9705

• UCREFRP Catalog Number: 9705
• Author: Green River Study Plan ad hoc Committee.
• Title: Study plan for the implementation and evaluation of flow and temperature recommendations for endangered fishes in the Green River downstream of Flaming Gorge Dam.
• USFW Year: 2007.
• USFW - Doc Type: Upper Colorado River Endangered Fish Recovery Program
• Copyright Material: NO

GREEN RIVER STUDY PLAN

30

February 2, 2007

Integration and synthesis of existing data on larval presence in the river and a correlation
of these data with flow and temperature conditions plus sediment dynamics (e.g., project 85f,
SWMS model) is recommended to gain a better understanding of this relationship. Otolith
analyses performed as part of this study should be continued to determine the age and growth of
young razorback suckers (e.g., Muth et al. 1998; Bestgen et al. 2002). This information will help
to determine the timing of reproduction by razorback suckers and hatching of larvae to better
understand cues for spawning, and to more accurately pinpoint factors that affect availability and
abundance of naturally produced larvae. In addition, this sampling will provide ancillary data to
evaluate reproductive viability of stocked razorback suckers.

Hypotheses to Be Evaluated and Information Needs to Be Filled

· Temporal relationships between drifting larvae, hydrology, and sediment dynamics
needed to entrain larvae in floodplains (UI0); and

· Benefits of lower peak flows for longer duration vs. higher peak flow for a shorter
duration for a given volume (U14).

Implementation

· Ongoing Project 22F.-Project 22F (annual larval monitoring) should be revised to
include an evaluation of temporal patterns of larval presence in the river and the
relationship of larval presence to flow and temperature conditions. Monitoring would
continue indefinitely. The need for modifications of monitoring protocols and the need
for continued monitoring would be evaluated periodically.

· New Start.-Perform analysis of historical monitoring data (2001 and later) to determine
temporal patterns of larval presence in the river and the relationship of larval presence to
flow, sediment, and temperature conditions. This project should be started in FY 2008
and completed in FY 2009.

3.3.2 Backwater Formation and Maintenance for Y oun!! Colorado Pikeminnow

Backwaters are important in-channel habitats for endangered Colorado River fishes
particularly in Reaches 2 and 3, although releases from Flaming Gorge Dam primarily affect
habitats in Reaches 1 and 2. Backwaters are low-velocity, productive environments that serve as
nursery habitat for age-O Colorado pikeminnow. Colorado pikeminnow spawn from late June to
early August, and newly emerged larvae drift downstream during the descending limb of spring
runoff to become entrained in main channel backwaters. These fish generally remain in
backwaters until the following spring runoff when these habitats are inundated by high flows.

Young Colorado pikeminnow frequently use these habitats for shelter and feeding.
Nonnative fish also use these habitats and compete with and prey on especially the young
pikeminnow. Peak flows reshape the channel annually, and are important in the formation and
maintenance of these habitats. Peak flows and the descending limb of the peak flow hydro graph
are also important in establishing the elevation at which backwaters form. This elevation
determines the base flows at which backwater habitat availability is optimized. The effect of