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

3.0 Scientific Basis And Underlying Principles

3-2

April 2004

3.2 Underlying Principles Of Plan

This Plan is based on five underlying principles:

1. Structure and functiori of the Green River ecosystem are sufficiently intact to
support wild self-sustaining populations of razorback sucker and bonytail;
2. Floodplain restoration and flow re-regulation will enhance endangered fish
habitats;
3. Flow recommendations for the Green River will be evaluated through National
Environmental Policy Act (NEP A) compliance and implemented accordingly;
4. Wild populations of razorback sucker and bonytail must be initiated from hatchery
stocks and through habitat restoration to better understand specific life history
needs in the wild, including nursery and rearing habitats;
5. Young fish remaining in floodplain depressions for 2 years exhibit the best growth
and survival before recruiting to mainstem populations; and
6. Best management strategy is based on the "reset theory" of inundating floodplains
for 2 - 3 years to enhance growth and survival of razorback sucker and bonytail,
and allowing floodplains to become desiccated to periodically kill nonnative fish.

The first and second principles state that the Green River Subbasin retains many of its
natural ecological aspects and that floodplain restoration, combined with flow re-regulation, can
maintain the structure and function of these habitats to assist recovery of razorback sucker and
possibly bonytail. Although much of the Upper Colorado River Basin is flow-regulated, much of
the original structure and function of the ecosystem is intact. The upper basin supports the only
remaining wild self-sustaining populations of Colorado pikeminnow and five of the six known
wild self-sustaining populations of humpback chub. The upper basin also supports viable self-
sustaining populations of the four other native, non-endangered fish species: flannelmouth sucker
(Catostomus latipinnis), bluehead sucker (Catostomus discobolus), roundtail chub (Gila
robusta), and speckled dace (Rhinichthys osculus). This naturalized system provides the
opportunity for recovery of razorback sucker through habitat restoration and flow regulation with
the minimum necessary investment of resources. The estimated time to achieve recovery of the
razorback sucker is 22 years (U.S. Fish and Wildlife Service 2002a), and is based on the
assumption that self-sustaining populations can be established in the first 14 years.

The third principle assumes that flow recommendations for the Green River (Muth et al.
2000) will be evaluated through NEP A and ESA compliance and implemented accordingly.
Flows provided through this compliance process will insure inundation of floodplains on a
regular basis. The fourth principle is that wild populations of razorback sucker must be initiated
from hatchery stocks and habitat restoration to better understand specific life history needs,
including habitat requirements. Floodplain restoration activities will be conducted simultaneous
to releases of hatchery fish in order to better understand life history needs based on fish habitat
use and response. Larval entrainment, growth, and survival in floodplains can be confirmed from
wild, free-roaming fish.