9508

• UCREFRP Catalog Number: 9508
• Author: Valdez, R. A. and P. Nelson.
• Title: Green River Subbasin Floodplain Management Plan.
• USFW Year: 2004.
• USFW - Doc Type: Lakewood, Colorado.
• Copyright Material: NO

2.0 Planning And Development

2-3

April 2004

to enhance survival and recruitment. Monitoring drift and habitat use by larval razorback sucker
will provide a better understanding of the role of floodplain habitat in the life cycle of the
species, as well as differences between floodplain sites with respect to entrainment of larvae and
growth and survival. Initial management of selected Recovety Program sites will include
stocking and evaluation of hatchery fish (excess to meeting the State stocking plans) to guide
research and to supplement population augmentation efforts. Hatchery bonytail will also be
released in and near floodplains to describe habitat use and assess their growth and survival.

Hatchery culture and holding facilities for razorback sucker have been established at the
Ouray National Fish Hatchery, Ouray, Utah; and at the Service's Grand Junction Endangered
Fish Facility, Grand Junction, Colorado. Hatchery bonytail are available from Dexter National
Fish Hatchery, Roswell, New Mexico; Wahweap State Fish Hatchery, Big Water, Utah; and
Mumma Native Aquatic Species Restoration Facility, Alamosa, Colorado.

2.4 Role Of Floodplain Model

A Floodplain Model (Valdez 2004) was developed for the Recovety Program to estimate
the amount of floodplain habitat necessary to recover the razorback sucker and to support
recovered self-sustaining populations. This mathematical model is user interactive and consists
of 31 numbered steps, including 11 user-specified input variables (Box 2) and 20 automated
output variables (Box 3). Output variables include computations of total acres and hectares of
floodplains necessary to support specified densities of fish, number offish recruiting to maturity
at 400 mm TL, and recruitment rate as a percentage of the initial adult population.

The Floodplain Model is used in this management plan to help assess the importance of
river reaches and their potential for species conservation. The model considers the relationships
among the location of known and possible spawning sites and available floodplain habitats, both
managed and un-managed. The model is also used to assess the importance and role of specific
floodplain sites, the estimated contribution of
each site to recovery, identification of critical
and limiting factors, and identification of
management elements necessaty for gaining
full benefits of given sites. The Floodplain
Model estimates that 2,032 acres (823 ha) of
floodplain depressions that hold fish for 24
months are needed to support a self-
sustaining population of 5,800 adult
razorback sucker with an average annual
recruitment of 30%, at average fish growth
and density.

Floodplain Model Input Variables

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Initial population size,
Sex ratio,
Average total length (TL) of females,
Percent hatching success,
Percent larval emergence,
Survival rate of larvae per mile
Time in floodplains,
Survival in floodplains,
Fish growth rate,
Fish density, and
Annual survival in mainstem.

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