8135

• UCREFRP Catalog Number: 8135
• Author: Valdez, R. A.
• Title: Occurrence of Threatened and Endangered Fishes of the Colorado River in the Vicinity of the Proposed Jacobson Hydro No. 1 Project.
• USFW Year: 1984.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

3-1

3.0 METHODS

3.1 Field Sampling
The Colorado River was sampled between the Grand Valley Diversion Dam
(GVDD) and the Price-Stub Dam with electrofishing, seines, dip nets and
drift nets. The two structures are generally considered fish barriers to
upstream fish movement, except perhaps during spring runoff in June and in
early October when individual gates of the GVDD are opened to flush the
holding pool and perform maintenance on the structure (Personal
communication, Elmer Morris, GVID, Palisade, CO, September 23, 1984). No
record was found of any fishery work conducted in this 5.4-mile river reach,
except for gill nets set by Kidd (1977) in the GVDD spill pool at the upper
end of the reach.
The electrofishing was done with a 16-foot aluminum flatbottom boat
equipped with a 220-v DC Coffelt fish-shocking unit. Electrofishing was
conducted at randomly-selected sites and habitats throughout the 5.4-mile
river reach. The time of each effort, which lasted 15 minutes to 1 hour,
was recorded to compute the catch per unit effort. Electrofishing was
conducted during two periods, April 11-12 and September 22-23, 1984. Both
day and night-time electrofishing were conducted during these sample
periods.
Seines with 1/4 and 1/16-inch mesh were used to sample shallow areas in
a manner that sampled only one habitat type at a time. The smaller mesh
seine, which measured 10 feet long and 4 feet deep, was used to capture the
small larval and young-of-the-year fishes. The seine with the larger mesh,
which measured 15 feet long and 4 feet deep, was used to sample the larger
young-of-the-year fishes, juveniles and adults. The surface area of each
seine haul was estimated to enable computation of catch per unit effort.