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

27

February 2, 2007

1: Evaluate annual survival of young and movement of subadult razorback
suckers from floodplains into the mainstem in response to flow
recommendations.

Description

The purpose of this study should be to evaluate survival of young razorback suckers in
floodplains and subsequent movement of subadults into the mainstem. This study should
evaluate persistence of floodplain habitat and habitat quality after peak flows recede, and include
evaluation of survival of razorback suckers in floodplains through fall and winter. The
continuation of this study should be contingent on the results.

The study "C6-rz recruitment" was approved in 2001 but was not completed. This study
should be revisited and potentially revised if deemed appropriate to quantify the relationship
between the frequency, magnitude, and duration of peak flows and movement of subadult
razorback suckers from floodplains into the mainstem. Where appropriate, flows should be
experimentally manipulated to ensure timely completion of studies with adequate consideration
of the full range of recommended flows.

Densities of fish by cghort in floodplains should be tracked over time (i.e., among
seasons and successive years) to determine their movement into the mainstem and to determine if
there is need for annual inundation of floodplains to refresh water quality. Survival of
endangered fish entrained in floodplains in spring should be measured through the fall and
winter. Water quality and survival of native and nonnative fish also should be monitored year-
around where possible, but especially over winter.

Hypotheses to Be Evaluated and Information Needs to Be Filled

· Frequency of floodplain inundation relative to the hydrologic cycle (A5).

· Persistence of floodplains after peak flows recede (U7).

· Frequency of floodplain connection needed to recruit razorback sucker to the river (UII).

· Area of terrace and depression floodplains at different flows (U5).

· Rates of movement into the river of subadult razorback suckers reared in floodplain
nursery habitats (information need).

· Quality of floodplain nursery habitats (including water quality, nonnative fish)
(information need).

· Intra- and inter-annual persistence of water in floodplains (information need).

· Monitoring of geomorphic changes associated with floodplain nursery habitats through
time (information need).