7780

• UCREFRP Catalog Number: 7780
• Author: Brooks, J. E., et al.
• Title: San Juan River Seven Year Research Program Summary Report 1992.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

habitats to determine food item availability. Subsamples of
collections by New Mexico and Utah biologists for secondary channel
and juvenile studies will be analyzed for food habits of native and
nonnative species to determine dietary overlap. A literature
review of the presence of the white sucker in the Colorado River
Basin will be conducted to determine potential and likely inter-
relationships to San Juan River native fishes.
Tailwater Salmonid Fisherv - The impoundment and subsequent
filling of Navajo Reservoir in 1962 allowed for cold hypolimnetic
releases from the reservoir capable of supporting salmonids.
This tailwater salmonid fishery has developed into one of the
most popular trophy trout fisheries in the western United States.
The tailwater trout study area extends approximately 24 km (16
mi) downstream of the dam to Blanco, NM. It includes -three
reaches: 1) the 6.4 km (4 mi) long special regulation "Quality
Water" section, 2) the 5.3 km (3.3 mi) "regular regulation"
section extending downstream from the end of the Quality Water
section and 3) Gobernador Arroyo to Blanco. Divisions for each
were based on differences in regulations and/or habitat quality.
Tailwater trout studies conducted in 1992 included fish
population surveys, trout movement studies, water quality
monitoring and angler use and catch surveys. Two population
survey efforts were made using a raft-mounted electrofisher.
Radio telemetry studies were conducted in the upper 0.8 km (0.5
mi) of the tailwater to study the longitudinal movement of trout
in response to high spring releases. Water quality monitoring
data collection was for temperature, dissolved oxygen and
nitrogen supersaturation. Measurements of angling pressure and
success were conducted throughout the year.
In February, 46g of a sample of 998 rainbow trout from the
quality water section of the San Juan River were > 457 mm (18")
total length. In September, 51~ of 724 trout were > 457 mm. At
least 95~ of the fish in both samples were rainbow and the
remainder were brown trout. Mark and recapture population
estimates for the Quality Water section, excluding the Texas
Hole, were 3243 trout.(95~ C.I. 2700 - 3986) for February and
7505 trout (95~ C.I. 3595 - 11,415) for September. In the
regular regulation section 61~ of rainbow trout collected in
October were less than 305 mm (12 ") total length indicating that
they had been recently stocked. In February 20~ of the sample
from this section were brown trout compared to 42~ in October.
Sampling from Gobernador Arroyo to Blanco revealed that
flannelmouth and bluehead suckers were the most abundant species
prior to spring releases from the dam (59~ of total catch, both
suckers combined). Trout were more abundant in the fall (80°s of
total catch). Two mottled sculpin were collected during the fall
surveys, the first collected in this portion of the San Juan
since Navajo Dam was built.
19