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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The methodology for 1987 was similar to that conducted in 1986, except that in
1987, two "flatwater confluence trips" were added to the six "canyon trips" for
the purpose of assessing chub populations above the confluence.

This investigation was conducted in the Colorado River from the area of the
Goose Neck at river mile (RM) 37 downstream to Imperial Canyon at RM 200 (16.4
miles below the confluence), as well as that portion of the Green River from
Mineral Bottom at RM 52 downstream to the confluence of the Green and Colorado
rivers (Figure 1). This is identified as the "Cataract Canyon Region" in this
report. The effort was concentrated in the 16-mile whitewater reach of
Cataract Canyon below the confluence, but sampling for YOY was also conducted
in both rivers above the confluence. Six 10-day sample trips ("canyon trips")
were conducted through Cataract Canyon between June 23 and October 12, 1987.
Two additional 7-day trips ("flatwater confluence trips") were conducted to
look for chubs in the Colorado River above the confluence; one in mid-April and
one in early September.

Access to the area involved downstream travel by motorized rafts from launch
sites at either Potash (RM 47) on the Colorado River or Mineral Bottom (RM 52)
on the Green River. Launch sites were alternated in late summer to systemat-
ically sample larval and YOY endangered fishes. Of the six "canyon trips",
four were conducted in the Colorado River from Potash, and two in the Green
River from Mineral Bottom (Table 1). Both "flatwater confluence trips" were
conducted from Potash, using motorized 16-foot flatbottom boats.

Four motorized hypalon rafts were used, including one 18-foot Riken Havasu, one
17-foot Riken Havasu, one 17-foot Achilles "sportboat", and a 23-foot J-rig.
The Havasus were powered by XD-25 hp Mercury outboards, and were used for fish
sampling craft as described later in this document. The 23-foot J-rig was
powered by twin 20 hp Mercury outboards, and was used as a support craft. The
Achilles is a new addition to the sampling craft and is powered by a 40 hp
Yamaha outboard (see photos 1 and 2 in Appendix D). This raft was used to
decrease travel time to and from the principal study area, to provide greater
mobility in whitewater areas, to expand sample areas, and to provide the
capability for transporting endangered fish live from the area, if necessary.

Sampling was conducted where possible within Cataract Canyon, but often had to
be confined to the less turbulent water between rapids. Since the motorized
rafts were unable to ascend the larger rapids, sampling was concentrated in the
section of river accessible from camp sites between rapids (Table 2). Use of
the Achilles facilitated access to some areas that had not been sampled before.

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