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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EXECUTIVE SUMMARY

A fishery investigation was initiated on the Dolores River in 1990 to assess the suitability of this river
system for survival of native Colorado River fishes, particularly the Colorado squawfish (Ptychocheilus
lucius). The Colorado squawfish has historically been found in the endangered Colorado River
system, but runoff from stockpiled tailings generated by uranium mills killed most of these fish in the
lower 65 miles of the river in the 1960's. In addition, reduced flows from irrigation withdrawals left
remaining habitat marginally suitable for fish.

A recent Environmental Protection Agency court ruling under the Superfund Program ordered
removal of the Uravan mill tailings, while construction of McPhee Dam on the upper Dolores River
has augmented low summer and winter flows. These actions, combined with a desalinization program
in the salt-laden Paradox Valley, promise to improve water quality and flow conditions for Colorado
squawfish as well as other species.

Studies by the U. S. Fish and Wildlife Service in 1979 and 1980 and this investigation show a
repopulation of the Dolores River qy both native and exotic fishes. To date however, Colorado
squawfish continue to be absent from the system. Of 14 species reported in the river in 1990, native
species including flannelmouth sucker, roundtail chub, bluehead sucker, and speckled dace comprised
13% of the total catch. Exotics including red shiner, flathead minnow, and sand shiner comprised
83.8% of the catch. This figure is more than double the proportion of native fishes to exotics in the
Colorado and Green Rivers.

The Dolores River appears to have the potential to provide and support suitable habitat for Colorado
squawfish, including spawning areas, nursery backwaters, and juvenile and adult holding areas.
However, spring peak flows are dramatically reduced by McPhee Dam and low releases of 25 to 40
cubic feet per second in dry years such as 1990 appear to leave marginal habitat for the fish even in
the lower 65 miles where flows are supplemented by the San Miguel River.

Water quality appears to be suitable for survival of this fish during most of the year. However, during
spring runoff and rain spates, copper and iron are released into the system at potentially lethal levels.
Further analysis is needed to assess the potential impacts of heavy metals that remain trapped in
bottom sediments and tributaries.

1.0 INTRODUCTION

This document is the Annual Summary Report for 1990 submitted to the Utah Division of Wildlife
Resources (UDWR) in fulfillment of Contract No. 90-2559, entitled Dolores River Native Fish
Habitat Suitabilitv Study. Two trip reports were also submitted during the course of the
investigation, one for each of the first two sampling trips conducted during 1990. No trip report was
submitted for Trip 3. Results from Trip 3 have been summarized and integrated with the results of
the first two trips and are presented in this Annual Summary Report.

This investigation of the Dolores River is to be conducted in 1990 and 1991. The purpose of the
study is to determine the suitability of this river to the native Colorado River fishes, particularly the
endangered Colorado squawfish. Extending the current range of this species into the Dolores River
could significantly aid the recovery of the species.

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