9292

• UCREFRP Catalog Number: 9292
• Author: Trammell, M. and T. Chart.
• Title: Aspinall Unit Studies Nursery Habitat Studies Colorado River 1992--1996.
• USFW Year: 1998.
• USFW - Doc Type: Moab, Utah.
• Copyright Material: NO

Introduction
The Nursery Habitat (NITJ study on the Colorado River is part of the ongoing Aspinall Unit Five
Year Research Program administered by the Recovery Implementation Program. The study began
in 1992, and field investigations continued through 1996. The objectives of this study were: To
determine current status and characteristics of reproductive success by Colorado squawfish
(Ptychocheilus Lucius) in the upper mainstem Colorado River and the effect of experimental flows
from the Gunnison River created within the Aspinall Study Plan; and to determine the relationship
between habitat availability at recommended releases from the Aspinall unit on the Colorado River
to: a) the habitat actually utilized by young Colorado squawfish, b) the number of young Colorado
squawfish present in the Colorado River during the autumn nursery period, and c) determine the
effect of flow manipulation and habitat availability upon growing season and size of Colorado
r
squawfish YOY as it relates to potential overwinter survival.
Methods
Two 16.kilometer reaches on the Colorado River in Utah were studied. The reaches were selected
on the basis of high catch. rates for YOY squawfish in the preceding five years of the Interagency
Standardized Monitoring Program (McAda, 1992) study. The upper reach is located near Moab
between River Kilometer (RK) 104.5 and 88.5 (River NTile [RM] 65-55). The lower reach is below
the Potash Mine from RK 48.3 to 32.2 (RM 30-20) (Figure 1). Within each reach every backwater
and many other low-velocity habitats were measwed and seined similarly to the ISMP handbook
guidelines. Three sampling trips were executed each year, in spring, mid-summer, and fall.