7729

• UCREFRP Catalog Number: 7729
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Annual Summary Report - 1990\
• USFW Year: 1991.
• Copyright Material: NO

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1.1 Objectives

The objectives of this investigation are to:

1. Determine the extent and change in use of the Dolores River by native Colorado
River fishes with the advent of consistent flows, reduced pollutant inflow, and
reduced salinity now occurring in the Dolores River.Basin.

2. Assess suitability of chemical, physical and biological attributes of the Dolores River
for native and endangered Colorado River fishes.

3. Evaluate the feasibility of reintroducing Colorado squawfish into the Dolores River
to enhance recovery of the species in the upper basin.

4. Issue recommendations on reintroducing the Colorado squawfish into the Dolores
River.

1.2 Background

The Dolores River once supported unknown numbers of Colorado squawfish (Ptychocheilus lucius)
and perhaps functioned as a spawning tnoutary for this species in the upper Colorado River.
Seethaler (1978) reported that T.M. Lynch seined small squawfish from Paradox Valley in 1962.
Several other collections of Colorado squawfish were reported during the 1950's and 1960's by
Lemons (1955), Nolting (1956), and Coon (1965). The most recent collection of Colorado squawfish
in the Dolores drainage was by Horpestad in 1973, who reported the capture of seven individuals in
the San Miguel River, approximately 6 miles above it's confluence with the Dolores River (Horpestad
1973). However, no Colorado squawfish were captured during a fishery survey of the Dolores River
by Holden and Stalnaker (1975) during 1971. More recent surveys by the U.S. Fish and Wildlife
Service (USFWS) in the early 1980's also failed to locate Colorado squawfish in the Dolores River
(Valdez et aI. 1982).

Uranium processing facilities operated during the late 1940's through the 1960's caused severe
impacts to the stream biota and may have contributed greatly to the local demise of the Colorado
squawfish in the Dolores drainage (Sigler et at 1966). These uranium processing facilities include
a uranium concentrator at Naturita, Colorado and a large uranium mill at Uravan, Colorado, both
of which are located on the San Miguel River within 15 miles of its confluence with the Dolores
River. A uranium concentrator plant is also located on the Dolores River near the town of Slickrock,
Colorado, approximately 60 miles above the confluence of the Dolores and San Miguel Rivers.

Direct observations of stream impacts associated with effluent and "accidental" spills of uranium mill
wastes from the Uravan mill site on the lower San Miguel River were made by Sigler et al. (1966),
and included fish kills, fish avoidance movements and dramatic pH swings (7.6 to 4.3).

A recent court order under the EP A Superfund Program to remove mill tailings at the Uravan mill
site may significantly improve water quality in the Dolores River. Clean up operations as a result of
this court order are currently in progress at the Uravan site. Removal of mill tailings and stabilization
of riverside ponds are scheduled to be completed in phases within the next 2 to 6 years. Informal
site visits were made during each field trip by BIO/WEST in 1990, to observe progress of clean up

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