young Colorado squawfish.

4. Continued seining and drift netting are recommended, with samples sent to
the Larval Fish Laboratory, to determine the species composition of young
fishes in the region, and to confirm the presence of larval and yay
humpback chubs as an indication of ongoing reproduction.

Objective 3: Describe influence of BOR's operation of Lake Powell on nursery
habitat of Colorado squawfish.

1. Additional seining and larval drift netting are recommended at Upper Ten
Cent, in conjunction with the intensive 3 to 4-day efforts described in
Recommendation 1 of Objective 1 above. This effort should be made in order
to assess the contribution of larval and yay endangered fishes to Lake
Powell, as well as to assess the habitats used by these young fishes. We
also recommend that BaR continue their larval and yay sampling program at
and below Imperial Canyon. Lake levels should be recorded with each sample
to assess available habitat and the influence of Lake operation on that
habitat.

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