9691

• UCREFRP Catalog Number: 9691
• Author: Recovery Implementation Program.
• Title: Recovery Implementation Program For Endangered Fish Species in the Upper Colorado River Basin 25th Annual Recovery Program Researchers Meeting.
• USFW Year: 2004.
• USFW - Doc Type: Moab, UT.
• Copyright Material: NO

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geomorphologic response of the bottomland to a flow-through condition is uncertain.
Runoff of 2003 presented the first significant flow-through connection for these
bottom lands since the reconfiguration. Hydrographic survey crews from Tetra Tech
performed monitoring surveys in July of2003. Analyses of the data showed that the
bottomlands experienced localized scour and deposition without indications of
aggradation or degradation trends. These findings suggest that the flow-through
condition may help to maintain the bottomlands and refresh the bed of the bottomland
without negatively impacting the long-term function of the bottomlands. However, data
is limited and monitoring is expected to continue with future connectivity to better
understand the geomorphic response of these habitats.

A Generalized Interactive Model To Predict Floodplain Habitat Area Needed To
Recover The Endangered Razorback Sucker In The Upper Colorado River Basin

Valdez, Richard A.I and Pat Nelson2

I R.A. Valdez & Associates. Inc... 1 USFWS. Upper Colorado River Endangered Fish
Recovery Program

Floodplain Model was developed for the Recovery Program to estimate the amount of
floodplain habitat necessary to recover the razorback sucker (Xyrauchen texanus) and to
support recovered self-sustaining populations. This mathematical model was developed
on an Excel platform and is user interactive. It consists of 31 numbered steps, including
17 user-specified input variables and 48 automated output variables. Input variables
include initial population size, sex ratio, average total length (TL) of females, percent
hatching success, percent larval emergence, survival of larvae during drift, entrainment
rate oflarvae in floodplains at various river miles, time spent in floodplains, monthly
survival in floodplains, annual survival in the mainstem, and fish density. Automated
output variables include number of females based on initial number of adults and sex
ratio, average female fish weight, number of eggs produced, number oflarvae emerging,
number of larvae entrained, and number of fish surviving in floodplains. Output
variables also include computations of total acres and hectares of floodplains necessary to
support specified densities of fish, number of fish recruiting to maturity at 400 mm TL,
and recruitment rate as a percentage of the initial adult population. The model estimates
that 2,032 acres of floodplain depressions are necessary as nursery and rearing habitat to
support a self-sustaining population of 5,800 adult razorback sucker with average annual
recruitment of 30% (i.e., 1,740 adults; Recovery Goals target).

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